Enfys: A Near-Infrared Spectrometer for the ExoMars Rosalind Franklin Rover

Introduction

The main goal of the ESA ExoMars Rosalind Franklin (EMRF) rover mission is to search for past and present life on Mars [1]. Enfys is a new near-infrared spectrometer, added to the mission in 2023, currently under development, before Flight Model (FM) delivery in 2026 and launch in 2028. The EMRF rover will land in Oxia Planum in 2030, and Enfys will form part of the suite of remote sensing instruments used for exploration and target selection. Given the importance of near-infrared spectroscopy in selection of the landing site [2-4], Enfys will play a major role not only in mission operations, but also in helping to link orbital and in situ observations and interpretations, which has been shown to be vital in other rover missions [e.g. 5].

 

Instrument Design

The function of Enfys is based around utilizing two near-infrared Linear Variable Filters (LVTs), each with a dedicated detector. An uncooled InGaAs photodiode is paired with a LVF covering the wavelength range 0.9 – 1.7 mm. A cooled InAs photodiode is paired with a LVF covering the wavelength range 1.6 – 3.1 mm. Both LVFs are translated simultaneously on a mechanical stage. There are two main parts to the Enfys instrument. (1) The Optical Box (OB) sits on top of the EMRF mast, co-aligned with and directly underneath the High Resolution Camera (HRC) element of the Panoramic Camera (PanCam) instrument [6]. The OB contains the optics, detectors, mechanism, and associated electronics. (2) The Electronics Box (EB) is situated inside the EMRF ‘bathtub’, and provides power and control for the OB, and the data interface with EMRF. An umbilical cable running up the mast of EMRF connects the OB and EB.

 

Instrument Synergy

Embedded within the design is an overlap in wavelength range with PanCam, allowing synergy between multispectral imaging and point spectroscopy. Together these instruments provide contextual remote sensing information, prior to selection of drill sites. Enfys data will be complementary to the other near-infrared spectrometers on EMRF, namely Ma-MISS [7], which will collect data from within the drill hole, and MicrOmega [8], which will analyze the drill core once collected, prepared and delivered into the analytical suite inside EMRF.

 

Scientific Preparations

We are carrying out concurrent and complementary projects to ensure not only rigorous calibration, but also to maximize the scientific return from Enfys. The predicted spectral performance of Enfys suggests that identification of all mineral types identified from orbit to date should be feasible. Part of the preparation work includes devising operating procedures that will help identification of more subtle absorption features (e.g. vermiculite doublets), in order to discriminate between phyllosilicate mineral types for example. Future efforts will also derive a comprehensive component-level mathematical model of the spectro-radiometric response of Enfys, which will be validated and implemented in software.

 

Acknowledgements: We are grateful for support from the UK Space Agency (grants ST/Z510427/1, ST/Z510415/1, ST/Y005996/1, ST/Y005287/1).

 

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