9.5.  Bright Moving Object Avoidance

Bright inertial objects are automatically avoided when planning observations using the Herschel Bright Objects for AOR overlay described in Section, “ Add Moving Target ”. HSpot automatically reduces the visibility window if a bright object (Earth, Moon, Mars, Jupiter, Saturn, Uranus, Neptune, and the asteroids 4 Vesta, 6 Hebe, 1 Ceres, 7 Iris, and 15 Eunomia) passes close to your source.

The visibility window will be adjusted to preclude times when your target coordinates are within 7 degrees of the Earth and Moon, or within 30 arcminutes of other objects. The Earth and Moon can only interfere at extreme positions of the Herschel orbit. They will usually remove a small amount of time at the start or end of a visibility window. Bright planets and asteroids may cause a visibility window to be broken into two. If this happens the "Target Visibility" window will display a message in red stating that the visibility windows have been reduced to avoid bright moving objects.

Solar system observers planning to observe an object, or satellite of an object, on the bright moving object list (e.g., Neptune or Triton) can still observe without difficulties. HSpot is smart enough to know that you do not want to avoid your selected target.

For a fixed target near the ecliptic the visibility window will typically be about 60-65 days twice each year. Summer visibility windows will be longer than their winter equivalents because the Earth is at aphelion and thus moving more slowly in early July and at perihelion in early January and thus moving more quickly. The difference in length of visibility window is 3-4 days. At higher declinations the visibility window will increase until it reaches permanent visibility for objects within 30 degrees of the ecliptic pole.