Herschel Space Observatory
Planning and commissioning
The project started in 1984 under the name Far Infrared and Submillimetre Telescope ( FIRST). The budget is about 1.1 billion euros. The primary mirror has a diameter of 3.5 meters, which was sintered silicon carbide from twelve segments at EADS Astrium in Toulouse. Herschel thus had the largest one-piece mirror, which has been built for a space telescope. Herschel will thus be the space telescope with the largest mirror for a few years and are only replaced in that capacity by the James Webb Space Telescope ( expected 2018), which, however, have a hinged mirror. A space telescope with a larger one-piece mirror is not yet planned.
The main objectives of Herschel included studies on
- Formation and evolution of galaxies, particularly distant young galaxies that radiate due to their dust content mainly in the far infrared;
- Formation and evolution of stars, for example, by large-scale search for the earliest stages of development of the stars;
- Physics and chemistry of the interstellar medium;
- Objects in our solar system ( comets and planetary atmospheres ).
After several postponements of the launch took place on 14 May 2009 at 13:12 UTC clock. After the firing circuit of the high school the Herschel telescope was at 13:38 UTC exposed to a highly elliptical orbit a few minutes before the Planck space telescope with a Apogäumhöhe of 1.19708 million km and an inclination to the equator of 6 °. From this orbit, it was brought unmotivated within sixty days into the intended orbit around the Lagrange point L2 of the Sun-Earth system. The space telescope flies on a 0.8 - million -kilometer halo orbit around this point. This is seen from the Sun, about 1.5 million kilometers behind the earth.
Technology
Are operating at wavelengths 57-670 microns three instruments (cameras and spectrometers ), which in the far-infrared ( terahertz radiation) and submillimeter range of the electromagnetic spectrum on board. This area can not be observed from the ground due to the limited atmospheric window.
The experiments are:
- HIFI ( Heterodyne Instrument for the Far Infrared): high-resolution spectrometer ( 157-625 microns ) from the Netherlands Institute for Space Research
- PACS ( Photodetector Array Camera and Spectrometer): imaging photometer / spectrometer ( 57-210 microns ) from the Max Planck Institute for Extraterrestrial Physics in Garching near Munich
- SPIRE ( Spectral and Photometric Image Receiver): imaging photometer / spectrometer ( 200-670 microns ) of the University of Wales from Cardiff
Because of its size Herschel may not like previous infrared space telescopes (eg, Infrared Astronomical Satellite ( IRAS ), Infrared Space Observatory ( ISO), Spitzer Space Telescope) are completely cooled with liquid helium. Instead, his real telescope is shielded with a shield from the sun's rays, so that it can cool by radiation into space passively to below 90 Kelvin ( -183 ° C). Only the three instruments were cooled with liquid helium, which should be sufficient for operation of at least three years.
Results
On 19 June 2009, the ESA published the first photos of the in operation since June 14, 2009 Space Telescope. They show that about 37 million light- years distant spiral galaxy Messier 51 As a result, the Herschel advanced knowledge about the evolution of stars and also drew storms of molecular gas in distant galaxies by.
In January 2013 Herschel allowed a more accurate determination of the diameter of Apophis.
End of Mission
Herschel liquid helium, which cools its detectors with its evaporative cooling was early March 2013 evaporates almost completely. On 29 April, the observation mission of NASA and the ESA was declared over, since the liquid helium had been completely consumed. The lack of cooling the instruments because of their high temperature could no longer continue their observations.
Herschel was withdrawn from its orbit around L2 and sent to a graveyard orbit around the sun. By mid-June some tests and measurements were performed at the telescope. Finally, the remaining fuel was consumed and Herschel then finally shut down. A course to the moon with a subsequent controlled crash would have been possible, but was rejected as too expensive. On June 17, 2013, the mission was finally completed