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This document provides an overview of global calibration accuracies for the
ISOPHOT
instrument. It will be updated whenever revised or additional information will
be available. This can be expected in the context of an upgraded OLP version
which will involve a scientific validation of the products. The scientific
validation of a specific observing mode comprises the end-to-end evaluation
of a set of test cases, including the comparison with reference photometry
(high quality photometry from other observatories, standard star models, etc.).
This allows to establish the global calibration accuracies.
This version of the document contains information on
- 1)
- the photometric accuracy for point sources (including PHT-S)
- 2)
- the photometric accuracy for extended sources (including PHT-S)
- 3)
- polarimetric accuracy (including instrumental polarisation)
- 4)
- accuracy of PHT-S wavelength calibration
For an individual description of the well characterised instrumental effects,
please
refer to the ISOPHOT Data User Manual, for an overview
of the impact of
individual calibration steps on the accuracy, please refer to the
ISOPHOT
Error Budgets Document.
The two polarisation modes PHT50 (PHT-P) and PHT51 (PHT-C) are not end-to-end
processed by the OLP pipeline. Please contact the ISOPHOT Data Centre in
Heidelberg
or the ISO Data Centre in Villafranca for details of the data reduction and
calibration.
Currently there are instrumental effects of ISOPHOT which are not yet fully
assessed and
characterised. This means
- 1)
- the OLP processing of an invidual observation submode is not yet
declared
scientifically valid and no global calibration accuracies can be
provided.
An overview of the ISOPHOT Astronomical Observation Template (AOT)
validation
status is given in Table 1.2. This table
also lists planned
upgrades for both validated and unvalidated modes as well as the OLP
version
for which the upgrade is foreseen.
- 2)
- under certain circumstances, usage of extraordinary set-ups in a
validated
mode may have a significant impact on the final calibration accuracy
of a given measurement. Please consult the Caveat chapter
of the
ISOPHOT Data User Manual to which degree a certain observational mode
could be
affected.
Table 1.2:
Status of Scientific Validation of ISOPHOT OLP AOT Processing, July
98.
AOTs PHT03 - PHT19 are photometric modes with subinstrument PHT-P,
AOTs PHT22 - PHT39 are photometric modes with subinstrument PHT-C,
AOT PHT40 is the spectroscopic mode of PHT-S. AOTs PHT50 and PHT51
are
the two polarimetric modes with PHT-P and PHT-C, respectively. They
are processed by the pipeline only to raw data level. For a detailed
definition
of the individual AOTs, please refer to the ISOPHOT
Observer's Manual.
|
|
|
|
|
|
|
|
AOT |
observation |
submode |
scientifically |
next
upgrades |
foreseen in |
|---|
|
|
type |
|
valid since |
|
OLP Vx.y |
|
|
|
|
|
|
|
|
PHT03(P) |
multi- |
staring point source |
V6 |
non-lin R
& FCS aper |
8.2 |
|
|
filter |
staring ext. source |
no |
beam |
8.2 |
|
|
photometry |
nodding |
V6 |
non-lin R
& FCS aper |
8.2 |
|
|
|
chopped point source |
no |
chop |
8.2 |
|
|
|
raster map |
no |
map cal &
drift |
8.2/9.2 |
|
PHT04(P) |
multi- |
staring point source |
no |
beam &
FCS aper |
8.2 |
|
|
aperture |
staring ext. source |
no |
beam |
8.2 |
|
|
photometry |
chopped point source |
no |
chop &
beam |
8.2 |
|
PHT05(P) |
absolute |
staring point source |
V6 |
FCS aper |
8.2 |
|
|
photometry |
staring ext. source |
no |
beam |
8.2 |
|
PHT17(P) |
sparse map |
staring point source |
V6 |
non-lin R
& FCS aper |
8.2 |
|
18,19 |
photometry |
staring ext. source |
no |
beam |
8.2 |
|
PHT22(C) |
multi- |
staring point source |
V7 |
non-lin R |
8.2 |
|
|
filter |
staring ext. source |
V7 |
non-lin R |
8.2 |
|
|
photometry |
nodding |
V7 |
non-lin R |
8.2 |
|
|
|
chopped point source |
no |
chop |
8.2 |
|
|
|
raster map |
no |
map cal &
flat-field |
9.2 |
|
PHT25(C) |
absolute |
staring point source |
V7 |
|
|
|
|
photometry |
staring ext. source |
V7 |
|
|
|
PHT32(C) |
oversampled |
chopped mapping |
no |
chop &
map cal |
9.2 |
|
|
mapping |
|
|
|
|
|
PHT37(C) |
sparse map |
staring point source |
V7 |
non-lin R |
8.2 |
|
38,39 |
photometry |
staring ext. source |
V7 |
non-lin R |
8.2 |
|
PHT40(S) |
spectroscopy |
staring point source |
V5 |
|
|
|
|
|
staring ext. source |
V6 |
beam |
8.2 |
|
|
|
chopped point source |
V6 |
|
|
|
PHT50(P) |
aperture |
staring point & |
V7 |
interactive processing |
|
|
|
polarimetry |
ext. source |
|
& special FORTRAN routine |
|
|
PHT51(C) |
array |
staring point & |
V7 |
interactive processing |
|
|
|
polarimetry |
ext. source |
|
& special FORTRAN routine |
|
|
|
|
raster |
V7 |
|
|
meaning of calibration upgrades:
non-lin R : correction for non-linearity of detector responsivity
for measurement sets covering a large flux range
FCS aper : correction for inhomogeneous illumination of PHT-P apertures by FCS
beam : beam profile corrections
chop : chopped photometry corrections
map cal : surface brightness calibration in maps
drift : correction of non-linear lon-term drifts
flat-field : refined flat-field corrections
Next: 2 Photometric Accuracies
Up: 1 Introduction
Previous: 1.1 Short Instrument Overview
ISOPHOT Calibration Accuracies, Version 2.0, SAI/98-092/Dc