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The purpose of adding elements in the HDUs when they are missing is
that the libmrtcal does not have to worry about this element existing
or not, and and doing different things (different code) in one case or
the other. The following elements are added:
- POLEX and POLEY are absent under V1.35: they are
defined and default to 0,
- SYSOFF, XOFFSET, and YOFFSET columns in the
Scan table can have 0, 1, or 2 rows. They are forced to 2 rows
providing Nasmyth and projection offsets (default to 0
if they were absent),
- the LINENAME column in the BackEnd HDU is built from the
LINENAME column in the FrontEnd HDU for IMB-FITS version lower
than 2, or for 4MHz backend,
- MJD_BEG and MJD_END keywords are added as
convenient duplicates of DATE-OBS and DATE-END keywords
in all HDUs of each subscan. They offer MJD values instead of ISO
strings,
- the column TSTAMPED is added to BackendDATA tables in
IMB-FITS version lower or equal to 1.35. Its defaults to 1. Remember
that this value is sensitive (it introduces a shift on the time
stamps) and is actually backend-dependent.
- an IFRONT column is added as a convenient backpointer from
the BackEnd table to the FrontEnd table, i.e. each chunk knows
easily to which receiver it is associated.
Next: Modified elements
Up: Patching IMB-FITS at read
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Gildas manager
2023-06-01