DMSP and other things

From: Bart De Pontieu <BDP_at_MPE.MPE-GARCHING.MPG.DE>
Date: Sun, 9 Apr 1995 12:49:18 -0400

The following mail to seesat was diverted from the list because it came
from a Mailer-daemon. Since it contains recent observational information,
I decided to forward it. Author is Tristan Cools.

Last week (April 2nd, for some reason this message didn't get on Seesat L
last week), I had, at last, a good observational session again so
I've got a chance to observe some new objects.

One of these seems to be 88-6A(a DMSP satellite) which is probably tumbling
out of control. I found it(by coincidence while looking at 91-9J) to be
irregular flashing with approximately 9.4s. I hope this will be confirmed
in the near future because confusion with Okean 1 is possible.(although I
think the angular motion was showing that this object must have been in a
higher orbit than Okean 1)

DMSP satellites are strange objects. It is believed that the recent DMSP
satellites are based on NOAA satellites, and that they aren't spinning. So
why do we often observe a flash period of 1.9s with the 90-105A and is it
visible with other DMSP satellites ? Only the 87-53A does have a similar
flash pattern. The latest observation with flashes showed it also te be
flashing with 1.9s on 10 January 1992. The observation came from Peter
Wakelin although he wasn't the first to see it with this period.
Last night I saw 90-105A again in the West, flashing during the whole
transit with 1.9s. The flashes were very clear with invisible minima.
Other transits(in the East) show that this object is mostly steady.
What is the cause of those flashes ?(as I believe that they aren't spinning)
Could it be a strong flashlight system and if so which purpose could it have
as I think that flashlight systems are only usefull for geodetic missions.

94-74B is flashing(1.2s) with a small amplitude. Flashes were only distinct
in the descent fase of its transit. Once passed Polaris, the maximum
magnitude seemed to drop slightly but flashes were much more easy to measure
because of its greater amplitude.

Another interesting object is the 94-68B, the PSLV fourth stage which put
IRS P2 in orbit. The mean period was 6.6s although I must say that
individual flash timings showed it to be varying from 4 to 8s, exactly as my
observation on 23 March. I hope some more observations will follow soon.

I didn't expect to see it but yesterday I saw the 94-85B, the Rokot third
stage which was launched at the end of last year.
It must be rather large(like a Tsyklon upper stage) because of its bright
appearence with a maximum magnitude of 6 to 6.5 compared with a hight of
2100 km. But I think this one is steady.


Tristan Cools
Received on Sun Apr 09 1995 - 12:08:50 UTC

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