In late December 2007 or early 2008, after the functional tests, the telescope and the solar arrays – two other fundamental parts of the payload module - will be mated to the rest of the spacecraft, completing Herschel.

Note for editors:
 

 
This picture shows an artist's impression of the view inside Herschel.

To protect the sensitive instruments from heat generated during operations and to achieve its challenging objectives, the satellite must operate at very low temperatures. This is why the spacecraft’s brain – or its payload module – hosts a cryostat, a cryogenic module inside which the cold components of the scientific instruments are mounted.

Inside the cryostat the sensitive instrument detectors are cooled down to about -273 ºC (0.3 degrees above absolute zero). This low temperature is achieved using superfluid helium (at about -271 ºC) and an additional cooling stage inside the focal plane units.

The service module is the spacecraft’s heart, which keeps the spacecraft going by caring for all its vital functions. It also carries the ‘warm’ components of the instruments – those that do not require cooling with the cryostat.


 
This picture was taken on 11 September during the mating of Herschel's cryostat (an important part of the payload module) and the service module at Astrium's facilities in Friedrichshafen. All that is now left to complete the spacecraft is the solar array and its telescope.

The cryostat contains the sensitive instrument detectors cooled down to about -273ºC (0.3 degrees above absolute zero). The service module is the spacecraft’s heart, which keeps the spacecraft going by caring for all its vital functions. It also carries the ‘warm’ instrument units – those that do not require cooling with the cryostat.

Between late July and early August this year, the cold and warm units of the instruments were mated with the cryostat and the service module respectively.

On 11 September, the cryostat containing the cold instrument units was finally mounted on the service module, mating Herschel’s heart and brain.

This fundamental step will be followed by functional and compatibility testing at Astrium before the spacecraft is sent to ESA’s European Space Research and Technology Centre (ESTEC) in November for final environmental (thermal, mechanical, acoustic) and functional acceptance tests.

In late December 2007 or early 2008, after the functional tests, the telescope and the solar arrays – two other fundamental parts of the payload module - will be mated to the rest of the spacecraft, completing Herschel.


 
This picture was taken on 11 September during the mating of Herschel's cryostat (an important part of the payload module) and the service module at Astrium's facilities in Friedrichshafen. All that is now left to complete the spacecraft is the solar array and its telescope.

The cryostat contains the sensitive instrument detectors cooled down to about -273ºC (0.3 degrees above absolute zero). The service module is the spacecraft’s heart, which keeps the spacecraft going by caring for all its vital functions. It also carries the ‘warm’ instrument units – those that do not require cooling with the cryostat.

Between late July and early August this year, the cold and warm units of the instruments were mated with the cryostat and the service module respectively.

On 11 September, the cryostat containing the cold instrument units was finally mounted on the service module, mating Herschel’s heart and brain.

This fundamental step will be followed by functional and compatibility testing at Astrium before the spacecraft is sent to ESA’s European Space Research and Technology Centre (ESTEC) in November for final environmental (thermal, mechanical, acoustic) and functional acceptance tests.

In late December 2007 or early 2008, after the functional tests, the telescope and the solar arrays – two other fundamental parts of the payload module - will be mated to the rest of the spacecraft, completing Herschel.


 
This is an image of the Heterodyne Instrument for the Far Infrared's (HIFI) focal plane unit. Clearly visible are 7 of the 14 mixer sub-assemblies, in which the signal received by the telescope is mixed with the signal generated by the local oscillator.

HIFI is a very high-resolution heterodyne spectrometer. The heterodyne detection principle involves translating the frequency range of the astronomical signal being observed to a lower frequency where it is easier to perform the required measurements.

This is done by mixing the incoming signal with a very stable monochromatic signal, generated by a local oscillator, and extracting the difference frequency for further processing.

HIFI observes in seven bands covering 480 to 1910 gigaHertz.


 
The Photoconductor Array Camera and Spectrometer (PACS) contains a camera and low to medium resolution spectrometer. It operates at wavelengths between 55 and 210 micrometres.

The opening of this infrared window by PACS to sensitive photometry and spectroscopy at high spatial resolution will address a wide range of key questions of current astrophysics concerning the origins of stars, planetary systems, galaxies, and the evolution of the Universe.


 
The Spectral and Photometric Imaging Receiver (SPIRE) comprises a three-band imaging photometer and an imaging Fourier transform spectrometer. The instrument will be used to undertake large area deep sky photometric imaging surveys and allow follow-up spectroscopic observations of selected sources.

These observations will help tackle two of the most fundamental questions in astronomy: how and when did galaxies form and how do stars form?



Release date: 26 February 2009