PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE =" 2006-11-27 MESS:mick V01 Draft; 2006-11-28 MESS:mick V02 Reviewed by Domingue; 2006-12-01 MESS:mick V03 Added Object Keys; 2007-08-16 MESS:mick V04 Added Reference, Mission Host, Formated Sections; 2007-11-27 NAIF:Semenov V05 minor spelling / date corections; 2009-02-04 GEO:ward V06 Updates from peer review." RECORD_TYPE = STREAM OBJECT = MISSION MISSION_NAME = "MESSENGER" OBJECT = MISSION_INFORMATION MISSION_START_DATE = 2004-08-03 MISSION_STOP_DATE = 2012-03-18 MISSION_ALIAS_NAME = "MESS" MISSION_DESC =" MESSENGER Mission Overview ========================== The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft was launched from the Cape Canaveral Air Station on 2004-08-03, on an approximately 8 year mission to become the first probe to orbit the planet Mercury. The MESSENGER payload consists of seven instruments and a radio science (RS) experiment. The instruments are the Mercury Dual Imaging System (MDIS), the Gamma- Ray and Neutron Spectrometer (GRNS), the X-Ray Spectrometer (XRS), the Magnetometer (MAG), the Mercury Laser Altimeter (MLA), the Mercury Atmospheric and Surface Composition Spectrometer (MASCS), and the Energetic Particle and Plasma Spectrometer (EPPS). The MESSENGER mission is fully described in [SOLOMONETAL2007]. MDIS ---- The MDIS instrument includes both a wide-angle (WA) and a narrow-angle (NA) camera and both are capable of summing pixels. This provides for images of the surface that are of nearly uniform horizontal resolution (125 m per pixel or better throughout MESSENGER's elliptical orbit). The WA and NA cameras are mounted on opposite sides of a pivot platform, making MDIS the only MESSENGER instrument capable of pointing independent of spacecraft attitude. MDIS contributes to the understanding of the geological landforms and processes that shaped Mercury's surface. GRNS ---- The GRNS instrument includes two sensors, a Gamma- Ray Spectrometer (GRS) and a Neutron Spectrometer (NS). The GRS is a germanium detector with an active shield capable of measuring the elemental abundances of O, Si, S, Fe, H, K, Th, and U. The NS sensor consists of two lithium glass scintillators separated by a thick slab of borated plastic scintillator. The glass scintillators measure thermal neutrons, while the borated-plastic scintillator counts fast neutrons. GRNS contributes to the understanding of surface elemental abundances and the composition of polar deposits. XRS --- The XRS detects solar-induced X-ray fluorescence to measure the surface abundances of Mg, Al, Si, Ca, Ti and Fe. Three proportional counters measure low- energy X-rays from the planet, while a Si-PIN detector located on the spacecraft sunshade measures the solar X-ray input. The XRS has a FOV of 12 degrees and covers an energy range from 1 to 10 keV. XRS contributes to the understanding of surface elemental abundances. MAG --- The MAG instrument is a miniaturized three-axis, ring-core, fluxgate magnetometer mounted on a lightweight 3.6 m carbon-fiber boom extending from the spacecraft in the anti-sunward direction. It samples the field at a 20-Hz rate with selectable readout intervals between 0.04 s to 1 s. Readout intervals of greater than 1 s generate a 0.5 s average. MAG contributes to the mapping of Mercury's internal magnetic field and to understanding the magnetospheric structure. MLA --- The MLA consists of a 1064 nm laser transmitter and four sapphire lens receiver telescopes. It is capable of measuring altitudes to a 30-cm precision at ranges up to 1000 km. Because of this range, the MLA will operate for about 30 minutes around the periapsis of each orbit. MLA contributes to the mapping of the northern hemisphere topography and the altimetry of polar craters and is instrumental in determining Mercury's gravity field, obliquity and libration amplitude. MASCS ----- The MASCS instrument combines a movable-grating Ultraviolet-Visible Spectrometer (UVVS) and a Visible-Infrared Spectrograph (VIRS) into one package. Both instruments share a single front-end telescope. UVVS spans the spectral range from 115 to 600 nm with an average spectral resolution of 1 nm, has a 25 km altitude resolution, and is optimized for measuring very weak exospheric emissions. VIRS measures the visible (300-1025 nm) and infrared (0.95-1.45 um) spectral ranges utilizing a 512 element detector for the visible and a 256 element detector for the IR. MASCS contributes to the understanding of the composition of Mercury's surface in association with particular geological units, and to the understanding of neutral species in the exosphere especially near the polar regions. EPPS ---- EPPS consists of an Energetic Particle Spectrometer (EPS)and a Fast Imaging Plasma Spectrometer (FIP). The EPS measures the time-of-flight and residual energy of ions from 10 keV/nucleon to ~3 MeV and electrons to 400 keV. Its FOV, 160 degrees by 12 degrees, is divided into six segments of 25 degrees each. The FIPS measures thermal and low-energy ions and is sensitive over nearly a full hemisphere, with energy per charge (E/q) up to > 15 keV/q. EPPS contributes to the understanding of the solar environment associated with Mercury and its magnetosphere. RS -- The spacecraft's radio frequency (RF) telecommunications system is for communications, navigation and radio science (RS). Precise observation of the spacecraft's Doppler velocity and range are used to assist in navigating the spacecraft. These observations will be inverted to determine the effect of the planet's gravitational field on the spacecraft. Occultation observations of the spacecraft's RF signal will provide necessary measurements of Mercury's shape in the southern hemisphere. RS contributes to the understanding of Mercury's gravity field, obliquity and libration amplitude (Doppler observations) and its global topography, especially the southern hemisphere (occultation observations). Mission Phases ============== Fifteen mission phases were defined for significant spacecraft activity periods. The large number of phases is due to the complex sequence of gravitational assists necessary to bring the spacecraft into orbit around Mercury while maintaining a minimal mass due to fuel. This consideration lead to one Earth flyby, two Venus flybys, and three Mercury flybys before orbit insertion at Mercury. The mission phases are defined naturally by the various planetary encounters and their intervening cruise periods. Given the short encounter times for each MESSENGER flyby, we define encounter phases on the basis of a 2 week period centered on the closest approach to each target body (one week before and one after) and separate such encounter segments by cruise phases. The cruise periods and flybys are named according to the planetary body involved. Also defined are a launch and an orbit phase. The mission phases are: Launch, Earth Cruise, Earth Flyby, Venus 1 Cruise, Venus 1 Flyby, Venus 2 Cruise, Venus 2 Flyby, Mercury 1 Cruise, Mercury 1 Flyby, Mercury 2 Cruise, Mercury 2 Flyby, Mercury 3 Cruise, Mercury 3 Flyby, Mercury 4 Cruise, and Mercury Orbit. Launch ------ The launch phase has been defined to capture instrument data produced between launch and the beginning of Phase E. Mission Phase Start Time : 2004-08-03 (2004-216) Mission Phase Stop Time : 2004-09-12 (2004-256) Earth Cruise ------------ Earth Cruise is the period of time between launch and the week before closest approach to Earth. Mission Phase Start Time : 2004-09-13 (2004-257) Mission Phase Stop Time : 2005-07-18 (2005-199) Earth Flyby ----------- Earth Flyby is defined as the two week (14 day) period centered on closest approach to Earth. Mission Phase Start Time : 2005-07-19 (2005-200) Mission Phase Stop Time : 2005-08-16 (2005-228) Venus 1 Cruise -------------- Venus 1 Cruise is defined as the period between the Earth flyby and the first Venus flyby. Mission Phase Start Time : 2005-08-17 (2005-229) Mission Phase Stop Time : 2006-10-09 (2006-282) Venus 1 Flyby ------------- Venus 1 Flyby is defined as the two week (14 day) period centered on the first of the mission's two closest approaches to Venus. Mission Phase Start Time : 2006-10-10 (2006-283) Mission Phase Stop Time : 2006-11-07 (2006-311) Venus 2 Cruise -------------- Venus 2 Cruise is defined as the period between the first and second Venus flyby. Mission Phase Start Time : 2006-11-08 (2006-312) Mission Phase Stop Time : 2007-05-22 (2007-142) Venus 2 Flyby ------------- Venus 2 Flyby is defined as the two week (14 day) period centered on the second of the mission's two closest approaches to Venus. Mission Phase Start Time : 2007-05-23 (2007-143) Mission Phase Stop Time : 2007-06-20 (2007-171) Mercury 1 Cruise ---------------- Mercury 1 Cruise is defined as the period between the second Venus flyby and first Mercury flyby. Mission Phase Start Time : 2007-06-21 (2007-172) Mission Phase Stop Time : 2007-12-30 (2007-364) Mercury 1 Flyby --------------- Mercury 1 Flyby is defined as the two week (14 day) period centered on the first of the mission's three closest approaches to Mercury. Mission Phase Start Time : 2007-12-31 (2007-365) Mission Phase Stop Time : 2008-01-28 (2008-028) Mercury 2 Cruise ---------------- Mercury 2 Cruise is defined as the period between the first and second Mercury flyby. Mission Phase Start Time : 2008-01-29 (2008-029) Mission Phase Stop Time : 2008-09-21 (2008-265) Mercury 2 Flyby --------------- Mercury 2 Flyby is defined as the two week (14 day) period centered on the second of the mission's three closest approaches to Mercury. Mission Phase Start Time : 2008-09-22 (2008-266) Mission Phase Stop Time : 2008-10-20 (2008-294) Mercury 3 Cruise ---------------- Mercury 3 Cruise is defined as the period between the second and third Mercury flyby. Mission Phase Start Time : 2008-10-21 (2008-295) Mission Phase Stop Time : 2009-09-15 (2009-258) Mercury 3 Flyby --------------- Mercury 3 Flyby is defined as the two week (14 day) period centered on the third of the mission's three closest approaches to Mercury. Mission Phase Start Time : 2009-09-16 (2009-259) Mission Phase Stop Time : 2009-10-14 (2009-287) Mercury 4 Cruise ---------------- Mercury 4 Cruise is defined as the period between the third Mercury flyby and Mercury orbit insertion. Mission Phase Start Time : 2009-10-15 (2009-288) Mission Phase Stop Time : 2011-03-03 (2011-062) Mercury Orbit ------------- The Orbit phase begins at Mercury orbit insertion and continues until the end of mission. This phase is the most intensive science portion of the mission with full instrument utilization through out the period. Mission Phase Start Time : 2011-03-04 (2011-063) Mission Phase Stop Time : 2012-03-18 (2012-077) " MISSION_OBJECTIVES_SUMMARY =" The MESSENGER mission has six guiding science questions, which in turn correlate to specific science objects and a set of measurement requirements related to specific instruments. These guiding questions are: (1) What planetary formational processes led to Mercury's high ratio of metal to silicate? (2) What is the geological history of Mercury? (3) What are the nature and origin of Mercury's magnetic field? (4) What are the structure and state of Mercury's core? (5) What are the radar-reflective materials at Mercury's poles? (6) What are the important volatile species and their sources and sinks on and near Mercury? The related science objectives and instrument measurement requirements are: (1) Map the elemental and mineralogical composition of Mercury's surface. GRNS and XRS: Provide major-element maps of Mercury to 10% relative uncertainty on the 1000- km scale. Elements to be measured include: O, Si, S, Fe, H, K, U (by GRS); thermal and epithermal neutrons (by NS), and Fe, Mg, Ca, Al, Si, Ti, S (by XRS). MASCS (VIRS): Determine local composition and mineralogy at the ~20-km scale. (2) Image globally the surface at a resolution of hundreds of meters or better. MDIS (WAC): Provide a global multi-spectral map at 2 km/pixel average resolution. MDIS (NAC): Provide a global map with >90% coverage (monochrome) at 250-m average resolution. MDIS: Image >80% of the planet stereoscopically. Provide color images with a resolution to 1 km/pixel. MLA: Sample half of the northern hemisphere for topography at 1.5-m average height resolution (3) Determine the structure of the planet's magnetic field. MAG: Provide a multipole magnetic-field model resolved through quadrupole terms with an uncertainty of less than ~20% in the dipole magnitude and direction. (4) Measure the libration amplitude and gravitational field structure. MLA & RS: Provide a global gravity field to degree and order 16 and determine the ratio of the solid-planet moment of inertia to the total moment of inertia to ~20% or better. (5) Determine the composition of the radar- reflective materials at Mercury's poles. GRNS: Identify the principal component of the radar-reflective material at Mercury's north pole. (6) Characterize exosphere neutrals and accelerated magnetosphere ions. MASCS (UVVS): Provide altitude profiles at 25-km resolution of the major neutral exospheric species. EPPS: Characterize the major ion-species energy distributions as functions of local time, Mercury Heliocentric distance, and solar activity. " END_OBJECT = MISSION_INFORMATION OBJECT = MISSION_HOST INSTRUMENT_HOST_ID = "MESS" OBJECT = MISSION_TARGET TARGET_NAME = {"CALIBRATION", "EARTH", "VENUS", "MERCURY"} END_OBJECT = MISSION_TARGET END_OBJECT = MISSION_HOST OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "SOLOMONETAL2007" END_OBJECT = MISSION_REFERENCE_INFORMATION END_OBJECT = MISSION END