Next: Patching IMB-FITS at read
Up: mrtcal-prog-manual
Previous: Contents
Contents
When a new scan is prepared6.1 at the telescope, the
associated IMBFITS file name is constructed with the current date. Later
in this process (up to several minutes after), the scan is actually
started6.2, and the current date and time are used to build
the MJD-OBS and DATE-OBS in the FITS Primary
header. If those two steps are performed exactly before and after midnight
respectively, the file name and the Primary header refer to 2 different
dates, e.g.
iram30m-fts-20120809s323-imb.fits:
MJD-OBS = 56149.0038078704 / MJD at observation start
DATE-OBS= '2012-08-10T00:05:29.000'
For several purposes, MRTCAL saves the observing date and time of
each file in the index. In order to deal correctly with the above issue, it
is decided
- to save the date as found in the file name, so that there is no
difference for the user between the file name and the date exposed by
MRTCAL;
- the time value saved for this file refers to the above date.
The direct consequence of those 2 rules is that, in case of the midnight
issue exposed above, the UT value will be larger then 24h. Note that the UT
value associated to each file is saved for bookkeeping purpose, e.g. for
analysis of the calibration though date and time. It is considered as a
typical value for the whole scan. Each individual spectrum produced by
MRTCAL uses its own date and time.
In details, the observing date saved in the index is used
- to check the entry uniqueness (date, scan and backend triplet should
be unique),
- to sort the entries (by date, scan and backend),
- through the command MFIND /DATE,
- in the output of the command MLIST,
- in the Sic variables MDX%DOBS and
MHEAD%KEY%DOBS
and the associated UT value is used
- to sort the entries,
- in the output of the command MLIST,
- in the Sic variables MDX%UT and MHEAD%KEY%UT
The user should be ready to encounter UT values larger than 24h in the
MLIST output and larger than
in the Sic variables.
Next: Patching IMB-FITS at read
Up: mrtcal-prog-manual
Previous: Contents
Contents
Gildas manager
2023-06-01