The ESA PROSPECT Payload: Science Activities and Development Status

Introduction:  PROSPECT is a payload in development by ESA for use at the lunar surface.  Development to date has been for implementation on the Russian-led Luna-Resours Lander (Luna 27) mission.  With the recent ESA Council decision to cease all cooperation with Russia on the Luna missions, the PROSPECT Project Team is in the process of redirecting the implementation towards flight on a NASA CLPS mission in the 2025/2026 timeframe.  This opportunity was already agreed and in place with NASA at the beginning of 2022. 

PROSPECT Overview: PROSPECT will perform an assessment of the volatile inventory in the near surface lunar regolith (down to ~ 1 m), and complete elemental and isotopic analyses to determine the abundance and origin of any volatiles discovered [1]. PROSPECT also has ISRU capabilities and will aim to complete in-situ extraction of oxygen from lunar minerals, which will constitute potential science return from anywhere on the Moon. PROSPECT is comprised of the ProSEED drill module and the ProSPA Analytical Laboratory (AL) plus the Solids Inlet System (SIS), a carousel of sealable ovens for evolving volatiles from regolith.

ProSEED can collect two icy samples of different sizes and mechanical properties in a single sampling operation, with the smaller sample of ~45 mm³ being delivered to ProSPA.  The drill rod also has integrated temperature sensors and a sensor to measure the electrical permittivity of the lunar soil along the borehole.

The ProSPA laboratory will receive samples from the drill, seal them in miniaturized ovens, and process them via ramped (EGA), stepped (isotopic) or single step (ISRU) heating up to 1000 °C, completing physical and chemical processing of released volatiles, and analysing the obtained constituents via Ion Trap or Magnetic Sector mass spectroscopy.

 

ProSEED and ProSPA will also each carry small cameras.  The ProSEED Imaging System (IS) has multispectral capabilities via 6 LEDs ranging from 451 to 970nm.  This will provide images of the drilling area and excavated subsurface regolith to monitor activities and deliver contextual information.  ProSPA’s Sample Camera (SamCam [2]) will provide multispectral 3-dimensional images of the samples in the ovens, providing information on their morphology, grain size, volume and mineralogy.

Development status: Development to date has been for Luna 27, where PROSPECT was entering Phase C/D.  As the package is the same for CLPS, this progress is not lost, and Critical Design Reviews for the major components will be completed this year in preparation for implementation on the NASA CLPS mission.

Drill Testing. The ProSEED Development Model was successfully tested in December 2019, demonstrating drilling and sampling in ambient, cold and thermal vacuum laboratory conditions.  Tests included drilling into a well-characterized NU-LHT-2M simulant mixed with inclusions [3] covering a plausible range of regolith characteristics [e.g. [4]].  The main functionalities of the drill system were successfully demonstrated and required performances were achieved in these tests.

ProSPA Bench Development Model (BDM). The BDM of the ProSPA analytical lab at the Open University has been tested to demonstrate science performance against measurement requirements, verifying the evolved gas analysis (EGA), demonstrating ISRU capabilities [5, 6], and testing the performance of oven seal materials [7].

Science Activities: a number of science activities are being pursued alongside and in support of the technical development.

Volatile Preservation: Efforts continue on understanding the capability of PROSPECT to sufficiently preserve the volatile content in regolith throughout the sampling-analysis chain for a range of expected volatile contents and operational environments, e.g. [8, 9].  Detailed modelling and experimental work are helping to constrain the potential effect on measured D/H of sublimation of lunar water ice (e.g. [10]).  Recent analysis has demonstrated that volatile loss is most significant during sample retrieval phase and work is underway to further investigate the effects of frictional heating during this critical phase.  This will help ensure that even in a ‘hot operational case’, the original volatile inventory can be determined with sufficiently small uncertainties.

ProSEED Imaging System Testing: In summer 2021, members of the Science Team at IAPS in Italy have successfully tested the Engineering Model of the ProSEED Imaging System.  Testing included measuring the spectral profile of each of the LEDs, characterizing the geometric, radiometric and spectral response of the camera, and assessing the impact that dust deposition may have on the camera sensitivity. Images taken of samples during the testing are now being analysed by the broader Science Team to see what can be ascertained from the multispectral data alone.

Contamination Analyses and Isotopic Measurement Capability: This year, a contamination framework has been developed to assess all vectors of potential contamination relevant to elemental and isotopic measurements.  Science performance looks good with the current approach to cleanliness and contamination.   The Science Team also recently revisited the science requirements related to isotopic measurements for ProSPA to allow for testing of instrument performance in line with the expected cleanliness and contamination parameters.

Landing site analyses: Existing work focusing on the 8 candidate sites for Luna 27 (e.g., [11]) is now being extended to more regional analyses in preparation for the NASA CLPS landing site selection process [12, 13]. Studies will target locations balancing science objectives, operational constraints and safety.  The complex thermal and radiative environment at potential landing sites will be a key part of this analysis.

References: [1] Trautner, R. et al., (2018) Proc. Int. Astronaut. Congr. IAC, Vol. 2018-October. [2] Murray, N. J. et al. (2020) LPSC, LPI, Abs #. 1918.  [3] Martin, D. J. P. and Duvet, L., (2019) LPSC, LPI, Abs #. 2663. [4] Hayne, P. O. et al., (2017) JGR Planets 122 (12), 2371–2400. [5] Sargeant, H. M. et al., (2020) Planet. Space Sci. 180 (104751). [6] Sargeant, H. M. et al., (2020) LPSC LPI, Abs #. 2058.  [7] Abernethy, F. A. J. et al., (2020) Planet. Space Sci. 180 (104784). [8] King, O. et al., (2019) Planet. Space Sci. 104790. [9] Formisano, M. et al., (2019) Planet. Space Sci. 169. [10] Mortimer, J. et al., (2018) Planet. Space Sci. 158, 25–33. [11] Boazman, S. et. al., (2022) LPSC LPI. [12] Boazman, S. et al., (2022) EPSC, this meeting. [13] Kereszturi, A. et al., (2022) EPSC, this meeting.