Calculate the distance between two points in a Frame AST_DISTANCE
For example, in a basic Frame, the distance calculated will be the Cartesian distance along the straight line joining the two points. For a more specialised Frame describing a sky coordinate system, however, it would be the distance along the great circle passing through two sky positions.
This function will return a "
bad"
result value (AST__BAD) if any of the input coordinates has this
value.
A "
bad"
value will also be returned if this function is invoked with STATUS set to an error value, or if
it should fail for any reason.