First day of SPIRE, switch on the Spectrometer

After we switched on successfully the Photometer we proceeded further to switch on the Spectrometer. Initially it was planned to switch only half of one of the spectrometer arrays, because the other half showed problems during ground tests, especially at low temperatures of the optical bench. But in day 6 the optical bench was at acceptable temperature and that is way it was decided that we switch on the whole bolometer array.

The half of the array that was problematic showed the same behaviour: it switched on first but then it switched off. We had to increase the voltage line feeding the JFETs in order to switch it on. The drawback of this is that the bolometers will be operating at non optimal conditions and the noise will be higher.

Fortunately, at the end of the test, when we switch back to low voltage the JFETs kept working and the noise properties were looking the same. We still have to see this when the instrument is at the nominal in flight conditions, which will be after few weeks.