[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.

We report initial measurements of atmospheric CO2 column density using a pulsed airborne lidar operating at 1572 nm. It uses a lidar measurement technique being developed at NASA Goddard Space Flight Center as a candidate for the CO2 measurement in the Active Sensing of CO2 Emissions over Nights, Days and Seasons (ASCENDS) space mission. The pulsed multiple‐wavelength lidar approach offers several new capabilities with respect to passive spectrometer and other lidar techniques for high‐precision CO2 column density measurements. We developed an airborne lidar using a fibre laser transmitter and photon counting detector, and conducted initial measurements of the CO2 column absorption during flights over Oklahoma in December 2008. The results show clear CO2 line shape and absorption signals. These follow the expected changes with aircraft altitude from 1.5 to 7.1 km, and are in good agreement with column number density estimates calculated from nearly coincident airborne in‐situ measurements.

Abstract:We have previously demonstrated a pulsed direct detection IPDA lidar to measure range and the column concentration of atmospheric CO 2 . The lidar measures the atmospheric backscatter profiles and samples the shape of the 1,572.33 nm CO 2 absorption line. We participated in the ASCENDS science flights on the NASA DC-8 aircraft during August 2011 and report here lidar measurements made on four flights over a variety of surface and cloud conditions near the US. These included over a stratus cloud deck over the Pacific Ocean, to a dry lake bed surrounded by mountains in Nevada, to a desert area with a coal-fired power plant, and from the Rocky Mountains to Iowa, with segments with both cumulus and cirrus clouds. Most flights were to altitudes >12 km and had 5-6 altitude steps. Analyses show the retrievals of lidar range, CO 2 column absorption, and CO 2 mixing ratio worked well when measuring over topography with rapidly changing height and reflectivity, through thin clouds, between cumulus clouds, and to stratus cloud tops. The retrievals shows the decrease in column CO 2 due to growing vegetation when flying over Iowa cropland as well as a sudden increase in CO 2 concentration near a coal-fired power plant. For regions where the CO 2 concentration was relatively constant, the measured CO 2 absorption lineshape (averaged for 50 s) matched the predicted shapes to better than 1% OPEN ACCESSRemote Sens. 2014, 6 444 RMS error. For 10 s averaging, the scatter in the retrievals was typically 2-3 ppm and was limited by the received signal photon count. Retrievals were made using atmospheric parameters from both an atmospheric model and from in situ temperature and pressure from the aircraft. The retrievals had no free parameters and did not use empirical adjustments, and >70% of the measurements passed screening and were used in analysis. The differences between the lidar-measured retrievals and in situ measured average CO 2 column concentrations were <1.4 ppm for flight measurement altitudes >6 km.