Student nanosatellite IGOSat
Université Paris Diderot develops a student project of nano-satellite creation, within the Labex UnivEarthS. It is a project of the program JANUS CNES – French Space Agency – to coaching students satellites in France.
Initiated in 2013, this small satellite (30 cm x 10 cm x 10 cm), designed entirely by students, should be launched in 2019.
IGOsat horizon is primarily an educational project and progresses through successive generations of student work. Since the beginning of development, more than 150 students participated in the design, testing or simulations of the mission. It also has the support and expertise of researchers and professors from the University Paris Diderot and associated laboratories: APC, IPGP and AIM.
The GPS Payload
The Radio-occultation payload is using the same measurement technique used already by various space missions, such as GPS/MET, CHAMP and FORMOSAT-3/COSMIC (Schreiner et al., 2007) mission (http://www.cosmic.ucar.edu). The FORMOSAT-3/COSMIC has been the first mission providing atmospheric profiling using a constellation of 6 microsatellites of 60 kg each. The Radio-occultation payload carried onboard IGOSat aim to prove that this science case can be investigated at a nano-satellite scale.
Measuring the TEC from space is in complementarity to ground-based observations, producing data over the oceans and different observational geometry. Among the science objectives of this payload, there is also the possibility to measure ionospheric scintillation indices for observing small-scale irregularities in the ionosphere. The response of the ionosphere to changes in solar activity and to magnetic storms will be studied and gravity waves propagation in the ionosphere will be investigated through the induced small variations of TEC. Those waves are generated in the ionosphere by various physical processes, including tropospheric convection and tsunamis (fig. 1).
Fig. 1. Vertical profile of a gravity wave detected using radio-occultation data from FORMOSAT/COSMIC3.
The final scientific products of this payload will be Vertical profiles of ionospheric electron density. They will be obtained using an inversion algorithm (“onion peeling”) based on the hypothesis of spherical symmetry of the ionosphere
GPS Payload Principal Investigator : Pierdavide Coïsson
The scintillator payload
The Scintillator payload principles are based upon the XGRE instrument onboard the TARANIS CNES microsatellite (https://taranis.cnes.fr/en/TARANIS/index.htm). The XGRE detection unit is made of a sandwich composed of a crystal superposed by two plastic scintillators, read with a photo-multiplier; it is designed to detect electrons and gamma rays coming from Transient Luminous Events. The Scintillator payload carried in IGOSat is using a Silicon Photomultiplier (requiring a voltage between 15 to 75 times lower than typical photo-multipliers) with CeBr3 crystal scintillator, that has never been flown in space before.
Flux map of 1 MeV electrons at 650 km simulation
with OMERE from the DEMETER mission.
Some observations of the electrons spectra around the Earth have already been performed in the past, mostly in the 60’s and 70’s, leading to the electrons space distribution model AE8 from NASA. The DEMETER mission from CNES (Sauvaud et al., 2006) updated the observational data between 2004 and 2006 in the energy range from 70 to 2500 keV, at an altitude around 710km. The DEMETER results demonstrated an evolution of the spectrum at low energy when local magnetic conditions (such as storms) where met, that will be interesting to follow at higher energy with IGOSat. On the other hand, the AMS-02 experiment (Battiston, 2008) carried onboard the ISS measured high energetic electrons (above 200 MeV). IGOSat will complete these data by observing spectra between 1 and 20 MeV.
There are few measurements of gamma rays in the magnetic belts for now, mostly because of the difficulty to do measurements above 1 MeV, as the flux to observe is commonly lower than the radioactivity induced by the interaction between the cosmic rays and the satellite itself. This noise is globally proportional to the mass of the satellite, and a nano-satellite should be therefore able to tackle this challenge, and the data may enable to separate the components between the internal radioactive noise, the Earth albedo and the belts emission. The CORONAS-1 (Bucik et al, 1999) mission measured spectrums between 0.12 – 0.32 MeV and 3.0 – 8.3 MeV, and a lot of instruments observed the gamma rays from the atmosphere below 1 MeV (such as Beppo-SAX, SWIFT, INTEGRAL) (Ajello et al., 2008). IGOSat will complete the data by observing the spectra between 20 keV and 2 MeV.
Scintillator Payload Principal Investigator : Philippe Laurent
Since the beginning of development, more than 200 students participated in the design, testing or simulations of the mission. It also has the support and expertise of researchers and professors from the University Paris Diderot and associated laboratories: APC, IPGP and AIM.
POSITION NAME SURNAME LABORATORY NAME GRADE, EMPLOYER WP leader Hubert Halloin APC Ass. Prof, Univ. Paris Diderot WP member Colin Gonzalez APC/IPGP Research Engineer WP member Hana Benhizia APC Research engineer (Informatique,
WP member Pierdavide Coisson IPGP Ass. Prof, Univ. Paris Diderot WP member Philippe Laurent APC CEA Agent WP member Hien Phan APC PhD Student, Univ Paris Diderot WP member Philippe Lognonné IPGP Professor, Univ. Paris Diderot WP member Antoine Petiteau APC Ass. Prof. Univ. Paris Diderot WP member Alain Givaudan APC Research Engineer, CNRS WP member Bernard Courty APC Research Engineer, CNRS WP member Pierre Prat APC Research Engineer, CNRS WP member Sylvain Tillier IPGP Research Engineer, CNRS WP member Bernard Pidoux Ham radio , VHF/UHF expert WP member More than 200 students since Sept 2012 – L2 to predoc students, from Paris Universities and beyond
IGOsat is primarily an educational project, meaning that its development is thought to give the best ‘return’ towards the involved students. In that kind of projects, it is often said that 90% of the success is to develop, based on students’ works, a flight-ready satellite. A successful launch and data acquisition account for another other 5%. The last 5% consist of the scientific return of the mission.
However, the satellite must be designed for a valuable science return, keeping in mind the intrinsic constraints of a students, nanosatellite’s project. IGOsat embarks two innovative scientific payloads onboard a 3U CubeSat platform.
We present below a summary of the work performed, mainly by students, since the beginning of the project, with an emphasis on the results obtained since the last scientific committee in 2017. Most of these studies have been performed in the Student Space Centre of the University in the Lamarck building (526B, 5th
Summary of the work performed before the 2018 scientific committee
The first 8 students from the University (from the EIDD Engineering School and from the OSAE started to work on the pre-design of the satellite between September and December 2012. During the first semester 2013 and the summer break, 7 additional students worked on the TEC measurements and science case, as well as on the first simulations of the scintillator performance and of the mission profile.
4 more students completed the feasibility study during the last trimester of 2013.
Based on the results from these studies, the phase 0 was reviewed and approved by the CNES in November 2013.
IGOSAT was then chosen as the name for the mission. IGOSAT stands for Ionospheric and Gammaray Observations Satellite. A project manager (N. Combier) has been recruited in October 2013. Her contribution to the development of the project was major and allowed a real acceleration of the achieved work. In 2014, most of the activities were focused on the completion of phase A (preliminary requirements study) and some items of phase B. From September 2013 to August 2014, about 75 students were involved in the project. At this stage of the project, most of the objectives of the training periods and engineering projects were dedicated to the first designs and/or preliminary tests of the different subsystems: electrical system, payloads, telecom, attitude control, etc. Each of these works was concluded by the redaction of (at least) one report and, often, a presentation. Due to serious health problems, Natacha had to cease her activities on the project mid-2014. IGOSAT therefore lacked a project manager until December 2014, when Marco Agnan was recruited.
During the Preliminary Requirements Review (PRR) concluding phase A, about 10 students presented their work and the status of the IGOSAT project. The results were reviewed by a panel of 11 reviewers from the CNES, the APC, the IPGP and from other nanosats projects in France.
The Phase A review was declared successful in July 2015.
The UnivEarthS funds were mostly used for the internship grants, the realization of the short movies and the acquisition of required equipment (GPS and communication cards, thermal modeling software license, monitoring devices, scintillator, etc.). The University year is usually organized as followed:
o The first semester (September to January) is dedicated to engineering projects, usually 4 to 10 students working a few hours per week on the subject. The subjects are often oriented towards system-level studies, progress / review / validation of the work performed by the trainees during the preceding semester.
o During the second semester and following summer period (until September), other students (usually dedicated to the evaluation of key concepts and hard points of the design) take place, as well as short to long internships periods (1 to 6 months). These training periods are the most effective times during which the students can perform in-depth studies and technical realizations.
The Preliminary Design Review (PDR), ending Phase B, was conducted in June 2016 and approved by the CNES in September 2016.
Entering the phase C was a major step in the development process of IGOSAT, since it triggered the direct funding from the CNES. The funding convention with the CNES was officially agreed in July 2016 and is effective since October 2016. The total funding amounts to 440 k€ over 4 years (2016 to 2019), with It should be noted that, except for the QB50 projects belonging to a ‘fast-track’ European Cubesat program, IGOSAT is the first ‘regular’ nanosat project funded on the long term by the Janus program of the CNES.
In addition, due to his ambition to create his own nanosatellite services company, Marco Agnan ceased his activities on IGOSat in October 2016, when Hana Benhizia was recruited. Moreover, a software engineer was recruited in April 2018 to support the activities on the software development of IGOSat. Globally, prior to the last science committee (in 2017), more than 200 students already participated to the IGOSAT project. Their work during phase 0 to phase B were focused on preliminary designs for most of the satellite’s and ground based subsystems: ground station, attitude control system, mechanical structure,
power management system, scintillator payload, GPS payload, etc.
All of these subsystems (and some others…) were designed in details during phase C (concluded in September 2017): see the following paragraph milestones every year (progress meetings and reviews).
Results achieved since the last scientific committee
Since the last scientific committee, the project followed the same working scheme: students’ projects during fall 2017 and training periods from March to September 2018. For clarity, the main actions performed since the last SC have been grouped in different paragraphs.
Since the beginning of the project, more than 230 students have now worked, in one way or another, for the IGOSAT project. It is used at the EIDD (Ecole d’Ingénieur Denis Diderot, M1 & M2), STEP and OSAE masters as applications subjects for teaching projects. During the internship periods, the IGOSAT project welcomed students from French Universities and Engineering Schools (Universities Paris 6, 7 and 11; ISAE/SUPAERO; ESTACA, EIDD, Université Toulouse III…) but also from other countries (University of Science And Technology in Hanoï ; National Institute of Technology in Rourkela, India ; University of Petroleum and Energy Studies; etc.).
Moreover, since November 2015, a Vietnamese student (Hien T. Phan) is working full time for the IGOSAT project, more specifically on the detailed design of the scintillator payload and the preparation of the science data analysis of the mission (PhD supervisors : Philippe Laurent and Hubert Halloin). The Vietnamese government funds Hien’s grant, with a small additional contribution (3 600 € / year) from the LabEx. Hien’s PhD defence is schcduled for December 2018 or Januray 2019 (depending on manuscript readiness and jury members availabilities).
We present hereafter the technical status of the main (sub)systems of the satellite. This work was presented at the Critical Design Review (CDR) in September 2017. The review board officially approved the completion of Phase C and the project has therefore entered Phase D, i.e. the Assembly, Integration, Tests and Qualification of the engineering and flight models.
We list here a few items of the results presented by the student during the CDR in 2017 in addition of the work done in 2018. They represent a good overview of the work performed during the last year:
• System studies for the IGOSAT mission: System engineering is crucial for the IGOSAT project (as it is for any space mission). Based on previous works performed by students during Phase B, various budgets (power, communication, mass, …) and mission profile are maintained to take into account the latest technical developments of the subsystems. For example, we have defined a set of semi-major axis, eccentricity, inclination and local time compatible with both the mission requirements (mostly a quasi polar orbit above 500 km), the space operations laws (natural return to Earth within less than 25 years) and power consumption (local time between 1:30 and 10:30 are acceptable). In September 2017, an intern from ISAESUPAERO workied on the system engineering of IGOSAT and provides the final system engineering of IGOSAT which will be used during the integration phase. In 2018, a new intern in system engineering worked on the AIVT procedures and provide us detailed assembly and integration procedures as well as subsystems follow-up sheets and design acceptance checklist.
• Detailed mechanical design and vibration studies : The mechanical design of the satellite has been updated in 2018 to take into account changes in the satellite configuration due to changes in IGOSat attitude (new position of the GPS payload and implementation of the required kill switches for launch operations, etc.).
This work was done an M2 student from ESTACA. In parallel, this student performed the required additional vibration studies (as compared to the in-depth simulations performed in 2016 on the ‘old’ configuration) on the new satellite design. These studies demonstrated that the vibrations levels are well within the requirements. ‘Real’ vibrations tests performed in August 2016 demonstrated a resonance frequency along the Z axis matching with less than 10% the expected results, giving high confidence into the numerical
• Design and test bench of the scintillator payload: One of the IGOSAT payload is a scintillator detecting electrons and gamma-rays, read by a SiPM matrix. Since November 2015, a Hien Phan (PhD student funded by the Vietnamese government) is working on the detailed design of this payload. A Master degree student set up a test bench and characterized the SiPM with a functional acquisition chain (SiPM + Scintillator Support board). The tested SiPM where then sent to SCIONIX (scintillator’s provider) for detector assembly (CeBr3 + EJ200 + SiPM). In parallel, tests on the prototype of the EASIROC card (i.e. the acquisition ASIC provided by Omega Micron), adapted to the CubeSat format, were performed and a basic acquisition software was implemented on the board controller. Two relatively major changes happened during the last year on the scintillator design:
o The size and the design of the scintillator changed according to student characterization tests (size of the plastic thinner and of the crystal larger to fit the dimensions of the SiPM matrix)
o Updates in the Readout board of the detector (new rad-tolerant microcontroller and new rad-hard ADC)
• Design and test beds for the GPS payload: The second IGOSAT payload is dedicated to the measurements of the Total Electronic Content of the ionosphere, thanks to a dual frequency GPS antenna (and associated receptor). A Novatel GPS board was identified long ago as the best candidate (due to its flight heritage). It was however required to adapt the card to the CubeSat standard. Recently, the Pumpkin company released
a space qualified version of this board, adapted to the CubeSat standard. We therefore modified the mechanical and electrical design of the satellite to accommodate this board. During the last year, two students worked on various subjects, such as the communication between the on-board computer and the GPS card, the post-processing of the scientific data (leading to observations requirements and data allocation budget) and the realization and exploitation of a test bench for the GPS acquisition chain. This latter experiment made use of realistic components for the full acquisition chain and allowed characterizing various parameters such as the effective field of view or the signal to noise ratio on both carrier frequencies.
• Design and realization of the Power Management System: The PMS turned out to be much more difficult to design than expected… Serious flaws were identified in the first version of the card and a complete re-design of the power management system (from solar panels to batteries and power distribution) had to be done and the corresponding electronics card produced. It has been decided last year for the second version of the
card to split it in two different modules to test it separately and easily identify problems if they occur. The two modules are now validated and we are expecting to receive the final card in the following weeks to start functional tests. In addition, a new version of the PCBs of the solar panels has been designed and procured according to updated CNES mounting requirements. They were sent to CNES for integration with the solar cells and are now ready to be tested.
• Attitude Control and Restitution System: In 2016, IGOSAT design assumed a nominal ‘Nadir’ pointing, i.e. the long axis towards the center of the Earth. After more simulation investigation and discussion with experts from CNES, it was however demonstrated that this orientation would be difficult to maintain. As a consequence, the GPS antenna (which should point towards the horizon) was moved to the bottom (See Figure 1). In this orientation, the spacecraft is in ‘plane’ mode (i.e. its long axis – almost – horizontal). During about 6 months in 2018, an engineering student (from ESTACA) modeled the dynamics, perturbing torques, sensors and actuators of the satellite and designed an attitude controller. The results are in good way to be encouraging, we hired him for one month to finish his simulation and get more accurate results. Moreover, practical ways of implementation of the algorithm in the on-board computer (via Matlab auto-coding) have been identified and tested. In addition, 1 USTH student designed and achieved a winding machine to make an in-house air coil for the magnetorquer on the ADCS board. A first prototype of this aircoil was made last year and the test results on deducing its magnetic moment fitted our requirements. Two magnetometers will also be used in IGOSAT. They have been selected, partially tested, and modeled for use in the attitude detumbling algorithm.
• Telecommunication systems: The development of the telecommunication system was addressed this year from the ground segment. We have a partially operational ground station, the decoding part is still under investigation. The UHF/VHF antennas are installed on the roof of the Lamarck building. First successful communication tests have been performed with the ground station of the Paris 6 University, and latter with other CubeSats currently in orbit. The ground station was characterized and calibrated (which was the subject of a master degree internship in summer 2017). Because of insufficient documentation, performance issues and retirement (due to health problems) of the telecommunication expert in charge of the AMSAT telecommunication board, we decided to change the design of the on-board telecommunication card and purchased a new, of-the-shelf, board from the ISIS company. This board is fully compatible with the other systems of the satellite and has a robust flight heritage, e.g. on the PHOENIX Cubesat mission. This telecommunication board was recently tested and is fully operational.
• On-board computer and data management: During spring and summer 2016, a major effort has been put on the development of the on-board computer. The chosen design was derived from QB50 satellites developed at the Ecole Polytechnique and Ecole des Mines de Paris. However, due to planning constraints and lack of expertise in the design of an On-Board computer (OBC), facing a high risk of non-reliability, we decided to purchase an OBC, of-the-shelf, from ISIS company. This board is fully compatible with the other systems of the satellite, has a robust flight heritage and software support package compatible with the telecommunication board. This latter helps to save precious time in developing the flight software of IGOSat.
These items represent only the most significant works performed by the students during the last year. Every training period, project and, of course, review led to an extensive documentation (reports, user manuals, drawings, etc) that will be used by future students. The studies becoming more and more technical as the project definition goes into the details, more scientists and research engineers from the APC and IPGP are involved in the supervision of the students.
Natacha Combier and Hubert Halloin,
IGOSAT : IONOSPHERIC AND GAMMA RAY OBSERVATION SATELLITE, THE NANOSATELLITE OF THE UNIVERSITE PARIS DIDEROT,
Proceedings of the Small Satellites and Services Symposium, 26-30 May 2014, http://congrexprojects.com/2014-events/4S2014/proceedings
Marco Agnan, Hubert Halloin, Pierdavide Coisson, Philippe Laurent, Thanh-Hien Phan,
IGOSAT (Ionospheric and Gamma-ray Observations Satellite): Feedbacks from an educational CubeSat with scientific returns through technology demonstration
Proceedings of the Nanosat Symposium, 18-19 October 2016, (link still not available).
Hien Phan et al.,
IGOSat – A 3U CubeSat for Measuring the Radiative Content in Low Earth Orbit and Ionosphere
Nuclear Instruments and Methods in Physics Reasearch A, March 2018
Apart from participating to various conferences, the IGOSat team, together with the communication team of the LabEx and the support from the Space Campus, organized the Second Workshop dedicated to students’ CubeSats. This workshop was held on July 6th and 7th 2017 at IPGP. It gathered students, engineers and scientists working on the different French CubeSat project (plus OPS-sat from ESA and different private companies). The first goal of this workshop (and its originality compared to other nanosat workshops) was to be focused on the students’ needs: what information is relevant and where to get it ?
The morning sessions were dedicated to short presentations of the projects and dedicated available tools for designing CubeSat missions. Afternoon sessions were organized as open discussions on different themes, in order to address the questions of the students (and others…) participating to nanosats’ projects. It is foreseen to organize a third workshop in the summer 2018. One improvement (suggested by the participants) would be to invite even more private companies to gather the return of experience, the required and available technologies and stimulate possible partnerships.
The presentations, movies of the workshop and photos can be found on the IGOSat website: http://www.igosat.fr.