From: Johns Hopkins University
Posted: Wednesday, October 8, 2008
By using solar sailing - rotating the spacecraft and tilting its solar panels to use the very small pressure from sunlight to alter the spacecraft's trajectory - MESSENGER navigators have achieved a new record for the smallest miss distance between the intended and actual closest approach distance during a flyby of a planet other than Earth.
On October 6, 2008, the probe flew 199.4 kilometers (123.9 miles) above the surface of the planet. "Our goal was to fly 200 kilometers from the planet's surface, and we missed that target by only 0.6 kilometers," explained MESSENGER Mission Design Lead Jim McAdams, of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.
That's pretty remarkable targeting, given that MESSENGER has travelled 668 million kilometers since its last deep space maneuver in March, McAdams says. "It's as if we shot an arrow from New York to a target in Los Angeles - nudged it three times mid-stream with a soft breath - and arrived within the width of the arrow's shaft at the target."
New Mercury Images Available
The MESSENGER Science Team has released five new images from the probe's second flyby of Mercury. When the spacecraft flew by Mercury in January, one of the more dramatic images captured was of the Vivaldi crater at sunset. Two days ago, MESSENGER's cameras took this image of Vivaldi at sunrise.
This striking view of Mercury, taken about 54 minutes before closest approach, shows the northern portion of the sunlit, crescent-shaped planet seen as the spacecraft approached Mercury. As MESSENGER continued toward Mercury, the Mercury Dual Imaging System (MDIS) captured this image of previously unseen smooth plains.
The MDIS Wide Angle Camera snapped this image, part of a high-resolution color mosaic of the planet, just 8 minutes and 47 seconds after the MESSENGER spacecraft passed above Mercury's surface. The probe's closest approach occurred over the dark night side of Mercury, as can be seen in this animation, so the MDIS cameras had to wait until the sunlit surface was visible before beginning to image while departing from the planet.
This image shows a view of Mercury as imaged by the Mariner 10 spacecraft in the 1970s, alongside a view of the planet with the gaps largely filled in by MESSENGER during the recent flyby. Filling in this gap will help the Science Team to use both Mariner 10 and MESSENGER data to characterize the diverse geological processes that shaped the surface of Mercury over time.
Additional information and features from this encounter are available online at http://messenger.jhuapl.edu/mer_flyby2.html. Check back frequently to see the latest released images and science results!
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
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