ESA Science & Technology - Herschel-SPIRE Testing at ESTEC

The Herschel cryostat and mock-up SVM in the ESTEC cleanroom

The Herschel flight cryostat was equipped with a mechanical thermal dummy of PACS (Photodetector Array Camera and Spectrometer) FPU (Focal Plane Unit), and the cryogenic qualification models of HIFI (Heterodyne Instrument for Far Infrared) FPU and SPIRE (Spectral and Photometric Imaging Receiver) FPU. The cryostat was mated to a Service Module (SVM) mock-up. On the mock-up, one panel simulator was installed, which houses three warm SPIRE units (DPU, FCU, DCU) required to operate the SPIRE instrument during the tests. No other instrument unit was present on the SVM, since SPIRE was the only instrument operated during the tests. SPIRE received the power from the satellite EGSE (Electrical Ground Support Equipment), but commanding and telemetry was done directly via the SPIRE instrument EGSE.

E-field Antenna in front of Herschel

The IR blackbody radiation source

The straylight test has been performed to determine if the measurements with SPIRE are not disturbed by straylight, in particular by straylight entering the cryostat via the HIFI LOU window. To this end the HIFI LOU window was illuminated by a hot black body source. During additional measurements, the thermal shield temperatures and the cryocover mirror temperatures were varied to analyse the impact on the scientific performance of SPIRE. Initial results indicate that the straylight level measured by SPIRE is negligible.