We present the RF model and correlation with measurements in K band (18.7 GHz) of a 5.1 m diameter deployable reflector antenna in lightweight mesh technology. The RF model includes the manufactured surface shape, electrical properties of the lightweight mesh, a designed and non-circular rim as well as feed tower and truss. Good agreement between main beam shape as well as sidelobe and grating lobe positions between measured and predicted patterns is found.

Strict requirements for future spaceborne ocean missions using multi-beam radiometers call for new antenna technologies, such as digital beamforming phased arrays. In this paper, we present an optimal beamforming algorithm for phased-array antenna systems designed to operate as focal plane arrays (FPA) in push-broom radiometers. This algorithm is formulated as an optimization procedure that maximizes the beam efficiency, while minimizing the side-lobe and cross-polarization power in the area of Earth, subject to a constraint on the beamformer dynamic range. The proposed algorithm is applied to a FPA feeding a torus reflector antenna (designed under the contract with the European Space Agency) and tested for multiple beams. The results demonstrate an improved performance in terms of the optimized beam characteristics, yielding much higher spatial and radiometric resolution as well as much closer distance to coast, as compared to the present-day systems.

The design of a push-broom multi-beam radiometer for future ocean observations is described. The radiometer provides a sensitivity one order of magnitude higher than a traditional conical scanning radiometer, and has the big advantage of being fully stationary relative to the satellite platform. Thanks to a dense focal plane array and a dedicated optimization procedure, the instrument can accurately measure in C, X and Ku band and as close as 15 km to the coast line.

Performance of a dense focal plane array feeding an offset toroidal reflector antenna system is studied and discussed in the context of a potential application in multi-beam radiometers for ocean surveillance. We present a preliminary design of the array feed for the 5-m diameter antenna at X-band. This array is optimized to realize high antenna beam efficiency (~ 95%) over a wide scan range (±20°) with very low side-lobe and cross-polarization levels.

Design considerations concerning a scanning as well as a push-broom microwave radiometer system are presented. Strict requirements to spatial and radiometric resolution leads to a multiple-beam scanner achieving good sensitivity through integration over many beams, or to a push-broom system where sensitivity is not a problem. Strict requirements to land contamination leads to a dense feed array system. Resource demands, especially power, are important issues, and first estimates are presented.

Novel antenna architectures for real aperture multi-beam radiometers providing high resolution and high sensitivity for accurate sea surface temperature (SST) and ocean vector wind (OVW) measurements are investigated. On the basis of the radiometer requirements set for future SST/OVW missions, conical scanners and push-broom antennas are compared. The comparison will cover reflector optics and focal plane array configuration.

Large deployable antennas are one of the key components for advanced missions in the fields of telecom and earth observation. In the recent past, missions have taken on board large deployable reflector (LDR) up to 22 m of diameter and several missions have already planned embarking large reflectors, such as the 12 m of INMARSAT XL or BIOMASS. At the moment, no European LDR providers are available and the market is dominated by Northrop–Grumman and Harris. Consequently, the development of European large reflector technology is considered a key step to maintain commercial and strategic competitiveness (ESA Large Reflector Antenna Working Group Final Report, TEC-EEA/2010.595/CM, 2010). In this scenario, the ESA General Study Project RESTEO (REflector Synergy between Telecom and Earth Observation), starting from the identification of future missions needs, has identified the most promising reflector concepts based on European heritage/technology, able to cover the largest range of potential future missions for both telecom and earth observation. This paper summarizes the activities and findings of the RESTEO Study.

This paper describes the design and measurements of low scattering posts for a Ku-band dual gridded reflector antenna for a space Tx/Rx communications application.

In numerous space applications, antenna performance is degraded by the scattering of electromagnetic waves on the antenna structure or on neighboring objects. The present paper describes the design and measurements of two types of low scattering antenna structures for space applications. The first type of structure is a low-scattering feed supporting structure or strut typically used for center-fed antennas. The second type of structure is a low-scattering post designed as a replacement for conventional dielectric posts used to mechanically connect the front and back shells of Dual-Gridded Reflector antennas. Measurements and simulations of center-fed antennas with conventional struts and with the low-scattering struts as well as measurements and simulations of the DGR with conventional posts and low-scattering posts show that the performance of space antennas can be improved, in some cases significantly, by using these novel low-scattering structures.

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In November 2010 the thermo-mechanical test campaign of a Ka-Band multi beam dual reflector antenna structure has been successfully finished. The innovation of this structure lies in the full CFRP sandwich design (including honeycomb core), the use of ultra high modulus fibres for all reflectors, tower panels, base panel, curved cleats, etc.) and in the bonded intersections (e.g. between base panel and tower structure), thus, reducing the in-orbit thermo-elastic distortion to a minimum.

Validation and calibration of optical full-field techniques that are used to measure strain and displacement in experimental mechanics is a prerequisite for validating numerical stress analyses. ICEM14 brings together practising engineers from around the world to exchange their experience regarding validation and calibration from everyday measurements with different optical techniques. The discussion addresses the following issues: (i) experience in calibrating measurement equipment based on imaging; (ii) reference measurements and calibration artefacts; (iii) validation of finite element analyses by comparison to experimental data; and (iv) uncertainties in full-field measurements.

In this contribution we show experimental results for combined thermal and DSPI measurements on several fiber reinforced polymer test samples that have been impacted in a drop tower. Active thermography can give complementary information with regard to the type and size of the damage, but DSPI is used for assessing the effect of the damage, i.e. the difference in the displacement or strain field of a damaged and undamaged specimen.