Optical alignment verification of the Herschel-SPIRE instrument

摘要

The SPectral and Photometric Imaging REceiver (SPIRE) will be launched in 2007 as one of three instruments on ESA's sub-millimetric space telescope Herschel. It covers the 200-670 micron spectral range with a three-band, 4'x8' field-of-view (FOV) photometer and a dual-band, 2.6' diameter FOV imaging Fourier transform spectrometer. Alignment verification of the instrument is accomplished optically by means of OGSE based on classical alignment telescopes and specially designed equipment. The main purpose of this process is to make sure the internal instrument cold stop is aligned with the telescope exit pupil, and that it stays aligned as the instrument is taken down to its 4K operating temperature. Optical alignment verification also includes measurement of pupil imaging quality and characterisation of the instrument wavefront error. For the latter, a Hartmann test is implemented, allowing estimation of the main aberration terms and comparison with the ideal instrument. This paper describes the philosophy of the alignment plan and presents the main results obtained during alignment of the structural and thermal model.