Environmental Engineering Reference
In-Depth Information
Virtual platform
A “virtual spacecraft” whose “payload” is composed of
the instrument(s) or payload(s) aboard two or more “real” spacecraft. By
extension, the virtual payload may also include instruments located at
ground-based observatories.
Zenith
In the context of the gravitational field of a massive body, the zenith
at a given point is the direction opposite to the force of gravity at that
point. See Nadir.
Zenith-pointer
A spacecraft whose primary science instrument(s) is (are)
directed “up” along the local vertical (i.e., along the zenith vector).
