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SOLVE SPIDX
CLIC\SOLVE SPIDX [NOREFERENCE] [BEST n] [REAL] [/RESET] [/OUTPUT
file]
Calculate the spectral indexes of the sources in the current index or
the antenna efficiencies (Jansky to Kelvin) if the source spectral index
is known. The command can also be used to bootstrap source spectral in-
dexes from a known source.
It should be used before computing any amplitude calibration, on an in-
dex covering a reasonably short time interval to avoid possible effi-
ciency variations.
The commands should be used in the following way:
- The command SET SPIDX is used to define the spectral index of one,
or several of the sources in the current index for which the spec-
tral index is known. Frequencies and dates may be specified.
- Then the command SOLVE SPIDX will use the sources of known spectral
index (optionally with matching frequencies and dates) to determine
the efficiencies for all antennas. SOLVE SPIDX now gives the decor-
relation factor relative to the efficiencies logged in the scan
headers (assumed to be the standard single-dish efficiencies).
- SOLVE SPIDX then uses these antenna efficiences to compute the spec-
tral indexes of all other sources. IF the keyword "BEST n" is
present, the n antennas giving the highest fluxes will be used for
averaging (n is 1 to the number of available antennas). Default is
n=3.
- The command SHOW SPIDX will give the current spectral index list.
The reference sources are listed with a "FIXED" keyword, while the
spectral indexes determined by SOLVE SPIDX are listed as "FREE".
- SOLVE SPIDX /RESET can be used to reset the spectral index list
(i.e. remove from the list all sources whose spectral index is not
fixed) before processing.
- SOLVE SPIDX /OUTPUT file [NEW] will produce an output file with the
results printed for each antenna. Use keyword NEW to open a new
file.
- The command STORE SPIDX will store the spectral indexes and effi-
ciencies in the headers of the observations in the current index.
If no reference sources are available, the keyword NOREFERENCE should be
given, and the default efficiencies stored in the data header will be
used (step 2 in the above list is bypassed).
The keyword REAL forces SOLVE SPIDX to use the real part of the visibil-
ities instead of the amplitude to derive the antenna efficiencies and
source spectral indexes. This is only for test purposes and must not be
used without asking an expert.
Gildas manager
2024-03-29