This is the standard definition version MPEG of the ICESat Data Accumulation Animation.
Accumulating Data: Glas Builds Its Facts One Point at a Time - The technology behind GLAS is called lidar. Lidar is a distance measuring system similar to radar, except that instead of radio waves it uses pulses of laser light for range finding. The name is a contraction based on the words light and radar: Light Detection And Ranging. A lidar system determines precise distances by measuring the amount of time necessary for a pulse of light to leave an emitter, hit a target, and return. In this case, distance measurements helped researchers determine changes in ice thickness, vegetation, cloud thickness, and much more.
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 220.127.116.11.0