XMM Users' Handbook

   
Celestial constraints

The visibility of sources on the sky depends on several constraints, including avoidance of solar system sources. These are:

• Earth limb avoidance

  Minimum avoidance angle: $47^\circ$.

• Solar avoidance

  A solar aspect angle within the range $70^\circ -110^\circ$ must be maintained at all times. Note that this is not a bright source avoidance cone, but driven by requirements on the spacecraft's alignment with respect to the Sun to ensure sufficient energy supply.

• Lunar avoidance

  Minimum avoidance angle: $22^\circ$.

The numbers listed here coincide with the avoidance angles used by the XMM Target Visibility Tool.