Namrah Habib

Abstract:

The Lunar Trailblazer mission launched in February of 2025 with the goal of characterizing lunar surface water through a targeted campaign. One instrument on the mission, the Lunar Thermal Mapper (LTM), was tasked with measuring the surface temperature to compare with maps of the form and abundance of water on the lunar surface. LTM's secondary science goals were to identify regolith composition and thermophysical properties as exhibited by mid‐infrared spectral features. Here we show the utility of LTM in distinguishing lunar regolith composition with its 11 narrow bands. Five spectral parameter products were developed to aid in early identification of regions of interest for follow‐on spectral analyses. These products include the Christiansen feature (CF) value, weighted absorption center (WAC) value, WAC band depth, Transparency Roll‐off, and a Diviner CF value equivalent. These products would be used mainly to flag these regions for more detailed follow‐up study with the entire spectral capabilities of the mission instrumentation. The Lunar Thermal Mapper (LTM) is one of two instruments on the Lunar Trailblazer mission launched in February 2025. LTM's primary goal is to provide surface temperature measurements for the lunar surface, in particular for identifying and mapping water on the Moon. LTM is also capable of identifying the compositional and physical properties of different rocks on the surface. Here, we test those capabilities and determine five methods for quickly distinguishing bulk properties of the lunar rocks that can be used by the community to identify regions of interest for further investigation. Mid‐infrared compositional parameters were created and tested for the Lunar Trailblazer mission Spectral parameters can distinguish bulk silicate mineralogy, and identify regions of compositional interest The Christiansen feature roll‐off parameter can provide an initial identification of areas with distinct thermophysical properties Mid‐infrared compositional parameters were created and tested for the Lunar Trailblazer mission Spectral parameters can distinguish bulk silicate mineralogy, and identify regions of compositional interest The Christiansen feature roll‐off parameter can provide an initial identification of areas with distinct thermophysical properties

Abstract:

Abstract The Lunar Thermal Mapper (LTM) instrument is a UK Space Agency funded infrared radiometer designed and built for the National Aeronautics and Space Administration Lunar Trailblazer mission launched in February 2025. LTM is a pushbroom imaging filter radiometer with 15 channels that cover the wavelength range from 6.25 to 100 μm with a 40–70 m/pixel ground sampling. Lunar Trailblazer's mission is to understand the form, abundance and distribution of water across the lunar surface. LTM provides an independent measure of temperature to investigate thermal effects on water's mapped distribution as well as an independent measure of surface mineralogy. The LTM instrument's 15 infrared channels include four broadband temperature sensing channels (6.25–12.5, 12.5–25, 25–50 and 50–100 μm) plus 11 additional narrow band (∼40 cm −1 ) filters from ∼7–10 μm to map and discriminate silicate composition. We review the LTM design and calibration campaign at the University of Oxford's Space Instrumentation facility and show that the instrument has sensitivity from 400 K with a Noise Equivalent Temperature Difference of <0.1 K to <1 K at 110 K for typical integration times (e.g., 30 Hz readout) from a nominal 70–130 km lunar orbit design altitude.

Abstract:

Plain Language Summary: In hot and wet “hothouse” climate conditions, rainfall transitions from a pattern that fluctuates from about a mean of 3 mm day − 1 ${\text{day}}^{-1}$ to more intense outbursts that are separated by multi‐day dry spells. Previous studies on hothouse climates did not consider the role of the diurnal cycle even though it strongly controls precipitation in Earth's current climate. This study uses radiative‐convective equilibrium simulations to investigate the impact of rising temperatures on the transition to hothouse conditions, incorporating the diurnal cycle with both swamp‐like and open ocean surface conditions. We find that episodic precipitation occurs at surface temperatures above 322 K even when accounting for the diurnal cycle. However, the diurnal cycle significantly influences the timing of convection and rainfall at high temperatures with precipitation primarily starting late at night or in the early morning.

Abstract:

Atmospheric convection behaves differently in hydrogen-rich atmospheres compared to higher mean molecular weight atmospheres due to compositional gradients of tracers. Previous 1D studies predict that when a condensable tracer exceeds a critical mixing ratio in H2-rich atmospheres, convection is inhibited, leading to the formation of radiative layers where the temperature decreases faster with height than in convective profiles. We use 3D convection-resolving simulations to test whether convection is inhibited in H2-rich atmospheres when the tracer mixing ratio exceeds the critical threshold, while including processes neglected in 1D, e.g., turbulent mixing and evaporation. We run two sets of simulations. First, we perform simulations initialized on saturated isothermal states and find that compositional gradients can destabilize isothermal atmospheres. Second, we perform simulations initialized on adiabatic profiles, which show distinct, stable inhibition layers form when the condensable tracer exceeds the critical threshold. Within the inhibition layer, only a small amount of energy is carried by latent heat flux, and turbulent mixing transports a small amount of tracer upward, but both are generally too weak to sustain substantial tracer or heat transport. The thermal profile gradually relaxes to a steep radiative state, but radiative relaxation timescales are long. Our results suggest stable layers driven by condensation-induced convective inhibition form in H2-rich atmospheres, including those of sub-Neptune exoplanets.