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Microwave Humidity Sounder (MHS) antenna

MHS is an atmospheric humidity sounder providing humidity profile sounding capability in the 89 - 190 GHz range. It is a five channels of self-calibrating microwave radiometer. Together with the complementary instrument AMSU-A, MHS provides the operational microwave sounding capability for the European METOP series and American NOAA-N onwards- meteorological satellites. The MHS instrument is being developed under contract to EUMETSAT. The present paper focuses on the electromagnetic design and development of the 22-cm diameter rotating antenna of the MHS instrument operating at 89, 157, 183 and 190 GHz. The primary feed network so-called Quasi-Optical Network (QON) is an essential part of the overall antenna. It has to provide not only the low-los frequency separation of the four bands but also the proper antenna illumination in amplitude and phase in order to satisfy the required resolution and high beam efficiency. This equipment has been undertaken by the MHS Receiver Team in Toulouse (Matra Marconi Space-France) using state of the art technologies. After a presentation of the antenna concept, the Quasi-Optical Network design is detailed and the electrical measurements results are presented. The antenna radiation pattern measurements at instrument level are used to derive the overall antenna electrical performance.