** UoSAT-C Spacecraft to be built at University of Surrey ** ------------------------------------------------------ UoSAT-C MISSION --------------- The UoSAT Spacecraft Engineering Research Unit at the University of Surrey (UK) is now building a third UoSAT-OSCAR spacecraft - UoSAT-C. NASA has agreed to provide a launch for UoSAT-C on a DELTA launch vehicle currently scheduled for late 1988. The DELTA should place UoSAT-C into a 43 degree inclination, 500 km circular orbit. UoSAT-C will carry experimental engineering, science and communications payloads developed in close collaboration between international professional engineering and amateur radio communities. These payload experiments develop further the mission objectives supported by the highly-successful UoSAT-1 & 2 (UoSAT-OSCAR-9 and UoSAT-OSCAR-11) satellites which are still operational after six and four years in orbit respectively. The UoSAT Programme and series of satellites are intended to compliment the AMSAT-OSCAR, RS and FUJI-OSCAR amateur radio communications satellites by providing a space science and engineering facility readily available to both amateur and professional experimenters alike thus generating a greater mutual awareness and collaboration. UoSAT-C, like the previous UoSAT missions, will have a strong element of international collaboration - specifically with members of AMSAT-UK, AMSAT- NA in the US and Canada, VITA, Quadron, NASA, the British National Space Centre and the European Space Agency. UoSAT-C PAYLOADS ---------------- Store-&-Forward Communications: Since 1983, UoSAT has played a major role in an international collaborative project developing cost-effective digital store-&-forward satellite communications techniques. The UoSAT-OSCAR-11 Digital Communications Experiment (DCE) - funded by the Volunteers In Technical Assistance (VITA) and built by VITA/AMSAT volunteers in the USA, UK and Canada - provided the first operational tests of store-&-forward PACSAT communications within the Amateur Satellite Service. Drawing on the operational and engineering data gained from the DCE, UoSAT and VITA are developing a high performance digital store-&-forward communications payload specially tailored for use by inexpensive ground stations. To test this payload, UoSAT-C will carry the PACSAT Communications Experiment (PCE). The PCE will be openly accessable to Radio Amateurs operating in the 2m and 70cm bands (Mode-J). VITA is seeking additional frequency allocations outside the amateur bands to allow limited use of the UoSAT-C PCE by VITA ground stations in remote areas to provide technical assistance and disaster relief. Radiation Studies Experiments: Microprocessor-controlled payloads such as the PCE cannot be built without VLSI semiconductors, and most recent and affordable VLSI devices have not yet been tested for space use. UoSAT-C will host several experimental payloads studying the effects of the space radiation environment on VLSI devices: Cosmic Particle Experiment (CPE) comprising an array of large-area PIN diodes, will detect energetic particles which cause single event upsets (SEUs) in VLSI circuits (such as high-density RAMs). CCD Single Event Upset Experiment (CCD-SEU) comprising an enclosed Charge- Coupled Device (CCD) array, will detect energetic cosmic particles and evaluate the effect of SEUs on CCD imagers. This data is of particular importance for scientists using sensitive CCDs as star sensors. Total Dose Experiment (TDE) using special FETs located around the spacecraft, will measure the total radiation dose accumulated by the on- board subsystems and payloads. These dose measurements will allow engineers to assess the shielding properties of the spacecraft structure, and to correlate changes in LSI-device power consumption and performance with total radiation dose. Satellite Technology Experiments: UoSAT-C will carry a range of satellite technology experiments associated with power systems, on-board data handling (OBDH), attitude determination, control & stabilisation (ADCS) and RF modulation. POWER: The spacecraft will be powered from GaAs solar cells and will include experimental patches of novel GaAs, InPe and Si solar cells with a variety of newly-developed cover-slides. The performance of these cells will be monitored throughout the mission as a function of radiation dose. The spacecraft onboard computers will constantly monitor and adjust the Battery Charge Regulator and Power Conditioning Module to optimise power conversion and storage efficiency. OBDH: UoSAT-C will include several computers. In addition to the primary RCA1802 on-board computer (OBC-1) running DIARY-type software, there will be a more powerful 80C86-based OBC-2 supporting complex attitude control algorithms and spacecraft data networks. Four TRANSPUTERS in a parallel-processing array will be available for highly sophisticated on-board image and data processing, and the PCE will employ an 80C186-family computer to manage high-speed communications links and several megabytes of RAM. A wide range of memory devices using different technologies and architectures will make up a total on-board capacity of around 5 megabytes of RAM. The radiation-induced effects on the processors and associated memories will be monitored and evaluated throughout the lifetime of the spacecraft. The network of computers on UoSAT- C will make this spacecraft the most computationally powerful of its class and will support demanding experiments in advanced spacecraft attitude determination and control, data communications and image processing. ADCS: The 43 degree inclination, non-sun-synchronous nature of the UO-C orbit will necessitate the use of new attitude determination and control mechanisms to maintain accurate Earth-pointing. In addition to more complex attitude control algorithms executed by OBC-2, improved analogue and digital sun sensors and Earth horizon sensors are being developed at UoS for the mission. DSP: If time and resources permit, a Digital Signal Processing Experiment may be included on UO-C to evaluate modulation/demodulation schemes. A new concept of highly modular construction has been developed and is under test for UoSAT-C. This new, modular structure should result in much improved utilisation of the available spacecraft envelope, greater ease of assembly and integration, and allow a more rapid response to future launch opportunities. FOR THE USERS ------------- Like UO-9 and UO-11, UoSAT-OSCAR-C will support a world-wide user community of engineers, scientists, educators and communicators. If all goes according to plan, UO-C will provide spacecraft housekeeping telemetry, long-term telemetry surveys, results from on-board experiments, news bulletins and communications facilities on a single downlink through packet-radio techniques. We will finalize and publish communications modem and protocol details as soon as possible, to allow groundstations to equip themselves. Whilst numerous international teams are already collaborating on UO-C, UoSAT is interested in hearing from others interested in possible collaboration, especially in the area of user groundstation support. The UoSAT team are happy to be able to make a public announcement of the UoSAT-C mission, and we hope that it will contribute to the long history of successful and technically important OSCAR and RS missions and maintain the tradition of international collaboration in the Amateur Satellite Service. Dr Martin Sweeting G3YJO Director of Satellite Engineering University of Surrey