Locating the LCROSS Impact Craters

Authors: William Marshall Mark Shirley Zachary Moratto Anthony Colaprete Gregory Neumann David Smith Scott Hensley Barbara Wilson Martin Slade Brian Kennedy Eric Gurrola Leif Harcke

Publish Date: 2011/05/06

Volume: 167, Issue: 1-4, Pages: 71-92

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Abstract

The Lunar CRater Observations and Sensing Satellite LCROSS mission impacted a spent Centaur rocket stage into a permanently shadowed region near the lunar south pole The Sheperding Spacecraft SSC separated ∼9 hours before impact and performed a small braking maneuver in order to observe the Centaur impact plume looking for evidence of water and other volatiles before impacting itselfThis paper describes the registration of imagery of the LCROSS impact region from the mid and nearinfrared cameras onboard the SSC as well as from the Goldstone radar We compare the Centaur impact features positively identified in the first two and with a consistent feature in the third which are interpreted as a 20 m diameter crater surrounded by a 160 m diameter ejecta region The images are registered to Lunar Reconnaisance Orbiter LRO topographical data which allows determination of the impact location This location is compared with the impact location derived from groundbased tracking and propagation of the spacecraft’s trajectory and with locations derived from two hybrid imagery/trajectory methods The four methods give a weighted average Centaur impact location of −846796° −487093° with a 1σ uncertainty of 115 m along latitude and 44 m along longitude just 146 m from the target impact site Meanwhile the trajectoryderived SSC impact location is −84719° −4961° with a 1σ uncertainty of 3 m along the Earth vector and 75 m orthogonal to that 766 m from the target location and 2803 km southwest of the Centaur impactWe also detail the Centaur impact angle and SSC instrument pointing errors Six highlevel LCROSS mission requirements are shown to be met by wide margins We hope that these results facilitate further analyses of the LCROSS experiment data and followup observations of the impact region

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