SB NEWS @ AMSAT $SPC0909 * SpaceNews 09-Sep-96 * BID: $SPC0909 ========= SpaceNews ========= MONDAY SEPTEMBER 9, 1996 SpaceNews originates at KD2BD in Wall Township, New Jersey, USA. It is published every week and is made available for non-commercial use. * AO-13 RE-ENTRY * ================== Based on the combined effects of the Earth's oblateness, atmosphere drag, rotation, and various other considerations, Miguel Kassis, PY5BYE expects re-entry of AO-13 on 30-Nov-96 at 11:42 UTC. At this time, atmospheric drag is the principal orbital perturbation. * UPDATE ON SUNSAT * ==================== The launch of SUNSAT, South Africa's first satellite carrying an Amateur Radio and Experimental commercial payload has been delayed till early August 1997. The delay is due to rescheduling by USAF of launch of the primary payload on a McDonald Douglas Delta II from Van den berg Airforce Base. SUNSAT is a 60kg, 45 by 45 by 62 cm micro satellite which is being designed, built and tested by twenty four M.Eng. students at the Electronic Systems Laboratory (ESL) in the Department of Electrical and Electronic Engineering at Stellenbosch University. The students have done all the detailed design and the software. System level design was done by lecturers, some of whom studied at the Universities of Surrey, Stanford and MIT. It is therefore not strange that the satellite is very similar to the UoSATs built at Surrey. SUNSAT carries a camera system that will produce stereo or side images in three colors with 15 m ground resolution from 800 km orbitally height. The resolution is in the order of the same magnitude as the SPOT 2 and Landsat satellites. The communications payloads comprise high speed datalinks as well as VHF and UHF transmitters and receivers operating in the 435 and 145 MHz bands. A 5w EIRP S-band downlink will transmit image data at 40 Mbit/s requiring only a 4.5 meter dish at the ground station. An L-band receiver permits uplinking data at 2Mbit/s and can be coupled to the Sband system for gateway operation. SUNSAT supports two modulation methods: a) 1200 baud AFSK which was the first choice of SA-AMSAT as it will afford many newcomers to the Amateur satellite scene to get a first shot at satellite operation without the need for an elaborate ground station. b) 9600 baud G3RUH compatible with the microsats, for those who have already invested in 9600 equipment, or who want better performance. Both these modulation methods use NBFM modulation, the G3RUH requiring 20 kHz of IF bandwidth. Note that +3 kHz and -3 kHz Doppler shift occurs on 145 MHz, which is accommodated in the above bandwidth of any receiver not tracking the Doppler shift. Consequently, the hard-wired systems are restricted to FM modulation. (There are some DSP options that the University will try and upload in 1997/8). The consequence is that the IF bandwidths are 20 kHz nominal, which makes 25 kHz channel separations reasonable. G3RUH in the documentation for his 9600 baud modem recommends 20 kHz IF bandwidth for receivers used with this modem. SUNSAT has two VHF TX's, two UHF TX's and two VHF Rx's and two UHF Rx's. Each of these has a single crystal in the amateur band, and an input from a synthesizer with 12.5 kHz channel spacing. The Design Engineers preferred to have the default operating frequencies on the crystals (switch synth off), but can run the synths to unplanned frequencies. There also is plenty of memory on board to synthesize speech messages informing users of mode switches - eg "Parrot" operation enabled with 145.825 MHz uplink for the next 120 seconds." The L-band uplink and S-Band downlink gateway capability is in response to Jan King's articles in QST of some years ago talking about `gateways' capable of high rate uploads and downloads to satellites. Sunsat is Stellenbosch's first satellite, and for a long time the university was unsure whether they would ever get Sunsat into orbit. The strategy has thus been to include the `gateway' capability in a simple way and test to see if and how well it works. If results are positive, the ground station will then see if there is support to establish such `gateways' at major locations. The S-band downlink is also used for the image data, which the Stellenbosch hopes to license in the 2200 - 2290 MHz earth exploration downlink band. The final Memorandum Of Understanding was signed between NASA and the South African Foundation for Research and Development (FRD). This secured the NASA launch in return for a inclusion of a NASA GPS receiver in the payload. Currently the launch is scheduled for early August 1997. In June, Garth Milne, ZS1AFH attended a ground operations meeting at Vandenberg, USA to finalize the integration details with the launch vehicle. The substrates for the four solar panels were manufactured by Somchem, a company near Stellenbosch. The substrate have been manufactured from carbon fiber. The students have completed the magnetorquer coils which were wound around the honeycomb structure of the substrate. Currently, the GaAs solar cells are being fitted by EEV in England and the solar panels will be shipped back to South Africa within the next few weeks for integration. The flight model assembly is progressing well. All mechanical items on the top of the satellite have been assembled. This includes 4 monopole antennas for VHF, a modified turnstile antenna with elements bent at 30 degrees, a UHF monopole, the GPS Antenna, two horizon sensors, the star camera, magnetometer and tipmass and folded boom. The tipmass contains a star camera, a magnetometer and 8 laser reflectors. The boom was designed and constructed at the University and will undergo a final set of extensive deployment tests later this month. The PACSAT BSS is currently being tested and operating well with WISP. The operational frequencies are currently being finalized and will be announced soon. SUNSAT information is also available on the SUNSAT home page: http://sunsat.ee.sun.ac.za [Info via Hans, ZS5AKV] * FEEDBACK/INPUT WELCOMED * =========================== Comments and input for SpaceNews should be directed to the editor (John, KD2BD) via any of the paths listed below: WWW : http://www.njin.net/~magliaco/ PACKET : KD2BD @ KS4HR.NJ.USA.NA INTERNET : kd2bd@amsat.org, magliaco@email.njin.net SATELLITE : AMSAT-OSCAR-16, LUSAT-OSCAR-19 <<=- SpaceNews: The first amateur newsletter read in space! -=>> /EX