Satgen283 UNAMSAT Meteor Radar by GM4IHJ 27th Aug 94 BID of this msg is SGEN283 Please use this BID if you retransmit this msg DJ0MY recently published a bulletin giving details of UNAMSAT, due to launch from Russia, in a month or so. Several correspondents have asked about the meteor radar on 40.997 MHz which UNAMSAT will carry. So here are some tentative answers. There appear to be two ways in which this innovative satellite might be used. Firstly it will send radar pulses and listen for echoes from meteor trails. It will then report on a packet downlink, details of what it hears. Eg you copy the sats BBS during a good meteor shower ( Quadrantids, Lyrids, Leonids, or Geminids , but not recent Perseids which was a dud Hi ) and the BBS will carry reports of meteor counts. Then perhaps later , software will be available to calculate the speeds of meteors relative to the satellite , so that MS fans can look for high speed meteors arriving from outside our solar system. The second method of usage is more complex. You use the radar and make your own meteor counts. This method works by using what the Electronic Intelligence gurus call " Pulse Stealing". When the sat is above your horizon , you feed the audio from the 40.997 MHz signal to an oscilloscope and arrange for the main radar pulse to trigger the scopes line time base. Depending on what pulse repetition rate or modulation the satellite uses you set the trace length to give you several thousand kilometres of range - say 20 milli seconds of trace, and look for meteor echoes on the trace. This sort of facility could provide a new view of both major and minor meteor showers, and be an excellent monitor of the every day 0600 local time sporadic meteor scatter peak flux. Remember however that this second method can only work when UNAMSAT is above your horizon. Given its 72 degree orbit inclination and roughly 700 kms altitude, UNAMSAT should be heard 5 or 6 times a day by equatorial station, and on almost all 13 orbits per day by near polar stations. It remains to be seen how well UNAMSAT will work, but there has been lots of excitement following the recent release by the US Department of Defense , of details of meteor/asteroid observations by their Early Warning satellites. These satellites some in geostationary orbit and some even higher, passively observe one hemisphere of the earth, each ,in both visual light and infra red, looking for the flashes of nuclear weapons and, the dense infra red output from rocket missile trails. Between 1975 and 1992, this warning network witnessed 136 major meteoric outbursts each exceeding 1000 tons of TNT. This number may only be a proportion of what actual hit the earth because the scanners on the warning sats only cover 10 degree bands at a time and may have missed many short duration bursts. Because of the fragile nature of much of the meteoric/cometary/asteroidal material , most of the energy is dissipated high at the top of the atmosphere, and fortunately has little effect down at the earths surface. But occasionaly,as at Tunguska in Siberia in 1908, a 10 million ton TNT equivalent exploding just above the earth , caused immense surface damage. Fortunately in this case in a sparsely populated region.So stay tuned to UNAMSAT, it could be interesting. For more info on meteor burst statistics see Sky and Telescope Feb 1994 on page 26. 73 de GM4IHJ @ GB7SAN