ISOPHOT: In-flight performance report

Dietrich Lemke, Ulrich Klaas, P. Abrahám, J. A. Acosta Pulido, H. Castaneda, L. Cornwall, C. Gabriel, Ulrich Grözinger, M. Haas, Ingolf Heinrichsen, Uwe Herbstmeier, Josef Schubert, Bernhard Schulz, Manfred Stickel, L. V. Tóth

Research output: Contribution to journalConference article

2 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)627-636
Number of pages10
JournalProceedings of SPIE - The International Society for Optical Engineering
Publication statusPublished - Dec 1 1998
EventInfrared Astronomical Instrumentation - Kona, HI, United States
Duration: Mar 23 1998Mar 23 1998

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering

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  • Cite this

    Lemke, D., Klaas, U., Abrahám, P., Acosta Pulido, J. A., Castaneda, H., Cornwall, L., Gabriel, C., Grözinger, U., Haas, M., Heinrichsen, I., Herbstmeier, U., Schubert, J., Schulz, B., Stickel, M., & Tóth, L. V. (1998). ISOPHOT: In-flight performance report. Proceedings of SPIE - The International Society for Optical Engineering, 3354, 627-636.