SB SAT @ AMSAT $ANS-065.06 PHASE 3D MEETING REPORT HR AMSAT NEWS SERVICE BULLETIN 065.06 FROM AMSAT HQ SILVER SPRING, MD MARCH 6, 1993 BID:$ANS-065.06 TO ALL RADIO AMATEURS BT Phase 3D Design Meeting Held in Orlando A meeting of some 20 people from the U.S. Canada, Germany and Japan; participating in the Phase 3D design program was held in Orlando, Florida February 25 through 28. This meeting represented an important milestone in the Phase 3D project. At it, the overall design of the satellite was agreed upon. It will be a hexagonal design 1120 mm ( 44 inches) on each side and 675 mm ( 26-1/2 inches high). The spacecraft's mass will be about 400 kg (880 lbs). Solar panels will cover two of the flat side surfaces and two more panels will unfold using a double hinge mechanism. The total span, with these panels deployed will be about 6450 mm (21 feet). Phase 3D will be carried by the Ariane 5 launcher inside a large cylinder and ejected from it. A major decision reached involved relocating the high gain antennas. In previous designs, these antennas were on the side opposite the nozzle. While this provided more area for them, it also entailed a severe restriction on their height caused by potential mechanical interference with parts of the launching rocket. This height restriction dictated the use of low profile patch arrays for most bands. By locating the antennas to the motor nozzle side of the spacecraft, they can project farther above the surface - making possible the use of more conventional antennas. For example, S and C bands are now expected to share a dish with a dual band feed. This can be contrasted with the very flat patch arrays which would be required in the original location, on the side opposite the nozzle. The 70 cm antenna will continue to use patches - in this case a six patch array, surrounding the motor nozzle. For 2 meters, three half wave dipoles will be used and 10 meters will employ whips to form a 2 element beam. Estimated gains for the various bands are: 10 meters 4 dBi 2 meters 8.4 DBic 70 cm 13 dBic 1.2 Ghz 15.5 dBic 2.4 GHz 17 dBic 5.6 GHz 19 dBic 10 GHz 20 dBic The design architecture for the computers which will control the satellite and handle data, along with the local area network (LAN), which will connect them with the various on-board systems; was presented in some detail by Peter Gulzow DB2OS. The LAN will employ two busses, one at about 100 to 200 kilobits per second while the other will run at about 1 megabit per second. The high speed LAN will handle the data, and the other will take care of control functions. The concept of using GPS, in addition to optical sensors, for attitude determination, as proposed by Tom Clark W3IWI, was also discussed and found to provide real benefits. Tom also offered a concept of providing a central oscillator to control all receivers and transmitters. This suggestion was accepted in principle, although it was emphasized that each receiver and transmitter should also provide its own frequency source. Tom also proposed that correction be applied to the output of the central oscillator to remove the effect of Doppler as the satellite traverses its orbit. He noted that, unless something is done, Doppler will be particularly troublesome at 10 GHz. W3IWI's concept also calls for the central oscillator to be referenced to GPS to provide very accurate frequency. Miki Nakayama JR1SWB reported on the camera experiment, being provided by the JANSAT group. This seems well along, including the building of some prototype hardware. Two earth-looking cameras plus another, longer focal length unit, looking out into space are being proposed. It was noted that the camera looking into space may provide the opportunity for doing some interesting astronomy while the others should produce some worthwhile wide and narrow angle views of the earth. It was noted that, from the high elliptical orbit which Phase 3D will use, it should be possible to obtain pictures of the northern auroral oval. The systems which seem the least well along are the RF units. Karl Meinzer DJ4ZC said that the 70 cm transmitter is expected to be built in Germany, but no solid offers from potential builders of the 2 meter, 2.4 GHz and 5.6 GHz transmitters have yet materialized. On the other hand, quite a bit of work has been accomplished on the antennas, although some of this will have to be redone with the move to the nozzle side of the spacecraft. But since more height is now available, the job should be much easier than before. Bob Stilwell along with several Johns Hopkins students, and Stan Wood WA4NFY are those principally working on the Phase 3D antennas. Keith Baker KB1SF presented a proposal to provide a more formalized scheduling structure using a commercial software package. His offer was accepted with thanks. It was also decided to employ interface documentation much like that used on earlier Phase 3 satellites. Upon completion of the meeting, Dick Jansson WD4FAB went to work to produce the many drawings which will be necessary before actual fabrication of the satellite's structure can begin.