Greg I was very interested to read this topic. Back in the 1970s and 80s there was a whole series of Molnija 1s and their rockets which decayed in this way. I spent hours with a Moonwatch telescope making precise positions on them. Because apogee was close to N apex, there was excellent visibility from the UK. Peter Wakelin was posted to the Falkland Islands for a while, and could see them near perigee, but illuminated passes were few and far between. If I remember correctly, the Molnija 2s were placed in slightly different orbits so that their perigee height tended to increase rather than decrease. Cheers David. ----- Original Message ----- From: "Greg Roberts" <grr@telkomsa.net> To: <Difflimited@aol.com> Cc: <SeeSat-D@satobs.org> Sent: Wednesday, February 11, 2009 6:41 AM Subject: Re: Low perigee question > Morning > > This is not uncommon - many of the high altitude objects- especially those > in GTO orbits have a low perigee and a high apogee and decay rapidly. The > mechanics of how the orbit decays is quite interesting-I think it was > discussed on SeeSat quite some time ago - Im not an expert on this so had > best not say too much but the orbit tries to circularize with apogee > coming down very rapidly whilst perigee height tries to increase but > eventually the satellite looses its battle.. > > On the 23 Jan 2009 I reported to SeeSat an observation of an Atlas 5 > Centaur rocket - 08016B- catalog number #32764. > At the time of observation the prediction program used gave an apogee of > 4300 kms but a perigee of 87 kms and doing 10 revs/day. Ive just checked > on this object and the program reports "Object decayed" . At the end of > Jnauary it had decreased its orbital period to around 14 revs/day and had > an enormous drag term. > > Guess this could make an interesting amateur observation program -- try > and observe objects like this as they speed through perigee - just how low > can one go without being destroyed ? For the bigger/brighter objects it > might even produce quite a spectacular display - there are plenty of > objects to watch .... > > Cheers > Greg > > ------------------------------------------------------------------------- > Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: > http://www.satobs.org/seesat/seesatindex.html > ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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