covers method
override
Whether the files have data for target at et – along the whole
chain up to the solar system barycentre.
Implementation
@override
bool covers(int target, double et) {
for (var b = target; b != Naif.solarSystemBarycenter;) {
final segment = _segmentOrNull(b, et);
if (segment == null) return false;
b = segment.center;
}
return true;
}