The Mercury Laser Altimeter Instrument for the MESSENGER Mission

Abstract

The Mercury Laser Altimeter (MLA) is one of the payload science instruments on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission, which launched on 3 August 2004. The altimeter will measure the round trip time-of-flight of transmitted laser pulses reflected from the surface of the planet that, in combination with the spacecraft orbit position and pointing data, gives a high-precision measurement of surface topography referenced to Mercury's center of mass. The altimeter measurements will be used to determine the planet's forced librations by tracking the motion of large-scale topographic features as a function of time. MLA's laser pulse energy monitor and the echo pulse energy estimate will provide an active measurement of the surface reflectivity at 1064 nm. This paper describes the instrument design, prelaunch testing, calibration, and results of post-launch testing.

Despinning plus global contraction and the orientation of lobate scarps on Mercury: Predictions for MESSENGER

“…MESSENGER is well poised to explore these possibilities. The global Mercury Dual Imaging System (MDIS) imagery (Hawkins et al, 2007), which is better optimized for morphometric analysis, and topographic data (from MDIS stereo images and Mercury Laser Altimeter ranges; Cavanaugh et al, 2007) can be used to search for this hidden strain (and estimate better the amount of strain recorded in the lobate scarps). Lack of additional tectonism would support a very restricted composition for Mercury's interior (e.g., Hauck et al, 2004); however leveraging the axiom of Occam's razor, it seems likely that MESSENGER will uncover this hidden strain.…”

The INPOP10a planetary ephemeris and its applications in fundamental physics

“…The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft, only the second probe to encounter the innermost planet, flew by Mercury on 14 January 2008, 6 October 2008, and in December 2009. The MESSENGER payload includes the Mercury Laser Altimeter (MLA) (Cavanaugh et al 2007) and a gravity science investigation that uses the spacecraft tracking system (Srinivasan et al 2007). During the flybys the spacecraft was tracked at X-band frequency by the Deep Space Network (DSN), the latter providing high-quality Doppler range-rate observations of the spacecraft motion relative to Earth.…”

The Lunar Orbiter Laser Altimeter Investigation on the Lunar Reconnaissance Orbiter Mission

“…Off-nadir observations are possible with LOLA and other laser altimeters. Notably, MOLA (Zuber et al 1992) at Mars and MLA (Cavanaugh et al 2007) at Mercury, have both obtained off-nadir observations; MOLA on a regular basis as the MGS spacecraft changed attitude to enable the imaging system to acquire specific targets (Smith et al 2001), and MLA during two flybys in which the emission angle exceeded 60 • (Zuber et al 2008b). The observation of potential landing sites and special locations, such as inside permanently shadowed regions (where LOLA is one of the few instruments capable of making observations), may require dense observations with coverage as uniform as possible.…”