Telescope Reviews: LCROSS photometry and survey

On October 9, 2009 at 11:39 19 UT the LCROSS vehicles impacted the Moon. Images taken by a wide variety of ground-based telescopes did not show a visible impact or the anticipated ejecta plume. LCROSS instruments captured all three phases of the Centaur impact: flash, ejecta plume, and crater. In a future article (in progress) we will present the first data of our survey about photometric observations and some preliminary conclusions that can be drawn. The light curve was obtained with the method of relative photometry. It is rather flat but shows, for both sequences analyzed, including Palomar images, and two images taken for a GLR survey, a slight brightening just after the impact.
The work in progress, for the journal Selenology Today, will describe the methods and the images used.
These results can be interpreted as being somewhat ambiguous. The enclosed images shows the light curve obtained with relative intensity versus time. Every point is the average of three measures. The error bar is 5%. Below the scaled curve on the y axis for Palomar images.However, a minor increase of brightness, detectable 10 seconds post impact, cannot be excluded and the slight intensity increase is not a certain detection, lacking as known an evident plume.A possible explanation of our data is that the ejecta plume, originated by the LCROSS impact produced only a slight brightening inside Cabeus due to the topographical masking by lunar mountain M1.
In this scenario the predicted sunlight-topography model was not correct and the curtain never reached the sunlight. The plume was blocked from Earth view because the first ejecta to reach sunlight is hidden by the flank of M1.

From GLR group data
Raffaello Lena
GLR group