The first observatory to cover the entire range from far-infrared to sub-millimetre wavelengths and bridge the two, Herschel will explore further in the far-infrared than any previous mission, studying otherwise invisible dusty and cold regions of the cosmos, both near and far.
Herschel will tap into unexploited wavelengths, seeing phenomena out of reach for other observatories, at a level of detail that has not been captured before. The telescope's primary mirror is 3.5 m in diameter, more than four times larger than any previous infrared space telescope and almost one and a half times larger than that of the Hubble Space Telescope. The telescope will collect almost twenty times more light than any previous infrared space telescope.
The cutting-edge spacecraft carries three advanced science instruments: two cameras and a very high resolution spectrometer; their detectors are cooled to temperatures close to absolute zero by a sophisticated cryogenic system.
Primary mirror: 3.5 m in diameter.
Launch: May 2009 on board an Ariane 5 from ESA's Spaceport in Kourou, French Guiana. The launch window opens at 15:34:32 CEST. Herschel will be launched along with Planck, ESA's microwave observatory which will study the Cosmic Microwave Background.
Status: Preparations for launch under way.
Journey: Herschel will separate from the upper stage of the launcher about 26 minutes after launch, Planck will follow a few minutes later. The two spacecraft will operate independently. Two weeks from launch, Herschel will be more than 1 million km away from Earth and will begin commissioning. The observatory will reach its operational orbit about a hundred days after launch.
Orbit: Herschel will operate from a Lissajous orbit around the second Lagrangian point of the Sun–Earth system (L2), a virtual point located 1.5 million km from Earth in the direction opposite to the Sun. The satellite's average distance from L2 will be 800 000 km.
Lifetime: A minimum of three years for routine science observations. The mission will last until the cryostat runs out of helium, about four years after launch.
Instruments:
HIFI (Heterodyne Instrument for the Far Infrared), a high-resolution spectrometer; PACS (Photoconductor Array Camera and Spectrometer) and SPIRE (Spectral and Photometric Imaging REceiver), PACS and SPIRE are both cameras and imaging spectrometers. Together, these instruments cover 55–672 microns. Their detectors will be cooled to temperatures very close to absolute zero.
Launch mass: About 3.4 tonnes.
Dimensions: About 7.5 m high and 4 m wide.
Operations: Herschel will be operated as an observatory. About two-thirds of its observing time will be available to the worldwide scientific community. The rest of the observing time has been allotted to the instrument consortia. It will operate autonomously, sending acquired data to Earth over a three-hour period every day.
Primary ground station: ESA's deep space antenna in New Norcia, Australia.
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