XMM-Newton Users Handbook

4.2.2 Celestial constraints

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

• 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 and thermal stability.

  For the same reasons, the position angle of the observation must be within $\pm20^{\circ}$ of the nominal position angle as defined in § 4.4.2

• Earth limb avoidance

  Minimum avoidance angle: 42.5$^\circ$.

• Lunar avoidance

  Nominal minimum avoidance angle: 22$^\circ$.
  Minimum avoidance angle during eclipses: 35$^\circ$.