The Complete Book of Spaceflight: From Apollo 1 to Zero Gravity

and provides the operational support to implement that
policy.
Darwin
A future ESA (European Space Agency) mission, under
study, that will look for signs of life on extrasolar planets
using a flotilla of six orbiting telescopes. Each telescope
will be at least 1.5 m in diameter and will operate at
infrared wavelengths in order to pick out planets more
clearly from the glare of their parent stars. (At optical
wavelengths, a star outshines an Earth-like planet by a
billion to one; in the mid-infrared, the star-planet con-
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trast drops to a mere million to one!) Another reason for
observing in the infrared is that gases, such as water
vapor, associated with life as we know it, absorb especially
strongly at certain infrared wavelengths, leaving clear
spectral fingerprints in this region. Working together,
Darwin’s multiple telescopes will be about as sensitive
as a single instrument 30 m in diameter. A second advantage
of the array is that it enables a technique called
nulling interferometry to be used to cancel out most of the
light from the central star. In about 2014, Darwin will be
launched into solar orbit at the second Lagrangian
point, well away from terrestrial interference. It will be
Darwin An artist’s rendering
of Darwin’s flotilla of spacecraft
observing an extrasolar planet.
European Space Agency