| Here's an article on DIMES, the system JPL developed in the early 2000s to address the problem of estimating horizontal velocity for the Mars landers: https://robotics.jpl.nasa.gov/media/documents/DIMES-ai-space... Martian winds make this more important there than on the Moon. The DIMES system integrates radar, visual images, and IMUs. They did not have a dedicated Doppler radar for horizontal velocity, for technical and cost reasons it was not workable. From the introduction: > Some of the challenges were subtler — and one in particular was subtle enough that it wasn’t fully appreciated until mission development was well underway. > This was the challenge of martian winds. How to detect and compensate for them? In the worst-case scenario, they could tip the vehicle over in the final stages of descent such that the powered thrust intended to eliminate downward velocity might actually drive the platform sideways and down into the surface beyond the safety envelope of the airbag cushions. > This article tells the story of how this late-understood challenge was addressed successfully — and, as it turned out, critically, for Spirit. The system was improved and re-fielded for the successor missions - I think it goes under the name LVS now. One reference appears to be here: https://www-robotics.jpl.nasa.gov/what-we-do/applications/la... |