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| | | | | | | | | Herschel and Planck launch configuration | |
Journey
Herschel will be launched in spring 2009 on an Ariane 5 along with ESA’s Planck microwave observatory, which will study the Cosmic Microwave Background.
At launch, the Herschel-Planck combination will measure approximately 11 m in height and 4.5 m in width, with a weight of about 5.7 tonnes. They will separate soon after launch and head into different orbits. The two spacecraft will be operated independently.
If Herschel were placed in orbit around Earth, heat from our planet, the Moon and the Sun would interfere with its instruments, reducing their sensitivity. Instead, the telescope will orbit the second Lagrange point of the Earth-Sun system (L2), a point in space located 1.5 million km from Earth.
L2 is a local gravitationally-stable point that is fixed in the Earth-Sun system and is situated on Earth’s night-side. It is an excellent location for Herschel: the solar array and sunshade will always face the Sun, Earth and the Moon, sheltering the satellite from solar radiation and infrared emission from Earth and the Moon.
| | | Herschel and Planck launch configuration |
Because Earth and the Sun are in the same general direction, this orbit also offers good sky visibility for astronomical observations. In addition, it keeps Herschel outside Earth’s radiation belts, which may otherwise disturb observations.
For more information, see L2, the second Lagrangian point.
It will take Herschel about 60 days to enter its final operational orbit around L2. The observatory will settle into a quasi-halo orbit, i.e. an orbit that resembles a halo orbit, around L2 with an average amplitude of 800 000 km.
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| | Herschel: ESA's giant infrared observatory Spacecraft Operations Related articles Early operationsOperating HerschelRead more Revealing the invisible: Caroline and William HerschelObservations: Seeing in infrared wavelengthsThe electromagnetic spectrumL2, the second Lagrangian PointWhat are Lagrange points?Why infrared astronomy is a hot topicThe infrared explorersIn depth Herschel in depthHerschel spacecraft in depth
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