Mission Concept Maturation for the Next-generation Spaceflight Laser Altimeter Mapping Mission

The objective of the proposed work is technology maturation needed for a spaceflight mission that would conduct lidar mapping of the Earth's surface. Lidar mapping, done using a laser altimeter instrument, serves a diverse array of science and applications objectives, providing  foundation data on the Earth's surface properties and their change. Properties include land, ice sheet and glacier topography, 3-D vegetation structure, the height of water bodies and snow cover, and the extent and thickness of sea ice. The mission concept being developed would launch in the mid-2020's and be substantially more challenging than current lidar flight projects that will acquire altimeter profiles with a few laser beams.  This work will focus on advancing capabilities that have low technical readiness in three areas: (1) increasing laser transmitter efficiency to generate many more laser beams for mapping, (2) developing an approach to produce a monolithic laser transmitter array and  (3) evaluating  a novel method to maintain alignment of an array of many laser beams reflected from the Earth with a large detector array.  

The objective of the proposed work is technology maturation needed for a spaceflight mission that would conduct lidar mapping of the Earth's surface that the National Research Council recommended NASA conduct in their 2007 Earth Science Decadal Survey report. Lidar mapping, done using a laser altimeter instrument, serves a diverse array of science and applications objectives, providing  foundation data on the Earth's surface properties and their change. Properties include land, ice sheet and glacier topography, 3-D vegetation structure, the height of water bodies and snow cover, and the extent and thickness of sea ice.  These properties can be modified in response to climate change and natural hazards. The mission concept being developed would launch in the mid-2020's following NASA's ICESat-2 and GEDI lidar missions, that are scheduled for launch in 2017 and 2019.  The mission will be substantially more challenging than those missions which do not map the Earth's surface in but instead acquire a small number of altimeter profiles using a few laser beams.  This work will focus on advancing capabilities that have low technical readiness in three areas: (1) increasing laser transmitter efficiency to generate many more laser beams for mapping, (2) developing an approach to produce a monolithic laser transmitter array and  (3) evaluating  a novel method to maintain alignment of an array of many laser beams reflected from the Earth with a large detector array.  Advances will be made by (1) building and testing a double-pass Master Oscillator Power Amplifier laser transmitter to increase  output power and efficiency, (2) building and testing a hybrid, Q-switched, monolithic laser oscillator that is a first step toward producing an inherently fault-tolerant, monolithic, multi-beam laser transmitter array, and (3) developing an optical model of the laser to detector alignment approach and employing it in trade studies.   This work will build upon capabilities developed in an airborne instrument, described in the article in the project library, that need advancement in order to be appropriate for a spaceflight mission.