This attribute controls how a TimeFrame behaves when it is used (by
AST_FINDFRAME or AST_CONVERT) as a template to match another (target)
TimeFrame. It identifies the time scale in which alignment is
to occur. See the TimeScale attribute for a desription of the values
which may be assigned to this attribute. The default AlignTimeScale
value depends on the current value of TimeScale: if TimeScale is
UT1, GMST, LMST or LAST, the default for AlignTimeScale is UT1, for all
other TimeScales the default is TAI.
When AST_FindFrame or AST_CONVERT is used on two TimeFrames (potentially
describing different time coordinate systems), it returns a Mapping
which can be used to transform a position in one TimeFrame into the
corresponding position in the other. The Mapping is made up of the
following steps in the indicated order:
- Map values from the system used by the target (MJD, JD, etc) to the
system specified by the AlignSystem attribute.
- Map these values from the target's time scale to the time scale
specified by the AlignTimeScale attribute.
- Map these values from the time scale specified by the AlignTimeScale
attribute, to the template's time scale.
- Map these values from the system specified by the AlignSystem
attribute, to the system used by the template.