In-flight RF validation of the ISS Proximity Communication Equipment

We present the modification of two ESA ground stations carried out in order to support the in-flight RF validation of the Proximity Communication Equipment (PCE), part of the International Space Station (ISS). This subsystem plays a critical role during the docking of the Automated Transfer Vehicle (ATV), and has to be tested prior to each ATV launch, to ensure that the RF performance is as expected. For the check-out, an unmodulated signal is transmitted by the PCE during an ISS pass, and received by the two ground stations. Based on the strength of the received signal, the radiation characteristic of the complete PCE can be assessed, and compared with the nominal performance. The measurement process requires calibrating the receiving subsystem, including antenna, front-end and back-end equipment. The adopted calibration procedure, only relying on radio stars measurement, does not require the use of a calibrated source external to the ground station.