Herschel to observe in HiFi

ESA's infrared observatory rebooted its third instrument dedicated to the search for water.

 

Herschel space telescope (illustration). Credit: ESA

Herschel is an infrared telescope equipped with the biggest mirror ever sent into space (it has a diameter of 3.5m). Successfully launched in May 2009, this enormous "light funnel" is nothing without the cutting-edge instruments that analyse harvested photons. The European Space Agency's observatory boasts 3 such instruments: PACS, SPIRE and HiFi. Each one specialises in well-defined areas (see this Enjoy Space feature for more details).
In the video below, scientist Jean-Paul Baluteau from Marseille's Astrophysics Laboratory, shows us round Herschel.



Remote repairs
PACS and SPIRE have functioned perfectly since they were activated. HiFi (Heterodyne Instrument for Far-Infrared), on the other hand, broke down. Despite an initial successful observation in June 2009, the instrument was closed down as early as the following August: its abnormal behaviour triggered fears of irreversible damage. The main problem is that Herschel orbits at 1.5 million kilometres from the earth and cannot therefore be repaired like the Hubble space telescope. The European observatory was not designed that way. Engineers had to determine the cause of the breakdown - and come up with a solution - remotely, studying incoming data and plans of the HiFi instrument.

HiFi , like PACS and SPIRE, is located inside Herschel's cryostat. This "cold room" keeps the 3 instruments just a few degrees above absolute zero. Without this precaution, even in space, heat would prevent delicate detectors from functioning correctly in infrared. Credit: ESA/AOES Medialab

According to ESA, overvoltage affecting control electronics, the LCU (Local oscillator Control Unit) to be precise, is to blame. Overvoltage that is "probably" (we quote) the consequence of cosmic rays, full of energy, that can indeed interfere with electronics or onboard computers in space. This is why some delicate, vital systems are doubled up on satellites and other space craft, providing a "spare part" already on the spot and ready to function – just in case! Once the necessary precautions had been taken and the breakdown duly analysed, a new computer programme was sent to Herschel; it should prevent overvoltage if a problem arises, and start the back-up for the faulty LCU. The HiFi instrument would thus be back up and running instantly.

The Orion great nebula (this picture is from Hubble's telescope) is a veritable nursery of stars. It will be Herschel's next target. The HiFi instrument is to give a better understanding of water's role in the formation of suns and planets. Credit: NASA/ESA

Infrared high fidelity for water
As we know, in the audio world, the term HiFi refers to High Fidelity, a standard that guarantees high-quality sound restitution on consumer devices (amplifiers, speakers, etc.). There is no doubt that the name of Herschel's "HiFi" instrument is an allusion to its outstanding performance levels: it is a high-resolution infrared spectrometer. It breaks down light to facilitate the identification of the different molecules present in the objects being observed, notably water. Although the precious liquid remains difficult to characterise because of its complicated "profile", HiFi's precision will make it easier to detect. Herschel's next observation using HiFi concerns the nebula Orion, where stellar systems are born. Astronomers hope to get a better understanding of the role water plays in the formation of suns and their attendant strings of planets.

Published on 20 January 2010