The spacecraft was launched in August 2004. It completed one flyby of Earth, two of Venus, and three of Mercury before entering an orbit around Mercury in March 2011. The prime mission was successful and the mission has been extended to March 2015. For more information on the mission and other data sets see the GEO help pages.

Mercury Atmospheric and Surface Composition Spectrometer (MASCS)

MASCS consists of a small Cassegrain telescope with 257-mm effective focal length and a 50-mm aperture that simultaneously feeds an UltraViolet and Visible Spectrometer (UVVS) and a Visible and InfraRed Spectrograph (VIRS). The VIRS data (for mapping the surface) are archived in the GEO node while UVVS data (capable of detecting the atmosphere) are available in both the GEO and ATMOS nodes.

The instrument and mission plan were designed to address the following questions:

MASCS Exospheric Key Questions:

1. What are the composition, structure, and temporal behavior of the exosphere?

2. What are the processes that generate and maintain the exosphere?
(Note: The Magnetometer and EPPS data needed to address that are archived in the PPI node)

3. What is the relationship between exospheric and surface composition? (Note: The MDIS imaging data that provides surface maps is archived in the Imaging node and the Gamma Ray and Neutron Spectrometer data are in the GEO node).

4. Are there polar deposits of volatile material, and how are the accumulation of these deposits related to exospheric processes (Note: UVVS OH data can address this.)?

MASCS Formation and Geological History Key Questions:

1. What is the mineralogy of Mercury's surface and its variation with geological unit?

2. What is the rate of space weathering on Mercury, and how does it affect spectral interpretations?

Characteristics of UVVS

The system has a 125-mm focal length, scanning grating and a Ebert-Fastie monochromator equipped with three photomultiplier tube detectors that cover far ultraviolet (115-180 nm), middle ultraviolet (160-320 nm), and visible (250-600 nm) wavelengths with an average 0.6-nm spectral resolution and high sensitivity. The UVVS operates as a scanning-grating monochromator, obtaining one wavelength at a time.

UVVS Measurements

1.The UVVS investigates the composition and structure of Mercury's exosphere by measuring altitude profiles of known species (H, O, Na, K, and Ca), which can be used to determine exospheric temperature and density and to map the extended distributions of these species. It makes observations at a series of fixed wavelengths to search for predicted species that have not been previously detected (e.g., Si, Al, Mg, Fe, S, OH) and in spectral scans (115-600 nm) to search for new species. In addition to determining the composition and structure of the exosphere, It provides the basis for determining exospheric processes, studying the relationship between surface and exospheric composition, and studying surface-exosphere-magnetosphere interactions.

2. Together, the UVVS and VIRS measure surface reflectance at middle ultraviolet to visible to near infrared wavelengths to search for ferrous-bearing minerals (spectral signatures near 1 μ), Fe-Ti-bearing glasses (spectral signatures near 340 nm), and ferrous iron (strong band near 250 nm). These measurements are made with a spatial resolution of 5 km or better.

Mission Phases
      Start timeEnd time
   Phase NameDate (DOY)Date (DOY)Operations & Targets
IauLaunch03 Aug 2004 (216)12 Sep 2004 (256)Calibration
eacEarth Cruise13 Sep 2004 (257)18 Jul 2005 (199)Calibration
eafEarth Flyby19 Jul 2005 (200)16 Aug 2005 (228)Earth(2)/Moon(17), Calibration
vc1Venus 1 Cruise17 Aug 2005 (229)09 Oct 2006 (282)Calibration, Vega, Fomalhaut, Sirius
   Venus 1 Flyby10 Oct 2006 (283)07 Nov 2006 (311)   
vc2Venus 2 Cruise08 Nov 2006 (312)22 May 2007 (142) Spica, Sirius, Space, Venus
vf2Venus 2 Flyby23 May 2007 (143)20 Jun 2007 (171)Venus
mc1Mercury 1 Cruise21 Jun 2007 (172)30 Dec 2007 (364)Calibration, Sirius, Alpha_Ori, Space
mf1Mercury 1 Flyby31 Dec 2007 (365)28 Jan 2008 (28)Mercury, Space
mc2Mercury 2 Cruise29 Jan 2008 (029)21 Sep 2008 (265)Fomalhaut, Calibration, Dirus Dark Sky
mf1Mercury 2 Flyby22 Sep 2008 (266)20 Oct 2008 (294)Space, Mercury,Sirius, Lyman Alpha
mc3Mercury 3 Cruise21 Oct 2008 (295)15 Sep 2009 (258)Sirius, Calibration, Dark Sky, Venus, Space
            Alpha_Ori. Fomalhaut, Arcturus, Mercury
mf1Mercury 3 Flyby16 Sep 2009 (259)14 Oct 2009 (287)Mercury, Space
mc4Mercury 4 Cruise15 Oct 2009 (288)03 Mar 2011 (062)Venus, Alphs_Ori, Sirius, Space
            Spica, Calibration, Vega
orbMercury Orbit04 Mar 2011 (063)17 Mar 2012 (077)Mercury, Sirius
ob2Mercury Orbit Year 218 Mar 2012 (078)17 Mar 2013 (076)Mercury
ob3Mercury Orbit Year 318 Mar 2013 (077)17 Mar 2014 (076)Mercury
ob4Mercury Orbit Year 418 Mar 2014 (077)17 Mar 2015 (076)Mercury
ob5Mercury Orbit Year 518 Mar 2015 (077)30 Apr 2015 (120)Mercury
                              Beginning of Mercury Years

The Data Delivery Schedule:

The EDR and CDR data are delivered every 6 months (March & September) with the delivery spanning the previous 12 to 6 months.
The DDR data are delivered once per year in March.

Useful Documents Characterizing the Mission and Instrument

Step One - Read the AAREADME file

The following documents introduce you to the mission - Describes the scientific goals and objectives of the MESSENGER program. - Describes the MESSENGER spacecraft. - Describes physical attributes of the MASCS instrument and provides relevant references to published literature.

Available UVVS Products and Documentation

MESSENGER UltraViolet and Visible Spectrometer (UVVS) archive contains the raw (ERDs) and 2 versions of the Calibrated (CDR) and Derived (DDR) data.

Raw Data - See detailed specifications (SIS and cat files)
There are three UVVS EDR data products, one for each detector (FUV, MUV, VIS) and a MASCS housekeeping EDR data product. The UVVS EDR data products all have the same binary table format but contain data specific to the FUV, MUV, or VIS detector.

Options for Calibrated and Derived Data

The latest data delivery (accessed below) contains files that are improved on the previously released products, however the older data remains available in PDS. The UVVS calibration is documented in the MASCS Instrument Calibration Report.

Calibrated Data

Derived Data


For basis instrument description see McClintock, W. E. and M. R. Lankton, 2007, The Mercury Atmospheric and Surface Composition Spectrometer for the MESSENGER Mission, Space Science Reviews, 131, p. 481-521.

Ongoing Publication List