Renewed request for observations of Abrixas

Roland Vanderspek (roland@space.mit.edu)
Wed, 9 Jun 1999 13:36:26 -0400 (EDT)

Dear Seesatters:

I have received a new request for observations of ABRIXAS from the
ABRIXAS team at Potsdam.  Their golden window of opportunity to
reacquire ABRIXAS starts in a couple of weeks, so observations soon
are important to them.  

I attach a note from the team at AIP which describes the state of
observations and things to look for.

Thanks.

Roland Vanderspek
roland@space.mit.edu




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Request for Observation of the Satellite ABRIXAS (NORAD Number 25721)
=====================================================================

The scientific institutes involved in the astronomical X-ray
satellite ABRIXAS ask for further observations of the satellite.
In particular, the interest is directed to the light variations 
and eventually flashes from directly reflected sunlight.

The aim is to determine the rotation behaviour of ABRIXAS.

Video observations are potentially very useful to record the 
possibly faint periodic light variations.
 
 
Background:
-----------

Because of the failure of the batteries ABRIXAS is in a severe
situation; the knowledge about its rotation can be of great 
importance for the revival planned for the next weeks since 
it is essential to reestablish the contact to the satellite 
and send commands at the right time.

In addition to the optical observations it is planned to obtain 
information from radar measurements. A first result suggests  
that the satellite is tumbling in a complex mode with a main 
period of about 177 seconds.
 
 
Hints for observations:
-----------------------

Apart from the solar panel itself reflections can occur at the edges
of the solar panel array and at the inner side of the radiator's 
thermal baffle. The satellite is almost completely wrapped in a
diffusely reflecting white MLI foil. Because of the elongated shape
of ABRIXAS some variations of the satellite's brightness are expected
within each rotation period.

Sketches and photos of the satellite can be found on the following
web page:
http://www.aip.de/groups/xray/abrixas/abrixas_observation.html

The current orbit data can be taken directly from NORAD 
(http://oigsysop.atsc.allied.com/scripts/foxweb.dll/homepage@app01) 
or from GSOC (http://www2.gsoc.dlr.de/scripts/satvis/satvis.asp)