Herschel Cryostat Cooldown
20 March 2008The Herschel spacecraft is set up in the ESTEC cleanroom where it is going through a cooldown, with the main helium tank in the cryostat vacuum vessel (CVV) slowly being filled with liquid helium. The setup for this carefully monitored process was started end January with a smooth cooldown of the helium tank to a temperature of about 4 K and complete filling with more than 2000 litres of liquid helium.
The CVV comprises two helium tanks: the large superfluid helium II tank (HTT) and the smaller helium I tank (HOT). The main HTT will hold ~2300 litres of superfluid helium used to cool the payload to the required operational temperatures.
With the main HTT at 4 K, several tests, also essential functional tests of the scientific instruments, are being performed on the spacecraft.
After completion of these tests and the completion of the spacecraft integration, with the most spectacular ones the mounting of the telescope and the solar array, the satellite will enter the mechanical test phase with vibration and acoustic noise testing in May.