Phoenix CubeSat Mission
Phoenix is a 3U CubeSat designed by students from ASU (Arizona State University), Tempe, AZ, which aims to study UHIs (Urban Heat Islands) from LEO (Low Earth Orbit) through infrared remote sensing. The project is an interdisciplinary collaboration which has joined efforts of 5 major ASU schools to pursue a common goal and make the world a better place for generations to come. These collaborations include: 1) 2)
• Ira A Fulton Schools of Engineering
• School of Geographical Sciences & Urban Planning
• Herberger Institute of Design
• Walter Cronkite School of Journalism
• School of Earth & Space Exploration
The mission objectives are:
1) To successfully design, integrate, test, and launch a CubeSat into LEO
2) Collect infrared images of seven US cities to aid research on the Urban Heat Island Effect
3) Study the properties which contribute to the Urban Heat Island Effect and work with local communities to help develop a more sustainable urban infrastructure for future generations
4) Educate the community on the importance of Urban Heat Islands and inspire the next generation to pursue STEM fields.
Phoenix is the creation of more than 100 science and engineering students, faculty and researchers at Arizona State University. Students have made up by far the largest part of the Phoenix workforce. Ranging from those pursuing graduate degrees to first-year undergraduates, a total of 96 students are either working on or have contributed to the project, which began in April 2016. A number of students who contributed to the mission have already graduated from ASU, with several entering the national aerospace workforce.
"The Phoenix cubesat is a student-run project funded by NASA with an educational mission to train students in satellite development," said Judd Bowman, the mission's principal investigator and professor in the School of Earth and Space Exploration. "We have incorporated a student science team mentored by ASU professors to help provide scientific interpretation of the thermal images that the satellite will acquire from orbit."
As project head, Bowman is joined by Assistant Professor Daniel Jacobs, whose role is faculty mentor for the student workforce. Said Jacobs, "NASA's goal was space workforce education, but they required a real target for the program — a technology demonstration or a scientifically worthwhile project."
The orbit lifetime is designed for two years. The operational lifetime is baselined to 6-8 months. Almost all hardware was purchased COTS (Commercial-Off-The-Shelf), while some was developed by the student team.
Figure 1: Members of the Phoenix student engineering team gather in the lab, with team lead Sarah Rogers holding a 3D test model of the Phoenix CubeSat. Electronic components on the bench are part of the development hardware (image credit: Craig Knoblauch/Arizona State University)
Phoenix is a 3U CubeSat, 10 x 10 x 34 cm, a standard size, a mass of 4.2 kg, and shape devised to make it easier for anyone to develop a small satellite. Four ultra-high frequency antennas sprout from one end like stiff whiskers, and solar panels wrap around two long sides to provide power. Sun and Earth sensors feed data to a commercial gyroscope unit to keep Phoenix aimed at the ground.
Figure 2: Illustration of the Phoenix CubeSat and its subsystems (image credit: ASU)
ADCS (Attitude Determination & Control Subsystem): The ADCS COTS component was selected as the MAI-400 ADCS unit from Maryland Aerospace for its cost efficiency and ability to meet all mission requirements. Attitude control is performed using a set of three reaction wheels and three magnetorquers to control each axis of the spacecraft. Pointing knowledge is provided through a set of six external sun sensors, which track the orientation of the sun and an onboard magnetometer, which determines orientation based on the Earth’s magnetic field. The attitude rate is determined by an onboard MEMS gyroscope. Finally, the ADCS incorporates two Earth Horizon Sensors (EHS), which are infrared cameras that interpret the cold of space vs the warm temperature of the Earth to sense the spacecraft’s orientation based on the Earth’s horizon line. The EHS are the most accurate of the ADCS’s attitude determination sensors, and are essential for allowing the cubesat to track to ground targets with high fidelity.
The ADCS has a mass of 0.694 kg, a size of 10 x 10 x 5.59 cm, an operating voltage of 5 V, and a momentum storage capacity of 9.351 mNms.
Figure 3: Photo of the MAI-400 ADCS (image credit; MAI, ASU)
Figure 4: ADCS interconnect diagram (image credit: ASU)
OBC (Onboard Computer): The OBC uses a GomSpace NanoMind A3200, an AVR32 architecture processor with 512 kB built-in flash, 128 MB NOR flash, 32 kB FRAM for persistent configuration, 32 MB SDRAM (Synchronous Dynamic Random Access Memory ). 3)
EPS (Electrical Power Subsystem): The EPS consists of body-mounted solar panels, a 40 Whr Li-Ion battery, and an EPS supplied by ÅAC (Ångström Aerospace Corporation)/ Clyde Space. The solar panels collect energy from the sun which is then used to charge batteries. The EPS regulates how power is distributed to the various components as the spacecraft performs different operations. All EPS hardware was selected for its ability to support all spacecraft operations over the course of the mission operations timeline. A power budget was developed using MATLab and STK to visualize the battery level over time based on how often imaging and downlink operations were performed.
RF communications: Phoenix will operate in the amateur frequency bands under an open, but limited communication link. UHF amateur bands (435-438 MHz) will be used for uplinking mission operations schedules and for downlinking all housekeeping telemetry and images to support the science objective. At a baud rate of 9.6 kbit/s, it will take three full passes over the ground station to retrieve one full image at a size of 321 kB. The design originally incorporated S-band communications but was de-scoped from the design due to time constraints during development.
- Operating frequency: 437.35 MHz
- ITU emission: 20 K0F1D
- Packet protocol: KISS protocol with AX.25 & HDLC encapsulation
- Bit rate: 9.6 kbit/s.
All uplinked commands will be encrypted with a rotating cipher to maintain operational integrity while the spacecraft is in orbit. However, all downlinks will be left open to abide by the amateur communication protocol. Once the spacecraft has completed the minimum mission objective, a set of limited commands will be made available on the project website so that anyone with an amateur license may listen to and communicate with the spacecraft.
Licensing: In order to communicate with the ground station, the spacecraft must be authorized by the FCC (Federal Communications Commission) to transmit and receive information as well as be coordinated to operate in an open frequency band. Through working with the IARU (International Amateur Radio Union), the FCC, and the ITU (International Telecommunication Union), Phoenix is licensed to operate in the amateur bands at 437.35 MHz. All mission operators will be registered with a ham radio license in order to transmit to the spacecraft in orbit.
TCS (Thermal Control Subsystem): The satellite is modeled in Thermal Desktop to classify the thermal profile of the spacecraft in different orbital conditions and design thermal control methods to maintain all hardware within its allowable flight temperature range. Thermal Desktop is organized by C&R Tech, which offers free, limited licenses for university projects that are in need of thermal modeling software.
The design of the TCS was simplified to a single radiator panel, with the +X and +Y faces covered in thermal tape that was graciously donated to the student team by NASA Goddard.
FSW (Flight Software): The FSW is operated from an OBC (On Board Computer), which acts as the “brain” of the satellite. The OBC is the link to all peripheral hardware and acts as the central entity for sending commands and collecting all housekeeping information. Of all of the subsystems, the FSW is therefore one of the most critical to ensure is robust.
The FSW incorporates NASA’s Core Flight System (cFS), a software framework developed by the NASA/GSFC ( Goddard Space Flight Center) to provide mission-independent and reusable services. As the team developed the software applications, cFS was incorporated into the application framework to help bring everything together. Additional support is leveraged from NASA’s STF-1 (Simulation to Flight 1) mission. This partnership provides the team with access to FreeROTS (Realtime Operating System) software for use in developing satellite command sequences.
Figure 5: The Phoenix CubeSat (image credit: ASU)
• On 18 August 2019, the Phoenix spacecraft was hand-delivered by the student team to NanoRacks, the ISS launch integrator, at their facility in Houston. There it underwent final tests and preparations for its launch to the Space Station, planned for Oct. 21, 2019. After it arrives at the Space Station, Phoenix will be sent into low-Earth orbit sometime early next year (Ref. 2).
• March 24, 2017: Phoenix PDR (Preliminary Design Review) at ASU. 4)
• March 3, 2017: ASU’s Project Phoenix is preparing to run its first experiments after finishing its preliminary design review for launching a small satellite into space. 5)
- The project, part of the SDSL (Sun Devil Satellite Laboratory) and composed solely of undergraduates, aims to design a CubeSat, a satellite about the size of a loaf of bread and send it into space, according to key members of the team.
- Sarah Rogers, a sophomore studying aerospace engineering and project manager of Project Phoenix, also leads the mission. She said the team includes more than scientists and engineers. Rogers said she helps manage students at the ASU Herberger Institute for Design and the Arts who are making a documentary about the Phoenix program. She also manages PR specialists from the Walter Cronkite School of Journalism and Mass Communication.
- Sarah said the satellite will take measurements of 18 cities, seven of which are confirmed. “Those core seven, as we like to call them, are Phoenix, Chicago, Los Angeles, Minneapolis, Houston, Atlanta and Baltimore.” Project Phoenix chose these cities due to their high amount of human activity and number of clear, sunny days, which Rogers said helps their infrared camera gather data.
Figure 6: Cities that Project Phoenix will record (image credit: ASU)
• February 17, 2017: NASA has selected 34 small satellites from 19 states and the District of Columbia to fly as auxiliary payloads aboard missions planned to launch in 2018, 2019 and 2020. Launch opportunities are leveraged from existing launch services for government payloads as well as via dedicated CubeSat launches from the new Venture Class Launch Services contracts. The proposed CubeSats come from educational institutions, universities, non-profit organizations and NASA centers (Figure 7). The Phoenix CubeSat of the Arizona State University was part of this CSLI. 6)
- NASA has selected an Arizona State University undergraduate student team for a $200,000 grant to conduct hands-on flight research, through its NASA Space Grant Undergraduate Student Instrument Program (USIP). 7)
• November 11, 2016: Phoenix MDR (Mission Design Review) at ASU. 8)
Launch: The Phoenix CubeSat is scheduled for launch in October 2019 to the ISS aboard the Cygnus NG-12 vehicle of Northrup Grumman from MARS (Mid -Atlantic Regional Spaceport), Wallops Island, VA. The rocket will fly in the Antares 230 configuration, with two RD-181 first stage engines and a Castor 30XL second stage. Phoenix is part of NASA’s CSLI (CubeSat Launch Initiative).The Phoenix CubeSat will be deployed by NanoRacks into LEO. 9)
Orbit: Near circular orbit, altitude of ~ 400 km, inclination = 51.6º, period of~92 minutes.
Sensor complement (FLIR Tau Camera)
FLIR Tau 2 640 Thermal Imaging Camera
The science payload is the Tau 2 640 LWIR (Longwave Infrared) camera, which is an uncooled microbolometer developed by FLIR Technologies. The camera offers a 640 x 512 pixel resolution, and a 6.2° x 5.0° FOV (Field of View), which correlates to a ground footprint of 43.5 km x 35 km at an altitude of 400 km. A lens of 100 m/pixel has been selected in order to provide an angular resolution up to 68 m/pixel to clearly define the smallest Local Climate Zone, within the selected areas of the city. One image will be taken during each pass over a city. Slewing conducted by the ADCS system during imaging will be used to mitigate image blur. Due to time constraints, the camera was not filtered and will operate in the wavelength of 7-14 µm.
Figure 8: Illustration of FLIR Tau camera (image credit: FLIR Technologies, ASU)
Figure 9: Spectral response of the camera in the LWIR range (image credit: FLIR Technologies,, ASU)
A ground station will intercept the telemetry (health data and images) from the satellite when it passes overhead as well as uplink operations schedules for taking images and performing other maintenance operations. The ASU Ground Station will be the primary resource for communicating with the spacecraft to uplink commands and downlink housekeeping telemetry and images. UHF communications are supported by the ICOM-9100 UHF transceiver, the KPC-9612+ TNC, and a set of Yagi antennas.
In addition to learning the cubesat hardware, it is the responsibility of the communications team to test the hardware with the ASU ground station and ensure that the spacecraft can communicate with the ground while it is in orbit. The ICOM and TNC were both used as part of a lab-based ground station setup to allow the team to get acquainted with the hardware as well as fine-tune the hardware settings to minimize packet loss as much as possible. After all, as the saying goes, test as you fly!
Embry Riddle Aeronautical University, located in Prescott, AZ will serve as the backup ground station for UHF communications in the event where the ASU ground station is not operable.
The ground station will utilize GPredict for handling Doppler shifting and tracking the spacecraft as it passes overhead. Both yagi antennas are attached to a rotor system, which allows the antennas to track the spacecraft as passes overhead. GPredict can be programmed to operate the rotor system as well, allowing tracking to be precise and collect data without it being required that an operator is present at the time of the pass.
2) ”Mini-spacecraft built by ASU students will study urban heat island effect, Students get hands-on introduction to space workforce by building an operational satellite,” ASU, 27 August 2019, URL: https://asunow.asu.edu/20190827-mini-spacecraft-built-asu-students-will-study-urban-heat-island-effect
3) ”Phoenix PDR, March 24th 2017, ASU, URL: http://phxcubesat.asu.edu/sites/default/files/general/phoenix_pdr_part_2_1.pdf
4) ”Phoenix PDR,” 24 March 2017, URL: http://phxcubesat.asu.edu/sites/default/files/general/phoenix_pdr_part_2_1.pdf
5) Corey Hawk, ”ASU's undergraduate-run Project Phoenix enters its testing phase,” The State Press, 3 March 2017, URL: https://www.statepress.com/article/2017/04/spscience-project-phoenix-testing-phase
6) ”NASA Announces Eighth Class of Candidates for Launch of CubeSat Space Missions,” NASA, 17 February 2017, URL: https://www.nasa.gov/feature
7) ”NASA selects ASU undergraduate 'CubeSat' project to measure Phoenix urban heat islands,” ASU, 6 May 2016, URL: https://asunow.asu.edu/20160506-nasa-selects-
8) ”Phoenix Mission Design Review,” ASU, 11 November 2016, URL: http://phxcubesat.asu.edu/sites/default/files/general/phoenix_mdr_1.pdf
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).