ISOPHOT - Photometric Calibration of Point Sources

Abstract

All observations by the aperture photometer (PHT-P) and the far-infrared (FIR) camera section (PHT-C) of ISOPHOT included reference measurements against stable internal fine calibration sources (FCS) to correct for temporal drifts in detector responsivities. The FCSs were absolutely calibrated in-orbit against stars, asteroids and planets, covering wavelengths from 3.2 to 240 micron. We present the calibration concept for point sources within a flux-range from 60 mJy up to 4500 Jy for staring and raster observations in standard configurations and discuss the requisite measurements and the uncertainties involved. In this process we correct for instrumental effects like nonlinearities, signal transients, time variable dark current, misalignments and diffraction effects. A set of formulae is developed that describes the calibration from signal-level to flux densities. The scatter of 10 to 20 % of the individual data points around the derived calibration relations is a measure of the consistency and typical accuracy of the calibration. The reproducibility over longer periods of time is better than 10 %. The calibration tables and algorithms have been implemented in the final versions of the software for offline processing and interactive analysis.

21 pages, 16 figures, 5 tables, accepted by Astronomy & Astrophysics

Cited by in corpus (11)

• The Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory
• Absolute Calibration and Characterization of the Multiband Imaging Photometer for Spitzer. I. The Stellar Calibrator Sample and the 24 micron Calibration
• Absolute Calibration and Characterization of the Multiband Imaging Photometer for Spitzer. III. An Asteroid-based Calibration of MIPS at 160 microns
• The ISOPHOT-MAMBO survey of 3CR radio sources: Further evidence for the unified schemes
• Calibration and Performance of the AKARI Far-Infrared Surveyor (FIS) -- Slow-Scan Observation Mode for Point Sources
• The AKARI FIS YSO Catalogue
• Mid- to Far-Infrared spectroscopy of Sharpless 171
• Photometric Mapping with ISOPHOT using the "P32" Astronomical Observation Template
• A far infrared view of the Lockman Hole from ISO 95 $\mu$m observations - I. A new data reduction method
• Systematic characterisation of the Herschel SPIRE Fourier Transform Spectrometer
• Far-Infrared and Millimeter Continuum Studies of K Giants: Alpha Boo and Alpha Tau