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Subsections

• 4.9.1 Confusion
• 4.9.2 Zodiacal Light

4.9 Backgrounds  

During performance verification phase and routine phase the PHT Instrument team together with the PHT Consortium have undertaken programmes to investigate the astronomical backgrounds.

A study of the infrared background structure due to infrared cirrus and extragalactic emission based on ISOPHOT data can be found in Herbstmeier et al. 1998 [8].

4.9.1 Confusion

See ISOPHOT observers manual [10] Chapter 4 and [8].

4.9.2 Zodiacal Light

For many types of ISOPHOT observations knowledge of the emission contribution from the zodiacal dust cloud is necessary. Data from COBE can be used but have to be adapted to the higher angular resolution observations of ISOPHOT. Absolute photometric observations in a number of ISOPHOT bands at several ecliptic longitudes/latitudes were obtained to establish the zodiacal emission distribution as seen by ISO. These observations will be applied for the adaptation of the COBE data for ISOPHOT purposes.

COBE did not cover wavelengths between 5 and 12 m, in the range where the brightness of the zodiacal light rises very steeply. The first results obtained with PHT-S, PHT-P and ISOCAM suggest that the zodiacal emission spectrum can be well approximated by a blackbody of  260 K. In addition, ISOCAM CVF and ISOPHOT-S measurements demonstrated that the spectrum is featureless between 5 and 16 m.