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KRC allows homogeneous physical properties or two zones, each of which may have temperature-dependent thermal conductivity and specific heat, or a large table define material properties versus depth.

KRC uses a one-layer atmosphere that is gray in both the solar and infra-red regions. Radiative transfer and net atmosphere heating are based on a Two-stream Delta-Eddington model for insolation; direct onto sloped surface and diffuse, with possible twilight extension. Dust scattering uses a Henyey-Greenstein phase function [red link: https://en.wikipedia.org/wiki/Louis_G._Henyey}.

The atmosphere may contain a condensing gas, specified by its molecular weight, latent heat of condensation, and a Clausius-Clapeyron saturation relation.

Orbits are specified by Keplerian elements, pre-converted into a set of geometry terms and rotation matrices for rapid use ; seasons are at uniform increments of time. Mean orbital elements are pre-calculated for any epoch (all planets and several comets and asteroids).

The above capabilities are described in : H.H. Kieffer, Thermal model for analysis of Mars infrared mapping, J. Geophys. Res.: Planets, v.118, 451-570 (2013) Both solar and lunar-like eclipses are supported, with KRC automatically going into a thin-layer, fine-time mode during an eclipse. Both solar and thermal radiative flux from a planet onto its satellite may be included to first-order.

For sloped surfaces, the radiation from the far ground can be based on the surface and atmosphere temperatures of prior KRC runs, such as the upwind side of a dune viewing the temperatures of the down-wind side of a similar dune, with the atmosphere for a regional flat surface. The default is for far ground to be at the same temperature as the local slope and the atmosphere radiation exchange to be with the sloped surface; this is reasonable only for low slopes.

The KRC web-site allows several ways to access KRC: - Quick run of examples for Diurnal and seasonal temperatures - Submission of a formatted input file that allows access to all KRC features - An interactive interface which accesses most KRC features - Download of source code to build and run at your own site.

With 60+ peer-reviewed publications identified in the top tier literature, KRC is probably the most frequently used thermal model for planetary data analysis, with global, regional, and local studies. However, other models have been developed:

• The thermal model for the Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) standard data processing was based on the Mellon-Jakosky-Haberle model [Jakosky et al., 2000; Mellon et al., 2000] with direct heritage from KRC. This model has been used for global mapping with TES observations (Figure 2), [Mellon et al., 2000; Putzig et al.,2005] and a simplified interface running a version of this model is available online at https://marstherm.boulder.swri.edu/

• The thermal model used for Diviner (onboard Lunar Reconnaissance Orbiter) data analysis is mostly similar to the one used by Vasavada et al. [1999] for theoretical work on Mercury. This model differentiates itself from others by using direct and reflected solar ray tracing to take topography into account, necessary for the study of polar regions on the Moon [Paige et al., 2010]. The Diviner team model (“Digital Moon”) is not publicly distributed.

• The only model for airless body freely distributed has been developed by J. Spencer [1990] and includes sophisticated capabilities (e.g., eclipses, sublimation cooling, subsurface penetration of light, etc.) but also has important limitations (no temperature-dependent thermophysical properties, coded in proprietary language, and very limited documentation (https://www.boulder.swri.edu/~spencer/thermprojrs/).

• Thermal models have been developed specifically to predict the stability of subsurface ice on Mars, Mercury, the Moon, comets, asteroids, and other bodies. Schorghofer and Aharonson developed M-SIM to study the distribution of ice in current and prior climates [Schorghofer and Aharonson, 2005; Aharonson and Schorghofer, 2006; Schorghofer, 2008]. While M-SIM and its documentation are available for Mars it is distributed with only minimal documentation (www2.hawaii.edu/~norbert/code/).

• Helbert and Benkhoff have also developed a thermal model (Berlin Mars near Surface Thermal model, BMST) that allows detailed layering of properties and vapor diffusion [Helbert and Benkhoff, 2003]. This model is not publicly distributed.

• A model was also used largely for Mars’ polar studies [Paige, 1992; Wood and Paige, 1992; Paige et al., 1994; Paige and Keegan, 1994]. This model is not publicly distributed.

• One model focusing on liquid water stability [Clifford, 1987] was made publicly available in the past, but it doesn’t seem to be maintain and available.

• Other thermal models have been developed to address specific problems and their use is generally restricted to highly specific target bodies and physical situations. Many of these models are restricted to use within research groups, either due to complexity of compilation, ad-hoc computing environment, or lack of well-documented user guides and interfaces. For the rest of the community, these models are not accessible.

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