RE : SL-16

Kurt Jonckheere (
Fri, 20 Aug 1999 02:50:29 PDT

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
The first great Zenit flasher was 85- 97 B = 16182, several have

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 :
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 :
(it will be updated next week or so)

Please don't hesitate to send your timings (with date -time
in UT - observer - ...) to

Kurt Jonckheere (,
observations collector for the Belgian Working Group Satellites.

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