Explanation:
Featured in this artist's illustration,
NASA's NanoSail-Dfinally unfurled a very thin, 10 square meter reflective
sail on January 20th, becoming the first solar sail spacecraft
in low Earth orbit.
Often considered the
stuff
of science fiction, sailing through space
was suggested 400 years ago by
astronomer Johannes Kepler
who observed comet tails blown by the solar wind.
Modern solar sail
spacecraft designs, like NanoSail-D or the Japanese interplanetary
spacecraft IKAROS, rely on the small but
continuous
pressure from sunlight itself for thrust.
Glinting in the sunlight as it circles planet Earth, the NanoSail-D
solar sail will periodically be bright and easily
visible to the eye.
In fact, skygazers are urged to participate in an ongoing
contest to capture images
of NanoSail-D.
The images will help NASA monitor the satellite before it reenters
the atmosphere in April or May.
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