Target visibility rules have been updated

- Implication for user: Shortly before launch it was decided to slightly reduce the area of sky visibility for Herschel. The new sky visibility is from 60.6 to 119.4 degrees solar elongation (previously 60 to 120 degrees). This has slightly reduced the visibility windows for targets near the ecliptic (typically by about 1 day) and has a somewhat larger effect close to the zone of permanent visibility.

Warning

This change does not take into account an important issue with spacecraft pointing that has been found in flight. When the solar elongation is greater than 110 degrees, the star trackers receive direct sunlight and start to heat. This has been shown to degrade seriously telescope pointing for several hours afterwards until the startrackers have cooled again. The practical effect is that the scheduling of objects at solar elongations greater than 110 degrees has had to be restricted very seriously (no AORs with duration longer than 1 hour will be scheduled at all in this zone). A patch for HSpot 5.0 that provides this information to observers is currently under testing at HSC.

The AOR overlay bug has been fixed.

- Implication for user: HSpot 4.2 and 4.3 would often refuse to display an AOR overlay unless an extremely large image was defined. This was an extremely irritating problem for users, although a workaround could be found. This bug has now been fixed and AOR overlays work correctly.