A Mars-Orbiting 2-micron LIDAR System to Monitor the Density, Winds and Dust of the Atmosphere of Mars

Abstract

Future robotic missions to Mars and, eventually, human missions to Mars will require landing massive spacecraft with “pin point” accuracy, e.g., the planned Mars Sample Return (MSR) mission will require “pin point” landing accuracy to rendezvous with the previously cached Mars samples to be returned to Earth and the first human mission to Mars, with payloads estimated to be in excess of 40 metric tons, must land very close to the cargo spacecraft that precede it on the journey to Mars. Hence, “pin point” entry, descent and landing (EDL) has become a major technological driver in future massive robotic and human mission to Mars [1]. To achieve “pin point” EDL on Mars, we must predict the atmospheric density, atmospheric winds and atmospheric dust level to an accuracy previously unobtainable. To develop an accurate and precise predictive model of the atmosphere of Mars, we propose a Marsorbiting LIDAR system to measure/monitor the density, winds and dust in the atmosphere of Mars over two Mars years. The LIDAR measurements will be used to develop an accurate model of the atmosphere of Mars to be used for “pin point” EDL for future Mars missions. Introduction: Planetary winds have implications to understanding planetary weather and conducting planetary exploration. In the case of Mars, the interplay between winds, dust storms and the radiative feedback is critical to the prediction of operational meteorology but remains poorly understood. Two major components of the Martian weather are the episodically strong winds and the dust storms. Both have implications to understanding Martian weather and to the prediction of hazardous conditions for landing and exploration on the surface of Mars. The feedback between winds (driven by thermal gradients), dust storms (sustained suspension of high optical depth dust clouds) and the consequential changes in the thermal gradients, is recognized as fundamental to the Martian weather. In addition to the weather/climate issues, the knowledge of the 3-dimensional wind field would be beneficial and could be critical to both the design and execution of future robotic and human expedition missions. As an example, the wind field (and wind shear throughout the atmosphere) is a crucial factor in the entry, descent, and landing of instrumented craft and subsequent airborne and surface exploration. Approach: The lack of measurements of Martian atmospheric density in the 30-80 km range, dust storm formation and movements, and horizontal wind patterns in the 0-20 km range pose significant risks to aerocapture, and entry, descent, and landing (EDL) of future robotic and human Mars missions. Systematic measurement of the Mars atmospheric density and winds will be required over several Mars years, supplemented with day-of-entry operational measurements. To date, there have been 6 successful U.S. robotic landings on Mars (the two Viking landers, Mars Pathfinder, MER: Spirit and Opportunity, and Mars Phoenix). Atmospheric density and wind reconstruction has been performed for each of these entries. At present, all of NASA’s Mars atmospheric density and wind models have these 6 entries (at widely scattered positions and seasons) as their basis, supplemented by coarse orbital measurements of atmospheric opacity and temperature. This lack of data leads to a large uncertainty in prediction of the Martian atmospheric density and winds in the altitude regime where deceleration of landers will occur. This uncertainty will have a dramatically large impact on mass, cost and risk. The proposed 2-m Doppler/DIAL lidar system will provide the critically needed density and winds data to reduce the risks of future Mars landing missions. Research programs were initiated at NASA Langley Research Center during 2005, jointly funded by NASA Science Mission Directorate and Exploration Systems Mission Directorate, to first model the lidar’s performance and then build a breadboard lidar system demonstrating a measurement capability fo