Advanced Multispectral Infrared Microimager (AMIM) for Lunar Surface Exploration

Future missions to the surface of the Moon will need instruments that can maximize scientific return, but maintain low mass, size, and power to be accommodated on mass and power-constrained landers or rovers. We propose to mature to TRL-6 the Advanced Multispectral Infrared Microimager (AMIM) – a compact microscopic imager that provides spatially-correlated mineralogy and microtexture of rocks and soils at the microscale – for future small landed missions to the Moon.

AMIM consists of novel, low-power multispectral LED arrays coated with narrow-bandpass filters (> 25 bands with FWHM ≤ 50 nm), an adjustable focus mechanism for imaging from a few cms (spatial resolution ≤ 30 µm/pixel) to infinity with z-stacking and high depth of field, and a visible to shortwave-infrared detector (VIS-SWIR, 0.4 to 2.6 µm; expandable to 3.6 µm). This spectral range is well-suited for detecting and mapping minerals and ices relevant to lunar exploration, including Fe-bearing igneous (ex. low/high-Ca pyroxene) and oxide (ex. hematite) minerals, OH/H2O-bearing materials (ex. hydrated glass), and ices (ex. H2O ice), as well assessing effects of space weathering. Additional microthermopile infrared sensors on the arrays would provide concurrent in situ temperature data of the lunar regolith. By investigating these materials up-close using LED illumination and in survey-mode using a compact filter wheel, the instrument would play a critical role in characterizing the regolith near the lander/rover, support traverse characterization, identify potential resources for ISRU, facilitate the selection of samples for onboard analysis with other instruments or potential sample return, and provide ground truth to measurements from orbit. Furthermore, AMIM could support future human exploration by helping “high-grade” lunar samples.

Our instrument advances beyond the capabilities of current microscopic imagers in the visible or VNIR (0.4-1.0 µm), which are limited to detecting Fe-bearing minerals, while the expanded coverage in the SWIR and narrow bandpasses (FWHM ≤ 50 nm) enable the detection of a wider variety of minerals. By employing a compact, low-mass, low-power illumination system, AMIM eliminates the need for a grating system, multiple detectors, or tunable filters. This reduces mass, size, power consumption and complexity compared to larger imaging spectrometers, enabling the instrument to be deployed on small landers or rovers. Thus, AMIM would provide many of the capabilities that are associated with an orbital or rover/lander-mounted imaging spectrometer, but at a size and mass comparable to current microscopic imagers - a capability unmatched by any current microimaging instrument proposed for flight.

To advance the maturity from TRL-4 to TRL-6, we will focus on maturing the instrument design, prototype key components for environmental testing, and build an integrated instrument for testing under the Moon’s extreme environmental conditions. To achieve this, we will: 1) Refine the instrument requirements and environments/ Perform design trades; 2) Mature the instrument design, reduce size/mass, and develop thermal model; 3) Prototype the LED arrays, adjustable focus mechanism, and filter wheel, and test their performance under environmental conditions; 4) Refine the design and build an integrated instrument; 5) Validate instrument performance with relevant geologic samples; 6) Perform environmental and vibration testing for the harsh lunar environment; and 7) Demonstrate onboard processing algorithms to produce reduced-volume downlink products. This work is highly relevant to NASA’s DALI program by advancing the maturity of a compact, low-mass, low-power instrument that would be a key payload element on future commercial, Discovery, and New Frontiers lunar missions.