Servicing of the ORFEUS Echelle Detector

This Photo shows the servicing of the echelle detector in August 1996.

The ASTRO-SPAS is turned upside down to allow access to the service opening of the echelle spectrometer. The echelle spectrometer is seen, also part of the telescope and of the telescope door. At the top of the image a small part of the IMPAS instrument is to be seen.

A vacuum pump is connected to the echelle detector. The detector was evacuated for about 24 hours and then filled back with argon gas. Argon gas will prevent the detector box from being filled with air through small leaks. Moisture in the air would destroy the potassium bromide (KBr) photocathode of the echelle detector. Also the outgassing of the detector box would take much longer time in orbit after opening the detector shutter.

For these reasons it is important, that the detector box is filled with a very pure, dry inert gas, such as argon.