[1] As of June 19, 2010, the Lunar Orbiter Laser Altimeter, an instrument on the Lunar Reconnaissance Orbiter, has collected over 2.0 × 10 9 measurements of elevation that collectively represent the highest resolution global model of lunar topography yet produced. These altimetric observations have been used to improve the lunar geodetic grid to ∼10 m radial and ∼100 m spatial accuracy with respect to the Moon's center of mass. LOLA has also provided the highest resolution global maps yet produced of slopes, roughness and the 1064-nm reflectance of the lunar surface. Regional topography of the lunar polar regions allows precise characterization of present and past illumination conditions. LOLA's initial global data sets as well as the first highresolution digital elevation models (DEMs) of polar topography are described herein.

[1] The GLAS instrument on NASA's ICESat satellite has made over 904 million measurements of the Earth surface and atmosphere through June 2005. During its first seven operational campaigns it has vertically sampled the Earth's global surface and atmosphere on more than 3600 orbits with vertical resolutions approaching 3 cm. This paper summarizes the on-orbit measurement performance of GLAS to date. Instrument Description and Ground Testing[2] The Geoscience Laser Altimeter System (GLAS) is a new generation space lidar developed for the Ice, Cloud and land Elevation Satellite (ICESat) mission [Schutz et al., 2005]. The GLAS instrument combines a 3 cm precision 1064-nm laser altimeter with a laser pointing angle determination system and 1064 and 532-nm cloud and aerosol lidar [Zwally et al., 2002]. GLAS was developed by NASA-Goddard as a medium cost and medium risk instrument.[3] GLAS uses the 1064-nm laser pulses to measure the two way time of flight to the Earth's surface. The instrument time stamps each laser pulse emission, and measures its emission angle relative to inertial space, the transmitted pulse waveform and the echo pulse waveform from the surface. GLAS also measures atmospheric backscatter profiles. The 1064-nm pulses profile the backscatter from thicker clouds, while the 532-nm pulses use photon-counting detectors to measure the height distributions of optically thin clouds and aerosol layers [Abshire et al., 2003]. A GPS receiver on the spacecraft provides data for determining the spacecraft position, and provides an absolute time reference for the instrument measurements and the altimetry clock.[4] Before launch, GLAS measurement performance was evaluated with ''inverse lidar'' called the Bench Check Equipment (BCE). The BCE also monitored the transmitted laser energy and the other critical instrument measurements [Riris et al., 2003]. Before launch, the three GLAS lasers were qualified [Afzal et al., 2002] and fired a total of 427 million shots, or 11% of the planned orbital lifetime. This pre-launch testing also uncovered a few issues. The co-alignment of the laser beams to the receiver field of view was found to vary more than expected, with instrument temperature and orientation. Three of the eight 532-nm detectors failed during instrument vacuum testing. Laser 3 also showed an unexplained small drop in its 532 nm energy. Unfortunately, due to project deadlines, it was not possible to correct these issues before launch. Space Operation of Lasers and Laser Energy History[5] After the ICESat launch, GLAS Laser 1 started firing on February 20, 2003, and was operated continuously through the Laser 1 campaign. The GLAS 1064-nm measurements showed strong echo pulses from the surface and cloud tops and better than expected atmospheric profiles. Operation of the 532-nm detectors was delayed. Figure 1 shows the 1064 and 532-nm energy histories to date for all lasers, with Laser 1 shown in red. After day 10, Laser 1 showed unusual and faster than expected energy decline, and it failed on day 38. NAS...

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The Lunar Orbiter Laser Altimeter (LOLA) is an instrument on the payload of NASA's Lunar Reconnaissance Orbiter spacecraft (LRO) (Chin et al., in Space Sci. Rev. 129:391-419, 2007). The instrument is designed to measure the shape of the Moon by measuring precisely the range from the spacecraft to the lunar surface, and incorporating precision orbit determination of LRO, referencing surface ranges to the Moon's center of mass. LOLA has 5 beams and operates at 28 Hz, with a nominal accuracy of 10 cm. Its primary objective is to produce a global geodetic grid for the Moon to which all other observations can be precisely referenced.

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.