MESSENGER Mission News September 12, 2008
MESSENGER Finalizes Plans for Its Second Look at Mercury
It is now only slightly more than three weeks before the MESSENGER spacecraft flies by Mercury for the second time. At 4:40 a.m. ET on October 6, the craft will speed by the planet, passing within 125 miles (200 kilometers) and gaining a gravity assist that will tighten its orbit and keep it on its course to pass the planet one last time next year before becoming the first spacecraft ever to orbit Mercury, beginning in 2011.
A comprehensive set of observations of Mercury and its environment has been designed for this upcoming encounter – deploying all seven of the science payload instruments, in addition to the telecommunications system – to continue the investigations begun during the first encounter with Mercury last January.
Over the last six months, engineers have been building the software commands needed to implement these observations into one single sequence that will be loaded to the spacecraft to run automatically during the encounter. The development of this sequence included several levels of review and testing as it matured. Today, engineers successfully completed the final testing of the commands on the hardware simulator, and on September 29, engineers will send MESSENGER instructions on what observations to perform at each point along the flyby trajectory.
As MESSENGER flew by Mercury on January 14, its instruments imaged 20% of Mercury’s surface not previously seen by spacecraft. The spacecraft made measurements of the planet’s magnetic field, exosphere and sodium tail, surface color and composition, and gravitational field. On its second visit, MESSENGER will image an additional 30% of the surface never before seen by spacecraft.
“MESSENGER’s first flyby of Mercury produced many surprises,” offered MESSENGER Principal Investigator Sean Solomon. “The second flyby will bring us close to the opposite side of the planet from the one we visited in January, and the surface we will view at close range for the first time is larger in area than South America. The only safe prediction at this stage of exploring the innermost planet is that we will make new discoveries.”
Mercury – in 3D!
This graphic shows a portion of the fault scarp Beagle Rupes cutting through the highly elliptical crater Sveinsdottir in a three-dimensional (3D) representation. Standard 3D glasses (which can be assembled at home), with a red filter in front of the left eye and a blue filter in front of the right one, can be used to view this picture. By combining information from multiple images of the same portion of Mercury’s surface taken under different viewing angles, the topography of the surface was determined. A high-resolution image was then overlaid on the topography map, resulting in this 3D image.
More than 80 MESSENGER images were used to create this 3D view of Mercury’s surface. As the MESSENGER mission continues, many more images will be acquired, and these additional images will provide views of Mercury’s surface from a variety of illumination conditions and viewing geometries. These myriad views, anchored by topographic profiles to be acquired by MESSENGER’s laser altimeter, will enable large portions of the surface of Mercury to be studied in 3D.
Stat Corner
MESSENGER is about 51.8 million miles (83.4 million kilometers) from the Sun and 81.5 million miles (131.2 million kilometers) from Earth. At that distance, a signal from Earth reaches the spacecraft in 7.3 minutes. The spacecraft is moving around the Sun at 84,744.7 miles (136,383.4 kilometers) per hour.
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.
