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MESSENGER Only One Week From Mercury
MESSENGER’s mid-December trajectory correction maneuver (TCM-19) went so well that the mission design and navigation teams have decided that a TCM scheduled for January 10 will not be needed.
“Cancellation of this maneuver is a demonstration of the near-perfect execution of TCM-19 just prior to the start of the holiday season,” says Mission Systems Engineer Eric Finnegan of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.
On January 9, MESSENGER’s Mercury Dual Imaging System cameras will begin gathering pictures of Mercury as the probe zeros in on the planet. “With just one week to go before the flyby, the spacecraft is on target to encounter the planet at an altitude of 202 kilometers,” Finnegan says. “All subsystems and instruments are operating nominally and configured for the start of the flyby sequence, except for the Mercury Laser Altimeter and part of the Gamma-Ray Spectrometer, which we’ll turn on just before the flyby.”
Over the next week, the team will make final flyby preparations and upload the final command sequences for the encounter.
“We are about to visit Mercury for the first time in more than 30 years, and we can’t wait,” says MESSENGER Principal Investigator Sean Solomon of the Carnegie Institution of Washington. “In addition to providing the critical gravity assist that will move MESSENGER along its path toward Mercury orbit insertion in March 2011, this flyby will let us see parts of Mercury never before viewed by spacecraft. We’ll be making close-in observations of the composition of Mercury’s surface and atmosphere, and we’ll be probing deeper into the planet’s magnetosphere than we’ve ever been. We expect many surprises.”
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Upcoming Mercury Flyby 1 Events
- · January 10, 1 p.m. EST. NASA Media Teleconference to preview the flyby.
- · January 14, 2:04 p.m. EST. MESSENGER's closest approach to Mercury.
- · January 14, 7 p.m. EST. APL and The Planetary Society co-host a public lecture in APL’s Parsons Auditorium featuring University of Arizona Professor Emeritus Robert Strom, the only MESSENGER Science Team member who also participated in the Mariner 10 investigation of Mercury. RSVP online at http://messenger.jhuapl.edu/RSVP/.
- · January 30, 1 p.m. EST. NASA Space Science Update on the Mercury flyby. NASA Headquarters.
Details on all these events will be posted as they become available on the MESSENGER Mercury Flyby 1 Web site at http://messenger.jhuapl.edu/mer_flyby1.html.
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 Laboratorybuilt and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
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Where is Messenger ??click here
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Experience MESSENGER’s Mercury Flyby Virtually
See Mercury through the “eyes” of MESSENGER’s imagers with the Mercury Flyby Visualization Tool, now available at http://messenger.jhuapl.edu/encounters/. This new Web feature offers a unique opportunity to see simulated views of Mercury from MESSENGER’s perspective, during approach, flyby, and departure, or in real-time (as the observations actually occur).
This tool combines the best available image map of Mercury’s surface with observation sequences for the Mercury Dual Imaging System (MDIS), Mercury Atmospheric and Surface Composition Spectrometer (MASCS), and Mercury Laser Altimeter (MLA). The map of Mercury’s surface combines Earth-based low-resolution radar images from the Arecibo Observatory in Puerto Rico and image mosaics from the Mariner 10 spacecraft flybys of Mercury in 1974 and 1975.
There are many helpful tips available on the pages of this visualization tool. Pointing and clicking on any color bar will either reveal the projection of each completed image mosaic on Mercury or show the end of the active MLA or MASCS observation. Information accompanying each simulated image includes the latitude and longitude of the point at the center of each image, the resolution in meters (or kilometers when farther from the planet) per pixel (picture element) at the image center, the altitude (how far the spacecraft is above Mercury's surface), and the time relative to closest approach.
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Timeline, story so far
Critical Deep-Space Maneuver Targets MESSENGER for Its First Mercury Encounter
The MESSENGER spacecraft delivered a critical deep-space maneuver on Wednesday — 155 million miles (250 million kilometers) from Earth — successfully firing its large bi-propellant engine to change the probe’s trajectory and target it for its first flyby of Mercury on January 14, 2008.
“Completing this maneuver was a huge milestone for the mission,” offered MESSENGER Principal Investigator Sean Solomon. “We are now en route to the closest glimpse of Mercury that anyone has ever seen. Over the next three months the suspense about what we will find will steadily build.”
The maneuver was executed in two parts from the MESSENGER Mission Operations Center at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. At 6 p.m. EDT on October 17, the probe fired its large main engine for just over five minutes, using about 70 kilograms (154 pounds) of propellant to change its velocity by 226 meters per seconds, or just over 505 miles per hour.
Then, at 6:30 p.m. EDT, the small thrusters were fired for about two minutes, changing the probe's velocity by an additional 1.4 meters per second. This burn redistributed the propellant in the main tanks to manage location of the probe’s center of mass, putting the spacecraft in a more stable mode of operation. “This action lowers the risk of having to do momentum correction maneuvers during November, when interference from the Sun will prevent communication with the spacecraft,” explained APL’s Jim McAdams, who helped design this maneuver.
“Everything went as planned, and we are now on target for a flyby of Mercury in January 2008,” said Mission Operations Manager Andy Calloway of APL, adding that this maneuver was the most critical of the mission other than orbit insertion, primarily because of the timing. ”Deep-Space Maneuver-2 (DSM-2) was executed just nine days prior to the start of the longest solar conjunction communications outage period of the mission,” he said. “So there was limited opportunity to correct problems and to obtain good orbit determination data for the navigation team.”
“The MESSENGER team is breathing a lot easier now that we’ve seen the successful completion of this most important course-correction maneuver before Mercury orbit insertion,” McAdams said. “Not only did DSM-2 put MESSENGER on target for the first spacecraft encounter with Mercury in nearly 33 years, it was completed with the least margin for error of all five DSMs before Mercury arrival in March 2011.”
This was the second of five deep-space maneuvers that will help the spacecraft reach Mercury orbit. The first, on December 12, 2005, positioned the probe for its October 2006 flyby of Venus. DSM-3 on March 17, 2008, will position the probe for the second flyby of Mercury on October 6, 2008. DSM-4 on December 6, 2008, positions MESSENGER for Mercury flyby 3, scheduled for September 30, 2009. And the final deep-space maneuver on November 29, 2009, targets the probe for Mercury orbit insertion on March 18, 2011.
“Now that we are past DSM-2, we will complete our solar conjunction preparations and begin testing our final version of the Mercury encounter sequence,” Calloway said. “Once we exit the solar conjunction, we will finalize plans for the two December trajectory-correction maneuvers — TCM-19 and TCM-20 — as we correct any propagated errors from DSM-2 so we can put MESSENGER right on the flyby aim point. It has been over three years of densely-packed cruise operations, and we are finally about to fly by and begin collecting data at Mercury.”
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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