Small tools for calculating environmental heat fluxes in orbit


Duncan Gibson, ESTEC/ESA

Thermal Analysis, ESTEC/ESA


Frédéric du Laurens d’Oiselay, during his time as a stagiare in the Analysis and Verification section at ESA/ESTEC in 1996, developed a small tool to help verify the environmental heat fluxes in orbit calculated by ESARAD. The capabilities of the tool were later improved, and the tool was renamed ARTIFIS.

During a subsequent year as a young graduate trainee in the section, Frédéric integrated the flux calculations from ARTIFIS into code that calculated the evolution of orbital parameters during the lifetime of a mission of a simple spacecraft in Earth orbit, and called the new tool TOPIC.

Both tools were intended to be disposable, in-house, verification and proof-of-concept prototypes. Despite their prototype nature, they were adopted by thermal engineers for making quick estimates of fluxes for design cases before building more complex models using more advanced tools.

An early version of ARTIFIS and TOPIC was made available to the European space thermal community. Since then, there have been several minor improvements and code refactorings which have resulted in a dramatic improvement in calculation speed, but there has been little active development of new functionality.

At the annual European Workshop on Thermal and ECLS Software, reference is often made to ARTIFIS and TOPIC as “the sort of small tool that many thermal engineering groups have developed for themselves” and as such there continues to be some interest in them. Recently these tools have been requested for evaluation purposes by various ESA projects, and therefore it has been decided to make the latest versions available “as is”.

Users should note that although during initial development the results were compared against other software packages (most notably ESARAD and STK), the fact that ARTIFIS and TOPIC were prototypes means that they have not been through the rigorous validation and verification process that would be expected of an industrial release. The availability of these tools does not imply an endorsement of their use by ESA. See the Disclaimer section below for more details.


ARTIFIS stands for ‘ Accurate Reference Tool for Incident Fluxes Impinging on Spacecraft’. The software uses analytical expressions to calculate the solar, albedo and infra-red planet fluxes incident on simple, isolated geometric shapes in orbit.

It was written as a disposable in-house tool to verify the fluxes calculated by other spacecraft thermal radiation tools such as ESARAD. However, its simple user interface has made it popular with some users for performing initial design estimates without the need for building more representative models in more complex tools.


TOPIC stands for ‘ Thermal and Orbital Propagated Information Calculator’. The tool takes the initial description of a space mission and calculates the orbital parameters at regular intervals during the lifetime of the mission. It then applies the same algorithms developed for ARTIFIS to calculate the mean incident fluxes for each of these orbits. Finally it produces tabular output of the important thermal information along with dates and orbital information corresponding to maximum and minimum fluxes, etc.

The software currently has Earth-specific properties and calculations hard coded in it, so it can only be used for simple Earth-orbiting surfaces.

Material available for download

  • Artifis User Manual
  • Topic User Manual
  • ESTEC Working Paper 2016: Thermal Analysis to Thermal Design via Mission Analysis
  • Artifis-1.27 executables and test cases for Windows, Linux, Sun
  • Topic-1.27 executables and test cases for Windows, Linux, Sun

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