converts signal into fluxes:
fluxcon performs the flux conversion from signal in [µV/s] to
flux density in [Jy]. The photometric check is used to include the current
performance of the individual detectors in the flux calibration:
- the measured signal is multiplied by the ratio of the known flux of an
astronomical calibration target over its observed signal at key-wavelenghts
determined during calibration observations.
- this scaling factor is weighted by the ratio of the current photometric
response of the detectors over their photometric response at the time of
the calibration observations.
- the photometric response is determined by the photometric check, a short
scan of a spectral feature of the grating calibrator source.
- currently only the first photometric check with
GRCAL=LOW appearing in the data is used; if there are more
photometric checks they are ignored.
- band 1 photometric checks with GRCAL=HIGH are not
used at all, unless the keyword /grcalhigh is set.
- such photometric checks are only present in observations from the very
beginning of the mission (see comment below).
Cal-files:
Help text: IA auto analysis
Comment on band 1 photometric checks:
The grating calibrator used for the photometric checks illuminates all detector
arrays simultaneously. It can be operated at two levels: LOW
and HIGH. While a photometric check with
GRCAL=LOW is sufficient to flux calibrate band 2 to band 4 detectors,
the flux calibration of band 1 requires a photometric check with
GRCAL=HIGH. This high-level photometric check has, because of memory
effects, a disastrous influence on the long-term behaviour of the other bands,
especially of band 4, for which it can even affect the following AOT! As it
turned out during PV-phase, that band 1 photometric checks are rather constant
in time and vary definitely less than the error quoted for the flux calibration
of this band, photometric checks with GRCAL=HIGH were
dropped. Flux calibration for band 1 since then is solely done by scaling with
the ratio of known flux over observed signal from the calibration observations.
Warning:
During execution fluxcon reports the number of unvalid (e.g. glitched)
data, detected in the photometric check used. If this number exceeds two, a
careful look at the photometric check with the plot_phot tool is
strongly recommended.
If fluxcon reports unvalid data for all data of the photometric check,
its highly probable, that the user tries to perform the photometric check for
the second time.
SWS TUTORIAL /
PIPELINE /
SPD to AAR : ...
respcal <
fluxcon >
velcor ...
Last update: 30-Jul-1998 by D. Kunze ( mail to:
isodata@mpe.mpg.de )