FIREBIRD-I (Focused Investigations of Relativistic Electron Burst Intensity, Range, and Dynamics-I)
FIREBIRD-I is a collaborative CubeSat space weather mission of two 1.5U CubeSats, designed and developed by Montana State University (MSU, Bozeman, MT), University of New Hampshire (UNH, Durham, NH), The Aerospace Corporation (El Segundo, CA), and LANL (Los Alamos National Laboratories, Los Alamos, NM). The collaboration is referred to as the FIREBIRD consortium. The mission objective is to assess the spatial scale and spatial temporal ambiguity of magnetospheric microbursts in the Van Allen radiation belts. The FIREBIRD mission is funded by NSF (National Science Foundation).
Background: Relativistic electron microbursts appear as short durations of intense electron precipitation measured by particle detectors on low altitude spacecraft, seen when their orbits cross magnetic field lines which thread the outer radiation belt. Previous spacecraft missions (e.g., SAMPEX) have quantified important aspects of microburst properties (e.g., occurrence probabilities), however, some crucial properties (i.e., spatial scale) remain elusive owing to the space-time ambiguity inherent to single spacecraft missions. While microbursts are thought to be a significant loss mechanism for relativistic electrons, they remain poorly understood, thus rendering space weather models of Earth's radiation belts incomplete. FIREBIRD's unique two-point, focused observations at low altitudes are expected to answer three fundamental scientific questions with space weather implications: 1) 2) 3) 4) 5) 6)
1) What is the spatial scale size of an individual burst? The study should gain a better insight into the causes as well as a better insight into total radiation belt losses due to microbursts. Generally, microbursts occur in discrete "packets". FIREBIRD will help resolve the spatio/temporal ambiguity and determine the size of the microburst region as the spacecraft drift apart.
2) What is the energy dependence of an individual burst? The study should provide a better insight into the causes and a better insight into total radiation belt loss due to microbursts. What resonance conditions are occurring?
3) How much total electron loss do bursts produce globally? The study should provide an estimate of how important microbursts are in the system as a whole and give a better insight into total radiation belt loss due to microbursts.
Current and planned measurements alone cannot answer these questions, it takes low-altitude multi- point measurements. Microbursts are short (~100 ms) bursts of precipitation. Initial work in this field started in the 1960s from balloon measurements and has been studied sporadically since then.
In addition to addressing fundamental space physics research and space weather applications, the FIREBIRD investigation also contributes to the training and educations of a diverse population of university students in all phases of the project. Students will have major responsibility for the design and implementation of the instruments and the spacecraft while at the same time being mentored by professionals in each expert area.
To achieve the spatial and temporal requirements of the mission, a GPS (Global Positioning System) receiver, for the purpose of navigation position and timing, is to be implemented on both satellites within the constellation. The integration and testing of this subsystem is integral to the mission's success. The GPS hardware must be capable of fulfilling the requirements of the mission in order for the science data to be interpreted reliably.
The operational mission has a timeline of ~ 3 years. In 2009, the FIREBIRD project was awarded a funding contribution by NSF (National Science Foundation).
Figure 1: Photo of the two FIREBIRD nanosatellite flight units (image credit: MSU/SSEL)
The mission uses two identical CubeSats (1.5U form factor) each with a size of 10 cm x 10 cm x 15 cm and a mass of ~2 kg. The CubeSats features passive magnetic attitude control. In addition, use of a single frequency GPS receiver (NovAtel OEMV-1), a 16-channel device in a 46 mm x 71 mm form-factor with low power consumption. 7) 8)
The two nanosatellites were developed by SSEL (Space Science and Engineering Laboratory) at MSU (Montana State University), Bozeman, MT, USA.
Figure 2: Schematic view of the CubeSat structure and payload accommodation (image credit: MSU)
Figure 3: View of the spacecraft layout (image credit: FIREBIRD consortium)
CDHS (Command and Data Handling Subsystem): The CDH board was purchased from Pumpkin Inc. Containing a PIC24 microcontroller, a FLASH RAM chip, and an SD card reader. This allows the software to process and store data in multiple formats all on one board. The PIC24 microcontroller is the brain of the FIREBIRD system. It is a 16 bit, modified Harvard architecture that can reach 16 MIPS when run at 32 MHz. The 32 MHz clock is accomplished by using a PLL (Phase Lock Loop) on the internal 8 MHz oscillator. FIREBIRD uses this PLL to reach these higher speeds and to allow for faster inter-hardware communication.
EPS (Electrical Power Subsystem) of Tiger Innovations:
- SA inputs: 4 independent PPTs (Peak Power Trackers) with 2.5 A max per channel
- Battery: Li-ion1.8 Ah 4.2 V cells (x 2)
- Shunt: Dissipates excess array power
- Power: < 50 mW quiescent draw
- Size: 96 x 90 x 20 mm (w/battery)
- Mass: 167 g (w/battery)
- Output voltages: 8.4 V (2 switchable channels) (unregulated bus voltage). 5 V @ 2 A, 3.3 V @ 2 A.
Figure 4: Photo of the EPS (image credit: FIREBIRD consortium)
RF communications: Data transmission is provided in UHF (437.405 MHz and 437.230 MHz) at a data rate of 9.6 kbit/s. Use of GMSK (Gaussian Minimum Shift Keying) modulation and Ax.25 protocol.
Figure 5: Engineering model of a single FIREBIRD satellite (image credit: FIREBIRD consortium)
The two nanosatellites of the FIREBIRD-I mission are referred to as FIREBIRD-U1 and FIREBIRD-U2.
Table 1: Overview of implementation responsibilities
Figure 6: Exploded view of FIREBIRD-I (image credit: FIREBIRD consortium)
Launch: The two FIREBIRD-I CubeSats were launched as secondary payloads on Dec. 6, 2013 (07:14:30 UTC) on an Atlas-5-501 vehicle from VAFB, CA. The primary payload on this flight was the classified NROL-39 reconnaissance mission of NRO (National Reconnaissance Office). The launch provider was ULA (United Launch Alliance). 9) 10) 11) 12) 13)
Note: The NROL-39 is reported to be a Topaz radar-imaging reconnaissance satellite with the FIA Radar-3 payload of the cancelled FIA (Future Imaging Architecture) program. FIA was a program to design a new generation of optical and radar imaging US reconnaissance satellites for NRO. Despite the optical component's cancellation in 2005, the radar component, with a code name of Topaz,has continued, with two satellites in orbit as of November 2013; these are: NROL-41, launched on Sept. 21, 2010, and NROL-25, with a launch on April 03, 2012. A total of 5 radar satellites are in the Topaz program (Ref. 10). 14)
Secondary payloads: Next to the NROL-39 primary payload, the Atlas-5 hosts the GEMSat/ELaNa-2 mission for the NRO and the NASA/LSP ( Launch Services Program), lifting 12 CubeSats/nanosatellites to orbit as secondary payloads. All 12 CubeSats/nanosatellites are considered to be technology missions. 15) 16)
• AeroCube-5a and -5b, two 1.5U CubeSats of The Aerospace Corporation.
• ALICE (AFIT LEO iMESA CNT Experiment), a 3U CubeSat of AFIT (Air Force Institute of Technology)
• CUNYSAT-1 (City University of New York-1), a 1U CubeSat of Medgar Evers College, Brooklyn, N.Y. of the City University of New York.
• FIREBIRD-I (U1 and U2), two 1.5U CubeSats of Montana State University, University of New Hampshire, Los Alamos National Laboratory, and The Aerospace Corporation.
• IPEX, a 1U CubeSat of Cal Poly (California Polytechnic State University) and NASA
• MCubed/COVE-2, a 1U CubeSat of the University of Michigan, Ann Arbor, MI and NASA/JPL
• SMDC-ONE-2.3 (Charlie) and SMDC-ONE-2.4 (David), two 3U CubeSats of the U.S. Army SMDC/ARSTRAT (Space & Missile Defense Command/Army Forces Strategic Command) of Huntsville, AL (Redstone Arsenal)
• SNaP (SMDC Nanosatellite Program), a 3U CubeSat of the U.S. Army SMDC/ARSTRAT
• TacSat-6, a 3U CubeSat of the U.S. Army SMDC/ARSTRAT.
The CubeSats are integrated into 8 P-PODs (Poly-Pico Orbital Deployers ), which are contained in the NPSCuL (Naval Postgraduate School CubeSat Launcher), built by NPS students. The NPSCuL, together with the 8 P-PODs and 12 CubeSats, is referred to as GEMSat (Government Experimental Multi-Satellite), and is attached to the Centaur upper stage's ABC (Aft Bulkhead Carrier). The assembled GEMSat is shown in Figure 7 ready for mate to the launch vehicle along with the members of the various institutions from NPS, OSL (Office of Space Launch), ULA (United Launch Alliance) and Cal Poly. 17)
Figure 7: Photo of the GEMSat/ELaNa-2 secondary payload along with all team members (image credit: GEMSat Team)
Orbit: The primary payload was launched into a Sun-synchronous near-circular orbit, altitude of ~1075 km x 1089 km, inclination of 123º (deployment ~07:32 UTC).
• The Centaur AV-042 upper stage then made two orbit lowering burns to a SSO of 467 km x 883 km at an inclination of ~120.5º. Attached to the AV-042 was GEMSAT, the second NPSCuL CubeSat launcher, which ejected 12 CubeSats between around 10:22 and 10:38 UTC. 18)
The two FIREBIRD satellites will remain within ~400 km of one another for up to four months, allowing characterization over the spatial scale regime from 10-300 km.
• The FIREBIRD-I mission continued to return science data through 14 June 2014. The original mission goal was to collect science data for three months. The team is pleased that the first mission actually surpassed that goal by an additional four months. As of 2015, the CubeSats are still in orbit, even though the science mission is over, and will be until they reenter the atmosphere years from now. 19)
- The purpose of the FIREBIRD-I mission was to study the properties of so-called "relativistic electron microbursts", a phenomenon whereby extremely energetic electrons from Earth's radiation belts are rapidly and impulsively dumped into Earth's atmosphere. FIREBIRD-I was able to measure these electrons as they "precipitate" (to use a meteorological analogy) into the upper atmosphere. The project used two identical spacecraft in the same orbit, but separated slightly in time, to discover the unknown properties of microbursts needed to understand their role in how the radiation belts vary with time, in particular how they are emptied.
• Dec. 09, 2013: The orbiting FIREBIRD-I nanosatellites have begun probing a mysterious physical process within our planet's dangerous radiation belts. That process, known as microbursts, involves electrons moving at nearly the speed of light during short-duration (< 100 ms) events. Microbursts are thought to be one of the primary mechanisms by which the outer radiation belt loses energetic particles to Earth's atmosphere after the occurrence of powerful solar storms. Such storms can dramatically change the intensity of the radiation belts. 20)
Sensor complement: (FIRE)
FIRE (Focused Investigations of Relativistic Electrons)
UNH developed the FIRE assembly. FIRE employs a heritage sensor design based on a single large-geometry-factor, solid-state detector set on each of the two spacecraft, sensitive to electrons precipitating from the radiation belts.
Each satellite carries two solid-state detector charged particle sensors with different geometric factors optimized to cover electron measurements over the energy range from 0.25 to ~1 MeV in six differential energy channels. 21)
Figure 9: Photo of a single engineering unit sensor assembly (image credit: UNH)
Legend to Figure 9: The sensor assembly houses two solid-state detectors, one (bottom right corner) collimated and the other (top left corner) uncollimated.
The detectors are read out by a customized ASIC (Application-Specific Integrated Circuit), designed by The Aerospace Corporation, called the Dual Amplifier Pulse Peak Energy Rundown ASIC. Onboard memory stores fast sample observations needed to resolve the spatial structure; survey observations identify times of interest to download the highest temporal resolution data within the limited telemetry stream. While all data from the instruments are saved on board for ~4 weeks, FIREBIRD telemeters a reduced event identification data product to the ground each day in order to select particular intervals with microbursts to download for scientific analysis. 22) 23)
FIREBIRD-II (Focused Investigations of Relativistic Electron Burst Intensity, Range, and Dynamics-II)
FIREBIRD-II is functionally identical to FIREBIRD-I, with two 1.5U CubeSats that are called FIREBIRD-U3 and FIREBIRD-U4.
The mission goal duration of FIREBIRD-II is the same as that of FIREBIRD-I. The project is aiming for a mission to last at least three months. But it is expected that FIREBIRD-II will last much longer than FIREBIRD-I, given the design improvements implemented in various subsystems between the first and second mission. The science payload, though, is identical for all four flight units.
The science objectives of FIREBIRD-II are essentially the same as those of FIREBIRD-I. However, one particular science question remains to be answered from the first mission, that FIREBIRD-II will resolve if all goes according to plan. That particular goal is the simultaneous measurement of individual microbursts from both spacecraft.
In addition, FIREBIRD-II will be orbiting in conjunction with several other missions related to the radiation belts, some already in orbit (such as NASA's Van Allen Probes and THEMIS missions) and others slated for launch soon — such as NASA's MMS (Magnetospheric MultiScale) constellation (launch in spring 2015) and the Japanese ERG (Exploration of energization and Radiation in Geospace) mission (launch planned in 2015). Even though FIREBIRD science can be done as a stand-alone mission, the value of FIREBIRD-II data will be enhanced through joint studies with these other complementary missions that will be operating at the same time (Ref. 19).
Figure 10: Photo of the twin FIREBIRD-II CubeSats (image credit: UNH) 24)
FIREBIRD-II bus: Excluding several key changes, the FIREBIRD-II spacecraft are identical to the original FIREBIRD-I spacecraft design. For the FIREBIRD-II mission no changes were made to the design of the FIRE instrument. — Based on the overcharging and boot problems with the COTS EPS used on FIREBIRD-I, it was decided to switch to a simpler in-house design for the FIREBIRD-II mission. This new design leveraged designs used on MSU's first satellite, HRBE, which is still operational, even 4 years after launch. Figure 11 shows a high-level block diagram of the FIREBIRD-II EPS (Electrical Power Subsystem) design, known as Phoenix. The primary design methodology idea behind the Phoenix EPS was to use KISS (Keep It Simple Stupid). 25)
The Phoenix EPS is based on a Direct Energy Transfer system, meaning the battery pack is directly connected to the solar arrays via protection diodes. To protect the battery cells from over and undercharging, a COTS battery protection circuit configuration was used. This battery circuit disconnects the battery cells from the system bus whenever the bus exceeds a set voltage. This means, if the battery is fully charged and the solar arrays are still providing power; the batteries will be disconnected from the system and the solar array will power the entire spacecraft. If the batteries are disconnected and a sudden load is applied, such as the COMM transmitter, the system bus voltage will drop and the batteries will be reconnected as a result.
Figure 11: Phoenix EPS block diagram (image credit: MSU)
Initially, the Phoenix EPS design called for each solar panel to be connected to a COTS buck/boost voltage regulator. This regulator would allow power to be harvested from a panel when the incident power was not great enough to produce a voltage greater than that of the battery pack. However, early testing showed that this design was not functional. The regulators chosen were not designed for use with solar cells and would pull down the voltage of the cells, by attempting to draw too much current. The final Phoenix EPS design called for the regulators to be no-loaded and bypassed with a jumper.
Another key feature of the Phoenix EPS is the hardware WDT (WatchDog Timer). This WDT is implemented using basic logic gates that count up to 12 hours then power cycle the entire spacecraft for 10 seconds. This 12 hour reset is used to resolve any single event upsets due to radiation strikes or software bugs.
The second major change from the FIREBIRD-I design was the switch to solar arrays assembled by Vanguard Space Technologies, Inc. For the FIREBIRD-I mission, MSU hand assembled solar panels through the CIC (Coverglass/Interconnect/Cell) assembly process followed by adhering them to PCB substrates. The CIC and PCB (Printed Circuit Board) bonding process was very labor intensive and motivated the switch to professionally assembled panels. For FIREBIRD-II, as quid pro quo for Vanguard high efficiency solar panel assembly, MSU added an I-V curve measurement circuit to the back of one panel on each spacecraft. These instrumented panels are known as the FISCE (FIREBIRD IMM Solar Cell Experiment). The FISCE panels are testing a proprietary THINS assembly technique, developed by Vanguard Space Technologies, Inc. The FISCE panels are equipped with a photodiode sensor that is used to determine when the panel is at normal incidence to the light source. The I-V curves are only taken, when the photodiode sensor reaches a configurable threshold, indicating normal incidence.
Based on the on-orbit performance of the FIREBIRD-I spacecraft, two minor issues were found with the science data storage and downlink process. The NAND flash used to store science data on the MFIB (MSI-designed Fire Interface Board) partitions data into 4 kB "pages." Due to the downlink data rate of 19.2 kbit/s and flight software packet size, each page has to be divided into multiple packets for downlink. The FIREBIRD-I software divided pages for downlink in a way that allowed single data samples to span multiple downlink packets. This required that all packets within a page be received sequentially in order to reconstruct the individual data samples. If one packet within a page was not decoded during downlink, all subsequent packets from that page could not be decoded. To fix this issue, logic was added to the MFIB flight software that only downlinks an integer number of data samples within one packet for the FIREBIRD-II mission. With this new downlink packet structure, an individual packet can easily be decoded, regardless of whether or not other packets from the same page were received. This reduces losses in science data downlinks.
Launch: The FIREBIRD-II mission was launched on 31 January 2015 as a secondary payload to the SMAP mission (primary payload) of NASA. The launch provider was ULA; launch vehicle: Delta-2; launch site: VAFB, CA. 26) 27)
Orbit of primary payload: Sun-synchronous dawn/dusk orbit, altitude = 685 km, inclination = 98º, period = 98.5 minutes, LTAN (Local Time of Ascending Node) = 18:00 hours, exact repeat cycle = 8 days after 117 orbits, (near-global coverage of Earth can be obtained every three days, 44 orbits). — The radar data will provide the freeze/thaw measurement with 3 km spatial resolution at an interval of every two days for each location north of 45º north latitude — about the latitude of Minneapolis.
Secondary (auxiliary) payloads:
ELaNa X (Educational Launch of Nanosatellite X), which consists of three P-PODs (Poly Picosatellite Orbital Deployers) containing a total of four CubeSats (representing three CubeSat missions). The three CubeSat projects on ELaNa X include: 28) 29)
• GRIFEX (GEO-CAPE ROIC In-Flight Performance Experiment), a 3U CubeSat flight test experiment and a collaborative mission of the University of Michigan with NASA ESTO (Earth Science Technology Office) and JPL (Jet Propulsion Laboratory.
• ExoCube,a space weather nanosatellite (3U CubeSat) developed by the California Polytechnic State University (Cal Poly), San Luis Obispo. The payload is developed by NASA/GSFC.
• FIREBIRD-II (U3 and U4), each a 1.5U CubeSat collaborative mission of the University of New Hampshire, Montana State University, LANL (Los Alamos National Laboratory), and the Aerospace Corporation. Each CubeSat has a mass of ~ 2 kg.
Orbit of secondary payloads: The CubeSats will be deployed after separation of the SMAP (Soil Moisture Active Passive) observatory, into an elliptical orbit of 440 km x 670 km of 99.12º inclination.
• August 2015: The FIREBIRD-II twin mission is operating nominally. Since launch, the FIREBIRD-II spacecraft have been performing phenomenally. For the first two months both FU3 and FU4 were in a full-sun orbit. The COTS battery protection circuit worked as intended, despite higher than expected solar array voltages.
- FU3 and FU4's orbits have processed to now have 30 minutes of eclipse per orbit. However, both units are still able to maintain a high state of charge, due to the low power consumption of the system. Temperatures have shifted from 30ºC in full-sun to 10ºC in the eclipse season.
- The improvements to the MFIB science data storage and downlink system has greatly increased the throughput of the downlinks, by reducing information lost when a single packet is not decoded. - The changes to the CDH-GPS processing system have also been successful. Both flight units regularly achieve several GPS locks each week and are able to sync their onboard RTC to GPS time.
- Dozens of data sets have also been collected from the FISCE experiment and are under joint analysis by MSU and Vanguard Space Technologies Inc.
- The scientific success achieved with the FIREBIRD-II satellites has been enabled in part through the evolution made possible by the opportunity to discover operational vulnerabilities in the on-orbit performance of FIREBIRD-I satellites. A careful analysis of engineering data downloaded from the first pair of satellites pointed to software and hardware changes that would make the FIREBIRD-II satellites more robust. A key enabler was the presence of a fully functional Engineering Design Unit in the laboratory that could be operated and reprogrammed to diagnose issues arising during the first flight and to use as a testbed for possible work-arounds (Ref. 25).
- The FIREBIRD missions are highly complementary to NASA's Van Allen Probes mission, a strategic mission aimed at studying the physics of Earth's radiation belts. The FIREBIRD instrumentation is designed to cover a key energy range (~200 keV to ~ 1 MeV) of electrons that make up the outer radiation belt. These energetic charged particles can penetrate spacecraft components and structures, leading to deleterious effects such as deep dielectric discharge. FIREBIRD complements the Van Allen Probes mission by measuring electrons that are lost through scattering to the upper atmosphere in a process known as a microburst; this loss mechanism has been implicated as a major source of loss of the radiation belts, and thus is important to quantify in order to develop useful predictive models of the belts. FIREBIRD provides key measurements in LEO that Van Allen Probes cannot, demonstrating the power of CubeSats in answering focused but important science questions in a synergistic way with larger spacecraft missions even when studied in a standalone manner.
• In mid-February 2015, the FIREBIRD-II mission is operational. In the words of Harlan Spence: "The FIREBIRD-II data look utterly incredible! We are well on our way to accomplishing full mission success (Ref. 19)."
• All four CubeSats deployed successfully.
The FIREBIRD MOC (Mission Operations Center) is located at MSU and is responsible for monitoring spacecraft health, routine commanding, and downlinking payload data. The Science Operations team (SO) consists of collaborators at MSU and across the United States who are responsible requesting processing payload data. GPS data runs occur autonomously once per day, as do FISCE data runs. If a GPS run results in a lock, the CDH (Command and Data Handling) subsystem will automatically update its RTC (Real Time Clock) with the current GPS time. Both FISCE and GPS data are downlinked on a regular basis.
MSU operates its own ground station for the FIREBIRD mission, with callsign K7MSU. An avid community of Ham radio enthusiasts dedicated to tracking satellites has provided beacon data from stations located in Germany, Japan and other countries. This supplemental data represents a valuable mission asset by providing spacecraft engineering telemetry in near real time from orbit locations and local times far removed from the primary ground station in Bozeman, Montana. Because FIREBIRD and previous MSU satellites have operated in the Amateur radio bands, much of the ground station is built from Amateur radio hardware, including the Yagi antennas, antenna rotators, uplink TNC, and uplink transmitter. Figure 12 shows a block diagram of the K7MSU ground station, as configured for the FIREBIRD-II mission. The ground station requires three computers, labeled SSEL-Ground1 through SSEL-Ground3 in the figure.
Figure 12: Block diagram of the K7MSU ground station (image credit: MSU)
1) Brian Larsen, Harlan Spencer, David Klumpar, Larry Springer, J. Bernard Blake,"Focused Investigations of Relativistic Electron Burst Intensity, Range, and Dynamics (FIREBIRD)," CubeSat Developers' Workshop, CalPoly, April 22-25, 2009, URL: http://mstl.atl.calpoly.edu/~bklofas/Presentations/DevelopersWorkshop2009/2_Science/2_Larsen-FIREBIRD.pdf
2) David. M. Klumpar, Harlan E. Spence, Bernie Blake, "Overview: The Dual-CubeSat FIREBIRD Mission (Focused Investigations of Relativistic Electron Burst Intensity, Range, and Dynamics)," Nov. 30, 2009, URL: http://mstl.atl.calpoly.edu/~bklofas/NSF_comm/20091130_telecon/FIREBIRD
3) Mackenzie Charles Wilz, "Focused Investigations of Relativistic Electron Burst Intensity, Range and Dynamics Space Weather Mission Global Positioning System," Thesis for Master of Science in Electrical Engineering, Montana State University, Bozeman, MT, January 2011, URL: http://etd.lib.montana.edu/etd/2011/wilz/WilzM0511.pdf
4) Ian Lyon, "The Separation of a Two-Nanosatellite System via Differential Drag," Thesis at MSU, April 2011, URL: https://www.carroll.edu/forms/library/theses/LyonIFinal_2011.pdf
5) Ehson Mosleh, "FIREBIRD and SSEL Space Weather Missions," CubeSat Developers Workshop, San Luis Obispo, CA, April 20, 2011, URL: http://mstl.atl.calpoly.edu/~bklofas/Presentations/DevelopersWorkshop2011/6_Mosleh_FIREBIRD.pdf
6) Marcello Ruffolo, Nathan Hyatt, Jordan Maxwell, "FIREBIRD Science Overview," Aug. 2, 2013, URL: http://solar.physics.montana.edu/www/REU/2013/mruffolo/FB_Science_Final.pdf
10) William Graham, "Atlas V launches NROL-39 from Vandenberg," NASA Spaceflight.com, Dec. 5, 2013, URL: http://www.nasaspaceflight.com/2013/12/atlas-v-launch-nrol-39-vandenberg/
11) Stephen Clark, "Government spy satellite rockets into space on Atlas 5," Spaceflight Now, Dec. 6, 2013, URL: http://www.spaceflightnow.com/atlas/av042/131206launch/#.UqHYgCeFdm4
12) NROL-39, United Launch Alliance Atlas V Rocket Successfully Launches Payload for the National Reconnaissance Office," ULA, Dec. 6, 2013, URL: http://www.ulalaunch.com/site/pages/News.shtml#/163/
13) "UNH Scientists Launch "CubeSats" into Radiation Belts," UNH, Dec. 9, 2013, URL http://www.unh.edu/news/releases/2013/12/ds09cubesats.cfm
14) "Future Imagery Architecture," Wikipedia, URL: http://en.wikipedia.org/wiki/Future_Imagery_Architecture
15) Patrick Blau, Atlas V to launch with classified NROL-39 & 12 CubeSats in December, Nov. 15, 2013, URL: http://www.spaceflight101.com/atlas-v-nrol-39-launch-updates.html
17) "Atlas V GEMSat Launch 2013," URL: http://www.cubesat.org/index.php/missions/upcoming-launches/134-l39-launch-alert
19) Information provided by Harlan Spence, PI (Principal Investigator) of the FIREBIRD mission, UNH (University of New Hampshire), Durham, NH, USA
20) David Sims, UNH, Dec. 09, 2013, URL: http://www.eos.unh.edu/news/indiv_news.shtml?NEWS_ID=1433
21) H. E. Spence, J. B. Blake, A. B. Crew, S. Driscoll, D. M. Klumpar, B. A. Larsen, J. Legere, S. Longworth, E. Mosleh, T. P. O'Brien, S. Smith, L. Springer, M. Widholm, "Focusing on Size and Energy Dependence of Electron Microbursts From the Van Allen Radiation Belts," Space Weather, Vol. 10, S11004, 2012, doi.10.1029/2012SW000869, URL: http://scholars.unh.edu/cgi/viewcontent.cgi?article=1170&context=physics_facpub
23) "Big Science in a Pintsize Package," UNH EOS Spheres Newsletter, Summer 2012, URL: http://www.eos.unh.edu/Spheres_0812/firebird.shtml
24) David Sims, "UNH Scientists Launch "CubeSats" into Radiation Belts," UNH, Jan. 28, 2015, URL: http://www.eos.unh.edu/news/indiv_news.shtml?NEWS_ID=1510
25) David Klumpar, Larry Springer, Ehson Mosleh, Keith Mashburn, Seth Berardinelli, Adam Gunderson, Matthew Handley, Nicholas Ryhajlo, Harlan Spence, Sonya Smith, Jason Legere, Mark Widholm, Steven Longworth, Alex Crew, Brian Larsen, J. B. Blake, Nicholas Walmsley, " Flight System Technologies Enabling the Twin-CubeSat FIREBIRD-II Scientific Mission," Proceedings of the 29th Annual AIAA/USU Conference on Small Satellites, Logan, Utah, USA, August 8-13, 2014, paper: SSC15-V-6, URL: http://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=3199&context=smallsat
26) Steve Cole, Alan Buis, NASA Launches Groundbreaking Soil Moisture Mapping Satellite ," NASA, Release 15-016, Jan. 31, 2015, URL: http://www.nasa.gov/press/2015/january/nasa-launches-groundbreaking-soil-moisture-mapping-satellite/#.VM3oYC7-Y_c
27) "United Launch Alliance Successfully Launches Important Earth Science Mission for NASA," ULA, Jan. 31, 2015, URL: http://www.ulalaunch.com/ula-successfully-launches-nasa-smap.aspx
28) "ELaNa X CubeSat Launch on SMAP Mission," NASA Factsheet, January 2015, URL: http://spacegrant.montana.edu/documents/ElaNa-x-Factsheet-v3.pdf
29) "ELaNa-10 Delta II launch," Jan. 31, 2015, URL: http://www.cubesat.org/index.php/missions/upcoming-launches/148-elana-10-delta-ii-launch-2015
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).