The search binary searches the sample list to interpolate between the two
samples that straddle a crossing, and a binary search over an unordered
list returns a wrong index instead of failing. Only the first and last
times were checked, so a sequence whose ends were in order but whose
middle was not refined each crossing against the wrong pair of positions
and reported a pass that never happened. On a circular ground track,
shuffling two samples changed the result from three passes to two and
still returned Ok.
The whole sequence is now checked, with a new UnorderedSamples error kind
that says which pair is out of order. The test covers the middle-of-
sequence case that the end check missed.
Two comments also described something other than what the code does, and
two Option-returning accessors did not say what makes them None:
- GravityModel::x2o3 is the constant 2/3, used as an exponent in the
mean motion and drag corrections, not 2 * xke^2 as its comment claimed;
the sgp4 reference implementation uses the same constant the same way.
- WalkerPattern::plane_spacing and phase_offset returned None without
saying so, which is the case a caller has to handle.
Both READMEs claimed twelve expect sites where there are thirteen, because
apsis-math/src/parallel.rs added one and the count was not carried over.
A ground station's access schedule is one search per satellite, each
independent of the others, and a shell gives enough of them to pay for the
threads. The parallel form returns the same summaries in the same order as
the sequential one, including an error at the position the sequential form
would put it, so one bad track does not hide the rest.
ApsisRS contributors