The objective of this activity is the development of the methodology and set-up for an innovative system enabling the accurate and coherent characterisation of antennas over a large temperature range. This will make the best usage of existing Spherical Near Field Testing techniques and facilities.

The increased need for accurate knowledge of amplitude and phase antenna patterns for a very broad frequency range and over a large thermal range is a reality for a multitude of space applications. Among them are the high accuracy Radio Science Experiments for ranging and radio occultation that require accurate knowledge of the phase information. This enable the characterisation of the thermo-elastic effects provided that test techniques are developed in a temperature range down to -140C. In addition, state-of-the-art SAR antennas for Earth Observation, often using active antennas, have high accuracy calibration requirements which can be significantly improved by characterizing the antenna at operational temperatures. Here, for LEO orbit operation, a temperature range of ?120C is considered. Additional needs are found in Telecommunication applications, where the increased frequency (Ka and Q/V band) and the very narrow beamwidth required for broadband missions push the limits of the antenna technology and require a precise characterisation of thermo-elastic effects made possible by the coherent accurate testing at operational frequencies. Taking full benefits from existing spherical range facilities available in Europe, innovative capability can be added and enable the characterisation of the performance over their operational temperature range. This is particularly relevant for antennas using innovative materials and dielectrics and complex beam forming networks which are known to be sensitive to temperature effects. The targeted temperatures at which the sub system shall allow characterising the antenna or instrument performance shall lay within -120C and +120C in order to cover all the spectrum of the space applications. This activity will investigate the testing methodologies and corresponding constraints for their deployment in standard Spherical Near Field test facilities that have the required load capacity. Full use shall be made of the positioner and the possibility to attach the cooling/heating set-up to the interface while allowing for roll-over-azimuth acquisition schemes. The state of the art will be first elaborated with the identification of possible set-ups and an analysis of all expected parasitic effects will be conducted. All terms impacting the error budget will be assessed and quantified. The expected measurement accuracy will be compared to the requirements coming from the different applications and a final test set-up and procedure will be selected. Test and validation on a well-known test object will be performed.