International Mars Ice Mapper Mission: Detection, mapping and characterization of subsurface water ice and overburden on Mars with Synthetic Aperture Radar combined with VHF Sounding and High-Resolution Imaging

The primary goal of the International Mars Ice Mapper (I-MIM) mission concept is to identify and characterize accessible water-ice and its overburden in the upper 0-10 m of the Martian subsurface in preparation for future human-robotic exploration. The I-MIM concept mission has been developed by the Italian, Canadian, Japanese, and US space Agency Partners (ASI, CSA, JAXA, and NASA).

In 2021, the Agency Partners competitively selected a Measurement Definition Team (MDT) to define the core measurements for the mission’s primary payload, to suggest possible augmentations, and to develop a concept of operations. In August 2022, the MDT released a Final Report [1], concluding that the mission’s primary instrument, a Synthetic Aperture Radar (SAR) centred at 930 MHz, would satisfy all of the Reconnaissance Objectives (ROs) and would provide the opportunity to accomplish unique new science covering a broad range of international science priorities. In order to expand the capabilities of I-MIM to undertake high-priority science investigations, the MDT also recommended that the concept team consider the inclusion of complementary payloads identified as highest priority: a very high frequency (VHF) radar sounder, a high-resolution optical imager, and a sub-millimetre sounder for atmospheric profiling.

Based on the MDT inputs, the Agency Partners have updated the I-MIM mission architecture to consist of three spacecraft elements with complementary science payloads:

Element 1 – Ice-Mapping Orbiter: Provided by JAXA, with two radar instruments and an atmospheric sensor: a CSA-provided polarimetric L-band (930 MHz) SAR, an ASI-provided Very High Frequency (VHF) Shallow Radar Sounder (100-200 MHz), and a JAXA-provided sub-millimetre sounder. Moreover, an ASI-provided Large Deployable Reflector (LDR) would support the SAR and act as part of the ASI-provided telecommunications subsystem.

Element 2– Demonstration Lander: A JAXA-provided demonstration lander would piggyback on the main orbiter to provide ground-truthing capabilities with a potential complementary small instrument package.

Element 3 – Free-flying Smallsat: A NASA-provided, free-flying smallsat with a high-resolution imager would provide high-resolution imaging for context and continuity under a small low-cost mission profile and to meet the requirements for multiple scientific investigations and future mission site selection.

Mapping the unstudied near surface of Mars thanks to the synergic observations L-band SAR and the VHF Sounder, augmented by the High-resolution Imager, has the potential to fill a major data gap unmet by prior instruments sent to Mars and provide a broad evaluation of the abundance of water ice reservoirs at medium latitudes.

In order to characterize variability in the ionosphere both the SAR and the sub-millimeter sounder further addresses key questions about the connections in Mars’s dynamic climate regions and seasonal interactions of shallow subsurface volatiles with the atmospheric structure, of critical importance to both science and human-robotic mission planning.

In the International Moon to Mars objectives context, I-MIM would provide core information about the role of water ice and other volatiles in prior and active changes globally on Mars, identifying landed locations in ice-rich areas that represent potential habitable environments, for future robotic and human missions.

References: [1] I-MIM MDT Final Report (2022) 239 pp., online: https://science.nasa.gov/researchers/ice-mapper-measurement-definition-team