Support extracting UTC ISOTime from 'GPS' and 'TT' timescales. #5
Description
The VOEvent spec specifies that timestamps (TimeInstant) for event details in the WhereWhen section can use the follow timescale standards:
UTC (Coordinated Universal Time [26]), TT (Terrestrial Time, currently 65.184
seconds ahead of UTC), GPS time, or TDB (Barycentric Dynamical Time).
The pull_isotime convenience routine currently supports extracting/converting UTC timestamps from UTC and TDB format.
If I understand correctly, TT and GPS timestamps should be specified using the TimeOffset sub-element of the TimeInstant, because that's how those standards work - but this isn't actually made explicit in the VOEvent standard, and there's no example other than UTC time. As a result I'm putting off implementing this until there's actually a use-case / example packet for it. If you have one, get in touch and I'll be happy to help with it.