Max-Planck-Institut für Astronomie Heidelberg
(On behalf of the ISOPHOT Consortium and the Instrument Dedicated Team)
The imaging photopolarimeter ISOPHOT performed well during the entire mission: the cryovacuum filter wheels stepped forward 1 million times, the stressed Ge:Ga array behaved excellently, the straylight was negligible. At present the most productive modes seem to be mapping near 200 micron, low resolution spectroscopy for wavelengths shorter than 12 micron and wide beam photometry of extended sources.
Arcminute resolution studies of the cold cirrus in the Milky Way were performed, and in cirrus free regions the extragalactic background studied, including the first resolution of the contributing faint galaxies. Interstellar dust was studied in external galaxies and in numerous galactic sources in different radiation environments, such as faint cirrus clouds and HII regions, where the line ratios of PAH features were studied. Intergalactic dust was studied in galaxy clusters and detected for the first time in Coma. Circumstellar disks have been studied in clusters of different ages; a definite result is that the Vega phenomenon is less frequent than predicted following IRAS. Spatially resolved scans of the Vega and beta Pic discs were obtained.
Far infrared polarization was measured for the first time on quasars, SNRs and asteroids. Several nearby galaxies have been mapped in the far IR; often the cold dust content has increased considerably. The same holds for large samples of luminous galaxies, where in addition, PHT-S spectra allow the energy sources to be identified. The far infrared spectra of several types of quasars were recorded, most of them for the first time. The 175 micron Serendipity mode used 500 h slew time which would otherwise have been lost. The 150 000 degrees strip maps contain information on the galactic structure as well as on the FIR flux of several thousand galaxies.
The photometric calibration of the ISOPHOT data is moving ahead on schedule, despite challenges caused by the influence of cosmic particle hits and signal transients. More than half of the observing modes have now been scientifically validated and have accuracies of 10 .. 30%. The recently installed pipeline version 7, as the first post-mission pipeline, was upgraded in particular for beam size effects of the PHT-C arrays and the orbit dependent dark currents and responsivities. Version 8, now in progress, will correct all chopped measurements and beam size effects of PHT-P. Finally, version 10, to be released in 2001 will contain more orbit dependent corrections, such as space weather influences. The ISOPHOT Data Centre at MPIA Heidelberg is meanwhile offering help on an individual basis.