Multi-Frequency Feeds for Earth Observation Applications

In preparation of the EUMETSAT post-EPS user consultation process the European Space Agency has studied future operational meteorological microwave missions including the EGPM (European contribution to the Global Precipitation Measurement mission) type requirements at Pre-Phase A level. These requirements include a dual 54/119 GHz channel capability. ASTRIUM has been selected by ESA to carry out the Multi- Frequency Feeds for Earth Observation Applications Study. The main objective of this activity is to design and test a defocused dual-frequency horn, operating at frequencies 54 and 119 GHz, to be combined with an offset reflector. To derive the required precipitation products from the measurements, both frequency bands (54 and 119 GHz) have to be optimised for a footprint overlap of at least 90% of the largest footprint and for high beam efficiency (> 95%). The Dual-Frequency Feed (DFF) includes the dual-frequency horn and the diplexer for 54/119 GHz channels separation. ASTRIUM, as Study responsible, is in charge of the overall antenna engineering, including the reflector, the diplexer design and the DFF manufacturing and test. IEEA is responsible for the horn design. The horn shall exhibit high level performance in both 54 and 119 GHz frequency bands (VSWR, cross-polar, sidelobes) whilst the diplexer shall discriminate both channels with high level isolation (>40 dB) and with minimum insertion loss (<0.15 dB at 119 GHz).