SEDS (Students for the Exploration and Development of Space) Homepage
Upcoming Transits of MercuryTransit of Mercury, 15 November 1999
Mark Robinson has some reprocessed images of Mercury available on his web site
Boston University Press release, 5/26/00
Ever since Galileo first used a telescope in 1609, astronomers have tried to capture images of the surface of Mercury with a ground-based telescope. Now, a team of astronomers from Boston University released images revealing details of Mercury's surface in the May issue of The Astronomical Journal and at the American Geophysical Union in Washington, DC.
"More than a quarter-century ago, the Mariner 10 spacecraft flew past Mercury and for the first and only time transmitted satellite-based photos of half of the surface of the planet closest to the Sun.," says lead author Jeffrey Baumgardner, senior research associate in the Center for Space Physics at BU. "Capturing similar images from a ground-based telescope represents a significant milestone in advanced instrumentation," he adds.
The BU images, taken on August 29, 1998, at the Mt. Wilson Observatory in California, reveal surface markings similar to the bright craters and dark lunar mare found on the Moon. The BU images captured using a digital camera and stored on CD-ROMs for subsequent processing show never-before- seen-portions of Mercury.
Photographing Mercury is challenging because of the planet's proximity to the Sun. Mercury only has a few viewing times, before sunrise or shortly after sunset. At rare times when 'the seeing' is right, the air is clear and researchers are looking through less turbulence in Earth's atmosphere. Opportunities to photograph Mercury from space are also limited because light sensitive equipment, such as the Hubble Space Telescope, are not allowed to look at objects close to the Sun, such as Mercury or Venus. This restriction has been established to avoid the possibility of an accidental pointing error causing too much light to fall upon an instrument.
"The observations were made shortly after sunrise before the Sun's heating of the atmosphere distorted the images captured by the telescope," says Michael Mendillo, professor of astronomy at BU.
In order to obtain a clear photograph Baumgardner took images with very short exposures, 1/60th of a second, continuously for 90 minutes. "That comes to 340,000 pictures," Mendillo added. "The trick to getting a clear image was then to find the best ones, say 30 to 60, that could be added together by computer to create a time exposure of sufficient duration (.5 to 1 second) in order to capture detail on Mercury's surface."
Baumgardner and Research Associate Jody Wilson assisted by Mead Misic, a sophomore in the College of Engineering, all took part in the search for the perfect images. They developed sophisticated computer techniques to identify the best images with detail taken during rare instances of 'perfect seeing.'
"We captured multiple images of Mercury during these rare instances of 'perfect seeing,'" says Wilson. "and by combining these images, a unique photograph with details and clarity resulted. "
The Boston University team plans to make additional observations of Mercury this fall, even pushing the technique to try to image the planet's weak atmosphere. "Mercury has a thin atmosphere created by the ejection of atoms from its surface, a process that also occurs on our Moon," Mendillo explained. One of the chemical elements in Mercury's atmosphere is sodium, a gas somewhat easy to detect because it reflects sunlight very efficiently. "We hope to try our first sodium detection experiments this fall," Baumgardner said. "But that will first involve building a more sensitive detector system."
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NASA Press Release
The first comprehensive mission to map pockmarked Mercury and a radical mission to excavate the interior of a comet have been selected as the next flights in NASA's Discovery Program.
The Mercury Surface, Space Environment, Geochemistry and Ranging mission, or Messenger, will carry seven instruments into orbit around the closest planet to the Sun. It will send back the first global images of Mercury and study its shape, interior and magnetic field. Dr. Sean Solomon of the Carnegie Institution, Washington, DC, will lead Messenger.
The Deep Impact mission will send a 1,100-pound (500- kilogram) copper projectile into comet P/Tempel 1, creating a crater as big as a football field and as deep as a seven-story building. A camera and infrared spectrometer on the spacecraft, along with ground-based observatories, will study the resulting icy debris and pristine interior material. Dr. Michael A'Hearn will lead Deep Impact from the University of Maryland in College Park.
Messenger, to be launched in spring 2004, will be NASA's first mission to Mercury since the Mariner 10 flybys in 1974 and 1975, which provided information on only half the planet. Its challenging flight plan begins with two Venus flybys, then two Mercury flybys in January and October 2008 and a subsequent orbital tour of Mercury beginning in September 2009.
Among Messenger's goals will be to discover whether Mercury has water ice in its polar craters. The cost of Messenger to NASA is $286 million. It will be built and managed by the Johns Hopkins University's Applied Physics Laboratory, Laurel, MD. Further information about the mission is available on the Internet at: http://sd-www.jhuapl.edu/MESSENGER
Deep Impact will be launched in January 2004 toward an explosive July 4, 2005, encounter with P/Tempel 1. It will use a copper projectile because that material can be identified easily within the spectral observations of the material blasted off the comet by the impact, which will occur at an approximate speed of 22,300 mph (10 kilometers per second.) The total cost of Deep Impact to NASA is $240 million. Deep Impact will be managed by NASA's Jet Propulsion Laboratory in Pasadena, CA, and built by Ball Aerospace in Boulder, CO.
NASA selected these missions from 26 proposals made in early 1998. The missions must be ready for launch no later than Sept. 30, 2004, within the Discovery Program's development cost cap of $190 million in Fiscal 1999 dollars over 36 months and a total mission cost of $299 million.
The Discovery Program emphasizes lower-cost, highly focused scientific mission. NASA has developed six other Discovery Program missions. Two have completed their primary missions, two are operational and two more are under development:
-- The Lunar Prospector orbiter has mapped the Moon's composition and gravity field for the past 18 months. It will complete its highly successful mission on July 31, when it is sent on a controlled impact into a crater near the south lunar pole. Scientists hope to observe a resulting plume of water vapor that would help confirm the presence of water ice in some of the Moon's permanently shadowed craters. In 1997, the Mars Pathfinder lander, carrying a small robotic rover named Sojourner, landed successfully on Mars and returned hundreds of images and thousands of measurements of the Martian environment.
-- The Near Earth Asteroid Rendezvous (NEAR) spacecraft is scheduled to enter orbit around the asteroid Eros in February 2000, after a problem with its initial attempt to do so early this year. The Stardust mission to gather samples of comet dust and return them to Earth was launched in February 1999.
-- The Genesis mission to gather samples of the solar wind and return them to Earth and the Comet Nucleus Tour (CONTOUR) mission to fly closely by three comets are being prepared for launch in January 2001 and June 2002, respectively.