hello all, Paul J Henney wrote : >Other SL-16's have also been launched(zenit's) but are not known tumblers. SL-16 or Zenits are almost ALL known to be great bright easy-to-spot tumblers. The first great Zenit flasher was 85- 97 B = 16182, several have followed... These second stages are seperated from the active payload by explosive bolts. They are usually flashing quite fast after lauch with less than one second. Because they are about 10 meters long, they become as bright as mag +2. Due to magnetic friction their rotation period slowly goes down, so the time between two flashes become greater. For Zenits, it usually take about five months for the period to become about 3 times larger (in fact 2.71...=e times larger). This time is known as the charateristic time of the rocket and depends (mainly) on the rocket itself, its inclination and semi-major axis. This means that after 2-3 years they become steady. You can find more about flashing satellites, theory and practice on the VSOHP : http://www2.satellite.eu.org/satintro.html especially at the "flashing satellites" part. In the PPAS - BWGS part you can find a link to the PPAS database. There you can check that SL-16s were nice tumblers. In our program of flashing satellites you can also notice some Zenits : 96- 51 B b 24298/Zenit 98- 43 G b 25400/ "Zenit" Resurs 1-x rocket 98- 45 B b 25407/ "Zenit" C 2360 rocket 99- 39 B b NEW, Okean-O Zenit, bright, fast flashing ! 96- 51 B is nearly Steady right now, the two launched in 1998 have a period of 40 to 50 seconds. Only the last one is still quite spectacular and will stay like that for two years or so ! You can find the program overview at : http://www2.satellite.eu.org/sat/program.rob (it will be updated next week or so) Please don't hesitate to send your timings (with date -time in UT - observer - ...) to ppas@lists.satellite.eu.org. Kurt Jonckheere (kjon@mail.dma.be), observations collector for the Belgian Working Group Satellites. ______________________________________________________ Get Your Private, Free Email at http://www.hotmail.com