Satgen 383 Ao13 Visual by GM4IHJ 27th July 1996 Radio Amateurs have been visually observing satellites and spacecraft for years. Favourite targets, because of their large sunlight reflecting area and low altitude , being the Shuttle and Mir. But even small low earth orbit Amsats are visible as they reflect sunlight back to a ground station in darkness, if you know where and when to look. Computer software for calculating where and when, has been available since 1985, but the idea of watching a Phase 3 orbiter has not been commonplace up till now. However Ao13's decline in perigee altitude now makes it a possible visual target. Modifying LEO visual software for Ao13 produced a few surprises. 1. Ao13 comes up from the horizon roughly half as fast as Mir, but when half way across your sky it stops moving to the far horizon and start to descend very slowly whilst quickly increasing its range and thereby reducing its apparent target size. 2. Because Ao13 travels very quickly round the earth at perigee, it gives visual opportunities to widely separated ground stations So now that the SEE13 Ao13 software is up and running what does it predict in terms of useful visual opportunities. Exact timing of predictions is nearly impossible a month or two ahead with Ao13 mean motion dropping so quickly ( Eg Note how quickly Amsats recent eclipse prediction times have become out of date). So the events may occur a couple of days earlier than predicted here. But should show a clear pattern whereby useful visual opportunities seem to come after sunset on several successive nights with about 10 days between the start of each group of useful nights. Tentative dates are :- Western Europe 31/7 to 3/8; 10/8 to 13/8; 20/8 to 23/8; 30/8 to 1/9 , Eastern USA 29/7 to 31/7 ; 6/8 to 10/8; 17/8 to 20/8; 27/8 to 30/8 Western USA 3/8 to 7/8; 14/8 to 17/8; 24/8 to 27/8 Japan 28/7 to 1/8; 7/8 to 11/8; 18/8 to 21/8; 29/8 to 31/8 Getting exact dates+times will depend critically on your Keplerian elements being less than 2 or 3 days old. Southern hemisphere stations see Ao13 only when away from perigee, as a poor slow moving target, at long range. The SEE13 software model clearly shows that the initial rise up from your horizon occurs at about half the speed of Shuttle or Mir, then at or near maximum elevation, the Ao13 track slows up fast and as it then descends in elevation, it comes nearly straight down , perhaps even turning back on its track slightly, and only rarely actually reaching your horizon before its rapidly increasing range makes it too small a target to be seen. The assistance of sharp eyed youngsters and a pair of binoculars is recommended, at all stages of viewing. So please try to see if you can follow it. Better still, why not try to photograph its track, for Amsat Journal. Act now. We are all likely to be a great deal older before, we get a repeat performancece