Nasa gears up for Venus fly-by
Messenger flying by Venus
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Tuesday, 05, Jun 2007 10:14
Nasa's Messenger spacecraft is set to fly past Venus at its closest point today, providing scientists with an insight into the planet's atmosphere and surface.
Messenger is en route to its mission at the planet Mercury, which it is expected to reach next year.
By flying past Venus the spacecraft is able to use the pull of the planet's gravity to guide it closer to Mercury.
During the fly-by, Venus' gravity will change Messenger's direction around the Sun and will decelerate it from 22.7 to 17.3 miles per second.
"Typically, spacecraft have used planetary fly-bys to speed toward the outer solar system," said Andy Calloway, Messenger mission operations manager.
"Messenger, headed in the opposite direction, needs to slow down enough to slip into orbit around Mercury."
It is the second fly-by of Venus, but during the first one in October last year the planet was lying in a position on the opposite side of the Sun from Earth, leading to a two-week radio contact blackout between the spacecraft and its operators.
This time scientific observations are able to be made which will act both as a practice run for the Mercury mission and as an insight into Venus.
Observations of Venus' atmosphere, cloud structure, space environment and possibly its surface are expected.
"By coordinating and comparing these observations, we will be able to maximise the science from both missions and potentially learn things that would not be revealed by one set of observations alone," said Ralph McNutt, Messenger project scientist.