Optimum observing modes for the Herschel/SPIRE photometer system

Abstract

SPIRE is one of three instruments on board ESA's Herschel space observatory, due for launch in 2008. The instrument comprises both a photometer and Fourier transform spectrometer. The Herschel mission has a limited operational lifetime of 3.5 years and, as with all space-based facilities, has very high development and operational costs. As a result observing time is a valuable and limited resource, making efficiency of crucial importance. In this paper we present recent results derived from the SPIRE photometer simulator, detailing the optimum observing mode parameters to be employed by the Herschel/SPIRE system. We also outline the efficiency of various modes, leading to the conclusion that scan mapping is the optimal mode for the mapping of regions greater than ∼4 × 4 .

The Herschel–SPIRE instrument and its capabilities for extragalactic astronomy

“…The good 1/f stability of the detectors means that the beam steering mirror does not need to be operatedsignal modulation is provided by the telescope motion. To give the beam overlap needed for full spatial sampling over a strip defined by one scan line, and to provide a uniform distribution of integration time over the area covered by the scan, the optimum scan angle is 12.5°with respect to one of the array axes (Sibthorpe et al, 2006).…”