Present day robotic missions to other planets require extensive knowledge of the terrain in order to pre-determine a landing zone that is relatively devoid of hazards. Without hazard avoidance systems mission planners have to compromise on scientific objectives for a safe landing site. Future robotic exploration missions should be capable of autonomously identifying a safe landing target within a specified target area selected by mission requirements. Recent advances in radar technology have resulted in small, lightweight, low power radars that are used for collision avoidance and cruise control systems in automobiles. Such radar systems warrant testing for use in hazard avoidance systems for planetary landers. This CIF proposal seeks to complete the evaluation and characterization of an automotive radar system in the MSFC lunar terrain field under various simulated robotic lander descent profiles.
NASA Headquarters chartered the Autonomous Precision Landing and Hazard Avoidance Technology (ALHAT) project in 2005 to enable precision landing at any site under any lighting conditions. In 2014 ALHAT conducted a series of flight tests aboard the Morpheus vertical testbed at the KSC terrain field. One of the findings of the Morpheus/ALHAT tests is lidar-based systems struggle when moving dust and/or rocket exhaust is between the sensor and the target being mapped. The same phenomena was also observed with the Mighty Eagle testing of a stereo camera for hazard avoidance. Rocky planetary surfaces are dusty; hazard detection systems must deal with dust on close approach.
The proposed activity continues a FY2014 CIF project. The two-year activity seeks to test a commercial, automotive interferometric radar for detection of hazards by autonomous landers. Advancement in radar and computer technologies has resulted in such radars being used in many vehicles. These interferometric radar systems typically use 37GHz or 77GHz to identify hazards around a vehicle. The systems are lightweight, low power, and small enough to fit into a vehicle’s fender. The signal processing capabilities integral to the automotive units fundamentally change the cost/performance relationships normally associated with the aerospace uses of radar. These automotive systems have enormous potential to perform an analogous function for planetary landers. Further, compared to systems dependent on optical wavelengths, suspended dust, small particles and aerosols are transparent to these radar’s much longer wavelengths.
In Year 1 we procured a radar, developed a portable data acquisition system, wrote software to handle the data, and tested the unit in multiple environments. A literature review found that rocket exhaust interference with radar wavelengths is very specific to the particular characteristics of the exhaust, especially its composition. In this year we plan to characterize the radar reflectivity of the various hazards on the terrain field, evaluate the radar under various lander descent profiles (simulated using the Aerial Trolley), characterize and evaluate the sensitivity of the results to moisture content in the simulant, and study (through simulation) the interaction of various exhaust gases with radio frequency signals.More »
Hazard Avoidance is one of the greatest technical challenges for autonomous missions to planetary objectives. The problem’s importance is well known and validated by the Agency’s investment in systems such as ALHAT. The proposed radar system is much less expensive, lower weight, and draws less electric power than the highly capable ALHAT system. For small, low cost missions these are vital considerations. Compared to optical technologies, radar is more robust in the face of dust and possibly to exhaust turbulence, making the technology especially attractive. Therefore, this proposal explicitly aligns with the strategic areas “Propulsion testebeds” and “Robotic capabilities to accomplish or enhance exploration objectives." This proposal seeks to improve MSFC’s current technical capability to meet current/future NASA mission needs. Our work also contributes to new NASA capability to land payloads and instruments at targets currently unreachable. This proposal compliments the ALHAT effort and is submitted with the endorsement of the ALHAT project.
MSFC has created a new and unique asset, ideal for testing lander hazard avoidance technology, the Lunar Terrain Testbed. The 30mx30m field is covered with high fidelity regolith simulant mined from Merriam Crater, AZ, the source for the JSC-1 family of lunar simulants. It reproduces lunar mineralogy, particle shape, reflectivity, glass content and other characteristics to the maximum practical extent. The testbed responds to rocket exhaust in a manner very comparable to what was observed in the Apollo landings. The field cost ~$60,000 for procurement and site preparation, not counting FTE. At this time (October 2014) the aerial trolley is about to enter service. The aerial trolley is a carrier for sensor packages that rides on a zip line from the top of the Saturn V test stand to a point beyond the lunar terrain field. Testing the radar system on the aerial trolley will enable us to “fly” representative landing profiles at much lower cost and higher frequency than possible on a flight system like the Mighty Eagle.
|Organizations Performing Work||Role||Type||Location|
|Marshall Space Flight Center (MSFC)||Lead Organization||NASA Center||Huntsville, Alabama|