The Source rule, which picks what a position or a Pass is computed from:
the Ephemeris when it covers every instant
of the interval and was issued less than freshnessDays before now,
otherwise the Elements. For a single instant, pass an interval of no
length; for a Pass search, extend the interval by longestPassSeconds at
both ends.
How long an Ephemeris keeps answering after it was
issued, in days: how far the caller trusts an operator's prediction over
fresher Elements is a policy, not geometry, so the caller states it.
The Source rule, which picks what a position or a Pass is computed from: the Ephemeris when it covers every instant of the interval and was issued less than
freshnessDaysbeforenow, otherwise the Elements. For a single instant, pass an interval of no length; for a Pass search, extend the interval bylongestPassSecondsat both ends.