Search

Herschel cryogenics instrument (HIFI, PACS, SPIRE) flight models have been delivered to ESA & Prime contractor Thales Alenia Space mid 2007, to be integrated and tested on the Herschel spacecraft, for a launch mid May 2009. The instrument integration and test campaign at spacecraft level was performed between mid 2007 and end 2008 in Astrium GmbH, Immenstadt (Gernany) and later in ESA’s test facilities at Estec, Noordwijk (Nederland). The objective of these tests was to demonstrate full operability and performances of the instruments in spacecraft configuration, and their compatibility with the launch and space environment, while maintaining full compliance with the underlying requirements. A set of short functional tests were developed and used repeatedly to quickly check the health of each instrument at key points in the test campaign. Typically, this was after integration of a major component, prior to a major environmental test or before/after movement of the spacecraft. A set of full functional tests were also performed after launch vibration tests, and during Thermal vacuum test in order to provide a more complete picture of the instruments functional health. Finally a set of unstrument specific tests were performed to verify the performance of the instrument under the most representative operational conditions possible on ground (i.e. the environmental test compaign). The paper will describe instruments and the instruments related tests performed at spacecraft level, focusing on cryogenics aspects. [ABSTRACT FROM AUTHOR]

The bolometers (and readout circuitry) in the SPIRE instrument on the Herschel Space Observatory are among the best understood and well characterised of any sub-mm astronomy instrument to date. SPIRE contains five arrays of NTD germanium spiderweb bolometers with up to 139 pixels per array. Their behaviour has been shown to be extremely stable as seen by repeated measurements in the years between initial array level and final instrument level tests, and can be described extremely well by a simple physical model (the ideal bolometer model). Calibration of the bolometers must take into account the non-linear response when viewing bright sources, and the effect of fluctuations in the heat sink temperature. The simple and well-understood behaviour of the detectors, coupled with the stable conditions expected in flight, mean that in contrast to previous sub-mm instruments, physical models can be used to improve or possibly replace empirical calibration methods. We describe how this can be done, and use the large amount of data from ground measurements to show that we can use models to accurately calculate the absolute power detected by the bolometers. [ABSTRACT FROM AUTHOR]