This places the first satellite in
orbit around Mercury and will be a trove of new data. As this item makes clear, it was a tough nut
to crack even though we are doing this routinely with other planets.
I expect we will soon have a good
grasp of the possibilities in terms of establishing a real presence on the
planet itself or even landing a Lander as we have done on Mars.
I wonder if there is a major
mountain on Mercury as on Mars?
Watch the video simulation.
Finally! NASA Prepares to Orbit Mercury
March 15, 2011: On March 17th, NASA's MESSENGER probe will become
the first spacecraft to orbit Mercury. It's a seminal moment in planetary
exploration. Researchers can finally take a good long look at a rocky world
that is both akin to Earth and shockingly alien.
An artist's concept of MESSENGER gliding over the surface of Mercury.
[more]
There's just one question: What's taken so long? Mercury is one of the
closest planets to Earth and, at first glance, would seem to be readily
accessible. Jim McAdams, mission design lead engineer, explains the problem:
"Mercury is going so much faster than Earth that a spacecraft must
gain about 65,000 mph to catch it. And once you get there, you're face to face
with the searing heat of the sun."
Only Mariner 10, which flew past the small planet briefly in 1974 and
1975, and MESSENGER itself have made the attempt to go there. Even after
MESSENGER's own flybys in 2008 and 2009, Mercury remains the least explored
planet.
Deep in the sun's gravitational well, Mercury is the planet most
subject to the sun's powerful grip. The closer a planet gets to the sun, the
faster it has to travel to balance the pull of gravity. Mercury travels at an
average speed of 106,000 mph.
"MESSENGER must gain tremendous speed to catch Mercury,"
explains McAdams. "That's quite a challenge with current propulsion
systems. But Chen-wan Yen, an engineer from JPL, came up with a clever
trajectory that uses gravity assists from Venus and Mercury. I started with
that trajectory, adding additional flybys to adjust both the launch and Mercury
arrival dates."
The resulting loop-de-loop path MESSENGER has followed to slip into
planet number one's orbit has covered about 5 billion miles, including 15 loops
around the sun, and flybys of multiple planets.
As a spacecraft flies by a planet, the tug exerted by the planet flings
the spacecraft in a new direction, giving it a boost and reshaping its orbit.
The final itinerary for MESSENGER included flybys at Earth, Venus and Mercury
itself to accelerate the spacecraft and deflect its path inward toward
Mercury's path – all using very little fuel.
"With each flyby, MESSENGER's average speed relative to the sun
increased," explains McAdams. "But the spacecraft's speed relative to
Mercury decreased." (Sound confusing? Read the footnote.1)
Meanwhile another challenge awaits – Mercury's "warm"
welcome. The sun blazes up to 11 times brighter there than at Earth, and
surface temperatures at Mercury’s equator can reach 450 degrees Celsius (840
degrees Fahrenheit). The small planet's hot dayside radiates much of that
thermal energy back into space at a rate four times that at Earth.
Watch this
animation to view the Mercury orbit insertion maneuver and the
spacecraft’s first orbit around the planet.
"We solve this problem with a large sunshade made of ceramic
fabric that withstands heat and protects the rest of the spacecraft,"
explains principal investigator Sean Solomon. "And the mission is designed
to limit the time the spacecraft spends over Mercury's hottest areas."
Other high-tech materials are used in the solar arrays and science
instruments to keep them within their working temperature ranges.
Researchers are anxious for new discoveries at Mercury. It's a planet
of many mysteries: the most active planetary exosphere in the whole solar
system, a surprisingly "live" magnetic field that has puzzled
scientists for years, a core that makes up 60% of the planet's mass and is at
least partially liquid, an intriguing landscape pitted with an interesting
variety of craters and volcanic vents and marked by towering scarps that snake
hundreds of miles across the planet's face. And that's just for starters.
MESSENGER is bristling with scientific instruments – high resolution
imagers, lasers, and magnetometers – designed to solve these mysteries once and
for all.
Finally!
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