Oxford researchers propose Infrared Thermal Mapper for Enceladus

University of Oxford researchers proposed the Enceladus Thermal Mapper (ETM), an infrared instrument designed to produce detailed global temperature maps of Saturn’s moon Enceladus, in a feasibility and design study submitted to arXiv on Oct. 29, 2026.

The instrument would operate from a 150 km orbit around Enceladus using a 384 × 288-pixel sensor capable of 80 m per pixel resolution, producing a 31 km wide track. In a 100 to 30 km orbit, resolution would fall to 40 to 70 m per pixel with a swath width of 14 to 27 km. ETM is a push-broom imager; the detector sweeps across the surface, and each of its 15 channels consists of 16 detector rows coadded to increase signal-to-noise.

ETM would measure surface temperature variations across the moon, including polar winter conditions that can reach as low as 45 K. Its bandpasses cover filters from 6.25 mm to 200 mm, enabling detection of polar winter below 50 K, nighttime temperatures of 50 to 60 K, daytime temperatures of 70 to 80 K, and active regions above 170 K. Enceladus is a very cold target of 30 K. Researchers developed a digital model of the filter assembly for thermal emission measurements.

ETM builds on flight heritage from TechDemoSat-1, Mars Climate Sounder, and Lunar Trailblazer. ETM derives from Oxford’s Lunar Thermal Mapper, which launched on Lunar Trailblazer. The miniaturized thermal infrared multispectral imager has a five-mirror telescope and an uncooled microbolometer detector array (a microbolometer senses heat). It would likely carry just four to six vertically aligned filters rather than the horizontally aligned 15 filters shown in the Lunar Thermal Mapper assembly image, and not all channels must map temperature, leaving some free for studies such as searching for salt.

Specifications include a mass of 4.5 kg with margin and a 3.8 kg actual proto-flight model mass, average power of 6 W with about 12 W peak, and a volume of 262.5 by 214 by 100 mm excluding MLI blankets. The instrument carries 1 GB of internal storage, uses an RS422 power connector, and operates on 28 V nominal voltage. Its detector is a 35 µm pitch INO array with an instantaneous field of view of about 540 µrad per pixel.

Radiation testing found that most of the current design is highly radiation tolerant, and that added shielding plus one component change would enable operation in the Saturn system, with shielding potentially coming from the spacecraft structure. The UK Space Agency’s Bilateral Program funded the ETM development work. Sensitivity testing for surfaces below 50 K will take place during the Lunar Thermal Mapper calibration campaign, anticipated to continue through 2025 and 2026.

Enceladus is a 252 km radius moon with a global ocean beneath its icy crust, and south pole tiger stripe fractures erupt water vapor and organic compounds. Cassini orbited Saturn from 2004 to 2017 and detected geyser-like plumes coming from cracks in the moon’s icy shell in 2005, though its infrared spectrometer provided few high-spatial-resolution observations and sparse south polar coverage. ETM follows Cassini’s Composite Infrared Spectrometer to map the moon’s thermal properties, with aims covering geothermal activity, global surface properties, and constraining global conductive heat flow for habitability.

Analysis of early Cassini samples found sodium salts, pointing to a subsurface liquid water ocean touching a rocky bottom, and observations of the moon’s wobble show its icy exterior shell is probably detached from the rocky core below. The subsurface ocean spans the entire globe and is probably maintained by tidal flexing from Saturn’s gravity.

Every CHNOPS element except sulfur has been detected with confidence in the plumes, as have organics such as amines, which can be precursors to amino acids, and larger macromolecules whose exact identity remains uncertain. Photosynthesis is unlikely to be viable because the ocean is buried under kilometers of ice and is almost certainly dark, but carbon dioxide and hydrogen are available in sufficient quantities for some chemosynthetic pathways, and the large hydrogen amount requires a present-day source, likely hydrothermal vents.

Research by Fabian Klenner at the University of Washington found that mass spectrometry could detect one bacterial cell in an ice grain, meaning biosignatures could be identifiable even in small samples. Nozair Khawaja of the Free University of Berlin led a team that re-analyzed a Cassini sample of material from Enceladus’s south pole, and Cassini sampled younger plume material during a particularly fast flyby over the south pole, a method the study says guarantees removal of radiation interference.

ESA plans a mission launching in the 2040s for Enceladus flybys, possible orbit and landing, to search plume material for evidence of life, using an upgraded suite of instruments to look for biosignatures. Some newly detected substances in plume samples hint at a hydrothermal origin, though plume formation may dilute or concentrate substances and harsh radiation may alter chemicals, making material unrepresentative of the ocean.

ETM would tighten constraints on Enceladus’s global conductive heat loss and characterize its active South Polar Terrain, supporting studies of the moon’s geology and assessments of its habitability. The authors present the lightweight, low-power instrument as capable of advancing understanding of the moon’s geological behavior, and describe comprehensive temperature data as essential for interpreting Enceladus’s evolution. The authors also describe it as the ideal choice for future missions to study surfaces of outer solar system moons, asteroids, comets and other such targets.

The study’s authors are D. G. Lyster, C. J. A. Howett, N. E. Bowles, K. Nowicki, R. Evans, and T. J. Warren, and version 1 was submitted on Thursday, 29 October 2026 at 17:01:35 UTC as a 2,523 KB file from Duncan Lyster. Duncan Lyster delivered the EGU24 presentation at the University of Oxford under supervisor Dr. Carly Howett, working with Drs. Neil Bowles, Rory Evans, Tristram Warren, and Keith Nowicki.

arXiv categorizes the study as instrumentation and methods for astrophysics under identifier 2610.40456.