Re: IUE, etc
Fri, 27 Mar 1998 19:20:28 +0100

Juergen Faelker, the former IUE Spacecraft Operation Manager, read abou=
your observation and sent me this
comment I am forwarding to you.


What your collegues have observed is likely to be the decommissioned IU=
spacecraft. I should mention that the S/C has not  self-destroyed itsel=
What has been done at end of life  was to vent the remaining Hydrazine =
17.7 Kg), to discharge the batteries and to switch off the s-band
transmitter (30 September 96 at 18:44 UT) with the goal to prevent
destruction of the craft and hence, not to create unnecessary space deb=
Venting the hydrazine has a delta-v effect. In the case of IUE this was=

primarily done to spin-up the S/C about  the  Roll axis (X-axis) and in=

negative (-) sense after the S/C was put before in a positive (+) spin
about the roll axis, i.e. to compensate for and not to introduce a very=

fast spin, which would have caused a rupture of the solar array hinges.=

Since no attitude control was available during the venting of the hydra=
it was done in an uncontrolled way.

X-axis and the  flashes observed most likely stem from the two solar ar=
mounted along the S/C  =B1  Y-axis. The structure of the IUE solar arra=
ys  is
as follows:     Each of the two fixed solar arrays has 3 sub-panels. Th=
lower and upper panels are mounted =B1 45 =B0  offset from the centre p=
The latter is tilted  - 22.5 =B0 from the telescope + X -axis (telescop=
boresight). When the solar arrays are  facing the Sun,  reflections sho=
be seen but it is rather difficult to pinpoint  the relation between
flashes, solar arrays and the  S/C body, which is of octagonal structur=

You may forward this info to your collegues.