Flight receivers for orbital remote sensing of buried lunar ice deposits via CoRaLS: the Cosmic Ray Lunar Sounder

We propose to develop the technology readiness of the critical receiver system that is central to CoRalS: a sounder for extensive ice deposits in the lunar regolith using the radio signals produced by ultra-high energy cosmic rays incident on the surface of the Moon. While extensive ice deposits have been found in the permanently shadowed regions (PSRs) of Mercury, only traces of water ice have been found on the surface of lunar PSRs, and active radar measurements sensitive to the top meter or so of regolith show no clear signal yet from extensive deposits. Given expectations from impact gardening, the extensive ice deposits on the surface of Mercury are expected to be recent (<10 Myr), suggesting that their source is sudden and voluminous. These considerations leave the possibility for relic extensive ice deposits below the first meter of regolith provided that a sudden and voluminous source, similar to Mercury, emplaced ice within the last Gyr. The CoRaLS mission will complement active radar by probing depths well below the first meter, using a known source of coherent radio impulses that are effectively implanted into the regolith. The lunar regolith is continually bombarded by cosmic rays, from GeV energies up to ZeV (10^21 eV). Ultra-high energy cosmic rays (UHECR) (energies > 10^18 eV) provide a natural signal that can be exploited to search for extensive ice deposits within the first ~10-20 m of the lunar subsurface. Due to the lack of a lunar atmosphere, the UHECR particles enter the regolith unimpeded with their full energy. The highest energy cosmic rays produce strong secondary particle cascades within the regolith, extending for up to 10 meters at the highest energies. These particle cascades are now known to produce strong, coherent, linearly-polarized radio pulses, demonstrated in numerous measurements over the last two decades. Such UHECR-induced pulses are routinely observed in the terrestrial atmospheric cascades by ground arrays, and have been observed by suborbital payloads from distances up to 700km or more. Accurate parametric models for this process, known as the Askaryan effect, have been validated in particle accelerator experiments. These observational results confirm that such pulses will be observable from lunar orbit with appropriate radio receiver and digitizer technology. The advantage of this technique over orbiting radar sounders is that the source essentially acts as a dipole antenna embedded in the regolith within tens of meters of the targets of interest, avoiding decoherence, andsurface clutter or losses, over the much larger radar beam area. The presence of extensive ice is inferred based on observation of reflections of the radio signal: its spectrum, amplitude, and polarization. We propose to build on existing and proven suborbital receiver systems for measurement of cosmic-ray radio pulses, and extend this to the development of a receiver, trigger, and digitizer system that can be deployed into lunar orbit for the purpose of precision measurements of these radio signals. These receivers are unique in that they require a real-time interferometric beam-forming search of the signals from several antennas to achieve optimal sensitivity, since UHECR radio signals originating in the upper regolith have random arrival times and directions at the payload. Breadboard-level lab-based systems, based on our proven suborbital receivers will be upgraded to prototypes and fully tested to achieve TRL6. Once detected, such signals provide a form of passive bistatic radar for the coherent detection of reflective subsurface layers within the regolith. Our investigations and modeling show that they have unique sensitivity to the presence of buried ice deposits, such as may occur in permanently shadowed regions near the lunar poles. Our proposed development will establish the flight readiness of an enabling technology for the crucial and compelling search for lunar extensive ice deposits.

Developing Instrument or spacecraft technology to improve measurements for future lunar missions

This is a mature technology (TRL 7+) — the realistic path in is usually NASA's Technology Transfer Program: licensing an existing NASA patent, or a Space Act Agreement to use NASA facilities/expertise directly. NASA also runs a startup licensing program with no upfront fee for companies formed to commercialize a specific NASA technology.

None of these are guaranteed paths for this specific project — TechPort itself doesn't have an "apply" button. Reaching out to the contact(s) above with a specific question is usually the fastest way to find out what's actually open.