Astron. Astrophys. Suppl. Ser. 141, 533-544
Transient correction of the LW-ISOCAM data for
low contrasted illumination
A. Coulais - A. Abergel
Send offprint request: A. Coulais
Institut d'Astrophysique Spatiale,
Bâtiment 121, Université Paris XI,
91405 Orsay Cedex, France
Received May 25; accepted September 15, 1999
The detector of the Long Wavelength channel of the ISOCAM camera on-board
the Infrared Space Observatory (ISO) presents systematic memory effects
of the response which can bias the photometry by a factor as high as 40
We show that, for uniform illumination,
the non linear
model developed by Fouks and Schubert
for the detector of
PHT-S channel of the ISOPHOT instrument allows us to
describe the LW-ISOCAM response to
upward and downward steps of flux with an accuracy better than 1
For each pixel of the detector, only two parameters have to be used.
These parameters are constant over the whole life of ISO.
On the other hand, spatial variations from pixel to pixel are significant.
We present an inversion method of the Fouks-Schubert model. Without
any fitting and for low contrasted illumination, data are corrected with
a photometric accuracy of
which is typically ten times better
than previous methods. We suggest that the same approach could be used
for others ISO detectors, and in the future for other experiments.
Key words: instrumentation: detectors -- methods: data analysis -- methods: numerical
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