Bibcode
Lemke, Dietrich; Klaas, Ulrich; Abraham, P.; Acosta Pulido, J. A.; Castaneda, H.; Cornwall, L.; Gabriel, C.; Groezinger, Ulrich; Haas, M.; Heinrichsen, Ingolf; Herbstmeier, Uwe; Schubert, Josef; Schulz, Bernhard; Stickel, Manfred; Toth, L. V.
Bibliographical reference
Proc. SPIE Vol. 3354, p. 627-636, Infrared Astronomical Instrumentation, Albert M. Fowler; Ed.
Advertised on:
8
1998
Citations
0
Refereed citations
0
Description
The imaging photopolarimeter ISOPHOT on-board the European satellite ISO
houses 144 background detectors of Si:Ga, Si:P, Ge:Ga and stressed
Ge:Ga, all sampled by newly developed cold read-out electronics. There
is large temporal radiation damage to most of these detectors on the
daily passage through the earth's radiation belts. In addition the Ge:Ga
detectors exhibit a continuous responsivity increase caused by the
cosmic radiation far off the earth. Effective curing procedure shave
been developed to heat out these effects. The in-flight sensitivities
achieved are close to the pre-flight predictions for most channels. At
100-200 micrometers cirrus confusion is a serious limit for the
detection of faint objects on large parts of the sky. The cold filter
wheel carrying 56 optical elements, such as filters, apertures and
polarizers, as well as the focal plane chopper, operate with high
precision and very low power consumption. Due to an effective cold
internal baffle system the measured near-field straylight was close to
the pre- flight theoretical prediction based on APART simulations. THe
sun and moon straylight at 25 and 175 micrometers was measured during
several solar eclipses. Drift and transients of the detectors,
non-linearities of the preamplifiers, ionizing radiation effects and a
complex optical path make the photometric calibration of this instrument
challenging. Because most of these effects are reproducible, a
calibration accuracy of < 30 percent is already available for most
photometric modes. Examples of observations, including the 175
micrometers Serendipitous Sky Survey, will highlight the capabilities of
the instrument.