Dr Tristram Warren

Abstract:

Astrobotic's Peregrine Mission-1 spacecraft experienced a propulsion system anomaly that prevented the lander from reaching the Moon. During the mission, several instruments operated successfully in cis-lunar space. Among them, the Peregrine Ion Trap Mass Spectrometer (PITMS) measured both the presence of outgassing water and nitrogen oxides traceable to the MON-25 oxidizer. We performed Direct Simulation Monte Carlo (DSMC) studies of the oxidizer leak on Peregrine to characterize the gas diffusion from the leak to the instrument, mediated by inter-species collisions and gas–surface interaction. We conclude that the latter process was prevalent and that diffusion paths through Peregrine are necessary to explain the PITMS detections. Our DSMC study and estimation of Peregrine's outgassing rate suggest that, at the early stage of the mission, the spacecraft released water at a rate comparable to the Space Shuttle and at a much larger rate than typical spacecraft during science operations. This provides useful information for planning future operations of science instruments on commercial missions.

Abstract:

The Peregrine Ion Trap Mass Spectrometer (PITMS) was a mass spectrometer designed to measure lunar gases. PITMS flew on the first flight of Astrobotic’s Peregrine lander via the Commercial Lunar Payload Services (CLPS) program in 2024 January. After launch, the lander suffered a propulsion system anomaly that prevented the mission from reaching the Moon, but PITMS collected 80 high-quality spectra while in cislunar space. PITMS observed abundant outgassing products from the Peregrine lander, including water, MON-25 oxidizer from the propulsion system leak, and traces of combustion products. PITMS data help constrain the nature of the propulsion system failure: oxidizer molecular ratios show that the leak released molecules rapidly enough for them to fully dissociate, and the high observed abundances imply that the oxidizer traveled within the lander surfaces rather than jetting into space. The amount of water offgassed by the spacecraft is substantially more than other planetary spacecraft, so the PITMS results suggest that instruments flying in the CLPS paradigm need to consider lander cleanliness. Though not successful in measuring the native lunar exosphere, the PITMS results showcase the capabilities of a mass spectrometer on board a lunar lander, along with lessons in pragmatism and flexibility that would enable such an instrument to ultimately be successful in the CLPS initiative.

Abstract:

A laboratory study was performed using the Visible Oxford Space Environment Goniometer in which the broadband (350–1250 nm) bidirectional reflectance distribution functions (BRDFs) of two representative Apollo regolith samples were measured, for two surface roughness profiles, across a range of viewing angles—reflectance: 0–70°, in steps of 5°; incidence: 15°, 30°, 45°, and 60°; and azimuthal: 0°, 45°, 90°, 135°, and 180°. The BRDF datasets were fitted using the Hapke BRDF model to (1) provide a method of comparison to other photometric studies of the lunar regolith and (2) to produce Hapke parameter values which can be used to extrapolate the BRDF to all angles. Importantly, the surface profiles of the samples were characterized using an Alicona 3D® instrument, allowing two of the free parameters within the Hapke model, φ and θ ¯ $$ \overline{\theta} $$ , which represent porosity and surface roughness, respectively, to be constrained. The study determined that, for θ ¯ $$ \overline{\theta} $$ , the 500–1000 μm size‐scale is the most relevant for the BRDF. Thus, it deduced the following “best fit” Hapke parameters for each of the samples: Apollo 11 rough— w $$ w $$ = 0.315 ± 0.021, b $$ b $$ = 0.261 ± 0.007, and h S $$ {h}_S $$ = 0.039 ± 0.005 (with θ ¯ $$ \overline{\theta} $$ = 21.28° and φ = 0.41 ± 0.02); Apollo 11 smooth— w $$ w $$ = 0.281 ± 0.028, b $$ b $$ = 0.238 ± 0.008, and h S $$ {h}_S $$ = 0.032 ± 0.006 (with θ ¯ $$ \overline{\theta} $$ = 13.80° and φ = 0.60 ± 0.02); Apollo 16 rough— w $$ w $$ = 0.485 ± 0.155, b $$ b $$ = 0.155 ± 0.083, and h S $$ {h}_S $$ = 0.135 ± 0.007 (with θ ¯ $$ \overline{\theta} $$ = 21.69° and φ = 0.55 ± 0.02); Apollo 16 smooth— w $$ w $$ = 0.388 ± 0.057, b $$ b $$ = 0.063 ± 0.033, and h S $$ {h}_S $$ = 0.221 ± 0.011 (with θ ¯ $$ \overline{\theta} $$ = 14.27° and φ = 0.40 ± 0.02). Finally, updated hemispheric albedo functions were determined for the samples, which can be used to set laboratory measured visible scattering functions within thermal models.

Abstract:

Many upcoming lunar missions and payloads are targeting the south pole of the Moon, due to the volatiles potentially harboured in this region including ESA's PROSPECT instrument. PROSPECT is designed to sample the lunar regolith within the first meter of the surface and to analyse any volatiles found. Remote sensing methods and a range of datasets including thermal models, illumination models, LRO NAC images, LOLA DEMs and LRO NAC DEMs generated with shape-from-shading, were used to identify suitable areas for PROSPECT science within the south polar region (84–90°S). Sites identified were down selected using a science matrix and scoring sites of interest based on if and how well the point of interest met the science requirements of PROSPECT. The highest scoring sites are presented and proposed to be ideal candidate landing sites for missions targeting the lunar south polar region, especially for missions that are interested in sampling volatiles, micro cold traps and Permanently Shaded Regions (PSRs). Understanding and sampling these colder areas within the south polar region will advance the understanding of volatiles within the lunar surface and volatile transfer.