Satgen 19 9th August 89 The Polar "Bear " Facts Radio Amateurs around Europe have been following a group of at least two, and possibly 3, polar orbit satellites which transmit on 435.974 MHz since March of this year. RadCom Aug 89 page 64 contains a report on Polar Bear, one of the satellites said to be involved.This report is almost wall to wall errors. As these satellites are very useful, the following data may assist would be users. Two satellites Hilat and Polar Bear are being used for Polar Auroral research. They have identical Txs, and transmit unmodulated continuous carrier signals on primary frequencies 137.676 and 413.028 MHz. Sharp readers will note these frequencies are harmonically related, and that they like the Tx secondary 435.974 MHz are all harmonics of 22.946 MHz. This is deliberate .All the signals are phase coherent, and by receiving any pair,either or both primaries,and, or one secondary,very detailed ionospheric studies are possible. Polar Bear orbits with a period of 105 minutes at an inclination of 89.56 degrees.This seems to match the track of one of the mystery satellites ,which presently comes over UK south to north roughly every 106 mins between 0400 and 1100 ut, and again, between 1600 to 2300 ut with its track roughly north to south. The second mystery satellite may well be Polar Bear's partner Hilat, but this is not yet confirmed. Both satellites constitute one leg of a major series of experiments being led by UCLA (University of California at Los Angeles ), from its polar research base near Fairbanks in Alaska. Far from being covert clandestine military activity these signal are legitimate and are following in the footsteps of several famous predecessors which have used the 70cms band, EG DNA P76 of Auroral fame, the Space Shuttle VLF Plasma monitor relay, and a host of non amateur Shuttle Get Away Special experiments Polar bear is not a navigation satellite and it is not designated to use 149.97 MHz, nor does it transmit on that frequency. The mistake arises because Polar Bear was built by Johns Hopkins , Baltimore on a surplus navsat frame. It has no navsat electronics whatsoever. Would be users of what is believed to be Polar Bear will find that as it overflies UK its signal is usually steady, but when its signal path to UK transits the Polar Front, as it does every orbit. The scintillation of the disturbed signal is a good indicator of the degree of disturbance of the Polar Aurora. Packsats... Questions about Tx/Rx and Modems. Uplink Tx is 2m fM FSK, downlink Rx is BPSK on an SSB receiver which covers 437 MHz. Remember most UHF convertors cannot do this. The Fuji Oscar 12 1200 bps Modem will be OK when added to your TNC for use with Pacsat, Lusat Webersat and Jas1B. When much later the first 3 move up to 4800bps a new modem will be required.By contrast Uosat D and Uosat E are expected to start on 9600 bps which will require a special Modem. 73 de GM4IHJ@GB7SNE on 9th August 89