A few data reduction commands have been modified because of the new
functionnality offered by the Time data. Major commands include
- SPECTRUM
SPECTRUM has disappeared, because the correlator data is already
pre-calibrated. There is no longer any raw data.
- COMPRESS
COMPRESS now only works on Time data, since the Spectral data is
always scan averaged.
- ATMOSPHERE
ATMOSPHERE is a new command to recompute the atmospheric
calibration. This could formerly be done using the old SPECTRUM
command.
- SOLVE FOCUS
The FOCUS scans are now much like the POINTING scans: 3 scans
are produced instead of 1 previously. The SOLVE FOCUS command
accepts a /COMPRESS option to change the integration time of the
Time data.
- SOLVE POINT
The basic integration step being now 1 second, the sensitivity may be
insufficient in such a time to allow the derivation of antenna based
quantities from baseline visibilities in a pointing. SOLVE POINT
command now accepts a /COMPRESS Time option to allow adjustment of
the integration time of each dump to the source intensity. The default
is /COMPRESS 4, producing something similar to the old correlator.
- SOLVE PSEUDO
Because Time data can correspond to narrow bands, a pseudo-continuum mode
is available for total-power pointing on strong line sources (SiO masers
usually). If one subband group has been selected using command SET SUB,
the signal is the intensity measured by this subband group. If two
subband groups have bean selected (e.g. SET SUB C01 C02 TO C08 the
signal from the second group is subtracted from that of the first group
(which should thus contain the line emission) to produce true
pseudo-continuum data.
- SOLVE DELAY
The delay is no longer measured by scanning the delay line, but by
measuring the phase slope as a function of frequency in the line
subbands. The SOLVE DELAY/PLOT command will fit a straight line to
the phase versus frequency (allowing for 2
ambiguities).
