Antennas for space: Some recent European developments and trends

This paper reviews some of the requirements and proposed solutions for present and future space missions. Mobile Telecommunications at L and S bands require very large apertures and digital beam formers to generate multiple beams. New approaches are proposed for unfurlable reflectors and their feed systems. For navigation, the Galileosat dual-band array at L-band must provide isoflux on the Earth with a very accurate knowledge of antenna phase centre. Broadcasting at Ku-band remains a key application where flexibility in coverage pattern and channel allocation is a strong driver. New reconfigurable antennas are proposed to allow coverage and traffic flexibility. Two-way broadband multimedia broadband communications at Ka-band require affordable multiple beam antennas with wide beam scanning and low sidelobes. Both reflector and array solutions are being studied to replace the multiple reflectors with one feed per beam which are currently flown. Reconfigurable antennas with fade compensation are another challenging innovation. Low cost ground terminals are needed for all these applications with particularly challenging requirements for mobile users (Aircraft, ships, trains, cars, laptop users...). A breakthrough is still needed to make arrays affordable for the users. Future remote sensing missions will involve multi-band passive and active sensors from various orbits. At the low frequency end, P-Band Synthetic Aperture Radars (SAR) will require very large deployable apertures for which membrane solutions are being considered SAR at higher frequency will require more resolution and lower costs: reflector based SAR with multiple feeds and reflect-arrays are potential solutions under study. At millimetre-wave frequencies and higher, atmospheric sounding from low Earth orbit, and possibly from geostationary orbit, require innovative designs and solutions. Large scanning reflector systems as well as aperture synthesis schemes are being studied Science radio-astronomy missions also have very challenging requirements at these high frequencies, including extremely low levels for stray-light or sidelobes and detectors operating at close to 0 degrees K temperatures. The challenges and technologies outlined above will be discussed in the paper.