The requirements in this standard address the use of the STEP-TAS protocol for the exchange of thermal model data for space applications. The intended audience for the requirements contained in this document is the developers of space thermal analysis software. The overview of STEP-TAS provided in clause 4 can also be of more interest general to a wider audience. The requirements contained within this standard do not address the end users of the space thermal analysis tools namely thermal engineers and thermal analysts. The rationale for this decision is that the primary applicable document for space thermal engineers (working on European projects) is the thermal control standard ECSS-E-ST-31. As such the best location for requirements addressing thermal engineers and analysts is the top level standard ECSS-E-ST-31.