EduSat (Educational Satellite)
EduSat is a cooperative nanosatellite project proposed and coordinated by the Italian Space Agency (ASI) and funded by the Ministry for Education and Research. The project is being realized (design, manufacturing, launch and in orbit-operation) by the Group of Astrodynamics of the “Sapienza” University of Roma (GAUSS) on the basis of this previous experience, the UniSat program (University Satellite) with microsatellite launches in 2000, 2002, 2004 and 2006.
The primary goal of the program is to promote space education among high school students and to support the qualification and scientific careers of young people, as university students and young researchers. Another target of this program is to develop a small space mission for low cost scientific experiments and technological tests in orbit. The program involves courses and post-doc positions at several national universities. The educational activity involving high school students has been committed to IMT srl (company) with the contribution of the University of Roma “TorVergata”. The students are also involved in the development of a small payload (sun sensor) which will be hosted on board EduSat. 1) 2) 3) 4) 5) 6)
The microsatellite has the shape of a parallelepiped with dimensions 315 mm x 315 mm x 260 mm, and a mass of ~ 10 kg. The internal space is divided by vertical panels (Al+Al sandwich structure), which host subsystems hardware and electronic boards. The structure is modular and fast to assemble and disassemble, thus permitting a good flexibility even in substituting a complete section whenever it is needed and giving to the students the possibility to work, at the same time, on different subsystems.
The solar arrays are surface-mounted and the photovoltaic system is based upon triple junction solar cells (GaAs) which are glued to a non-conductive support. NiCd batteries are being used for energy storage.
The spacecraft attitude subsystem is based upon passive magnetic stabilization providing a restoring torque to align one of the satellite axis with the local direction of the geomagnetic field. This attitude system exploits a permanent magnet which produces the restoring torque and hysteresis rods for oscillation damping.
The OBC is an integrated system RCM3400 of Z-World based on the microcontroller Rabbit 3000.
Figure 1: CAD model of the EduSat nanosatellite (image credit: GAUSS)
Figure 2: Schematic view of the OBDH subsystem (image credit: GAUSS)
Figure 3: EduSat digital mockup (image credit: GAUSS)
RF communications: Use of the UHF/VHF (436/145 MHz) amateur bands for communications between the spacecraft and the ground. The data rates are 9.6 kbit/s in downlink and 1.2 kbit/s in uplink. In addition, a back-up S-band channel may be used with a downlink rates of 38.8 kbit/s. The SPIV (San Pietro in Vincoli) ground station of the School of Aerospace Engineering of Rome, operated by GAUSS, is used for communications with the spacecraft.
Figure 4: Functional configuration of the SPIV ground station (image credit: GAUSS)
Figure 5: Photo of the EduSat nanosatellite in the Yasny cleanroom (image credit: GAUSS) 7)
Figure 6: Photo of some payloads in the payload bay of the Dnepr Launch Vehicle (image credit: GAUSS)
Launch: The EduSat spacecraft was launched as a secondary payload on August 17, 2011 on a Dnepr-1 launch vehicle using the SHM (Space Head Module) configuration from the Yasny launch base located in the Orenburg Region, Russia. The launch provider is ISC Kosmotras. 8) 9)
The primary payload of the cluster launch is the Sich-2M spacecraft of NSAU (National Space Agency of Ukraine). The secondary payloads on this flight are:
• EduSat of the University of Rome, Italy
• RASAT of Tubitak Uzay, Turkey.
• AprizeSat-5 and AprizeSat-6 of Aprize Satellite Inc (Argentina, USA), each microsatellite features a next generation AIS (Automatic Identifictem System) payload.10)
• BPA-2 (Blok Perspektivnoy Avioniki-2 — or Advanced Avionics Unit-2) of Hartron-Arkos, Ukraine. The BPA-2 experimental payload remained attached to the upper stage of the Dnepr-1 launch vehicle.
Orbit: Sun-synchronous orbit, altitude altitude = 668 km, inclination = 98.8º, the orbital period is about 97.5 min, the equatorial nodal crossing time is at 10:15 LTAN (Local Time on Ascending Node). The orbit is slightly lower than the one of the DMC constellation. Global revisit opportunities of at least every 2 days are possible (70% of the Earth's surface can be revisited in one day).
Experiments: (Sun Sensor, MR-FOD, Magnetometer, Temperature Sensor, Deorbit)
The experiment complement of EduSat was changed considerably within the last year according to GAUSS information. Hence, only a listing of the experiments can be given at the time (except for the sun sensor). The documentation will be completed when available. 11)
Sun sensor experiment:
The sun sensor payload was designed and developed by high school students of several high schools in Italy. The EduSat team selected an analog sun sensor design capable of detecting the attitude of the satellite with respect to the sun. It is comprised of four solar cells (monocrystalline silicon, Figure 7), closed on a resistive load. The output voltages of the cells vary with the density of the solar radiation, and can be used to set the different attitude angles of the satellite with respect to the sun.
Figure 7: Sketch of of each solar cell mounted onto the sun sensor (image credit: GAUSS)
The four solar cells are mounted on the four sides of a metallic frustum of a pyramid (Figure 8). An electronic circuit, detects the voltage level at the terminal of each resistor, and provides two analog outputs (0-5 V range). Furthermore, a cylindrical shield protects the sun sensor from solar radiation coming from undesirable directions.
Figure 8: Metallic frustum of the pyramid onto which the solar cells are mounted (image credit: GAUSS)
Figure 9: The photovoltaic subsystem of EduSat (image credit: GAUSS)
• MR-FOD (Morehead Roma - Femto Orbital Deployer). An experimental PocketSat deployer, a joint development of Morehead University, Morehead, KY, USA and GAUSS.
• Magnetometer: A magnetometer board developed by the GAUSS team.
• Temperature sensor: An experiment developed by High School Students of Geymonat (Tradate, VA, Italy).
• A new deorbiting system (different from SIRDARIA - initially considered for EduSat). The system, which is based on a new concept, is using a passive system for the deployment of the sail allowing more reliability (the system works even when the satellite is defunct).
1) Filippo Graziani, Giuseppina Pulcrano, Maria Libera Battaliere, Fabrizio Piergentili, Fabio Santoni, Gabriele Mascetti, “Design of a small educational satellite for the Italian high school students: The EduSat Project,” 7th IAA Symposium on Small Satellites for Earth Observation, IAA-B7-0504, May 4-8, 2009, Berlin, Germany, URL: http://media.dlr.de:8080/erez4/erez?cmd=get&src=os/...
2) F. Graziani, F. Santoni, F. Piergentili, M. L. Battagliere, F. Paolillo, G. Pulcrano, G. Mascetti, “The EduSat Microsatellite,” 20th National Congress AIDAA (Associazione Italiana Di Aeronautica e Astronautica), Milan, Italy, June 29 - July 3, 2009
4) Filippo Graziani, Giuseppina Pulcrano, Fabio Santoni, Massimo Perelli, Maria Libera Battagliere, “EduSat: An Italian Space Agency Outreach Program,” Proceedings of the 60th IAC (International Astronautical Congress), Daejeon, Korea, Oct. 12-16, 2009, IAC-09.E1.3.12
5) Chantal Capelletti, Fabrizio Paolillo, Francesco Guarducci, Luigi Ridolfi, Filippo Graziani, Poalo Teofilatto, Fabio Santoni, Fabrizio Piergentili, Maria Libera Battagliere, “From UNISAT to UNICubeSAT,” 5th Annual CubeSat Developers' Workshop, San Luis Obispo, CA, USA, April 9-11, 2008, URL: http://mstl.atl.calpoly.edu/~bklofas/Presentations/...
7) “EduSat Photo Gallery,” GAUSS, Aug. 17, 2011, URL: http://www.gaussteam.com/index.php?option=com_content&view
9) “EduSat has been launched, GAUSS, Aug. 17, 2011, URL: http://www.gaussteam.com/index.php?option=com_content&view=article&id=135:launch&catid=35:edusa&Itemid=219
10) “Dnepr launches AprizeSat-5 and AprizeSat-6,” SpaceQuest, August 17, 2011, URL: http://www.spacequest.com/Articles/AprizeSat_Launch_8-17-11.pdf
11) Information provided by Luigi Ridolfi of GAUSS (Gruppo di Astrodinamica dell' Universita degli Studi “la Sapienza”), University of Rome, Italy
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.