OUFTI-1 (Orbital Utility For Telecommunication Innovation)
OUFTI-1 represents the first CubeSat mission of the University of Liege, Belgium. The main objective of the project is educational. It aims at providing hands-on experience to students in the design, construction, and control of complete satellite systems that will ultimately serve as the basis for a variety of space experiments. The long-term goal is to use CubeSat missions for scientific experiments. 1) 2) 3) 4) 5) 6)
The key innovative feature of the OUFTI-1 project is to test the D-STAR (Digital Smart Technologies for Amateur Radio) system communication technique of the amateur-radio digital-communication protocol. This means, radio-communication will be used for satellite control and telemetry. The telemetry will be made available to ham-radio operators worldwide. The goal is the space qualification of this new technology so that a functional D-STAR repeater can be given to the amateur radio community. In the future, the D-STAR concept may also be used to control space experiments.
The OUFTI project was initiated in Sept. 2007 when Mr. Luc Halbach, sales manager of Spacebel, proposed to three professors of the University of Liege to test a new amateur radio digital technology in space on board of a CubeSat: the D-STAR protocol. It did not even take one month for a team of students and professors to set up around the newborn project (Ref. 14).
Some background: D-STAR is an enabling communication technology, a digital voice and data protocol specification on VHF/UHF, and microwave amateur radio bands (1.2 GHz, 23 cm wavelength). D-STAR connects repeater sites over microwave and internet links to provide a wide area ham radio network. It supports Ethernet at 128 kbit/s DD (Digital Data) and DV (Digital Voice) at 4.8 kbit/s in GMSK transmission. DV uses 3600 bit/s for voice (2400 AMBE encoding, 1200 bit/s FEC) and 1.200 kbit/s for synchronization and multi-use (~ 900 bit/s is available for general use). 7) 8) 9)
The D-STAR specification defines the repeater controller/gateway communications and defines the general D-STAR network architecture.
Note: AMBE (Advanced Multi-Band Excitation) is a speech coding standard developed by Digital Voice Systems, Inc. and used in telephony systems.
• In 1999 the Japanese government funded JARL (Japanese Amateur-Radio League) to investigate new approaches to digital amateur radio technology. This extensive research involved Japanese radio manufacturers and other observers and resulted in the publication of the D-STAR protocol specification in 2001 and 2003.
• In the timeframe 2002, the Japanese company Icom Inc. provided the equipment used for development and testing of the D-STAR specification. Icom then started with the construction of the new digital technology by introducing a number of radios with D-STAR capability. D-STAR® is a registered trademark of the Icom Inc., a radio manufacturing company with HQ in Osaka, Japan.
• The D-STAR technology is in global use (the largest group of ham users is established in the USA); it is relatively affordable and is finding an increasingly large pool of ham operators with its increasing network of repeaters.
• So far (i.e., up to 2009), the D-STAR technology has only been used on the ground. It is the goal of the OUFTI-1 project to test the D-STAR technology in a satellite system. The open standard D-STAR protocol allows significant flexibility in experimentation.
However, a major problem has to be confronted: the general D-STAR radio system has no way to deal with the Doppler correction. What becomes of D-STAR in space? In fact, using D-STAR in space will have some consequences. The frequency shift due to the Doppler effect during one pass of the satellite is indeed too large for the acceptable bandwidth of the ICOM 2820 transceiver compensation capabilities of the Doppler effect. Unfortunately, this transceiver is, at the moment, the only one able to deal with D-STAR protocol available on the market.
Hence, the D-STAR Doppler effect will have to be compensated on board the OUFTI-1 spacecraft. Realizing this, there will be two system-selected doppler-compensated coverage zones: the first around ULg (University of Liege) for control and another one must be determined dynamically. Concerning the second zone, there will probably be a registration procedure on the Ulg website for the user community to reserve one pass of the satellite over a specific region (Ref. 14).
Figure 1: Illustration of Doppler effect compensated zones (image credit: University of Liege)
The OUFTI-1 spacecraft complies to the CubeSat standard of 10 cm side length and a mass of ≤ 1 kg. The CubeSat structure is based on Pumpkin's CubeSat kit. It comprises the main structure together with the FM430 flight module (FM430 flight module with Texas Instruments single-chip 16-bit MSP430). The spacecraft configuration is achieved using CATIA software. The objective is to position the different satellite components, 5 PCBs (Printed Circuit Boards), in an optimal manner (temperature and radiations issues) and within the available volume. Constraints on the location of the center of mass specified by the CubeSat design specifications must also be fulfilled. 10) 11) 12) 13) 14) 15) 16)
Figure 2: Illustration of the Pumpkin CubeSat kit structure (image credit: Pumpkin Inc.)
The ADCS (Attitude Determination and Control Subsystem) relies on simple passive magnetic stabilization since the D-STAR telecommunications subsystem does not require the satellite to point into a specific direction. The ADCS is of Delfi-C3 heritage. Use of permanent magnets with hysteretic materials.
The EPS (Electrical Power Subsystem) provides power using surface-mounted triple-junction GaAs solar cells (5 solar panels with 30% efficiency). The mean power available is 3.1 W. The energy is stored in Li-polymer batteries. OUFTI-1 features two PCDUs (Power Control and Distribution Units): one "classical" PCDU and an experimental PCDU developed in collaboration with Thales Alenia Space ETCA, Belgium. The regulated power bus provides power at 3.3 V, 5.0 V and 7.2 V.
The OBC subsystem controls the data flow on board the spacecraft. Its main tasks involve supervision of OUFTI-1 operation, telemetry data formatting and storage, telecommand data decoding and management. It must also provide a time reference. Pumpkin's FM430 is the prime OBC (On-Board Computer) and use of a homemade microcontroller (OBC2) for reasons of redundancy (only one is active at a time to save power). Use of FreeRTOS, open-source, lightweight, real-time OS (Operational System). 17)
Figure 3: Exploded view of the general CubeSat structure (image credit: University of Liege)
Figure 4: Photo of Pumpkin's FM430 on-board computer (image credit: University of Liege)
Figure 5: Illustration of the OBC2 (image credit: University of Liege)
The thermal control subsystem is fully passive. Thermal control is achieved using carefully selected surface finishes and appropriate configuration.
The monopole antennas will be folded during launch and have to be deployed once in-orbit. The two antenna rods have a length of 170 mm (beacon) and 500 mm (D-STAR and AX.25). The design of the mechanical antenna release system uses a thermal knife and retention wires.
Figure 6: Illustration of deployed antenna rods (image credit: University of Liege)
RF communications: The OUFTI-1 implementation of the subsystem relies on three channels of communication: 18)
• D-STAR: Use of VHF (145 MHz) for the uplink and UHF (435 MHz) for the downlink. Simultaneous data and voice digital transmission (data at 1.2 kbit/s, voice at 3.6 kbit/s with AMBE encoding, GMSK modulation).
• AX25: Ham radio protocol (G3RUH modem, 9.6 kbit/s, 2 FSK modulators). AX.25 is mainly used for telecommands & telemetry (CCSDS format). The AX.25 protocol has been selected for TC/TM to avoid TC/TM relying on the experimental communication payload.
• CW (Continuous Wave) beacon. The beacon is active at all times. The independent system contains some housekeeping data. In the event of a failure of main communication channels, the beacon data can be used to determine the cause of a possible malfunction.
Figure 7: Overview of the RF communications subsystem (image credit: University of Liege)
Launch: A launch of the OUFTI-1 CubeSat is planned for the end of 2014. OUFTI-1 has been selected for the Fly Your Satellite ESA program. Launch arrangements are in progress.
Note: In Oct. 2007, the OUFTI-1 project was selected as one of 9 CubeSats by ESA's Education Office for a free launch on the maiden flight of the Vega vehicle of ASI and ESA. However, in 2011 it turned out that the student-run project OUFTI-1 was not ready for a launch on Vega in January 2012 from Kourou. 19)
Experimental payloads: (D-STAR, Solar cells, PCDU)
D-STAR (Digital Smart Technologies for Amateur Radio):
The OUFTI-1 mission represents the first implementation of the D-STAR communication technology on a satellite. The overall system provides a lot of new built-in features including digital communication (i.e., the quality of the data received is better than an analog signal at the same strength), simultaneous voice and data transmission, complete routing over the internet and callsign-based roaming on a worldwide basis. Therefore, the D-STAR system provides a new capability and functionality to the ham radio world and increases the efficiency of emergency communications.
The D-STAR capability of OUFTI-1 is used to provide a repeater functionality to any D-STAR equipped ham-radio operator, as long as he lies in the footprint of the satellite. User 1 may communicate via OUFTI-1 with user 2 or another ground-based repeater which also has to lie within the current footprint of the satellite.
There are several possibilities for establishing a communication between two users.
1) Direct communication: The simplest one is a direct communication from one user to the other. Of course, the two users must be close enough to establish the link. Users can operate from a fixed ham-radio station, from a “mobile” station (typically in a car), or even from a “portable” station. In the OUFTI-1 context, direct communication is possible when user 1 and user 2 happen to be in the same footprint of the satellite.
Figure 8: Direct communication scenario (image credit: University of Liege)
2) Indirect communication: Users can communicate over longer distances, and/or overcome obstacles, by using a repeater. Of course, they must both be within radio coverage of the repeater. To increase coverage, repeaters can also be linked together to constitute a so-called “D-STAR zone”. This is typically done by microwave links.
Figure 9: Local D-STAR communication via a repeater in the same D-STAR zone (image credit: University of Liege)
3) Indirect communication: Finally, a repeater can be connected to other repeaters (and thus to other zones when available) anywhere in the world by a gateway computer connected to the Internet. This offers global connectivity.
Figure 10: Global D-STAR communication via a gateway in different D-STAR zones (image credit: University of Liege)
In the indirect communication cases, user 1 is “local” and connects to the repeater by radio, while user B is “distant” and communicates with the repeater either by radio or over the Internet.
In D-STAR communications, users are characterized by identities called “callsigns“. The same is true for repeaters. There are typically a source user, a destination user, a source repeater, and a destination repeater. In the D-STAR terminology, the callsign of the source user (typically ourselves) is called the “MY” callsign and that of the destination user the “UR” (Your) callsign. Also in the D-STAR terminology, the source repeater is called “RPT1”, and the destination repeater “RPT2”.
Figure 11: Photo of the D-STAR hardware (image credit: University of Liege)
Experimental solar cells: Azur Space Solar Power GmbH proposed to test (and space qualify) their new solar cells. These are 30% efficiency triple junction GaAs cells.
Experimental PCDU (Power Control and Distribution Unit) of Thales Alenia Space ETCA: The objective is to demonstrate its functional operation. This innovative PCDU is digitally controlled and based on a PIC microcontroller and other components such as planar transformers. When the batteries voltage is high enough (and the CubeSat functions nominally), then the digital PCDU will be switched to the 3.3 V power bus.
The OUFTI-1 spacecraft can be used in two different modes. The first mode is the command-and control mode used to control the CubeSat and to downlink the telemetry to understand the operational of the spacecraft. This mode employs the AX.25 protocol. - The second mode is the D-STAR user-to-user mode in the D-STAR communication channel.
The OUFTI-1 ground system consists of the control segment and the D-STAR user segment as shown in Figure 12. The control and monitoring of the satellite is performed by the satellite operators at the University of Liege. The user segment involves the use (testing and demonstration) of the D-STAR relay service by the global amateur radio community.
Figure 12: The OUFTI-1 ground segment consisting of the control segment and the D-STAR segment (image credit: University of Liege)
Figure 13: Overview of the ground station architecture (image credit: University of Liege)
Figure 14: The D-STAR ground segment (image credit: University of Liege)
2) S. Galli, J. Pisane, P. Ledent, A. Denis, J. F. Vandenrijt,P. Rochus, J. Verly, G. Kerschen, L. Halbach, “OUFTI-1 - The CubeSat developed at the University of Liege, Belgium,” Proceedings of the 5th CubeSat Developers' Workshop, San Luis Obispo, CA, USA, April 9-11, 2008, URL: http://mstl.atl.calpoly.edu/%7Ebklofas/Presentations/DevelopersWorkshop2008/session1/6-Oufti1-Amandine_Denis.pdf
3) Jonathan Pisane, “Design and implementation of the terrestrial and space telecommunication elements of the student nanosatellite of the University if Liege,” Masters Thesis, 2008, URL: http://www.leodium.ulg.ac.be/cmsms/uploads/07-08_Pisane.pdf
4) Amandine Denis, Jonathan Pisane, “OUFTI-1 - The educative nanosatellite of the University of Liege, Belgium,” Proceedings of the 60th IAC (International Astronautical Congress), Daejeon, Korea, Oct. 12-16, 2009, IAC-09.E1.1.9
5) Amandine Denis, Jerome Wertz, Jonathan Pisane, Gaetan Kerschen, “Holding a technical review in an educational project: implementation and lessons lerned,” Proceedings of the 61st IAC (International Astronautical Congress), Prague, Czech Republic, Sept. 27-Oct. 1, 2010, paper: IAC-10.E1.2.7, URL: http://www.leodium.ulg.ac.be/cmsms/uploads/IAC-10_E1_2_7.pdf
6) Amandine Denis, Jonathan Pisane, Jacques Verly, Gaetan Kerschen, “Educational assessment of four years of CubeSat activities at the University of Liege, Belgium,” Proceedings of IAC 2011 (62nd International Astronautical Congress), Cape Town, South Africa, Oct. 3-7, 2011, paper: IAC-11.E1.2.8
7) Peter Loveall, “D-STAR® Uncovered,” URL: http://www.aprs-is.net/downloads/DStar/DSTARUncovered.pdf
10) Renaud Henrard, Gauthier Pierlot, Damien Teny, V. Beukelaers, L. Chiarello, N. Evrard, S. Hannay, J. Hardy, L. Jacques, P. Ledent, F. Mahy, P. Thirion, J. Wertz, “OUFTI-1 - The CubeSat developed at the University of Liege, Belgium,” URL: http://www.leodium.ulg.ac.be/cmsms/index.php?page=satellite
11) “OUFTI-1 - Realizations and prospects,” June 18, 2009, URL: http://www.leodium.ulg.ac.be/cmsms/uploads/2009_06_18_Realisations-prospects.pdf
12) L. Chiarello, M. Kaut, L. Rainaut, J. Wertz, “OUFTI-1 - The first nanosatellite developed at the University of Liege, Belgium,” PiNa Workshop, Würzburg, Germany, Oct. 1, 2009, URL: http://www.leodium.ulg.ac.be/cmsms/uploads/2009_10_01_Wurzburg_OUFTI-1_ULG.pdf
13) Damien Teney, “Design and implementation of on-board processor and software of Student nanosatellite OUFTI-1,” Master thesis, 2009, URL: http://www.leodium.ulg.ac.be/cmsms/uploads/08-09_Teney.zip
14) Lionel Jacques, “Thermal Design of the OUFTI-1 Nanosatellite,” Master thesis, 2008-2009, URL: http://www.leodium.ulg.ac.be/cmsms/uploads/08-09_Jacques.pdf
15) “OUFTI-1 Status and perspectives,” June 29, 2011, URL: http://www.leodium.ulg.ac.be/cmsms/uploads/2011_06_29%20Status%20and%20perspectives.pdf
16) Sebastien De Dijcker, Nicolas Crosset, Jacques Verly, Amandine Denis, “OUFTI-1 Design of the On-Board Computer of the Belgian OUFTI-1 CubeSat,” 8th Annual Developer's Workshop, April 20-22, 2011, San Luis Obispo, CA, USA, URL: http://www.leodium.ulg.ac.be/cmsms/uploads/2011_04_22_CalPoly_De_Dijcker_OUFTI-1.pdf
17) Sebastien De Dijcker, Nicolas Crosset, Jacques Verly, Amandine Denis, “OUFTI-1 : Design of the On-Board Computer of the Belgian OUFTI-1 CubeSat,” 8th Annual CubeSat Developers’ Workshop, CalPoly, San Luis Obispo, CA, USA, April 20-22, 2011; URL: http://www.cubesat.org/images/2011_Spring_Workshop/fri_a11.30_dedijcker_oufti-1.pdf
18) OUFTI-1 Newsletter No 2, Jan. 20, 2010, URL: http://www.leodium.ulg.ac.be/cmsms/uploads/OUFTI-1%20Newsletter%202.pdf
19) Information provided by Amandine Denis of the University of Liege, Belgium.
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.