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Phoenix CubeSat Mission

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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.

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.

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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)

 

Science: The Urban Heat Island (UHI) Effect is a phenomenon in which the temperature of the urban area is much warmer than its surrounding rural outskirts. During the day, materials such as concrete and asphalt, which have a lower emissivity and are better at conducting heat, retain more energy from the sun over the course of the day. During the evening, this energy is released back into the environment, which reheats the ground and air, creating warmer nighttime temperatures. However, while UHIs are largely influenced by building materials, other factors such as how closely grouped structures are to one another, local geography, city size, also contribute to the UHI phenomenon.

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Figure 2: How the Heat Island Phenomenon occurs (image credit: ASU)

The objective of the science investigation aims to better classify how these factors of surface structure and surface cover relate to one another to produce the magnitude of the UHI Effect that we observe in cities today. Local Climate Zones (LCZs) offer a direct classification to the influence of the UHI Effect, as these describe land based on building materials and how compact, tall, or short buildings are relative to one another. Thermal images which are taken by the spacecraft will be overlaid with maps of Local Climate Zones (LCZs) to study how heat is influenced by the way cities are structured. From there, the team aims to share its scientific findings with urban planners to create a more sustainable urban environment for future generations. In all, Phoenix will study several major cities within the U.S. including: Phoenix, Los Angeles, Chicago, Houston, Atlanta, Baltimore, and Minneapolis. These cities will be studied in different diurnal and seasonal conditions as well to analyze how the effects of UHIs change over time based on the structure of LCZs. All images and scientific findings will be made available on the project's website (phxcubesat.asu.edu) throughout the course of the mission.

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Figure 3: Local climate zone map of phoenix, AZ – taken from our MDR slideshow (image credit: ASU)

 


 

Spacecraft

Phoenix is a 3U CubeSat, 10 x 10 x 34 cm, designed from commercial off-the-shelf components. The spacecraft also incorporates interface boards designed by the student team, which manage power and data interfaces for various components. The 3U structural components were designed and fabricated by the student team in Kingman, AZ and at Arizona State University. The spacecraft has a flight mass of 3.9 kg.

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Figure 4: 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.

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Figure 5: Photo of the MAI-400 ADCS (image credit; MAI, ASU)

OBC (Onboard Computer): The OBC used for Phoenix is the 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 ). — A GPS receiver was incorporated into the system design to provide clock synchronization during operations. Ultimately, the NovAtel OEM-615 GPS module was selected for its ability to meet system requirements as well as for its compatibility with the GOMSpace Nanodock DMC-3 Motherboard. The GPS is further supported by a patch antenna developed by NanoAvionics.

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. Communications are facilitated by the GOMSpace NanoCom AX-100 UHF Transceiver and a deployable UHF antenna developed by EnduroSat. 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 TCS consists of a single radiator panel, with the +X and +Y faces covered in silver teflon tape to increase the spacecraft's emissivity. In addition, as the payload is an uncooled microbolometer, temperature fluctuations will impact the scene temperature it is interpreting. Therefore, G-10 washers placed between the brackets and the CubeSat rails provide additional thermal isolation for the payload to reduce thermal effects during imaging. The ClydeSpace 40 Whr battery incorporates heaters to keep the batteries within its allowable temperature range during cold orbits.

The TCS was developed by modeling the spacecraft in Thermal Desktop. This allowed the team 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.

FSW (Flight Software): The FSW architecture was designed and written by the student team. It further 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.

 

Development status

• 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).

- August 20, 2019: Official handover to Nanoracks

- August 19, 2019: Flight Acceptance Vibe Testing

- July 19, 2019: Phoenix Hardware Acceptance Review (HAR)

- July 10, 2019: Qualification Vibe Testing

- July 6-8, 2019: Flight assembly

- June 18, 2019: Phoenix CDR (Critical Design Review)

• March 24, 2017: Phoenix PDR (Preliminary Design Review) at ASU. 3)

• 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. 4)

• November 11, 2016: Phoenix MDR (Mission Design Review) at ASU

• April 2016 –NASA selects Phoenix for a $200,000 grant to conduct hands-on flight research, through its NASA Space Grant Undergraduate Student Instrument Program (USIP).

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Figure 6: Cities that Project Phoenix will record (image credit: ASU)

- 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). 5)

• November 11, 2016: Phoenix MDR (Mission Design Review) at ASU. 6)

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Figure 7: CSLI (CubeSat Launch Initiative) 2017 selection (image credit: NASA)

 

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 on the NASA sponsored ELaNa (Education Launch of Nanosatellites) 25 mission carrying 15 CubeSat missions to the ISS. The Phoenix CubeSat will be deployed by NanoRacks into LEO. 7)

Orbit: Near circular orbit, altitude of ~ 400 km, inclination = 51.6º, period of~92 minutes. The orbit lifetime is designed for two years. The operational lifetime is baselined to 6-8 months.

Secondary CubeSat payloads of the Northrop Grumman-12 Cygnus flight

• Argus, a 2U CubeSat (2.5 kg) of St. Louis University, Missouri. Argus' mission is to improve the ability to model the effects of space radiation on modern electronics.

• AzTechSat-1, a 1U CubeSat technology mission of NASA Ames Research Center, Moffett Field, California

• CAPSat Cooling, Annealing, Pointing Satellite), a 3U CubeSat (4 kg) of the University of Illinois at Urbana – Champaign

• CryoCube, a 3U CubeSat (3.8 kg) developed by NASA KSC (Kennedy Space Center) to perform cryogenic fluid management experiments.

• CySat-1 (Cyclone Satellite-1), a 3U CubeSat technology demonstration mission of Iowa State University.

• HARP (Hyper Angular Rainbow Polarimeter) – University of Maryland, Baltimore County, Maryland - to measure the microphysical properties of cloud water and ice particles.

• Neutron-1, a 3U CubeSat developed by students of the UHM (University of Hawaii, Manoa).

• Phoenix, a 3U CubeSat of ASU (Arizona State University), Tempe, AZ.

• RadSat-U (Radiation Satellite), a 3U CubeSat demonstration mission of Montana State University, Bozeman, MT.

• SOCRATES (Signal of Opportunity Cubesat Ranging and Timing Experiments), a 3U CubeSat of the University of Minnesota, Minneapolis.

• SORTIE (Scintillation Observations and Response of The Ionosphere to Electrodynamics), a 6U CubeSat led by ASTRA (Atmospheric & Space Technology Research Associates), Boulder, Colorado. The team is composed of ASTRA, COSMIAC, AFRL, University of Texas at Dallas and Boston College. COSMIAC is the satellite integrator.

• SPOC (Spectral Ocean Color), a 3U CubeSat (4 kg) demonstration mission of the University of Georgia, Athens, GA.

• TJREVERB (Thomas Jefferson High School for Science and Technology Research and Education Vehicle for Evaluating Radio Broadcasts), a 2U CubeSat for communication experiments, Alexandria, Virginia.

External Cygnus Deployments

• HuskySat, a 3U CubeSat technology demonstration mission (plasma propulsion) of the University of Washington, Seattle, WA.

• SwampSat II, a 3U CubeSat technology demonstration mission of the University of Florida, Gainesville, FL.

 


 

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 will operate in the unfiltered wavelength range of 7-14 µm.

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Figure 8: Illustration of FLIR Tau camera (image credit: FLIR Technologies, ASU)

 


 

Ground Station

While Phoenix is in orbit, all mission operations will be managed by the student team at ASU. The ASU ground station will will be utilized to intercept the telemetry (health beacons 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.

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.

 


1) Phoenix CubeSat -A Small Spacecraft with a Big Role," Phoenix home page, ASU, 2019, URL: http://phxcubesat.asu.edu/

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," 24 March 2017, URL: http://phxcubesat.asu.edu/sites/default/files/general/phoenix_pdr_part_2_1.pdf

4) 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

5) "NASA selects ASU undergraduate 'CubeSat' project to measure Phoenix urban heat islands," ASU, 6 May 2016, URL: https://asunow.asu.edu/20160506-nasa-selects-asu-undergraduate
-cubesat-project-measure-phoenix-urban-heat-islands

6) "Phoenix Mission Design Review," ASU, 11 November 2016, URL: http://phxcubesat.asu.edu/sites/default/files/general/phoenix_mdr_1.pdf

7) Stephen Clark, "Launch Schedule," Spaceflight Now, 30 August 2019, URL: https://spaceflightnow.com/launch-schedule/
 


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 (herb.kramer@gmx.net).

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