Mars 2020 rover mission of NASA/JPL
Mars 2020 Mission Overview. The Mars 2020 rover mission is part of NASA's Mars Exploration Program, a long-term effort of robotic exploration of the Red Planet. The Mars 2020 mission addresses high-priority science goals for Mars exploration, including key questions about the potential for life on Mars. The mission takes the next step by not only seeking signs of habitable conditions on Mars in the ancient past, but also searching for signs of past microbial life itself. The Mars 2020 rover introduces a drill that can collect core samples of the most promising rocks and soils and set them aside in a "cache" on the surface of Mars. The mission also provides opportunities to gather knowledge and demonstrate technologies that address the challenges of future human expeditions to Mars. These include testing a method for producing oxygen from the Martian atmosphere, identifying other resources (such as subsurface water), improving landing techniques, and characterizing weather, dust, and other potential environmental conditions that could affect future astronauts living and working on Mars. 1) 2) 3)
The mission is timed for a launch opportunity in July/August 2020 when Earth and Mars are in good positions relative to each other for landing on Mars. That is, it takes less power to travel to Mars at this time, compared to other times when Earth and Mars are in different positions in their orbits. To keep mission costs and risks as low as possible, the Mars 2020 design is based on NASA's successful Mars Science Laboratory mission architecture, including its Curiosity rover and proven landing system.
Mars 2020 Science
The Mars 2020 rover explores a site likely to have been habitable. It will seek signs of past life, set aside a returnable cache with the most compelling rock core and soil samples, and demonstrate technology needed for the future human and robotic exploration of Mars. 4)
Figure 1: Evolving science strategies for Mars Explorations (image credit: NASA)
Leveraging discoveries from past Mars missions about water and habitability on Mars, the Mars 2020 rover represents a shift toward directly seeking signs of past microbial life.
NASA's Mars Exploration Program has a long-term, systematic exploration plan for the Red Planet. Mars missions build on each other, with discoveries and innovations made by prior missions guiding what comes next. Mars missions are guided by evolving, discovery-driven science strategies that provide continuity in Mars science exploration themes.
The first framing theme guiding Mars exploration was "Follow the Water," as water is essential to habitable environments and life as we know it. It is also important to understanding the geologic and climatic history of Mars, and would likely play a role in supporting future human explorers.
With past orbiters, landers, and rovers finding evidence of water, the theme "Explore Habitability" emerged to look for additional conditions necessary to life, including chemical elements and compounds necessary for life as we know it. Findings from the Mars Science Laboratory's Curiosity rover marked a transition to the current science theme: "Seek Signs of Life."
While Curiosity is seeking evidence of habitable conditions (both past water and the chemistry needed for life), Mars 2020 is seeking signs of past life itself in the geologic record.
The Mars 2020 Mission Contributes to Four Science Goals for Mars Exploration
Studying Mars' Habitability, Seeking Signs of Past Microbial Life, Collecting and Caching Samples, and Preparing for Future Human Missions. The science strategy for NASA's Mars Exploration Program (MEP) is to Seek Signs of Life. The Mars 2020 rover contributes to this strategy, as well as to the Program's four long-term science goals: 5)
• Goal 1: Determine whether life ever existed on Mars. The mission of the Mars 2020 rover focuses on surface-based studies of the Martian environment, seeking preserved signs of biosignatures in rock samples that formed in ancient Martian environments with conditions that might have been favorable to microbial life.
- It is the first rover mission designed to seek signs of past microbial life. Earlier rovers first focused on and confirmed that Mars once had habitable conditions.
• Goal 2: Characterize the Climate of Mars. Past Martian climate conditions are a focus of the Mars 2020 rover mission. The rover's instruments are looking for evidence of ancient habitable environments where microbial life could have existed in the past.
• Goal 3: Characterize the Geology of Mars. The Mars 2020 rover is designed to study the rock record to reveal more about the geologic processes that created and modified the Martian crust and surface through time. Each layer of rock on the Martian surface contains a record of the environment in which it was formed. The rover seeks evidence of rocks that formed in water and that preserve evidence of organics, the chemical building blocks of life.
• Goal 4: Prepare for Human Exploration. The Mars 2020 rover is demonstrating key technologies for using natural resources in the Martian environment for life support and fuel. It is also monitoring environmental conditions so mission planners understand better how to protect future human explorers.
- This science goal relates to national space policy for sending humans to Mars in the 2030s. Similar to the history of the exploration of Earth's moon, robotic missions to Mars provide a crucial understanding of the environment and test innovative technologies for future human exploration.
- Investments in Mars 2020 technologies include contributions from NASA's Human Exploration and Operations (HEO) Mission Directorate and Space Technology Program (STP) as part of NASA's long-term efforts to develop future capabilities for human space exploration.
The spacecraft is the protective "spaceship" that enables the precious cargo (that is, the rover!) to travel between Earth and Mars. It is separate from the launch vehicle that carries the spacecraft and the rover outside of Earth's atmosphere and gravitational pull. The spacecraft includes the mechanical units that safely carry and maneuver the rover through the Martian atmosphere to a landing on Mars.
The three major parts of the Mars 2020 mission spacecraft design are based on the successful Mars Science Laboratory mission:
• Cruise Stage: The configuration for travel between Earth and Mars that includes an aeroshell (backshell with heat shield) in which the rover and its landing system are enclosed.
• Entry, Descent, and Landing System: The configuration for entry into the Martian atmosphere. Includes the aeroshell, parachute, descent vehicle, and structure for a sky-crane maneuver that will lower the rover to the Martian surface on tethers.
• Rover: A wheeled vehicle with science instruments for making discoveries on the Martian surface.
Figure 2: Illustration of the Mars 2020 spacecraft (image credit: NASA)
Technology development makes missions possible.
Each Mars mission is part of a continuing chain of innovation. Each relies on past missions for proven technologies and contributes its own innovations to future missions. This chain allows NASA to push the boundaries of what is currently possible, while still relying on proven technologies.
The Mars 2020 mission leverages the successful architecture of NASA's Mars Science Laboratory mission by duplicating most of its entry, descent, and landing system and much of its rover design.
The mission advances several technologies, including those related to priorities in the National Research Council's 2011 Decadal Survey and for future human missions to Mars. Plans include infusing new capabilities through investments by NASA's Space Technology Program, Human Exploration and Operations Mission Directorate, and contributions from international partners.
Many innovations focus on entry, descent, and landing technologies, which help ensure precise and safe landings. They include sensors to measure the atmosphere, cameras and a microphone, and at least two key ways to reach the surface of Mars with greater accuracy and less risk (Range Trigger and Terrain-Relative Navigation).
Figure 3: The cruise stage, aeroshell, descent stage, rover and heat shield together make up the spacecraft. As the spacecraft travels down through the Martian atmosphere, certain parts fall away one by one until the rover is safely on solid Martian ground (image credit: NASA)
Figure 4: Leveraging heritage technology: Mars Rover Curiosity's sky-crane maneuver. This artist's concept shows the sky-crane maneuver during the descent of NASA's Curiosity rover to the Martian surface. The Mars mission launching in 2020 would leverage the design of this landing system and other aspects of the Mars Science Laboratory architecture (image credit: NASA/JPL-Caltech)
Mars 2020 Rover
The Mars 2020 rover is car-sized, about about 3 m long, 2.7 m wide, and 2.2 m tall (not including the arm). But at 1,050 kg, it weighs less than a compact car. In some sense, the rover parts are similar to what any living creature would need to keep it "alive" and able to explore. 6)
Figure 5: The Mars 2010 rover is a wheeled vehicle with science instruments for making discoveries on the Martian surface (image credit: NASA)
Figure 6: Mars 2020 Rover build update. Tour the Spacecraft Assembly Facility at NASA's Jet Propulsion Laboratory and see the Mars 2020 mission under construction. Project System Engineer Jennifer Trosper explains the hardware being built and tested, including the rover, descent stage, cruise stage, back shell, and heat shield (video credit: NASA/JPL-Caltech, Published on 19 February 2019)
The Mars 2020 Rover has the following parts: 7)
• body: a structure that protects the rover's "vital organs"
• brains: computers to process information
• temperature controls: internal heaters, a layer of insulation, and more
• "neck and head": a mast for the cameras to give the rover a human-scale view
• eyes and ears : cameras and instruments that give the rover information about its environment
• arm and "hand": a way to extend its reach and collect rock samples for study
• wheels and legs: parts for mobility
• electrical power: batteries and power
• communications: antennas for "speaking" and "listening"
The Mars 2020 rover body is based on the Mars Science Laboratory's Curiosity rover configuration. However, the Mars 2020 rover has a new science and technology toolbox. An important difference is that this rover can sample and cache minerals. To do so, the rover has a new coring drill to collect samples. The samples are then sealed in tubes and placed on the surface of Mars. - In the future, another space mission could potentially pick up the samples and bring them to Earth for detailed analysis. 8)
Differences between Mars 2020 and Curiosity
The large robotic arm on the front of the rover differs from Curiosity's for two main reasons:
1) Mars 2020 will collect rock cores. Mars 2020 needs to collect rock core samples and save them for possible future study by scientists. Curiosity studied samples collected onsite, using the rover's onboard laboratory.
2) Mars 2020 has a larger "hand," or turret. Mars 2020's new functions and new science tools means it must accommodate a larger turret at the end of the robot arm. This turret has the coring drill and two science instruments, plus a color camera for close-up surface inspection and also "selfies" for engineering health checkups.
There is an internal workspace inside the rover body that is dedicated to picking up, moving and placing drill bits and sample tubes within the Sample Caching System. New motors that drive these specialized movements were needed beyond those used on rover Curiosity. The rover motor controller electronics have been modified from the Curiosity design to accommodate these motors.
New Software to Operate the Rover
Mars 2020 will operate very differently than Curiosity. The new rover will gather 20 sealed samples of Martian rocks and soil. The samples will be set aside in a "cache" on Mars. The team is building new software to run the rover. The software will be updated with improvements throughout the mission.
Besides just managing the new sampling operations, the Mars 2020 rover manages all of its daily activities more efficiently to balance its on-site science measurements while also collecting samples for potential future analysis. To do that, the rover's driving software - the "brains" for moving around — was changed to give Mars 2020 greater independence than Curiosity ever had.
This allows Mars 2020 to cover more ground without consulting controllers on Earth so frequently. Also, engineers have added a "simple planner" to the flight software. This allows more effective and autonomous use of electrical power and other rover resources. It allows the rover to shift the time of some activities to take advantage of openings in the daily operations schedule.
New Wheels for Mars 2020
Engineers redesigned the Mars 2020 wheels to be more robust due to the wear and tear the Curiosity rover wheels endured while driving over sharp, pointy rocks. Mars 2020's wheels are narrower than Curiosity's, but bigger in diameter and made of thicker aluminum.
The combination of the larger instrument suite, new Sampling and Caching System, and modified wheels makes Mars 2020 heavier than its predecessor, Curiosity.
The Mars 2020 Rover's "Brains"
The computer module is called the Rover Compute Element (RCE) - there are actually two identical RCEs in the body so there is always a spare "brain." 9)
The RCE interfaces with the engineering functions of the rover over two networks which follow an aerospace industry standard designed especially for the high-reliability requirements of airplanes and spacecraft. In addition, the RCEs have a special purpose to direct interfaces with all of the rover instruments for exchange of commands and science data.
- Processor: Radiation-hardened central processor with PowerPC 750 Architecture: a BAE RAD 750. It operates at up to 200 MHz speed, 10 times the speed in Mars rovers Spirit and Opportunity's computers.
- Memory: 2 GB of flash memory (~8 times as much as Spirit or Opportunity). 256 MB of dynamic random access memory. 256 kB of electrically erasable programmable read-only memory.
The Cameras on the Mars 2020 Rover
The rover has several cameras focused on engineering and science tasks. Some help us land on Mars, while others serve as our "eyes" on the surface to drive around. We use others to do scientific observations and aid in the collection of samples. 10)
- Main function: Take pictures, looking up and down, during descent through Martian atmosphere.
- Location: Mounted on the fore-port-side of the rover, pointing toward the ground.
- Main function: Used for driving around on Mars and for positioning the tools on the robotic arm
- Location: Various places on the rover
- Mass: < 425 grams
- Image size: 5120 x 3840 pixels
- Image resolution: 20 Mpixel
• Science Cameras The science cameras are:
- MastCam-Z is a pair of cameras that takes color images and video, three-dimensional stereo images, and has a powerful zoom lens. Like the Mastcam cameras on the Curiosity rover, Mastcam-Z on Mars 2020 consists of two duplicate camera systems mounted on the mast that stands up from the rover deck. The cameras are next to each other and point in the same direction, providing a 3D view similar to what human eyes would see, only better. They also have a zoom function to see details of faraway targets.
- SuperCam, fires a laser at mineral targets that are beyond the reach of the rover's robotic arm, and then analyzes the vaporized rock to reveal its elemental composition. Like the ChemCam on rover Curiosity, SuperCam fires laser pulses at pinpoint areas smaller than 1 mm from more than 7 meters away. Its camera and spectrometers then examine the rock's chemistry. It seeks organic compounds that could be related to past life on Mars. When the laser hits the rock, it creates plasma, which is an extremely hot gas made of free-floating ions and electrons. An on-board spectrograph records the spectrum of the plasma, which reveals the composition of the material.
- PIXL, uses X-ray fluorescence to identify chemical elements in target spots as small as a grain of table salt. It has a Micro-Context Camera to provide images of to correlate its elemental composition maps with visible characteristics of the target area.
- SHERLOC. Its main tools are spectrometers and a laser, but it also uses a macro camera to take extreme close-ups of the areas that are studied. This provides context so that scientists can see textures that might help tell the story of the environment in which the rock formed.
- WATSON. This camera is one of the tools on the "arm" or turret at the end of Curiosity's robotic arm. It is almost identical to the MAHLI hand-lens camera on the Curiosity rover. WATSON captures the larger context images for the very detailed information that SHERLOC collects on Martian mineral targets. WATSON provides views of the fine-scale textures and structures in Martian rocks and the surface layer of rocky debris and dust. Since WATSON can be moved around on the robotic arm, it also provides other images of rover parts and geological targets that can be used by other arm-mounted instruments. For example, it can be pointed at the oxygen-making experiment MOXIE to help monitor how much dust accumulates around the inlet that lets in Martian air for the extraction of oxygen. - A calibration target for WATSON is attached to the front of the rover body. It contains, a metric standardized bar graphic to help calibrate the instrument.
Figure 7: Overview of the Cameras on the Mars 2020 Rover (image credit: NASA)
Mars 2020 communications
Mars 2020 has three antennas that serve as both its "voice" and its "ears." They are located on the rover equipment deck (its "back"). Having multiple antennas provides operational flexibility and back-up options just in case they are needed. Antennas on rover deck: 11)
UHF antenna: Most often, Mars 2020 uses its ultra-high frequency (UHF) antenna (about 400 megahertz) to communicate with Earth through NASA's orbiters around Mars. Because the rover and orbiter antennas are within close range of each other, they act a little like walky-talkies compared to the long-range telecommunications with Earth provided by the low-gain and high-gain antennas.
It generally takes about 5 to 20 minutes for a radio signal to travel the distance between Mars and Earth, depending on planet positions. Using orbiters to relay messages is beneficial because they are much closer to the rover than the Deep Space Network (DSN) antennas on Earth. The mass- and power-constrained rover can achieve high data rates of up to 2 Mbit/s on the relatively short-distance relay link to the orbiters overhead. The orbiters then use their much larger antennas and transmitters to relay that data on the long-distance link back to Earth.
- Main function: Transmitting data to Earth through Mars Orbiters
- Radio frequency: UHF-band at ~400 MHz
- Transmission rates: Up to 2 Mbit/s on the rover-to-orbiter relay link.
X-band High-Gain Antenna: The high-gain antenna is steerable so it can point its radio beam in a specific direction. The benefit of having a steerable antenna is that the entire rover doesn't need to change position to talk to Earth, which is always moving in the Martian sky. Like turning your neck to talk to someone beside you rather than turning your entire body, the rover can save energy and keep things simple by moving only the antenna. Its high gain allows it to focus its beam, allowing higher data rates on the long link back to Earth.
- Main function: Transmitting data directly to and from Earth
- Radio frequency: X-band (7 to 8 GHz)
- Size: Hexagonally shaped, 0.3 m in diameter
- Transmission/ Reception Rates: 160/500 bit/s or faster to/from the Deep Space Network's 34 m diameter antennas or at 800/3000 bit/s or faster to/from the Deep Space Network's 70 m diameter antenna.
- Provided by: Spain.
X-band Low-Gain Antenna: Mars 2020 uses its low-gain antenna primarily for receiving signals. This antenna can send and receive information in every direction; that is, it is "omnidirectional." The antenna transmits at low data rate to the Deep Space Network antennas on Earth. Because it doesn't need to be pointed, it provides a robust way to always communicate with the rover.
- Main function: Receiving antenna
- Radio frequency: X-band (7 to 8 GHz)
- Reception rates: Approximately 10 bit/s or faster from the Deep Space Network's 34 m diameter antennas or approximately 30 bit/s or faster from the Deep Space Network's 70 m diameter antenna.
Mars 2020 robotic arm
Mars 2020's robotic arm can move a lot like yours. It has a shoulder, elbow and wrist "joints" for maximum flexibility. The arm lets the rover work as a human geologist would: by holding and using science tools with its "hand" or turret. The rover's own "hand tools" extract cores from rocks, takes microscopic images and analyzes the elemental composition and mineral makeup of Martian rocks and soil. 12)
- Length: 2.1 m
- Degrees of freedom:
- There are five. They are made possible by tiny motors called "rotary actuators." The five degrees of freedom are known as the shoulder azimuth joint, shoulder elevation joint, elbow joint, wrist joint and turret joint.
- "Hand" turret: At the end of the arm is the "turret." It's like a hand that carries scientific cameras, mineral and chemical analyzers for studying the past habitability of Mars, and choosing the most scientifically valuable sample to cache.
- Names of tools on the turret: SHERLOC and WATSON, PIXL, GDRT (Gaseous Dust Removal Tool), Ground Contact Sensor, Drill
- Drill: The drill is a rotary percussive drill designed to extract rock core samples from the surface of Mars.
- Drill bits: A suite of interchangeable bits: coring bits, regolith bit and an abrader.
- Main function: Assist in Mars surface investigation and sample collection
- Diameter of drilled holes: 27 mm.
The Mars 2020 mission will gather samples from Martian rocks and soil using its drill. The rover will then store the sample cores in tubes on the Martian surface. This entire process is called "sample caching". 13)
Mars 2020 will be the first mission to demonstrate this on Mars. It could potentially pave the way for future missions that could collect the samples and return them to Earth for intensive laboratory analysis.
The three major steps in sample handling are:
- Objectives: Collect and store a compelling set of rock and soil samples that could be returned to earth in the future.
- Witness tubes: 5 tubes
- Sample containers: 43 containers
- Samples to be collected: at least 20 samples
The Mars 2020 rover requires electrical power to operate. Without power, the rover cannot move, use its science instruments, or communicate with Earth.
Mars 2020 carries a radioisotope power system. This power system produces a dependable flow of electricity using the heat of plutonium's radioactive decay as its "fuel."
The power source is called the MMRTG (Multi-Mission Radioisotope Thermoelectric Generator). The MMRTG converts heat from the natural radioactive decay of plutonium into electricity. This power system charges the rover's two primary batteries. The heat from the MMRTG is also used to keep the rover's tools and systems at their correct operating temperatures.
- Objective: Provide electricity to the rover
- Location: Aft end of the rover
- Size: 64 cm in diameter by 66 cm long
- Mass: ~45 kg
- Power system: Uses 4.8 kg of plutonium dioxide as the source of the steady supply of heat
- Electrical power produced: About 110 W at launch, declining a few percent per year
- Batteries: Two lithium-ion rechargeable batteries to meet peak demands of rover activities when the demand temporarily exceeds the MMRTG's steady electrical output levels.
- Reliability: The electrical power system on the Mars 2020 rover is just like the one used on the Mars Science Laboratory Curiosity rover. NASA has used similar power systems reliably for decades, including the Apollo missions to the Moon, the Viking missions to Mars, and on spacecraft that flew to the outer planets and Pluto, including the Pioneer, Voyager, Ulysses, Galileo, Cassini, and New Horizons missions.
- Safety: Built with several layers of rugged protective material to contain its fuel in a wide range of potential launch accidents, verified through impact testing. The heat source plutonium is manufactured in a ceramic form, which helps it avoid being a significant health hazard unless broken into very fine pieces or vaporized, and then inhaled or swallowed. In the unlikely event of a Mars 2020 launch accident, those who might be exposed could receive an average dose of 15-60 millirem. A resident of the United States receives, on average, 310 millirem of radiation each year from natural sources, such as radon and cosmic rays from space.
This power system provides several advantages:
• The 14-year operational lifetime of an MMRTG provides significant reserve for Mars 2020 prime mission duration of 1.5 Mars years (three Earth years)
• It gives the rover greater mobility over a large range of latitudes and altitudes
• It allows scientists to maximize the capabilities of the rover's science instruments
• It provides engineers with a lot of flexibility in operating the rover (e.g., day and night, and through the winter season).
• August 5, 2019: Equipped with visionary science instruments, the Mars 2020 rover underwent an "eye" exam after several cameras were installed on it. The rover contains an armada of imaging capabilities, from wide-angle landscape cameras to narrow-angle high-resolution zoom lens cameras. 14)
- "We completed the machine-vision calibration of the forward-facing cameras on the rover," said Justin Maki, chief engineer for imaging and the imaging scientist for Mars 2020 at JPL. "This measurement is critical for accurate stereo vision, which is an important capability of the vehicle."
- To perform the calibration, the 2020 team imaged target boards that feature grids of dots, placed at distances ranging from 1 to 40 meters away. The target boards were used to confirm that the cameras meet the project's requirements for resolution and geometric accuracy. The cameras tested included two Navcams, four Hazcams, the SuperCam and the two Mastcam-Z cameras.
- "We tested every camera on the front of the rover chassis and also those mounted on the mast," said Maki. "Characterizing the geometric alignment of all these imagers is important for driving the vehicle on Mars, operating the robotic arm and accurately targeting the rover's laser."
- In the coming weeks, the imagers on the back of the rover body and on the turret at the end of the rover's arm will undergo similar calibration.
- Mounted on the rover's remote sensing mast, the Navcams (navigation cameras) will acquire panoramic 3D image data that will support route planning, robotic-arm operations, drilling and sample acquisition. The Navcams can work in tandem with the Hazcams (hazard-avoidance cameras) mounted on the lower portion of the rover chassis to provide complementary views of the terrain to safeguard the rover against getting lost or crashing into unexpected obstacles. They'll be used by software enabling the Mars 2020 rover to perform self-driving over the Martian terrain.
- Along with its laser and spectrometers, SuperCam's imager will examine Martian rocks and soil, seeking organic compounds that could be related to past life on Mars. The rover's two Mastcam-Z high-resolution cameras will work together as a multispectral, stereoscopic imaging instrument to enhance the Mars 2020 rover's driving and core-sampling capabilities. The Mastcam-Z cameras will also enable science team members to observe details in rocks and sediment at any location within the rover's field of view, helping them piece together the planet's geologic history.
Figure 8: In this image, engineers test cameras on the top of the Mars 2020 rover's mast and front chassis. The image was taken on July 23, 2019, in the Spacecraft Assembly Facility's High Bay 1 at NASA's Jet Propulsion Laboratory in Pasadena, California (image credit: NASA/JPL-Caltech)
• August 2, 2019: Hardware installed onto NASA's Mars 2020 entry vehicle this week will help to increase the safety of future Mars landings. 15)
- Charged with returning astronauts to the Moon by 2024, NASA's Artemis lunar exploration plans will establish a sustained human presence on and around the Moon by 2028. NASA will use its Moon missions along with robotic missions to Mars to prepare for human exploration of the Red Planet.
- The Mars Entry, Descent and Landing Instrumentation 2 (MEDLI2) project developed a suite of sensors that will measure aerothermal environments and the performance of thermal protection system (TPS) material during the entry phase on the Mars 2020 mission. Engineers installed the first batch of items delivered by MEDLI2 onto the heat shield of the entry vehicle this week. The aeroshell of the entry vehicle consists of a heat shield and backshell and will protect the Mars 2020 rover in transit from Earth to Mars and during the entry through the atmosphere of Mars on its way to the surface.
- "Understanding the actual performance of our current generation of entry vehicles is crucial to safe, reliable landing of future robotic and crewed Mars missions. MEDLI2 pressure and thermal measurements are the key to that understanding," said Todd White, MEDLI2 principal investigator.
- MEDLI2 recently completed environmental testing on flight hardware at NASA's Langley Research Center in Hampton, Virginia. The testing, including vibration and thermal vacuum testing, demonstrates the ability of the hardware to survive the large vibratory loads experienced during the launch and the extreme cold during the cruise to Mars. High-temperature sterilization of some of the hardware has also been successfully concluded, allowing MEDLI2 to minimize the potential of transporting terrestrial biological material unintentionally to the surface of Mars. All of the MEDLI2 components are set to be completely installed on the Mars 2020 aeroshell by the end of November 2019.
- MEDLI2 includes three types of sensors (thermocouples, heat flux sensors and pressure transducers), a data acquisition and signal conditioning unit (the Sensor Support Electronics Unit) to record the heating and atmospheric pressure experienced during entry and through parachute deployment, and the harnessing between the sensors and the Sensor Support Electronics unit. Building on the first MEDLI suite, which flew on NASA's Mars Science Laboratory mission, instrumentation is again being applied to the heat shield, but in a different configuration to better measure the flow characteristics. This time instrumentation is being installed on the backshell as well to collect measurements of the heating and the surface pressure to aid in reducing the large uncertainty applied to the current predicted results.
- The Mars 2020 spacecraft will enter Mars' atmosphere traveling about 12,500 mph (20,120 kph). MEDLI2 will start to collect data about five hours prior to the entry and continue to collect data throughout the entry and part of the descent phases. It will take about 6 minutes to slow the spacecraft from 12,500 mph (20,120 kph) to just under 2 mph (3 km/h). MEDLI2 will measure crucial entry and descent performance data on the Mars 2020 heat shield and backshell.
- The key objectives of MEDLI2 are to reduce design margin and prediction uncertainties for the aerothermal environments and aerodynamic database. Close analysis of MEDLI2 flight data is vital to future NASA exploration of the Red Planet. MEDLI2 will explore areas not addressed during the Mars Science Laboratory (MSL) mission and seek answers to questions generated from examining MEDLI/MSL data.
- MEDLI2 is a Game Changing Development project led by NASA's Space Technology Mission Directorate with support from the Human Exploration and Operations Mission Directorate and the Science Mission Directorate. The project is managed at Langley and implemented in partnership with NASA's Ames Research Center in California's Silicon Valley and the Jet Propulsion Laboratory in Pasadena, California.
Figure 9: Vibration testing of the MEDLI2 primary electronics box was successfully completed recently at NASA's Langley Research Center in Hampton, Virginia. Flight hardware is being shipped and installed on the Mars 2020 entry vehicle in preparation for next year's launch (image credit: NASA)
• July 24, 2019: NASA's Associate Administrator for the Science Mission Directorate, Thomas Zurbuchen, has given the go-ahead to begin fueling the Mars 2020 rover's MMRTG (Multi-Mission Radioisotope Thermoelectric Generator). The generator will power the rover and help keep it warm while exploring the Red Planet. 16)
- "The progression of the Mars 2020 rover project is on schedule," said Zurbuchen. "The decision to begin fueling the MMRTG is another important milestone in keeping to our timetable for a July 2020 launch."
- Essentially a nuclear battery, an MMRTG can provide about 110 W of electrical power to a spacecraft and its science instruments at the beginning of a mission. The excess heat from the generator can also serve to keep spacecraft systems warm in cold environments. In all, 27 past U.S. space missions have used radioisotope power - from the Viking missions on Mars to the Voyager spacecraft entering interplanetary space to, most recently, the Curiosity rover on Mars and the New Horizons spacecraft that sailed past Pluto.
- MMRTGs work by converting heat from the natural decay of radioisotope materials into electricity. The generators consist of two major elements: a heat source that contains plutonium-238 (Pu-238) and thermocouples that convert the plutonium's decay heat energy to electricity. The process of loading the heat source into the MMRTG, which the Department of Energy (DOE) manufactured, is timed to a mission's launch date. The Mars 2020 fueling process has been initiated thanks to the continued progress constructing the rover and the spacecraft that will get it there.
- "We are advancing on all fronts - including completion of the cruise stage that will guide us to Mars and the sky crane descent landing system that will gently lower us to the surface," said Project Manager John McNamee of NASA's Jet Propulsion Laboratory, which manages the mission in Pasadena, California. "And the rover is not only looking more and more like a rover each day, it's acting like one."
- With the exception of incorporating the Adaptive Caching Assembly, with its seven motors and more than 3,000 parts, work on the Mars 2020 rover's interior is 100% complete. On the exterior, the most visible additions have been the remote sensing mast, the mobility suspension system, the main robotic arm and the rover's high-gain antenna. The external components of the Mastcam-Z and SuperCam science instruments have been installed on the high perch of the remote sensing mast, and the PIXL and SHERLOC instruments' turret assemblies have been added onto the end of the robotic arm.
- "Our Mars 2020 rover is on a historic mission - the first leg of a round trip to Mars," said Zurbuchen. "We want everyone to come along for this extraordinary voyage, whether it's by watching the rover's final assembly online, literally sending your name to go to Mars or following NASA's updates on the mission."
- Mars 2020 will launch from Cape Canaveral Air Force Station in Florida in July 2020 and land at Jezero Crater on Feb. 18, 2021. It will be the first spacecraft in the history of planetary exploration with the ability to accurately retarget its point of touchdown during the landing sequence - technology that could prove essential to future crewed missions to the Moon and Mars.
- NASA will use Mars 2020 and other missions,including those to the Moon,to prepare for human exploration of the Red Planet. The agency plans to establish a sustained human presence on and around the Moon by 2028 through NASA's Artemis lunar exploration plans.
- JPL is part of the Radioisotope Power Systems program and manages several missions that utilize radioisotope power, including the Mars Curiosity rover and the upcoming Mars 2020 rover.
Figure 10: The electricity for NASA's Mars 2020 rover is provided by a power system MMRTG (Multi-Mission Radioisotope Thermoelectric Generator). The MMRTG will be inserted into the aft end of the rover between the panels with gold tubing visible at the rear, which are called heat exchangers (image credit: NASA/JPL-Caltech)
• July 17, 2019: The launch period for NASA's Mars 2020 rover opens exactly one year from today, July 17, 2020, and extends through Aug. 5, 2020. The mission will launch from Cape Canaveral Air Force Station in Florida and land at Mars' Jezero Crater on Feb. 18, 2021. 17)
- "Back when we started this project in 2013, we came up with a timeline to chart mission progress," said John McNamee, Mars 2020 project manager at NASA's Jet Propulsion Laboratory in Pasadena, California. "That every single major spacecraft component on a project with this level of innovation is synching right now with that timeline is a testament to the innovation and perseverance of a great team."
Figure 11: Engineers at JPL install a sensor-filled turret on the end of the rover's 2.1 m long robotic arm. The image was taken on July 11, 2019. The rover's turret includes HD cameras, SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals) science instrument, PIXL (Planetary Instrument for X-ray Lithochemistry), and a percussive drill and coring mechanism (image credit: NASA/JPL-Caltech)
• July 2, 2019: Engineers at NASA/JPL have installed the SuperCam Mast Unit onto the Mars 2020 rover. The instrument's camera, laser and spectrometers can identify the chemical and mineral makeup of targets as small as a pencil point from a distance of 6 m. 18)
- SuperCam is a next-generation version of the ChemCam instrument operating on NASA's Curiosity Mars rover. It has been developed jointly in the U.S., France and Spain. Once France delivered the last piece of flight hardware, the instrument was fully integrated on the Mars 2020 rover on June 25, 2019, in the Spacecraft Assembly Facility's High Bay 1 clean room at JPL.
- "SuperCam has come a long way from being a bold and ambitious idea to an actual instrument," said Sylvestre Maurice, the SuperCam deputy principal investigator at the Institut de Recherche en Astrophysique et Planétologie in Toulouse, France. "While it still has a long way to go - all the way to Mars - this is a great day for not only SuperCam but the amazing consortium that put it together."
- Mars 2020 scientists will use SuperCam to examine Martian rocks and soil, seeking organic compounds that could be related to past life on Mars.
- "SuperCam's rock-zapping laser allows scientists to analyze the chemical composition of its targets," said Soren Madsen, the payload development manager at JPL. "It lets the Mars 2020 rover conduct its cutting-edge science from a distance."
Figure 12: In this image taken June 25, 2019, engineers install the SuperCam instrument on Mars 2020's rover. This image was taken in the Spacecraft Assembly Facility at NASA's Jet Propulsion Laboratory, Pasadena, California (image credit: NASA/JPL-Caltech)
- Also to be installed in the next few weeks is Mars 2020's Sample Caching System, which includes 17 separate motors and will collect samples of Martian rock and soil that will be left on the surface of Mars for return to Earth by a future mission.
- Mars 2020 will launch from Cape Canaveral Air Force Station in Florida in July of 2020. It will land at Jezero Crater on Feb. 18, 2021.
- NASA will use Mars 2020 and other missions, including to the Moon, to prepare for human exploration of the Red Planet. The agency plans to establish a sustained human presence on and around the Moon by 2028 through NASA's Artemis lunar exploration plans.
- SuperCam is led by Los Alamos National Laboratory in New Mexico, where the instrument's Body Unit was developed. That part of the instrument was installed in the body of the rover in May and includes several spectrometers, control electronics and software. The Mast Unit was built with contributions from numerous academic laboratories in France, led by the French space agency Centre National d'Études Spatiales, and includes the high-powered laser, a telescope, a camera, an infrared spectrometer and a microphone. Calibration targets on the rover deck are provided by Spain's University of Valladolid.
• July 1, 2019: The view of the Sea of Tranquility rising up to meet Neil Armstrong during the first astronaut landing on the Moon was not what Apollo 11 mission planners had intended. They had hoped to send the lunar module Eagle toward a relatively flat landing zone with few craters, rocks and boulders. Instead, peering through his small, triangular commander's window, Armstrong saw a boulder field - very unfriendly for a lunar module. So the Apollo 11 commander took control of the descent from the onboard computer, piloting Eagle well beyond the boulder field,to a landing site that will forever be known as Tranquility Base. 19)
- "There had been Moon landings with robotic spacecraft before Apollo 11," said Al Chen, entry, descent and landing lead for NASA's Mars 2020 mission at the Jet Propulsion Laboratory in Pasadena, California. "But never before had a spacecraft on a descent toward its surface changed its trajectory to maneuver out of harm's way."
Figure 13: Landing NASA's Mars 2020 Rover with Terrain Relative Navigation. The Mars 2020 mission is facing the most challenging landing yet on the Red Planet. It will touch down on Feb. 18, 2021, in Jezero Crater, a 28-mile-wide (45-kilometer-wide) expanse full of steep cliffs, boulder fields and other things that could boobytrap the landing. A new technology called Terrain Relative Navigation (TRN) will allow the spacecraft to avoid hazards autonomously. It's the closest thing to having an astronaut piloting the spacecraft, and the technology will benefit future robotic and human exploration of Mars (NASA/JPL, Published on 1 July 2019)
- Chen and his Mars 2020 colleagues have experience landing spacecraft on the Red Planet without the help of a steely-eyed astronaut at the stick. But Mars 2020 is headed toward NASA's biggest Martian challenge yet. Jezero Crater is a 28-mile-wide (45 km wide) indentation full of steep cliffsides, sand dunes, boulders fields and small impact craters. The team knew that to attempt a landing at Jezero - and with a rover carrying 50% more payload than the Curiosity rover, which landed at a more benign location near Mount Sharp - they would have to up their game.
- "What we needed was a Neil Armstrong for Mars," said Chen. "What we came up with was Terrain-Relative Navigation."
- Carried aboard Mars 2020, TRN (Terrain-Relative Navigation) is an autopilot that during landing can quickly figure out the spacecraft's location over - and more importantly, calculate its future location on - the Martian surface. Onboard, the rover's computer stores a map of hazards within Jezero Crater, and if the computed landing point is deemed too dangerous, TRN will command Mars 2020's descent stage to fly the rover to the safest reachable landing point.
A Two-Part System
- To land an Apollo lunar module on the Moon required a crew of two (Armstrong had Buzz Aldrin feeding him information on their trajectory). Likewise, Terrain-Relative Navigation is actually two systems working together: the Lander Vision System and the Safe Target Selection system.
- "The first half of Terrain-Relative Navigation is the LVS ( Lander Vision System), which determines where the spacecraft is over the Martian surface," said Andrew Johnson, guidance navigation and control subsystem manager for Mars 2020. "If you say it quick - LVS - you'll understand why the team's unofficial mascot is Elvis Presley."
- LVS's operational lifetime is all of 25 seconds. It comes alive at about 13,000 feet (3,960 meters), commanding a camera on the rover to quickly take picture after picture of the Martian surface while still descending on a parachute. LVS scrutinizes one image a second, breaking each into squares that cover about 1,520 m of surface area.
- However, unlike Neil Armstrong, LVS's real-time analysis isn't looking for specific crater rims or mountain peaks. Instead, inside each of those boxes, or landmarks, the system looks for unique patterns in contrasting light and dark created by surface features like cliffs, craters, boulder fields and mountains. It then compares any uncommon pattern with a map in its memory. When it finds five landmark matches during Coarse Landmark Matching mode, it takes another image and repeats the process.
- After three successful image-to-map comparisons, LVS kicks into a mode called Fine Landmark Matching. That's when the system breaks the surface into boxes 125 meters across, scanning for unique patterns and comparing them with the map. LVS is looking for at least 20 matches in that one second of eyeballing an image but usually makes much more - up to 150 - in order to generate an even more accurate plot of Mars 2020's trajectory.
- "Each time a suitable number of matches is made in an image, in either Course or Fine Landmark Matching, LVS updates where the spacecraft is at that moment," said Johnson. "That update is then fed into the Safe Target Selection system."
- This second part of the Terrain-Relative Navigation system uses LVS's position solution, calculates where it will land and then compares it to another onboard map, this one depicting areas within the landing zone understood to be either good for landing ... or the kind with craters, cliffsides, boulders or rocks fields. If the plotted location isn't suitable, Safe Target Selection can change the rover's destiny, moving its landing point by up to 600 m.
Put to the Test
- While Safe Target Selection operations can be investigated in a computer testbed within the confines of JPL, to gather optical data, the team needed to go farther afield: the Mojave Desert and Death Valley.
- Over three weeks in April and May of 2019, LVS flew 17 flights attached to the front of a helicopter, taking and processing image after image over the Mars-like terrain of Kelso Dunes, Hole-in-the-Wall, Lava Tube, Badwater, Panamint Valley and Mesquite Flat Dunes.
- "We flew flight after flight, imitating the descent profile of the spacecraft," said Johnson. "In each flight we performed multiple runs. Each run essentially imitated a Mars landing."
- All in all, the equivalent of 659 Mars landings took place during the test flights.
- "The data is in - TRN works," said Chen. "Which is a good thing because Jezero is where our scientists want to be. And without TRN, the odds of successful landing at a good location for the rover are approximately 85%. With TRN, we feel confident we are up around 99%."
- But Chen is also quick to note that Mars is hard: Only about 40% of all missions sent to Mars - by any space agency - have successfully landed.
- "To go farther we have to look to the past, and in that respect who better than the first?" said Chen. "In an interview some 35 years after Apollo 11, Neil Armstrong said, 'I think we tried very hard not to be overconfident. Because when you get overconfident, that's when something snaps up and bites you.'"
- Mindful of that, the Mars 2020 TRN team's work will conclude only on Feb. 18, 2021, a little after 12 p.m. PST (3 p.m. EST), when their rover alights on Jezero Crater. But it is also just a beginning: Terrain-Relative Navigation's autonomous precision guidance could prove essential to landing humans safely on both the Moon and Mars. TRN could also be useful for landing equipment in multiple drops ahead of a human crew on either world - or others to be explored down the road.
• June 20, 2019: "Now that's a Mars rover," said David Gruel, the Mars 2020 assembly, test, and launch operations manager at JPL. "With the suspension on, not only does it look like a rover, but we have almost all our big-ticket items for integration in our rearview mirror - if our rover had one." 20)
- Within the next few weeks, the team expects to install the vehicle's robotic arm, the mast-mounted SuperCam instrument and the Sample Caching System, which includes 17 separate motors and will collect samples of Martian rock and soil that will be returned to Earth by a future mission.
- Both of the rover's legs (the starboard leg's black tubing can be seen above the wheels) are composed of titanium tubing formed with the same process used to make high-end bicycle frames. The wheels in this picture are engineering models and will not make the trip to Mars. They will be swapped out for flight models of the wheels sometime next year.
- Made of aluminum, each of the six wheels (each 52.5 cm in diameter) features 48 grousers, or cleats, machined into its surface to provide excellent traction both in soft sand and on hard rocks. Every wheel has its own motor. The two front and two rear wheels also have individual steering motors that enable the vehicle to turn a full 360 degrees in place.
- When driving over uneven terrain, the suspension system - called a "rocker-bogie" system due to its multiple pivot points and struts -maintains a relatively constant weight on each wheel and minimizes rover tilt for stability. Rover drivers avoid terrain that would cause a tilt of more than 30 º, but even so, the rover can withstand a 45º tilt in any direction without tipping over. With its suspension, the rover can also roll over rocks and other obstacles as well as through depressions the size of its wheels.
Figure 14: In this image, taken on June 13, 2019, engineers at JPL install the starboard legs and wheels - otherwise known as the mobility suspension - on the Mars 2020 rover (image credit: NASA/JPL-Caltech)
• June 12, 2019: When a female astronaut first sets foot on the Moon in 2024, the historic moment will represent a step toward another NASA first: eventually putting humans on Mars. NASA's latest robotic mission to the Red Planet, Mars 2020, aims to help future astronauts brave that inhospitable landscape. 21)
Figure 15: This artists concept depicts astronauts and human habitats on Mars. NASA's Mars 2020 rover will carry a number of technologies that could make Mars safer and easier to explore for humans (image credit: NASA)
- While the science goal of the Mars 2020 rover is to look for signs of ancient life - it will be the first spacecraft to collect samples of the Martian surface, caching them in tubes that could be returned to Earth on a future mission - the vehicle also includes technology that paves the way for human exploration of Mars.
Figure 16: Crazy Engineering explores a technology demonstration riding aboard NASA's Mars 2020 rover that's straight out of science fiction novels like "The Martian." It's an oxygen generator called MOXIE, designed to convert carbon dioxide - which constitutes about 96% of the Martian atmosphere - into breathable oxygen (video credit: NASA Jet Propulsion Laboratory, Published on 12 June 2019)
- The atmosphere on Mars is mostly carbon dioxide and extremely thin (about 100 times less dense than Earth's), with no breathable oxygen. There's no water on the surface to drink, either. The landscape is freezing, with no protection from the Sun's radiation or from passing dust storms. The keys to survival will be technology, research and testing.
- Mars 2020 will help on all those fronts. When it launches in July of 2020, the spacecraft will carry the latest scientific and engineering tools, which are coming together as the rover is built at NASA's Jet Propulsion Laboratory in Pasadena, California. Here's a closer look.
- Every landing on Mars offers a learning opportunity. With Mars 2020, that includes how the spacecraft's heat shield and parachute perform in the planet's atmosphere, and how well its radar can sense the approaching surface. Sensors in the spacecraft's aeroshell (the capsule that encloses the rover) will study how it heats up and performs during atmospheric entry. These Mars Entry, Descent and Landing Instrumentation 2 (MEDLI2) sensors could help engineers improve their landing designs for big payloads like astronaut equipment and habitats.
- Landing a rover like this one also gives NASA more experience putting a heavy spacecraft on the surface of Mars; the challenge of landing in the thin Martian atmosphere scales with mass. The first crewed spacecraft will be titanic by comparison, carrying with it life support systems, supplies and shielding.
- Finally, Mars 2020 has a guidance system that will take a step toward safer landings. Called Terrain Relative Navigation, this new system figures out where the spacecraft is headed by taking camera images during descent and matching landmarks in them to a preloaded map. If the spacecraft drifts toward dangerous terrain, it will divert to a safer landing target.
- Terrain Relative Navigation allowed the 2020 team to select a landing site, Jezero Crater, that was considered too risky for previous missions. This kind of autonomous guidance could prove essential to landing humans safely. It would also be useful for landing equipment in multiple drops ahead of a human crew.
- Living on Mars will require a steady supply of oxygen, which would be costly to transport from Earth in the necessary volumes. A cube-shaped device called the Mars Oxygen In-Situ Resource Utilization Experiment (MOXIE) is exploring a space-saving alternative that converts carbon dioxide - which constitutes about 96% of the Martian atmosphere - into oxygen. Although MOXIE is a small-scale demonstration, the hope is that its technology could evolve into bigger and more efficient oxygen generators in the future. Those would allow astronauts to create their own breathable air and would provide oxygen to burn rocket fuel needed to return humans to the Earth.
- More importantly, MOXIE's descendants would save precious space on the first crewed vehicle to Mars. Not only would that leave more room for supplies, it could also reduce the cost and difficulty of getting from Earth to Mars.
- Satellites orbiting the Red Planet regularly peek underground using radar, but Mars 2020 is carrying a ground-penetrating radar called the Radar Imager for Mars' Subsurface Experiment (RIMFAX) that will be the first operated at the Martian surface. Mars 2020 scientists will use its high-resolution images to look at buried geology, like ancient lake beds. But such a radar could one day be used to find stores of underground ice that astronauts could access to provide drinking water. Jezero Crater is unlikely to have any such caches, but many exist elsewhere on Mars.
- Dust and radiation are part of every Martian weather forecast. Dust blows everywhere, sticking to spacecraft and covering solar panels. And because the planet doesn't have a magnetic field, as Earth does, the Sun's radiation bathes the Martian surface. The orbits of Earth and Mars align best for interplanetary travel every two years, meaning the first astronauts on the Red Planet are likely to endure long exposures to radiation.
- To help engineers design spacesuits to shield astronauts from the elements, NASA is sending five samples of spacesuit material along with one of Mars 2020's science instruments, called Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals (SHERLOC). A piece of an astronaut's helmet and four kinds of fabric are mounted on the calibration target for this instrument. Scientists will use SHERLOC, as well as a camera that photographs visible light, to study how the materials degrade in ultraviolet radiation. It will mark the first time spacesuit material has been sent to Mars for testing and will provide a vital comparison for ongoing testing at NASA's Johnson Space Center.
- Humans exploring the Red Planet will need more than good spacesuits; they'll need a place to live. Mars 2020 will collect science that may help engineers design better shelters for future astronauts. Like NASA's Curiosity rover and InSight lander, 2020 has weather instruments to study how dust and radiation behave in all seasons. This suite of sensors, called the Mars Environmental Dynamics Analyzer (MEDA), is the next step in the kind of weather science Curiosity collects.
• June 11, 2019:
• May 31, 2019: One of the first operations the Mars 2020 rover will perform after touching down on the Red Planet's Jezero Crater on Feb. 18, 2021, will be to raise its RSM (Remote Sensing Mast), which carries important optics and instrumentation. 22)
Figure 17: In this picture - taken on May 23, 2019, in the Spacecraft Assembly Facility's High Bay 1 clean room at the JPL in Pasadena, California - engineers re-install the cover to the RSM head after integration of two Mastcam-Z high-definition cameras. Visible below the red lens cover is the left Mastcam-Z camera (with the "Remove Before Flight" labels); support equipment blocks the right Mastcam-Z from view. The RSM and its twin cameras will be installed on the rover's deck the week of June 3, 2019 (image credit: NASA/JPL, Caltech)
- Mastcam-Z is a multispectral, stereoscopic imaging instrument that will enhance the Mars 2020 rover's driving and core-sampling capabilities. It will also enable science team members to observe textural, mineralogical, structural and morphologic details in rocks and sediment at any location within the rover's field of view, helping them piece together the planet's geologic history.
- "Mastcam-Z will be the first Mars color camera that can zoom, enabling 3D images at unprecedented resolution," said Mastcam-Z Principal Investigator Jim Bell of Arizona State University in Tempe. "With a resolution of three-hundredths of an inch [0.8 millimeters] in front of the rover and less than one-and-a-half inches [38 millimeters] from over 330 feet [100 meters] away - Mastcam-Z images will play a key role in selecting the best possible samples to return from Jezero Crater."
- Mastcam Z's capabilities are not the only firsts of the mission. Mars 2020 will be the first spacecraft in the history of planetary exploration with the ability to accurately retarget its point of touchdown during the landing sequence. And the rover carries a sample-caching system that will collect Martian rock and soil samples and store them on the planet's surface for retrieval and return to Earth by subsequent missions.
• May 23, 2019: NASA's Mars 2020 spacecraft has completed acoustic and TVAC (Thermal Vacuum) testing at the Jet Propulsion Laboratory in Pasadena, California. The acoustic test of the spacecraft that will carry the Mars 2020 rover to a soft touchdown in Jezero Crater on Feb. 18, 2021, is the best Earthly approximation for what the spacecraft will endure during launch, where it will encounter potentially destructive levels of sound and vibration. TVAC introduces the vacuum and extreme temperatures of space that could cause components to malfunction or fail. 23)
- "First we blast it with sound to make sure nothing vibrates loose," said David Gruel, the Mars 2020 assembly, test and launch operations manager at JPL. "Then, after a thorough examination, we 'put it in space' by placing the spacecraft in this huge vacuum chamber we have here at JPL. We pump out the atmosphere, then chill parts of it and cook others while testing the performance of the entire spacecraft."
• May 17, 2019: From the top down, and suspended by cables, is the complete cruise stage, which will power and guide the Mars 2020 spacecraft on its seven-month voyage to the Red Planet. Directly below that is the aeroshell (white back shell and barely visible black heat shield), which will protect the vehicle during cruise as well as during its fiery descent into the Martian atmosphere. Not visible (because it's cocooned inside the aeroshell) is the completed rocket-powered descent stage and the surrogate rover (a stand-in for the real rover, which is undergoing final assembly in JPL's High Bay 1 cleanroom). 24)
Figure 18: An engineer inspects the completed spacecraft that will carry NASA's next Mars rover to the Red Planet, prior to a test in the Space Simulator Facility at NASA/JPL (image credit: NASA/JPL, Caltech)
- The Mars 2020 spacecraft was tested in the 8-meter-by-26-meter chamber in the same configuration it will be in while flying through interplanetary space. The 2020 rover carries an entirely new suite of instruments, including a sample-caching system that will collect samples of Mars for return to Earth on subsequent missions. The mission will launch from Cape Canaveral Air Force Station in Florida in July of 2020 and land at Jezero Crater on 18 February 2021.
• May 2, 2019: Protecting against the extremes of space travel is critical to the success of any mission. Lockheed Martin has successfully completed the flight hardware structure of the heat shield, validating the physical integrity with a final static test after exposing it to flight-like thermal conditions. The heat shield is half of the large and sophisticated two-part aeroshell that Lockheed Martin is designing and building to encapsulate NASA Jet Propulsion Laboratory's Mars 2020 rover from the punishing heat and friction of entry through the Martian atmosphere. 25)
Figure 19: The Lockheed Martin-built heat shield, shown here in the testing phase, is just one component in the final aeroshell that will protect the Mars 2020 rover on its long journey to Mars (image credit: Lockheed Martin)
- The Mars 2020 mission will be one of the most challenging entry, descent and landings ever attempted on the Red Planet. The heat shield aerodynamics serve as a "brake" to slow the spacecraft from about 19,300 km/h so the structure needs to be flawless. As the tenth aeroshell system that Lockheed Martin has produced for NASA, this is one of the largest at 4.5 meters in diameter.
- "Our experience building aeroshells for NASA Mars missions does not mean that it is 'easy'," said Neil Tice, Lockheed Martin Mars 2020 Aeroshell program manager. "Tests like this structural test are absolutely essential to ensuring mission success in the long-run."
- The static test was conducted on 25 April and was designed to mimic the load that the heat shield will experience during the most extreme part of its journey; the entry phase. To do that, engineers used vacuum pumps to simulate the pressure of approximately 140,000 pounds on the structure. The structure was tested to 120% of the expected flight load to push it to the limit.
- For this particular test, the team also integrated a new form of instrumentation. Historically, this test utilizes conventional strain gauges and extensometers to monitor structural response at distinct points during loading. Partnering with NASA Langley Research Center, the team also applied a new tool called Photogrammetry or Digital Image Correlation. This allowed the team to monitor full-field strains and displacements over the entire visible area of the structure in realtime. To use this technique, a vinyl wrap, similar to a decal, that has different visual cues (dark random speckles over a white background) was applied to the heat shield. During the test, a set of digital cameras optically monitor any changes in the pattern and generate a three-dimensional map of displacements and surface strains as the applied load increases.
- "While we have used this full-field photogrammetry technique on test articles in the past, this is the first successful implementation on official flight hardware," said Dr. Sotiris Kellas, NASA Langley aerospace engineer and lead for the technical demonstration. "This technology will allow us to safeguard hardware during testing but more importantly provide data for test analysis correlation and improvement of our design and analysis tools."
- Following this test, the Lockheed Martin team will apply Phenolic Impregnated Carbon Ablator (PICA) thermal protection system tiles to the structure. Once complete and through all environmental testing, the full heat shield will be mated to the backshell in early fall.
- The Mars 2020 Project at NASA/JPL manages the rover development for the Science Mission Directorate at NASA Headquarters in Washington. The NASA Engineering and Safety Center at NASA Langley Research Center provided the photogrammetry support for this test.
• April 24, 2019: Mars 2020 is Wired for Sound. 26)
Figure 20: Engineers and technicians working on NASA's Mars 2020 mission prepare spacecraft components for acoustic testing in the Environmental Test Facility at NASA's Jet Propulsion Laboratory in Pasadena, California. The spacecraft is being tested in the same configuration it will be in when sitting atop the Atlas rocket that will launch the latest rover towards Mars in July 2020. The image was taken on April 11, 2019, at NASA/JPL (image credit: NASA/JPL)
• March 19, 2019: In a little more than seven minutes in the early afternoon of 18 February 2021, NASA's Mars 2020 rover will execute about 27,000 actions and calculations as it speeds through the hazardous transition from the edge of space to Mars' Jezero Crater. While that will be the first time the wheels of the 1,050 kg rover touch the Red Planet, the vehicle's network of processors, sensors and transmitters will, by then, have successfully simulated touchdown at Jezero many times before. 27)
- "We first landed on Jezero Crater on 23 January," said Heather Bottom, systems engineer for the Mars 2020 mission at the Jet Propulsion Laboratory in Pasadena, California. "And the rover successfully landed again on Mars two days later."
- Bottom was the test lead for ST1 ( Systems Test 1), the Mars 2020 engineering team's first opportunity to take the major components of the Mars 2020 mission for a test drive. Over two weeks in January, Bottom and 71 other engineers and technicians assigned to the 2020 mission took over the High Bay 1 cleanroom in JPL's Spacecraft Assembly Facility to put the software and electrical systems aboard the mission's cruise, entry capsule, descent stage and rover through their paces.
Figure 21: Lonely Vigil: With the backshell that will help protect the Mars 2020 rover during its descent into the Martian atmosphere visible in the foreground, a technician on the project monitors the progress of Systems Test 1 (image credit: NASA/JPL-Caltech)
- "ST1 was a massive undertaking," said Bottom. "It was our first chance to exercise the flight software we will fly on 2020 with the actual spacecraft components that will be heading to Mars — and make sure they not only operate as expected, but also interact with each other as expected."
- The heritage for Mars 2020's software goes back to the Mars Exploration Rovers (Spirit and Opportunity) and the Curiosity rover that has been exploring Mars' Gale Crater since 2012. But 2020 is a different mission with a different rover, a different set of science instruments and a different destination on Mars. Its software has to be tailored accordingly.
- Work began in earnest on the flight software in 2013. It was coded, recoded, analyzed and tested on computer workstations and laptops. Later, the flight software matriculated to spacecraft testbeds where it was exposed to computers, sensors and other electronic components customized to imitate the flight hardware that will launch with the mission in 2020.
- "Virtual workstations and testbeds are an important part of the process," said Bottom. "But the tens of thousands of individual components that make up the electronics of this mission are not all going to act, or react, exactly like a testbed. Seeing the flight software and the actual flight hardware working together is the best way to build confidence in our processes. Test like you fly."
Making the Grade
- On the day before ST1 began, the High Bay 1 cleanroom was hopping with "bunny suit"-clad engineers and technicians assembling, inspecting and testing the mission's hardware. The next day, Wednesday, Jan. 16, the room was eerily quiet. The majority of workers had been replaced by two technicians there to monitor the flight test hardware. Lines of electrical cabling — "umbilicals" — were added to provide data and power to the spacecraft's cruise stage, back shell, descent stage and rover chassis, which have yet to be stacked together. The ground to in-flight spacecraft (and in-flight spacecraft to ground) communications were handled by X-band radio transmission, just like they would be during the trip to Mars.
- ST1 began with commands to energize the spacecraft's electrical components and set up thermal, power and telecom configurations. While all the spacecraft components remained in the cleanroom, Bottom and her team had them thinking they were sitting on top of an Atlas 541 rocket 58 meters above Launch Complex 41 at Cape Canaveral on July 17, 2020, waiting to be shot into space.
- Next, they focused on another part of cruise before testing the landing sequence. Then they did it all over again.
- After a successful launch, they time jumped 40 days ahead to simulate deep space cruise. How would the software and hardware interact when they had to perform navigation fixes and trajectory correction maneuvers? And how would they work when simulated events didn't go as planned? The team looked for answers on the operators' computer screens in the test operations room beside the cleanroom.
- "From the test operations room, you could look out the windows onto the cleanroom floor and clearly see the flight hardware," said Bottom. "Nothing was visibly moving, but underneath the outer structure, there were flight computers swapping sides, radios sending and receiving transmissions, fuel valves moving in and out, subsystems being energized and later turned off, and electrical signals being sent to nonexistent pyrotechnic devices. There was a lot going on in there."
- On 30 January, the Mars 2020 test team was able to close their 1,000-plus page book of procedures for ST1. They went two-for-two on Mars landings. They also launched four times, performed deep space navigation, executed several trajectory correction maneuvers and even tested a few in-flight off-nominal situations. This first evaluation of flight hardware and software, over a year in the making, had been a thorough success, demonstrating where things excelled and where they could be improved. When these new changes have been investigated on both a virtual workstation and in the testbed, they will have their chance to "fly" in one of the many other systems tests planned for Mars 2020.
- "One of the future scenario tests will place the rover inside a thermal chamber and simulate being on the surface. It will step through mission critical activities at some very low Mars surface temperatures," said Bottom. "Both literally and figuratively it will be a very cool test."
- The Mars 2020 Project at JPL manages rover development for NASA's Science Mission Directorate. NASA's Launch Services Program, based at the agency's Kennedy Space Center in Florida, is responsible for launch management. Mars 2020 will launch from Cape Canaveral Air Force Station in Florida.
• November 19, 2018: NASA has chosen the Jezero Crater as the landing site for its upcoming Mars 2020 rover mission after a five-year search, during which details of more than 60 candidate locations on the Red Planet were scrutinized and debated by the mission team and the planetary science community. 28)
- The rover mission is scheduled to launch in July 2020 as NASA's next step in exploration of the Red Planet. It will not only seek signs of ancient habitable conditions – and past microbial life – but the rover also will collect rock and soil samples and store them in a cache on the planet's surface. NASA and ESA (European Space Agency) are studying future mission concepts to retrieve the samples and return them to Earth, so this landing site sets the stage for the next decade of Mars exploration.
Figure 22: Chemical Alteration by Water, Jezero Crater Delta: On ancient Mars, water carved channels and transported sediments to form fans and deltas within lake basins (image credit: NASA/JPL-Caltech/MSSS/JHU-APL)
• December 4, 2012: NASA announced the Mars 2020 mission at the fall meeting of the American Geophysical Union in San Francisco. 29)
- In an ongoing effort to restructure its Mars exploration program in the wake of deep budget cuts announced earlier this year, NASA announced plans Tuesday to send a new $1.5 billion rover to the red planet in 2020 based on the design of the agency's hugely successful Curiosity.
Launch: The Mars 2020 mission will launch from the Cape Canaveral Air Force Station in Florida in July of 2020 on a two-stage Atlas V-541 launch vehicle, provided by ULA (United Launch Alliance). The launch site is Cape Canaveral Air Force Station, Florida. The mission will land at the Jezero Crater on 18 February 2021 (Ref. 17).
NASA's Launch Services Program at Kennedy Space Center in Florida manages the Atlas V launch service for Mars 2020. The two-stage Atlas V-541 launch vehicle lifts off from Launch Complex 41 at Cape Canaveral Air Force Station, Florida.
Mission duration: At least one Mars Year (about 687 Earth days).
Sensor complement of the MARS 2020 Rover (MastCam-7, SuperCam, PIXL, SHERLOC, MOXIE, MEDA, RIMFAX)
Scientists will use the Mars 2020 rover to identify and select a collection of rock and soil samples that will be stored for potential return to Earth by a future mission. The Mars 2020 mission is responsive to the science objectives recommended by the National Research Council's 2011 Planetary Science Decadal Survey.
Figure 23: This 2015 diagram shows components of the investigations payload for NASA's Mars2020 rover (image credit: NASA) 32)
MastCam-Z (Mast-mounted Camera system)
Mastcam-Z is an advanced camera system with panoramic and stereoscopic imaging capability with the ability to zoom. The instrument also will determine mineralogy of the Martian surface and assist with rover operations. The principal investigator is James Bell, ASU (Arizona State University) in Tempe. The instrument is based on the successful Mastcam instrument on NASA's Mars Curiosity rover. Mastcam-Z will be the main eyes of NASA's next Mars rover. 33)
From its position on the Mars-2020 Remote Sensing Mast (RSM), the Mastcam-Z imaging investigation acquires visible color (RGB), stereo panoramas of the Martian surface at resolutions sufficient to resolve ~1 mm features in the near-field (robotic arm workspace) and ~3-4 cm features 100 meters away. Mastcam-Z is also equipped with bandpass filters (400 - 1000 nm) that are used to distinguish unweathered from weathered materials and to provide important insights into the mineralogy of many silicates, oxides, oxyhydroxides, and diagnostic hydrated minerals. Mastcam-Z also images the sun directly using a pair of solar filters.
The Mastcam-Z cameras have the capability to zoom, focus, acquire data at high-speed (video rates of 4 frames/sec or faster for subframes), and store large amounts of data in internal storage. These capabilities permit investigators to examine targets that are otherwise out of the rover's reach. The cameras can observe time-dependent phenomena such as dust devils, cloud motions, and astronomical phenomena, as well as activities related to driving, sampling, and caching. Mastcam-Z has improved stereo imaging capabilities compared to the Mars Science Laboratory rover's Mastcam and the Mars Exploration Rovers' Pancam. Mastcam-Z provides important advances in navigational and instrument-placement capabilities that help support and enhance the Mars 2020 rover's driving and coring/sampling capabilities.
Figure 24: MastCam-Z lens packaging (image credit: NASA/JPL Caltech, ASU, MSSS)
Mastcam-Z observes textural, mineralogical, structural, and morphologic details in rocks and fines at the rover's field site. The cameras allow the science team to piece together the geologic history of the site via the stratigraphy of rock outcrops and the regolith, as well as to constrain the types of rocks present (e.g., sedimentary vs. igneous). The Mastcam-Z cameras also document dynamic processes and events via video (e.g., dust devils, cloud motions, and astronomical phenomena, as well as activities related to driving, sampling, and caching), observe the atmosphere, and contribute to rover navigation and target selection for investigations by the coring/caching system, as well as other instruments.
- Objectives: To take high-definition video, panoramic color and 3D images of the Martian surface and features in the atmosphere with a zoom lens to magnify distant targets.
- Location: Mounted on the rover mast at the eye level, 2 meters tall. The cameras are separated by 24.2 cm to provide stereo vision.
- Mass: ~4g
- Power: ~17.4 W
- Volume: Camera head, per unit: 11 x 12 x 26 cm; Digital electronics assembly: 22 x 12 x 5 cm; Calibration target: 10 x 10 x 7 cm.
- Data return: ~ 148 Mbit/sol on average
- Color quality: Similar to that of a consumer digital camera (2-megapixel)
- Image size: 1600 x 1200 pixels max
- Image resolution: Able to resolve between about 150 µm/pixel to 7.4 mm/pixel depending on distance.
SuperCam, an instrument that can provide imaging, chemical composition analysis, and mineralogy. The instrument will also be able to detect the presence of organic compounds in rocks and regolith from a distance. The principal investigator is Roger Wiens, Los Alamos National Laboratory, Los Alamos, New Mexico. This instrument also has a significant contribution from the Centre National d'Etudes Spatiales,Institut de Recherche en Astrophysique et Plane'tologie (CNES/IRAP) France.
SuperCam is a remote-sensing instrument for the Mars 2020 mission that uses remote optical measurements and laser spectroscopy to determine fine-scale mineralogy, chemistry, and atomic and molecular composition of samples encountered on Mars. 34)
To enable these measurements, SuperCam is, in fact, many instruments in one.
• For measurements of elemental composition, it integrates the remote Laser Induced Breakdown Spectroscopy (LIBS) capabilities of the highly successful ChemCam instrument included in the payload of the Curiosity rover currently exploring Mars. LIBS uses a 1064 nm laser to investigate targets up to 7 m distance from the rover.
• In addition, SuperCam also performs Raman spectroscopy (at 532 nm to investigate targets up to 12 m distance from the rover), Time-Resolved Fluorescence (TRF) spectroscopy, Visible and InfraRed (VISIR) reflectance spectroscopy (400 – 900 nm, 1.3 – 2.6 µm) at a distance in order to provide information about the mineralogy and molecular structure of samples under consideration, as well as being able to search directly for organic materials.
• Finally, SuperCam also acquires high-resolution images of samples under study using a color remote micro-imager (RMI). The collection of data provided by this suite of correlated measurements on a sample can be used to determine directly the geochemistry and mineralogy of samples.
SuperCam measurements can be rapidly acquired without the need to position the rover or rover arm upon the target, facilitating rapid and efficient measurements during Mars operations. As demonstrated by ChemCam, the SuperCam laser can be used to "blast off" dust from surfaces at a distance in order to get a better look at solid surfaces on Mars, without having to drive up to samples and perform manipulations with the rover arm or associated tools.
SuperCam is a continuing effort between Los Alamos and the IRAP research institution in Toulouse, France, and the French Space Agency (CNES), with additional collaboration from the University of Hawaii and the University of Valladolid (UVA) in Spain.
- Objectives: To identify the chemical composition of rocks and soils, including their atomic and molecular makeup
- Location: The SuperCam instrument is mounted on the "head" of the rover's long-necked mast.
- Mass: The mast-mounted sensor head has a mass of 5.6 kg, the Rover body-mounted electronics have a mass of 4.8 kg. The calibration target has a mass of 0.2 kg.
- Power: 17.9 W.
- Volume: The volume of the Mast-mounted sensor head is 38 x 24 x 19 cm.
- Calibration target: 3 cm in size.
- Data return: 15.5 Mbit per experiment or about 4.2 Mbit per day.
SuperCam's laser is uniquely capable of remotely clearing away surface dust, giving all of its instruments a clear view of the targets.
PIXL (Planetary Instrument for X-ray Lithochemistry)
PIXL is an X-ray fluorescence spectrometer that will also contain an imager with high resolution to determine the fine scale elemental composition of Martian surface materials. PIXL will provide capabilities that permit more detailed detection and analysis of chemical elements than ever before. The principal investigator is Abigail Allwood, NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California. 35)
The PIXL for the Mars-2020 rover is a microfocus X-ray fluorescence instrument that rapidly measures elemental chemistry at sub-millimeter scales by focusing an X-ray beam to a tiny spot on the target rock or soil and analyzing the induced X-ray fluorescence.
Scanning the beam reveals spatial variations in chemistry in relation to fine-scale geologic features such as laminae, grains, cements, veins, and concretions (Figure 25).
The high X-ray flux enables high sensitivity and short integration times: most elements are detected at lower concentrations than possible on previous landed payloads to Mars, and several new elements can be detected that were not previously detectable on these missions. Fast acquisition allows rapid scanning so that PIXL reveals the associations between different elements and the observed textures and structures. The same spectra can be summed for bulk analysis, allowing comparison with bulk chemistry measurements at sites previously explored on Mars. With PIXL's simple design comes operational efficiency and experimental flexibility—an instrument that can adapt to different scientific opportunities to produce a diverse set of scientifically powerful data products within the constraints of the mission.
Figure 25: PIXL breadboard maps of a paleoarchean altered conglomerate with unconformity surface, revealing complex lithology including rounded pyrite, chromite, zircon, K-Al-Cr clay in the fuchsitic mudstone, Mn,Fe,Ca-carbonate in alteration vein, silicification of the conglomerate matrix. Map size is 20 mm by 10 mm with a step size of 0.15 mm (image credit: NASA/A. Allwood)
The instrument consists of a main electronics unit in the rover's body and a sensor head mounted on the robotic arm. The sensor head includes an x-ray source, X-ray optics, X-ray detectors, and high-voltage power supply (HVPS), as well as a micro-context camera (MCC) and light-emitting diode (LED). The PIXL can detect elements: Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Br, Rb, Sr, Y, Ga, Ge, As, and Zr, with important trace elements such as Rb, Sr, Y and Zr detectable at 10's ppm level. An example is shown in Figure 26.
Figure 26: This Figure demonstrates that the PIXL instrument detects important trace elements (red) at 10's ppm. Insert: Rb, Sr, Y, Zr are clearly detected due to the lack of interfering excitation lines at 13-17 keV in PIXL (continuum subtracted using a modeled fit to Bremsstrahlung), image credit: NASA/JPL-Caltech
The advantages of the PIXL instrument are:
• High spatial resolution with a 0.12 mm-diameter beam enabling sub-mm scale geochemistry correlated with texture
• Spatial coverage, targeting and position knowledge: fine step size and micro-context camera will provide resolution and footprint at hand-lens scale
• Fast spectral acquisition: measure most major and minor elements at 0.5 wt% in 5 seconds.
• Large range of detectable elements (26+ elements)
• High sensitivity: detect important trace elements at 10's ppm level
• Operational efficiency: The combined effect of PIXL's speed, sensitivity, resolution, coverage/targeting, and measurement flexibility allows PIXL to search efficiently and locate the places of interest and to observe small patches of clean rock
• Operational robustness: tolerant to surface roughness.
- Objectives: To measure the chemical makeup of rocks at a very fine scale
- Location: Mounted on the turret at the end of the robotic arm
- Mass: Arm-mounted sensor head: 4.3 kg; Body-mounted electronics: 2.6 kg; Calibration target: 0.015 kg
- Power: ~25 W
- Volume: Arm-mounted sensor head: 21.5 x 27 x 23 cm
- Calibration targets: Diameter of each of four disks: 5 mm; Pedestal base: 39 x 30 mm
- Data return: About 16 Mbit/experiment or about 2 MB/day.
If you are looking for signs of ancient life, you want to look at a small scale and get detailed information about chemical elements present.
SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics and Chemicals)
SHERLOC is a spectrometer that will provide fine-scale imaging and uses an ultraviolet (UV) laser to determine fine-scale mineralogy and detect organic compounds. SHERLOC will be the first UV Raman spectrometer to fly to the surface of Mars and will provide complementary measurements with other instruments in the payload. The principal investigator is Luther Beegle, NASA/JPL. "Key, driving questions are whether Mars is or was ever inhabited, and if not, why not? The SHERLOC investigation will advance the understanding of Martian geologic history and identify its past biologic potential." 36)
SHERLOC is an arm-mounted, Deep UV (DUV) resonance Raman and fluorescence spectrometer utilizing a 248.6 nm DUV laser and <100 µm spot size. The laser is integrated to an autofocusing/scanning optical system, and co-boresighted to a context imager with a spatial resolution of 30 µm.
SHERLOC enables non-contact, spatially resolved, and highly sensitivity detection and characterization of organics and minerals in the Martian surface and near subsurface. The instrument goals are to assess past aqueous history, detect the presence and preservation of potential biosignatures, and to support selection of return samples. To do this, SHERLOC measures CHNOPS-containing mineralogy, measures the distribution and type of organics preserved at the surface, and correlates them to textural features.
SHERLOC operates over a 7 x 7 mm area through use of an internal scanning mirror. The 500 µm depth of view, in conjunction with the MAHLI heritage autofocus mechanisms, enables arm placements from 48 mm above natural or abraded surfaces without the need for rover arm repositioning/movement. Additionally, borehole interiors, after sample core removal, can be analyzed as a proxy for direct core analysis.
In addition to the combined spectroscopic and macro imaging component, SHERLOC also integrates a "second-eye" with a near-field-to-infinity imaging component called WATSON (Wide Angle Topographic Sensor for Operations and eNgineering), which is used for engineering science operations and science imaging. WATSON is a build-to-print camera based on the MSL (Mars Science Laboratory) Mars Hand Lens Imager (MAHLI). Integration is enabled by existing electronics within SHERLOC.
Deep UV-induced native fluorescence is very sensitive to condensed carbon and aromatic organics, enabling detection at or below 10-6 w/w (1 ppm) at <100 µm spatial scales. SHERLOC's deep UV resonance Raman enables detection and classification of aromatic and aliphatic organics with sensitivities of 10-2 to below 10-4 w/w at <100 µm spatial scales. In addition to organics, the deep UV Raman enables detection and classification of minerals relevant to aqueous chemistry with grain sizes below 20 µm grains.
SHERLOC's investigation combines two spectral phenomena, native fluorescence and pre-resonance/resonance Raman scattering. These events occur when a high-radiance, narrow line-width, laser source illuminates a sample. Organics that fluoresce absorb the incident photon and reemit at a higher wavelength. The difference between the excitation wavelength and the emission wavelength indicates the number of electronic transitions, which increases with increasing aromatic structures (i.e. number of rings). This phenomenon is highly efficient, with a typical cross section 105x greater than Raman scattering, and enables a powerful means to find trace organics.
The native fluorescence emission of organics extends from ~270 nm into the visible. This is especially useful, because it "creates" a fluorescence-free region (from 250 – 270 nm) where Raman scattering can occur. With SHERLOCs narrow-linewidth 248.6 nm DUV laser, additional characterization by Raman scattering from aromatics and aliphatic organics and minerals can be observed. Furthermore, excitation with a DUV wavelength enables resonance and pre-resonance signal enhancements (>100 to 10,000 x) of organic/mineral vibrational bonds by coupling of the incident photon energy to the vibrational energy. This results in high-sensitivity measurements, with low backgrounds, without the need of high-intensity of lasers, and avoids damage or modification of organics by inducing reactions with species such as perchlorates.
SHERLOC Ops: An Example Measurement on Fig Tree
Using the SHERLOC testbed, an analysis of a piece of the astrobiologically interesting chert obtained from the Fig Tree Group is shown.
A context image of the sample is acquired. Using the internal scanning mirror, a 50-micron laser spot is systematically rastered over the surface. On the same CCD, spectra in the range 250-360 nm are obtained. Analysis of the fluorescence region (>270 nm) identifies regions where organic material is present. Analysis of the fluorescence spectra identifies number of aromatic rings present, and identifies regions of high organic content. In order to achieve higher specificity, a longer integration can be used to collect deep UV Raman spectra. The Raman spectra shown on the right are from the two circles shown in the context image.
By studying the fluorescence and Raman data we can conclude that our analysis indicates that:
• The chert has not been altered uniformly — pressure/temperature exposures are evident from carbon maturity variation.
• The majority of matrix is thermally mature carbon — anthracitic to sub-bituminous.
• An intrusion of silica with much younger carbon invaded the main matrix.
Potential for biosignature preservation in the matrix is low due to thermal history of the sample, with high preservation in the thermally unaltered vein material.
- Objective: Fine-scale detection of minerals, organic molecules and potential biosignatures
- Location: SHERLOC is mounted on the turret at the end of the robotic arm
- Mass: The turret is 3.11 kg; the body is 1.61 kg
- Power: The turret consumes 32.2 W, the body 16.6 W
- Volume: 26.0 x 20.0 x 6.7 cm
- Data return: 79.7 Mbit (raw)
- Spatial resolution: Context imager: 30 µm; Laser: 50 µm
- FOV (Field of View): Imaging: 2.3 x 1.5 cm; Spectroscopy: 7 x 7 mm.
Key, driving questions are whether Mars is or was ever inhabited, and if not, why not? The SHERLOC investigation will advance the understanding of Martian geologic history and identify its past biologic potential.
Figure 27: Calibration target for the Mars 2020 SHERLOC instrument (image credit: NASA/Johnson Space Center) 37)
The SHERLOC instrument will be used to detect chemicals on the Martian surface that are linked to the existence of life. To keep the instrument working well, a team from the Astromaterials Research and Exploration Science (ARES) division at NASA's Johnson Space Center (JSC) recently built a new calibration device for the rover to check SHERLOC's function and properly tune it during the upcoming mission.
"SHERLOC is pretty complicated, and we came up with a list of 11 things that all have to be calibrated on this instrument," said Marc Fries, ARES planetary scientist and Mars 2020 instrument co-investigator. "This sophisticated calibration device is also going to be used for a lot of other scientific and engineering investigations, and we're really excited that it's JSC's contribution to the Mars 2020 rover."
SHERLOC is mounted on the end of the rover's 2.1 m robotic arm and includes a laser, camera and chemical analyzers, called spectrometers. The sensitive components will be used together to search for substances that have been altered by water and possibly reveal evidence of past microscopic life on Mars.
"The rover's scientific instruments go through all sorts of harsh conditions from the time they leave the lab until they arrive on the surface of Mars. SHERLOC needed a way to make sure it still operates as expected once it's on the surface and throughout the duration of the mission," said Trevor Graff, a scientist from Jacobs who works for ARES.
The solution was to create the calibration target, or "cal target" for short. The device is approximately the size of a large cell phone and mounted on the front of the rover. On its face are 10 "targets," which consist of samples of different materials. The idea is that researchers will occasionally check SHERLOC's function by directing it to scan the different materials on the cal target. The researchers will already know what the readings on those materials should be when SHERLOC is working correctly. If the actual readings are off, they'll make adjustments to SHERLOC to get it set properly, or know to compensate for the errors when they analyze the data later.
Figure 28: Image of engineers with the Mars 2020 SHERLOC Calibration Target in a clean room at NASA/JSC (Johnson Space Center). This is the first Mars flight hardware that has been designed, assembled & tested at NASA/JSC, led by Jacobs/JETS Chief Scientist Trevor Graff. It will carry the first space suit materials to Mars and will carry a piece of a martian meteorite back to the surface of Mars (image credit: NASA/JSC) 38)
Science on the Side
In addition to tuning SHERLOC, the targets on the calibration device are serving double duty in other tests and experiments. For example, a number of the targets hold spacesuit materials that could one day be used to protect astronauts exploring Mars. SHERLOC's scans of those materials will not only help tune the instrument, but measure how the advanced fabrics and other suit materials will hold up in the Martian environment, too.
"We also plan to build a small Mars exposure instrument here at JSC, and match the conditions inside it with weather data from the rover," Fries said. "We'll then place an identical set of spacesuit samples inside the chamber and periodically remove them to, for example, test the strength of fabrics or the clarity of helmet visor plastics. The result is we'll be able to test spacesuit materials in Mars-like conditions long before astronauts ever go there."
Another target contains an actual sample of a meteorite ejected from Mars long ago and discovered on Earth in 1999. Researchers plan to closely watch the rock sample to see how the Martian environment alters it over time, which will help them understand the chemical interactions between the planet's surface and its atmosphere.
Finally, the target includes the first off-planet "cache" for geocaching enthusiasts to locate, with more details on that to be released soon.
MOXIE (Mars Oxygen ISRU Experiment)
MOXIE is an exploration technology investigation that will produce oxygen from Martian atmospheric carbon dioxide. The principal investigator is Michael Hecht, MIT (Massachusetts Institute of Technology), Cambridge, Massachusetts.
"When we send humans to Mars, we will want them to return safely, and to do that they need a rocket to lift off the planet. Liquid oxygen propellant is something we could make there and not have to bring with us. One idea would be to bring an empty oxygen tank and fill it up on Mars."
NASA is preparing for human exploration of Mars, and the MOXIE investigation on the Mars 2020 mission aims to address key knowledge gaps, including: 39)
• demonstration of In-Situ Resource Utilization (ISRU) technologies to enable propellant and consumable oxygen production from the Martian atmosphere, and
• characterization of atmospheric dust size and morphology to understand its effects on the operation of surface systems.
MOXIE collects CO2 from the Martian atmosphere, then electrochemically splits the CO2 molecules into O2 and CO. The O2 is then analyzed for purity before being vented back out to the Mars atmosphere along with the CO and other exhaust products.
Figure 29 shows the MOXIE functional block diagram. The CO2 Acquisition and Compression (CAC) system pulls Martian atmosphere from outside the Rover through a filter and pressurizes it to ~1 atmosphere. The pressurized CO2 gas is then regulated and fed to the Solid OXide Electrolyzer (SOXE), where it is electrochemically split at the cathode to produce pure O2 at the anode, a process equivalent to running a fuel cell in reverse.
The SOXE operates at 800° C, requiring a sophisticated thermal isolation system, including input gas preheating and exhaust gas cooling. There are O2 exhaust and CO2/CO exhaust streams, which are then analyzed to verify O2 production rate and purity and for process control. The electrical current through the SOXE is a direct result of the oxide ions transported across the electrolyte, and provides an independent measurement of O2 production rate.
Based on conversion efficiency calculated from flow rates and composition measurements, SOXE control parameters such as CO2 input flow rate, temperature, and applied voltage are used to optimize O2 production under Mars environmental conditions. The cooled exhausts are then filtered to satisfy planetary protection requirements and vented from the Rover. Process telemetry is reported to the Rover for downlink.
Figure 29: MOXIE functional block diagram (image credit: NASA/JPL-Caltech)
- Objective: To produce oxygen from the Martian carbon-dioxide atmosphere
- Power: 300 W
- Volume: 23.9 x 23.9 x 30.9 cm
- Oxygen production rate: About 10 grams per hour
- Operation time: Approximately two hours of oxygen (O2) production per experiment, which will be scheduled intermittently over the duration of the mission.
MEDA (Mars Environmental Dynamics Analyzer)
MEDA is a set of sensors that will provide measurements of temperature, wind speed and direction, pressure, relative humidity and dust size and shape. The principal investigator is Jose Rodriguez-Manfredi, Centro de Astrobiologia, Instituto Nacional de Tecnica Aeroespacial, Spain. 40)
MEDA is a suite of environmental sensors designed to record dust optical properties and six atmospheric parameters: wind speed/direction, pressure, relative humidity, air temperature, ground temperature, and radiation in discrete bands of the UV, visible, and IR ranges of the spectrum.
The radiation sensor is part of an assembly with two arrays of photodiodes that also capture low elevation angle scattered light and a sky-pointing camera; these data are combined to characterize the properties of atmospheric aerosols.
Systematic measurement is the main driver for MEDA operations. Over the entire mission's lifetime, with a configured cadence and frequency in accordance to resource availability, MEDA records data from all sensors. Implementation of this strategy is based on a high degree of autonomy in MEDA operations. MEDA wakes itself up each hour and after recording and storing data, goes to sleep independently of rover operations. It records data whether the rover is awake or not, and both day and night.
The main science objectives for the science team are:
• Signature of the Martian general and mesoscale circulation on phenomena near the surface (e.g., fronts, jets)
• Microscale weather systems (e.g., boundary layer turbulence, heat fluxes, eddies, dust devils)
• Local hydrological cycle (e.g., spatial and temporal variability, diffusive transport from regolith)
• Dust optical properties, photolysis rates, ozone column, and oxidant production.
As an environmental instrument, MEDA's different sensors are in direct contact and exposed to the ambient:
• The radiation/dust sensor assembly is located on top of the rover deck.
• The pressure sensor is located inside the rover body and connected to the atmosphere through a dedicated pipe.
• All other sensors are located around the Remote Sensing Mast (RSM):
- Two wind sensor booms oriented at 120 degrees from each other measure winds approaching the RSM,
- Five sets of thermocouples measure the air temperature
- A thermal infrared sensor measures downward and upward thermal infrared radiation as well as surface skin temperature.
- The relative humidity sensor is also attached to the RSM.
The full set of sensors is controlled by the Instrument Control Unit (ICU) inside the rover body.
A suite of sensors to characterize the Martian low atmosphere and dust properties:
• Air temperature: Located around the RSM are three air temperature sensors (ATS). Two more are on the rover body to ensure that one of them is upwind. Placed on small thermal inertia forks, and outside the rover thermal boundary layers, these five sets of three thermocouples measure atmospheric temperature. The measurement range is 150 to 300 K, with a required accuracy of 5 K and a resolution of 0.1 K.
• Humidity: Located at the RSM inside a protecting cylinder, a humidity sensor (HS) measures the relative humidity with an accuracy of 10% in the 200-323 K range and with a resolution of 1%. A dust filter surrounds the cylinder to protect the sensor from dust deposition.
• Pressure: Located inside the rover body and connected to the external atmosphere via a tube, a pressure sensor (PS) collects pressure measurements. The tube exits the rover body through a small opening with protection against dust deposition. Its measurement range goes from 1 to 1150 Pa with an end-of-life accuracy of 20 Pa (calibration tests give values around 3 Pa) and a resolution of 0.5 Pa. As this component is in contact with the atmosphere, a HEPA filter is placed on the tube inlet to avoid contaminating the Martian environment.
• Radiation & dust: Located on the rover deck, the radiation and dust sensor (RDS) is composed of eight upward looking photodiodes in the following ranges:
- 255 ± 5 nm for the O3 Hartley Band center,
- 295 ± 5 nm for the O3 Hartley Band edge,
- 250-400 nm for total UV,
- 450±40 nm for MastCam-Z cross-calibration,
- 650 ± 25 nm for SuperCam cross-calibration,
- 880 ±5 nm for MastCam-Z cross-calibration,
- 950 ± 50 nm for NIR, and
- one panchromatic (at least 300-1000 nm) filter, with an accuracy better than 8% of the full range for each channel, computed based on Mars radiation levels and minimum dust opacity.
The photodiodes face the zenith direction and have a field of view of 30 degrees except for the panchromatic one with its 180º field of view.
A second array of side-looking photodiodes at 880 nm characterizes the low angle light scattering at different azimuth angles. They cover at least 270º or a circle with fields of view of ±15º and separated about 45º from each other.
A dedicated camera with ±60º around the zenith measures the intensity of the solar aureole.
The assembly of photodiodes and camera are placed on the rover deck without any dust protection. To mitigate dust degradation, magnetic rings are placed around each photodiode with the aim of maximizing their operational time. Nevertheless, to evaluate dust deposition degradation, images of the sensor are recorded periodically, with their readings compared with opacities from other Mars 2020 optical instruments such as MastCam-Z. A comparison of the differences in estimated sky opacities between MEDA and MastCam-Z permits evaluations of the level of dust deposition.
• Thermal radiation: Attached to the RSM and pointing to the front right side of the rover, the thermal infrared sensor (TIRS) measures the net infrared thermal radiation near the surface of Mars with a set of five thermopiles:
- three downward-pointing thermopiles with bands 16-20, 6.5-cut-on and 8-14 µm, and
- two upward-pointing thermopiles with bands 6.5-cut-on and 14.5-15.5 µm.
• Wind: Attached to the RSM, two wind sensors (WS) measure wind speed and direction. These magnitudes are derived based on the information provided by six two-dimensional detectors on each boom. The detectors are located on six boards 60 degrees apart around the boom axis. Each records local speed and direction in the plane of the board. The combination of the 6 boards per boom serves to determine wind speed, as well as pitch and yaw angle of each boom relative to the flow direction.
The requirement is to determine horizontal wind speed with 2 m/s accuracy in the range of 0 to 40 m/s, with a resolution of 0.5 m/s. The directional accuracy is expected to be better than 22.5 degrees. For vertical wind, the range is 0 to 10 m/s, and the accuracy and resolution are the same as for horizontal wind.
The booms hold the detectors out of the RSM's thermal boundary layer, aiming to minimize the wind flow perturbation by the RSM at the boom tip where the these detectors are located. The two booms are separated in azimuth to help ensure that at least one of them will record clean wind data when the other is in the wake of the rover.
To correct for the perturbations at the booms by the RSM and the rover on the environmental temperature and wind field, a variety of numerical analyses and wind tunnel tests are used during calibration under Mars conditions. Numerical simulations are used to obtain results where tests conditions cannot be reproduced on Earth.
- Objectives: To measure weather and monitor dust with sensors from the surface of Mars
- Location: Sensors are located on the rover's mast "neck" and on the deck, front and interior of the rover's body
- Mass: Approximately 5.5 kg for all components
- Power: Up to 17 W, depending on scheduled measurements
a) Air temperature sensors: Each of five sensors is 5.75 x 2.75 x 6.75 cm
b) Radiation and dust sensor: 13.2 x 11.5 x 12.5 cm
c) Relative humidity sensor: 6.25 x 5.75 x 5.75 cm
d) Wind sensors: Wind Sensor 1 is 5 x 17 cm, wind sensor 2 is 5 x 40 cm
e) Instrument control unit and pressure sensor: 14 x 14 x 13 cm
- Data return: Approximately 11 MB.
MEDA will help prepare for human exploration by providing daily weather report and information on the radiation and wind patterns on Mars.
RIMFAX (The Radar Imager for Mars' Subsurface Exploration)
RIMFAX is a ground-penetrating radar that will provide centimeter-scale resolution of the geologic structure of the subsurface. The principal investigator is Svein-Erik Hamran of FFI (Norwegian Defence Research Establishment), Norway.
"No one knows what lies beneath the surface of Mars. Now, we'll finally be able to see what's there."
RIMFAX builds on mature tried-and-true GPR technology used on Earth for a wide variety of scientific and engineering applications, adapted for use in a rover platform on the surface of Mars. Its ultra wideband design, operating from 150 MHz to 1.2 GHz, affords a theoretical limit of 14.2 cm for vertical (range) resolution in free-space. The instrument is composed of an electronics box, installed within the interior of the rover, and a nadir-point antenna affixed to the exterior (rear) of the rover. 41)
RIMFAX will operate as the rover drives and will be commanded to produce individual soundings in different modes, where some modes are for shallow and others are for deep penetration. The default operation will produce interleaved pairs of shallow- and deep-soundings at every 10 cm along a rover traverse. The expectation is for RIMFAX signals to achieve penetrations of 10 m, but it may well exceed that for subsurface conditions that are friendly to the propagation of radar waves.
The overarching goal of RIMFAX is to image the subsurface structure and constrain the nature of the material underlying the landing site. This is made possible because the propagation of radar waves is sensitive to the dielectric properties of materials, such that variations in composition and porosity across geologic strata yield radar reflections that can be identified, mapped, and interpreted in the geological sense.
Specifically, RIMFAX supports and enhances the Mars 2020 investigation in the following, but not limited, ways:
• Assess the depth and extent of regolith;
• Detect different subsurface layers and their relationship to visible surface outcrops;
• Characterize the stratigraphic section from which a cored-and-cached sample derives, including crosscutting relations and features indicative of past environments.
Figure 30: Sample radargram of a glacier in Svalbard obtained with the HUBRA radar instrument, a precursor of RIMFAX built by the FFI team (image credit: NASA, FFI)
Figure 31: Photo showing the prototype RIMFAX antenna attached to a snowmobile during tests in Svalbard, Norway (image credit: NASA/JPL-Caltech, FFI)
- Objective: To see geologic features under the surface with ground-penetrating radar
- Location: The radar antenna is on the lower rear of the rover
- Mass: < 3 kg
- Power: 5-10 W
- Volume: 196 x 120 x 66 mm
- Data return: 5 to 10 kB per sounding location
- Frequency range: 150 to 1200 MHz
- Vertical resolution: As small as about 7.5 - 30 cm thick
- Penetration depth: > 10 m deep depending on materials
- Measurement interval: About every 10 cm along the rover track.
NASA's Mars 2020 mission uses the NASA's Deep Space Network (DSN), an international network of antennas that provides communication links between planetary exploration spacecraft and their mission teams on Earth. 42)
The DSN consists of three deep-space communications complexes placed approximately 120 degrees apart around the world: at Goldstone, in California's Mojave Desert; near Madrid, Spain; and near Canberra, Australia. This strategic placement permits constant links to distant spacecraft even as the Earth rotates on its own axis.
As with previous Mars landers and rovers, the Mars 2020 mission relies on Mars-orbiting spacecraft to relay data from the rover to the antennas of the Deep Space Network.
Figure 32: The Goldstone 70 m antenna tracks under a full moon (image credit: NASA)
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42) " Communications with Earth," NASA, Mars 2020 Mission, URL: https://mars.nasa.gov/mars2020/mission/communications/
The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (firstname.lastname@example.org).