William Herschel was an Anglo-German astronomer who discovered infrared light in 1800. Thanks to his discovery, astronomers can now observe a facet of the universe that remains hidden to other telescopes. ESA's Herschel is the first space observatory covering a major part of the far-infrared and sub-millimeter waveband (from 57 to 670 microns) and its new name honors the astronomer on the 200th anniversary of his discovery.
Roger Bonnet explained, "It strikes me that we are at a key scientific conference devoted to the next ESA infrared space mission, gathering many infrared pioneers, 200 years after a famous musician and astronomer discovered that by placing a thermometer in the remote part of the solar spectrum, where apparently there was no light, he could detect heat -- what we call now infrared radiation. This meeting marks two events: the beginning of a very promising utilization of FIRST, and the adoption of a new name for the telescope: the Herschel Space Observatory."
Roger Bonnet also confirmed the February 2007 launch date of Herschel, and had some words of encouragement for the principal investigators of Herschel's instruments: "There is still much hard work ahead. It will not be easy, but it will pay off in the end," he said.
ESA will select an industrial prime contractor for Herschel next spring. The detailed design of the spacecraft will begin in June, and about one and a half years later assembly will start. Construction of the three instruments on board the observatory -- a high-resolution spectrograph and two infrared cameras -- will begin early next year. More than 40 institutions, mainly European, organized in three consortia, will collaborate in their design and development.
Primeval galaxies, molecules and comets
In light of the discoveries by ISO -- which operated from November 1995 until May 1998 -- scientists at the Toledo conference revised Herschel's scientific agenda. "This is the kind of input we need," said Göran Pilbratt, Herschel project scientist. "We want to make sure that we use the precious observing time for the most profound problems."
Herschel's wavelength range makes it the ideal instrument to decipher how the first stars and galaxies formed. These topics, always slated to be the observatory's main area of investigation, are hotter than ever thanks to the surveys by ISO and other ground-based infrared instruments.
But other goals, not originally highlighted in Herschel's scientific objectives, were identified in Toledo. Ewine van Dishoeck (Leiden University, the Netherlands), expert in space chemistry, stressed that "Herschel will continue the search for water in space, as initiated by ISO. It will give us an in-depth knowledge about how much water there is, its distribution and formation." Other compounds, detectable at the wavelengths covered by Herschel's instruments, were also listed. "Herschel will provide us with a much better understanding of the chemistry of the universe," said Van Dishoeck.
Observations of our own space neighborhood were also given high priority. As solar system expert Thérèse Encrenaz (Observatoire de Paris-Meudon, France) explained, detailed observations of comets by Herschel will contribute to the reconstruction of the past history of the solar system. Comets are made of material that has undergone very little processing. Therefore they might indicate the composition of the raw material that formed the solar system about 4.6 billion years ago.
Solar system astronomers defined yet another area of study -- the so-called transneptunian objects, poorly known asteroid-type bodies located beyond Neptune's orbit that form the Kuiper Belt. Though some scientists estimate that around 10,000 of these bodies may exist, only 300 have been observed so far.
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