Scientific Mission Planning and Scheduling

 

For each ISO revolution, that is the time the satellite passes once through the orbit, a schedule of astronomical observations is needed. It is generated with the scientific mission planning software, also known as Mission Planning Phase 1 (MPP1), which then translates this schedule into a timed sequence of instrument and spacecraft commands which are uplinked for execution.

The two main inputs to MPP1 are

1. information on SKY VISIBILITY,
2. OBSERVATIONS, including SCIENTIFIC GRADE.

For planning purposes the sky is divided up into sky bins of 10 by 10 degrees each. A data base is available to MPP1 which, per sky bin, contains all occasions when this bin is accessible without violating attitude constraints (described in Section 2.2.2). For any given revolution ISO can, due to attitude constraints, only view a limited area of the sky, which is about 12% of the sky.

The philosophy behind mission planning is to maximize the scientific return from the ISO mission. The selection of observations for a particular revolution is based on the sky visibility for that revolution along with a combination of parameters such as scientific grade, instrument mode, expected flux and others. On the basis of these, MPP1 produces a schedule with the aim to achieve a high efficiency, i.e. by minimizing spacecraft (cf. Part III) and instrument overheads.

Whether and when a specific observation is scheduled for execution depends on

• the number and duration of observations requested for that particular region of the sky (the sky bin) that have a similar or higher priority;
• the duration for which the sky bin containing the target is accessible under the ISO pointing constraints;
• the overlap in the sky bin's visibility with other bins that could be observed at the same time.

During the complete ISO operational phase (24 months) more than 90% of the sky will be visible.