Correspondence

New OSCAR To Be Launched In July '92

From AMSAT News Service Bulletin No. 116, with special thanks to G0K8KA for the information used in this bulletin.

introduction

In 1990, the University of Surrey started a collaborative educational program with the Korean Advanced Institute of Technology (KAIST). As a result of this program, KAIST student engineers are constructing the KITSAT-A satellite at Surrey, under the guidance of experienced UoSAT engineers. The KITSAT-A mission, as well as providing an educational opportunity for the KAIST engineers, will provide an operational satellite for the Amateur-Satellite Service. KITSAT-A will make several important contributions to the Amateur-Satellite Service. Satellite operators will have new opportunities, and satellite builders will gain important engineering information.

Orbit

KITSAT-A will be launched as a secondary payload onboard the Ariane V-52 mission. The primary passenger for this mission is the oceanographic satellite TOPEX/POSEIDON. The target orbit is nearly circular, with semi-major axis 7700 km and inclination 66 degrees. There are no other OSCAR satellites in such an orbit.

Payioad

KITSAT-A is based on the same satellite bus used by UO-14 and UO-22. This bus can carry several mission specific payloads. The KITSAT-A payloads are:

PACSAT Communications System (PCS)

The KITSAT-A PCS will provide open access store-and-forward digital communications for stations in the Amateur-Satellite Service. This system will use the standard protocols of the PACSAT Protocol Suite for message forwarding. The PCS will have 13 Mbytes of CMOS SRAM for message storage, and will use data links of 9.6 kbit/s or higher. This will be the second 9.6 kbit/s PACSAT available in the Amateur-Satellite Service. As such, it represents a valuable addition to the service and a consolidation of technical advances currently available on UO-14 and UO-22. More than 200 stations regularly access the UO-14 PACSAT transponder, and these stations will be immediately able to access the KITSAT system. It has recently been noted in the amateur press that all of the existing store-and-forward satellites (UO-14, PACSAT and LUSAT) are full to capacity over some parts of the world; the addition of a new high-speed satellite will help to solve this problem. KITSAT will provide valuable new communications bandwidth for direct users and for the growing network of PACSAT mail-forwarding gateways.

Earth Imaging System (EIS)

KITSAT's EIS will be an upgraded version of the UO-22 EIS which has conclusively demonstrated that amateur satellites can produce interesting meteorological-scale images. Equally important, the images can be downloaded and displayed by fairly simple ground stations. Unlike previous CCD systems, the UO-22 and KITSAT systems use standard, widely implemented protocols for image downloading.

The UO-22 images have been directly received by many radio amateurs and are available indirectly to a very wide audience. There are many educational uses for these images which are now being investigated.

The KITSAT-A EIS will consist of two chargecoupled device (CCD) imagers, two lenses, and a Transputer Image Processing Experiment. One of the imagers will provide a wide field of view with approximately 4-km ground resolution similar to the UO-22 camera but covering a larger area of the Earth. The second imager will provide a telephoto facility giving approximately 400 meters ground resolution. The use of the wide-angle camera as a spotting camera for detailed images from the narrow-field camera will greatly enhance the Amateur-Satellite Services imaging capabilities.

Digital Signal Processing Experiment (DSPE)

Digital signal processing is now finding wide application in Amateur Radio. Two DSP systems for amateurs have recently been placed on the market. On-board an amateur satellite, DSPE can provide great flexibility in signal modulation and demodulation formats. The KITSAT-A DSPE will be used for speech synthesis, store-and-forward speech relay, and high-speed modulation experiments.

Speech transmissions sending satellite telemetry, bulletins, or educational messages have been used on UO-9, UO-11, and AO-21. (Software permitting, DO-17 will soon begin its educational speech synthesis mission.) The KITSAT-A DSPE's primary mission will be similar to DOVE'S transmitting multilingual greeting messages. These will periodically replace data transmissions on the downlink. KAIST and the KARL intend to develop a dedicated 70-cm hand-held receiver to make reception of the KITSAT-A DSPE inexpensive and simple.

As well as supporting these easy-access speech broadcasts, the DSPE will be used for experimentation in digital voice relay and high-speed modulation. These experiments have not been completely defined, but are likely to include real-time conversion of a digital uplink signal to an FM voice downlink signal for "repeater" type operations. As a platform for voice coding experiments, the KITSAT DSPE may provide useful data for future amateur satellite missions.

Cosmic Ray Experiment (CRE)

Radiation encountered in orbit can damage integrated circuits and can upset data stored in solid state memories. Amateur satellites now use advanced semiconductors in many critical systems, and designers are becoming increasingly interested in radiation. (AO-10 and FO-12 have both been crippled by radiation damage.) UO-14 and UO-22 have already begun to measure the space radiation environment and its effects on advanced electronics. These measurements have been from the relatively benign environment of a low-altitude, high-inclination orbit. KITSAT-A will be placed into a high-altitude, low-inclination orbit, which has a much worse radiation characteristic. In this orbit, KITSAT-A will measure the total radiation dose and the occurrence of highly energetic cosmic rays. In parallel with this environment data, effects of the radiation on microcomputers, power systems, memories and solar panels will be monitored.

This information, which will be freely available to amateur satellite designers, may be of great importance for future amateur satellite missions. For example, the Phase-3D satellite will experience a radiation environment similar to that of KITSAT-A. If Phase-3D is to safely take advantage of new electronic technologies, KITSAT-A radiation studies will be invaluable. (The radiation environment data will be available to any suitably equipped Amateur Radio station for downloading. Data formats will be supplied by KAIST via KARL and by UoS via AMSAT-UK).

Choosing the uplinks in the crowded 2-m band is very difficult. Every frequency in this band is already occupied by a satellite uplink or downlink. Many of these links are not spectrally efficient KITSAT-A's single 9600-baud uplink will provide the same communications capacity as the 8 uplinks of LUSAT and PACSAT combined. Clearly, as technology advances, frequencies in the 2-m band must be reused for more efficient links. Fortunately, frequency sharing amongst low-Earth orbiting satellites is a viable option; the satellites are sometimes visible together, interfering with each other. At other times, the satellites are not visible to each other and there is no interference. This variable-interference frequency sharing is already used on almost all 2-m satellite frequencies.

For KITSAT-A, we have elected to place one receiver on 145.900 MHz, the channel already shared by UO-14 (secondary uplink), UO-22 (primary uplink), LUSAT and PACSAT. This will be KITSAT-A's secondary uplink, and will generally not be used. The primary KIT-SAT-A uplink will be on 145.850 MHz, a frequency shared with FO-20. (The argument for this is that F0-20 is the oldest of the packet satellites, and must be nearest to the end of its lifetime; furthermore, with 3 other uplinks available, some sharing is not likeiy to affect F0-20 greatly.)

Summary and Conclusions

KITSAT-A, scheduled for launch July 1,1992, will be a valuable addition to the fleet of Amateur Radio satellites. Using advanced technology, KIT-SAT-A will provide store-and-forward communications and Earth imaging as its primary missions. The DSPE and radiation experiments will return data of value to the whole amateur satellite program. It will certainly further the lARU's goals as expressed in Resolution 89-3, particularly: "the encouragement of a wide dynamic range of activities stimulating training through increasing intellectual challenge," and "the stimulation of young people in schools and universities to develop an interest in Amateur Radio through participation in amateur satellite activities."

We support the lARU's guidelines, and have planned KITSAT-A to be an interesting and useful addition to the Amateur-Satellite Service.

Operation

With so many onboard experiments, it is perhaps difficult to imagine how KITSAT-A will appear to the Amateur Radio operator. It is most useful to imagine a cross between UO-14 and UO-22. Like UO-14, KITSAT will transmit and receive 9600-bit/s FSK signals using the AX.25 protocol. Telemetry, experimental data, camera images and store-and-forward communications will be interleaved on this downlink using the techniques developed on UO-14 and UO-22. Radiation data and images will be stored in files that users will download using the standard PACSAT Protocol Suite. Current plans call for KITSAT-A to operate in this standard mode for about 95% of the time, with the remaining 5% taken up with digital voice broadcasts and/or high-speed modulation experiments. KITSAT-A operations will be managed by KAIST from their ground station (HL0ENJ) which is already active in Korea. KAIST and KARL will work together to ensure that the KITSAT-A "service" will be useful for radio amateurs and remains within the ITU regulations. Although UoS will have no formal control over KITSAT-A operations, UoS will advise KAIST when necessary.

Frequencies

KITSAT-A, being based on the UoSAT bus, will operate as a Mode-J satellite with a single active 70-cm transmitter, one or two user uplinks in the 145.Sxx-MHz satellite band and a secure command uplink.

KITSAT-A FREQUENCIES Uplinks: Command

145.850 MHz Primary access channel

145.900 MHz Secondary access channel Downlink: 435.175 MHz

Choosing a 70-cm downlink frequency is not difficult, as this band is relatively large and free of satellite activity, Taking into account the technical constraints on transmitter frequency synthesizers, the chosen downlink for KITSAT-A is 435.175 MHz.

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