Hermalyn, Brendan - Dust Around the Moon: Preliminary Results from the LADEE Ultraviolet Visible Spectrometer

A main scientific objective of the Lunar Atmosphere and Dust Environment Explorer (LADEE) mission is to directly measure the lunar exospheric dust environment and its spatial and temporal variability. Past studies have suggested that impacts could excavate material into a dust cloud surrounding the moon. Meteor showers, in particular, present a large number of concentrated impact events on the surface.  The Ultraviolet and Visible Spectrometer (UVS), a CCD spectrograph which operates between 230 – 810 nm with a spectral resolution of <1 nm, is designed to make observations of the lunar exosphere and search for dust.  Observations of the lunar limb using the UVS three-inch telescope include limb “stares” ranging from ~20 km above the surface at the terminators to ~40 km at around local noon time.  At the terminators, the spacecraft can “nod” the telescope between the surface and about 50 km.  Both “backward” looks (stares that point in the anti-velocity direction of the spacecraft), and “forward” looks (which flip the spacecraft to allow UVS to look in the ram direction) have been completed to permit observations in both back and forward scattering regimes.  The spectra are taken at relatively high cadence (between 1 and 10 seconds each) during these observations and allow a temporally and spatially resolved view of the scatter in the exosphere.  Convolution of these profiles with expected contributions from impact events can permit characterization of present day impacts on the moon. 

Over the course of the 140 day mission, UVS observed a dynamic and highly time-dependent dust and volatile environment on the Moon.  In this study, we will present preliminary results of lunar limb observations from the Ultraviolet and Visible Spectrometer and star tracker images onboard LADEE and discuss new experiments and modeling of the contributions to the lunar dust exosphere.