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.

The paper presents the design and validation of a dual band feed system for the reflector antenna of the CoReH2O (Cold Regions Hydrology High-resolution Observatory) SAR instrument, investigated under ESA contract. The antenna is a dual linearly polarized single-offset reflector, illuminated by two side feed arrays operating in X and Ku band respectively. Each array comprises seven compact multimodal horns in quasi rectangular waveguide. The horns are sequentially excited, a couple at a time, for optimum antenna pattern synthesis and secondary beams overlap. Each horn is a multiple step rectangular waveguide structure that provides the proper modal content at aperture, very close to the benchmark patterns analytically synthesized by modal superimposition at feed apertures level. The RF design has been validated through a complete characterization by test of the feeding system, proceeding from the single feeding elements to a complete feeding system composed by 4+4 elements. The measured results showed very good agreement with predictions at each stage of the campaign. Measured pattern has been used as primary source in the antenna model and very good performance have been predicted on secondary beams.

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.

In this contribution we outline our newest results in finding the true properties of the RPW antennas aboard Solar Orbiter with emphasis on our near-field measurement campaign and corresponding computer simulation. In the course of the project a scale model of the Solar Orbiter spacecraft was manufactured and placed in an anechoic near-field facility. The measurement campaign includes wave-length scaled illumination and scanning of the scale model antennas for finding individual radiation pattern, as well as measurements of the antenna scattering parameters. Overarching goal of the project was to investigate the possibility of using scale model measurements for verification of E-field instrument sensors in the regime above the quasi-static range, as well as provide useful calibration results for the RPW instrument team, allowing significant improvements of the corresponding scientific data analysis.

The microwave vacuum electronics is regarded to make sense only if producing sufficiently high powers at sufficiently high frequencies. And if intense microwave flows are produced, they may be transmitted only with oversized waveguides or mirror lines, such configurations being equipped with relevant miltiplexers, filters, duplexers and other components of quasi-optical types. Quasi-optical components applicable to control high power microwave flows are of interest also for electron-positron colliders, space communication and radar. In particular, arrivals of meteorites and asteroids stimulate the optics-microwave cooperation for tracking space debris; an expansion of the international multi-static interferometric network to the millimeter wave band is being discussed.

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.

The paper discusses considerations for a large 35 m ground-station antenna operating in Ka-band with a powerful amplification stage. It could give additional functionality for radar applications (investigations into imaging by inverse synthetic aperture radar (ISAR) of objects in space or Near Earth Objects (NEO)) and for Deep Space Telecommunication. Detection of space debris more near to Earth would obviously benefit from high power sources in Ka-band. However, the near-Earth target scenario is better handled with another type of antenna (phased array, mono/bi-static and other parameter scenarios).

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.

Deep Space Telecommunication with satellites to Jupiter and beyond require high power transmission capabilities for the ground-segment and highly sensitive reception capability. Radar functionality calls for high transmission power, for instance for imaging a Near-Earth Object. This paper discusses a perspective scenario to equip a 35 m ground-station antenna with a high power Ka transmitter and having available sensitive reception capability mono- or bi-static. A 35 m ground-station antenna as used in ESA's ground-segment is considered only for descriptive reasons. Consideration is given to a number of aspects (not-exhaustive), which need to be taken into account. Different frequency bands are used for Deep Space telecommunication for up and downlink, for radar functionality, the same frequency band is used in up- and down-link with consequences for a transmission-reception scenario. One needs duplexers, or more a use of a bi-static scenario. The authors discuss this scenario, which is not in any approved planning or program.

The RT22 CrAO radio telescope antenna has been observed with a C-band Synthetic Aperture Radar (SAR) for the purpose of deriving scattering properties and pointing information. Space-based radars benefit from accurate calibration targets and for the lower frequency bands such targets can be rather large in physical sense in order to derive level information. Active transponders are used. A large reflector antenna has a scattering pattern, which depends on a number of properties and compares with the actual radiation pattern of the antenna (minimum scattering antenna, depending on loading considerations). We have done preliminary investigations by measuring the responses with the SAR on-board ENVISAT.

In 2009, Astrium GmbH, RuagSpaceAB and ComDev Europe have been charged by ESA for a Ku-band antenna feed bread-board (B/B) activity. The scope of the activity is to establish sufficient technology readiness for the Ku-band part of the dual-band (X- and Ku-band) and dual-polarized CoReH2O (COld REgions Hydrology High-resolution Observatory) ScanSAR instrument. The low-cost feed system is proposed in this paper based on the multi-feed antenna (MFA) concept. The design, the simulated and measured performance are presented. The measurements of the prototype show very good matching with the simulations, which confirm high performance of the device and its ability of fast beam scan in elevation.

Recent space-based Synthetic Aperture Radar (SAR) observations are discussed of large reflector antennas on the ground. The results are elaborated with suggestions for further work to arrive at more precise information. Such targets might eventually receive further attention in applications with SAR operating at lower frequency than for which the ground-station antenna operates. Being below cut-off, the antenna becomes a passive scattering structure with a Radar Cross Section (RCS). Such antenna may function as stable target of opportunity, additional to transponders. Its response should be stable (even in complex vectorial sense). Precise prediction requires accurate modelling. A target is automatically available (“free of charge”), when the low-frequency SAR instrument is switched on over the ground-station antenna for data downloading and when the latter antenna is located within the SAR image coverage.

De status van een demontratie project voor een goep van dubbel polariseerde belichters voor de antenne voor BIOMASS wordt besproken. BIOMASS is een geselecteerde aard-observatie missie met een lanceer datum na 2021.

In this paper accurate material measurements at sub-millimetre wave frequencies performed with two different systems are compared. Transmission and reflection results of high quality samples measured with a quasi-optical open resonator and a quasi-optical free-space bench are presented. Based on the comparison between the two results, an accuracy assessment of the transmission set-up is performed.

New techniques for the analysis and design of large antennas systems which contain small-details geometries are presented. The specific purpose of this communication is the efficient analysis of parabolic reflector built with meshes of wires. The first technique considered is based on the combination of the Characteristic Basis Function Method (CBFM) and the Multilevel Fast Multipole Algorithm (MLFMA), which avoids the need of computing and storing all the terms of the reduced coupling matrix. The second technique is a “domain decomposition” approach. The geometry is compartmentalized into regions called “windows”, and we consider that only the current elements contained inside the same window are fully coupled. We compute then the interactions between different windows iteratively by applying ray-tracing. The third technique combines MLFMA-CBFM algorithm with the Impedance Boundary Condition.

Studies and predevelopments started in the early 80's for ERS, the first European remote-sensing satellite. ERS-1 was launched 17 July 1991. It has been operated until 10 March 2000. ERS-1 observed the Earth later on in tandem with ERS-2, (a similar satellite) which has been launched in 1995. Initially designed for maritime applications, these remote sensing satellites have produced very exciting results for land applications. Interferometry has been developed. ERS-2 is operated until end June 2011 clearly exceeding its operational lifetime. The paper recalls the satellite configuration with its antennas and results. Recently we had a “deviating“ observation with ERS-2 carried out on 12 April 2011 (50 years after Yu. Gagarin made as a first human a travel in space around the Earth), which will be described.

A reflectarray antenna that provides a focused beam in Ka band has been designed, manufactured and tested. The antenna demonstrator has been made up using two layers of patches printed on Kapton, which are bonded to low-loss prepreg quartz materials. The effect of the manufacturing tolerance errors in the dimensions and dielectric properties of the materials have been evaluated. A good concordance is achieved between simulations and measurements after taking into account the deviation in dimensions and dielectric constant. The measured 18-cm antenna provides a gain better than 33 dB in a frequency band from 31 GHz to 34 GHz.

The paper describes antenna activities for Meteosat program developed under ESA's technical management. The program started in the 70's and the first satellite was launched in 1977 with VLF, UHF, L- and S-band antennas. The operational Meteosat satellites carried UHF, L- and S-band antennas. Antennas for the Second Generation Meteosat have been discussed in. This paper contributes in complement with early antenna configurations as used for the pre-operational and operational Meteosat program. Together with it provides a description of > 35 year of antenna activities for spinning spacecrafts for the Meteosat program.