Flight Experience with the ROSAT Mission Planning System

R. Swoboda, H. Frank, D. Garton
swoboda@gsocmail.rm.op.dlr.de
CAM GmbH, DLR

Abstract:
ROSAT (ROentgen SATellit) is a scientific spacecraft designed to 
perform the first all-sky survey with a high resolution X-ray 
telescope and to investigate the X-ray emission of specific celestial 
objects. The scientific payload consists of two X-ray telescopes: a 
high resolution imager and a position sensitive proportional counter.
In addition there is a wide-field camera to observe in the extreme 
ultra-violet part of the spectrum.

The mission can be broadly divided into three main phases: the test
and calibration phase, the survey phase and the pointing phase. 
These three mission phases present very different requirements on 
a mission planning system. The generation of the mission timelines 
is performed by a system written at the German Space Operations 
Center called the ROSAT Mission Timeline Generator (RMTG). 
It is a menu based, interactive system providing the user interface 
functions needed for the calibration phase, automatic generation of 
the survey timeline and automatic generation of an optimised 
timeline for the pointing phase. The system has been in use
since the launch in June, 1990.

It is the main purpose of this article to present an evaluation of the
performance of the RMTG and the experience gained from mission 
planning in general on the ROSAT satellite over the past 6 years. 
The discussion includes the basic philosophy behind the mission 
planning such as the influence of the high-energy particle belts and 
the division into long and short-term planning activities. Interaction 
with the scientific management of the project (the Max Planck 
Institut für Extraterrestrische Physik in Garching) and with the 
attitude management and command systems is considered. The 
adaptation of the system to the many problems such as loss of 
gyros and degradation of star trackers which have beset ROSAT 
is also discussed. In each case, the advantages and disadvantages 
of the chosen approach will be presented. 

The article concludes with a discussion of the impacts of the 
lessons learned on mission planning of other satellites.