Kees van't Klooster

Very large antenna for low frequency space-borne SAR

The recent frequency allocations for space-borne radars in P band (432-438 MHz) have aroused the interest of the scientific community. Possible applications for radars operating in this frequency band range from ice sounding to biomass monitoring. Due to the low operational frequencies and accordingly long wavelengths, the required surface for a P-band radar antenna is in the order of 60 or more square meters. Such dimensions demand lightweight and robust mechanical structures, capable of a compact stowed volume in order to be compatible with small and low cost launchers. In the frame of the ESA contracts on Very Large Space Antenna Apertures and on Passive Subarray Technological Development, Thales Alenia Space studied and proposed an innovative architecture satisfying both the high performance requirements and the mechanical constraints. Several prototypes have also been manufactured and a test campaign validated the RF design.

Antenna technologies from 435 MHz to 356 GHz for ESA's candidate Earth Explorer satellite missions

As a result of down-selection after Phase 0 for the 7th Earth Explorer mission following the User Consultation Meeting held in Lisbon, Portugal in Jan 2009, three candidate missions were selected for further feasibility investigations (Phase A) [1]. Each of the candidate missions is now being defined in detail through two parallel and competing industrial system studies and supporting complementary science and technology studies, aiming to the final down-selection in 2012, followed by the mission implementation with a planned launch in the 2017 timeframe. The microwave payloads of those candidate missions cover the frequency range from 435 MHz to 356 GHz. The BIOMASS candidate mission aims to measure the global forest biomass at P-band (435 MHz) using the synthetic aperture radar (SAR) technique. Due to the long wavelength and large distance between the satellite and the Earth, a very large antenna aperture is required (50–100 m2). The CoReH2O candidate missions aims to quantitatively measure the global distribution of snow over land and sea ice at X-(9.6 GHz) and Ku-band (17.2 GHz) using the SAR technique. The PREMIER candidate mission, carrying an infrared limb sounder and a microwave limb sounder, the latter covering the frequency range of 313–356 GHz, aims to measure atmospheric composition in the upper Troposphere and lower Stratosphere. Three very distinct antenna technologies are required for enabling those satellite missions. This paper describes the different antenna concepts proposed and corresponding technology developments which are on-going.