SATMO: a Multi-Planet Thermal Analysis Tool for CubeSat Missions

TL;DR

SATMO delivers a lightweight, open-source six-node thermal analysis tool for CubeSats in circular orbits around Earth and other Solar System bodies, addressing the need for accessible early-mission thermal planning. The framework combines a box-shaped satellite model, energy-balance heat transfer with IR, solar, and albedo inputs, and beta-angle driven environmental forcing, including eclipse calculations and J2-based RAAN evolution. Validation against Thermal Desktop shows strong agreement in solar and IR heating, with albedo discrepancies and a maximum surface-temperature difference of about $1.17^\circ$C, demonstrating SATMO’s usefulness for rapid trade studies. An Mars-orbiting 1U example illustrates how SATMO can guide mission-design decisions, and the authors outline future enhancements to broaden planetary coverage, orbit types, and surface interactions, reinforcing its potential as a practical planning tool for interplanetary SmallSats.

Abstract

The expansion of commercial launch capabilities has significantly increased opportunities for interplanetary small satellite (SmallSat) missions. As researchers plan for more missions beyond Earth, there is a demand for accessible tools that help better predict and understand the thermal effects on their spacecraft in orbital environments around Earth and other bodies. While commercial thermal analysis tools offer high-fidelity modeling capabilities and results, they are often expensive and require extensive training to be used effectively. This paper details a framework for a user-friendly Satellite Thermal Model (SATMO) to support the early stages of space mission planning for CubeSats orbiting Earth and other Solar System bodies. SATMO is an open-source, MATLAB-based, six-node thermal analysis program designed for satellites in low-altitude circular orbits. Although SATMO requires a MATLAB license -- typically inexpensive or institutionally provided in academic settings -- it remains substantially more accessible than professional thermal analysis software. SATMO requires an internet connection for some features but does not rely on additional MATLAB toolboxes. The SATMO modeling approach is validated with the space industry standard Thermal Desktop software, with temperatures comparable to within 1.17$^\circ$C for a 10 cm $\times$ 10 cm $\times$ 10 cm CubeSat in various configurations, orbiting around primary bodies including Earth, Venus, and Mars. An example use case of SATMO is presented with a Mars-orbiting CubeSat to demonstrate its functionalities and the outputs available to users. SATMO offers increased accessibility to satellite thermal modeling for the research community, enabling quick thermal trade studies and interplanetary mission plans.

Figures (20)

• Figure 1: SATMO Analysis Inputs tab with example user inputs for the specific analysis mode.
• Figure 2: SATMO Satellite Data tab with example user inputs for the Zenith face. Each satellite face has inputs of this form.
• Figure 3: Depiction of an orbiting box and nomenclature used in SATMO, adapted from rickman_introduction_2014. Figure not to scale.
• Figure 4: Eclipse fraction versus beta angle for a spacecraft in 400-km circular orbit around Venus, Earth, and Mars. The lines for Venus and Earth are nearly overlapping due to their similar sizes.
• Figure 5: Orbit plane side view of Test Case 2 from Table \ref{['tab: test cases']} modeled in TD with multiple satellite positions shown. The grid lines represent the shadow zone, and the size of the spacecraft is enlarged for better display.