MESSENGER MISSION TO MERCURY
About MESSENGER
MESSENGER is a scientific investigation of the planet Mercury, the least explored terrestrial planet. Understanding Mercury and how it was formed is essential to understanding the other terrestrial planets and their evolution. Mercury has been visited by only one other spacecraft, Mariner 10, so we know little more than its average density (the second greatest of all the planets), the composition of its atmosphere (thinnest of the terrestrial planets), the fact that it posses a global magnetic field, and its extreme variations in temperature. MESSENGER will serve to lift some of the uncertainty about this innermost planet of our solar system.
The MESSENGER mission will orbit Mercury after making three flybys of the planet, using data collected during the flybys as an initial guide to perform a more focused scientific investigation of this mysterious world. MESSENGER will investigate six key scientific questions about Mercury's characteristics and environment with a set of miniaturized space instruments. The spacecraft will enter Mercury orbit in March 2011 and carry out comprehensive measurements for one full Earth year.
LASP Instrument:
MASCS: Mercury Atmospheric and Surface Composition SpectrometerLASP developed and built the MASCS instrument onboard MESSENGER. MASCS is designed to detect minerals on Mercury’s surface, and determine the abundance and components of its thin atmosphere. Data from MASCS will help answer the questions: What is Mercury’s surface made out of? How is Mercury’s atmosphere generated? Does Mercury have ice at its poles?
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MESSENGER Orbit Insertion Procedure:
On March 16 at 11:40 a.m. EDT, just over 33 hours before the main Mercury orbit insertion event, two antennas from the Deep Space Network - one main antenna and one backup – track the MESSENGER spacecraft continuously. Nearly thirty-one hours later, at 6:30 p.m. EDT on March 17, the number of antennas tracking MESSENGER becomes five – four of these are arrayed together in order to enhance the signal coming from the spacecraft, and the fifth for backup in case there is a problem.
About two and a half hours later, at 8:00 p.m., the solar arrays, telecommunications, attitude control, and autonomy systems are all configured for the main thruster firing (known as a “burn”), and the spacecraft is turned into the correct orientation for MESSENGER’s Mercury orbit insertion maneuver.
In order to slow the spacecraft down sufficiently so that it can be captured into orbit around Mercury, the main thruster will begin firing at 8:45 p.m. and will continue for 15 minutes until 9:00 pm. About 31% of the spacecraft's original allotment of propellant is required for Mercury orbit insertion, and MESSENGER's thrusters must slow the spacecraft by just over 0.86 kilometers (0.53 miles) per second. As the spacecraft approaches Mercury, the largest thruster must be pointed close to the forward velocity direction of the spacecraft. Ten minutes after the thruster has finished firing, at 9:10 p.m., the spacecraft will be turned toward Earth, and data from the maneuver will be sent back to the Deep Space Network antennas. This is the time when the MESSENGER team will be able to determine that everything has gone according to plan, and that the orbit insertion maneuver has been successful. It will take about 9 minutes for the data to be transmitted back to Earth, and additional time will be needed for the DSN station to process it and send it the Mission Operations Center at APL. It is expected that by about 11:00 p.m. EDT, the Mission Operations Team will be able to confirm that MESSENGER has successfully been captured into orbit around Mercury.
At the same time as the MOI data are being sent back to Earth, the spacecraft systems will be reconfigured into their normal post-maneuver operations mode, and just under an hour later, the Deep Space Network burn coverage will be stepped back to two stations. At 2.48 a.m. EDT on March 18, the spacecraft will begin its first full orbit around Mercury (as measured from the highest point in the orbit). At 12:00 p.m., the Deep Space Network coverage will be further reduced to continuous coverage with only one station.
Videos:
On March 17, 2011, MESSENGER will become the first spacecraft ever to enter Mercury's orbit. The probe will continue to orbit the planet once every 12 hours for the duration of its primary mission. Watch this animation to view the Mercury orbit insertion maneuver and the spacecraft's first orbit around the planet.
Orbit insertion animation on APL MESSENGER site (.mov)
release date: 2011
This animation shows the expected spacecraft orientation, thruster activity, and location relative to Mercury during the Mercury orbit insertion maneuver. The first few days after orbit insertion will be focused on ensuring that the spacecraft systems are all working well in the harsh thermal environment of orbit.
Spacecraft orientation animation on APL MESSENGER site (.mov)
release date: 2011
This animation illustrates the motion of the field of view of the Visible and Infrared Spectrograph (VIRS) channel of MASCS. Once the spacecraft finishes its slew, it executes an observing program that carries the VIRS field of view across the sunlit surface of Mercury (green). At a selected number of targets, the spacecraft rotates to freeze the field of view long enough for the Ultraviolet and Visible Spectrometer to acquire a complete ultraviolet spectrum (yellow).
release date: 9/28/2009
As MESSENGER crosses the terminator, it first briefly slews the instruments’ fields of view above the planet. It next executes a series of targeted observations. Blue flashes show when camera images are taken. Green lines outline the smaller, pinpoint field of view of MASCS.
release date: 9/28/2009
'Departure Observing Plan' for the September 29 flyby.
During Flyby 3, MESSENGER will specifically target for detailed spectral analysis by the MASCS instrument. A summary of the scientific significance of these targets is summarized. The above movies illustrate the observing program that the spacecraft and instruments will execute just after closest approach. 'Flashes' in the videos indicate the 'image frames' from the camera that provides geological context for the MASCS observations.
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