urn:nasa:pds:context:instrument:mla.mess 1.1 1.10.1.0 Product_Context 2016-10-01 1.0 extracted metadata from PDS3 catalog and modified to comply with PDS4 Information Model 2018-06-05 1.1 Minor updates to support PDS3 to PDS4 migrations. Added DOI for reference, removed optional attributes with N/A as values, added intstrument subtype, and did edits to the description field. urn:nasa:pds:context:instrument_host:spacecraft.mess instrument_to_instrument_host https://doi.org/10.1007/s11214-007-9273-4 Cavanaugh, J.F., J.C. Smith, X. Sun, A.E. Bartels, L. Ramos- Izquierdo, D.J. Krebs, A.M. Novo-Gradac, J.F. McGarry, R. Trunzo, J.L. Britt, J. Karsh, R.B. Katz, A. Lukemire, R. Szymkiewicz, D.L. Berry, J.P. Swinski, G.A. Neumann, M.T. Zuber, and D.E. Smith, The Mercury Laser Altimeter instrument for the MESSENGER mission, Space Science Reviews, 131, 451-479, 2007. Mercury Laser Altimeter Altimeter Laser Altimeter The Mercury Laser Altimeter (MLA) was one of the primary instruments on NASA's MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) mission, under NASA's Discovery Program. MLA ranged to the surface only during the periapsis of the 12-hour orbit, limited by its 1800-km maximum range. During the final months of the mission, the spacecraft altitude was reduced and MLA took measurements at altitudes as low as 25 km. The MLA was a bi-static system, meaning that it consisted of separate transmitter and receiver systems. The transmitter used a diode- pumped, Nd:YAG slab laser. The laser output was 20 mJ per pulse at 1064-nm wavelength. The instrument measured the time required for the light to reach the surface and return. MLA performed active and passive radiometric measurements in a narrow spectral band centered at 1064 nm. The active measurement employed a dual-threshold measurement of pulse width to infer the area and width of the return pulse. The pulse area, together with a transmit energy monitor, provided the reflectivity of the target within a 0.08-mrad-diameter laser spot. The passive measurement employed the noise counters and threshold settings on the detector subsystem to infer radiance from a 0.4-mrad-diameter field of view.