WELCOME & INTRODUCTION

• Piero Angeletti

Dual Polarisation 94 GHz Antenna for Spaceborne Doppler Radar

• Maurizio Lori (HPS-GmbH)

One of the most promising remote sensor for 3D mapping of wind vector is the Doppler Radar instrument. We present here the results of the DORA activity where the antenna and the main components which are necessary to make it work have been designed. The critical component has been identified in a special type of rotary joint able to pass two dual polarized RF channels from the fixed to the rotating part of the system. A breadboard of such component has been designed realized and tested with good results.

Next Generation SubMillimter Wave Focal Plane Array Coupling Concepts

• Trappe Neil (Maynooth University)

In this activity, we develop novel focal plane detector pixels for the next generation CMB B mode detection missions. Such future mission designs will require focal plane pixel technologies that optimizes the coupling from telescope optics to the large number of detectors required to reach the sensitivities required to measure the faint CMB polarization traces. As part of an ESA Technical Research Programme (TRP) programme we are tasked with developing, manufacturing and experimentally verifying a prototype multichroic pixel which would be suitable for the large focal plane arrays to reduce the focal plane size requirement. The concept of replacing traditional single channel pixels with multi frequency pixels will be a key driver in future mission design and the ability to couple radiation effectively over larger bandwidths (30 -100%) is a real technical challenge. In the initial part of the programme we reviewed the science drivers and this determined the technical specifications of the mission. Various options for focal plane architectures were considered and then after a tradeoff study and review of resources available, a pixel demonstrator was selected for design manufacture and test. The chosen design consists of a novel planar mesh lens coupling to various planar antenna configurations with Resonant Cold Electron Bolometer (RCEB) for filtering and detection of the dual frequency signal. The final cryogenic tests are currently underway and a final performance will be verified for this pixel geometry.

New Technology High Efficiency Horn Antennas For Cosmic Microwave Background Experiments and Far-Infrared

• Trappe Neil (Maynooth University)

In this research contract, we developed a number of different electromagnetic simulation tools targeting the development of focal plane detectors for future submillimetre astronomy and Cosmic Microwave Background (CMB) polarisation missions. We developed new technology solutions for the horn antenna feeds and detector coupling structures that can meet the technical requirements of the next generation of long-wavelength space missions building on the heritage and success of the Planck and Herschel Space Observatory missions. Based on modematching code techniques we have developed a number of modelling tools which incorporate coupling to free-space, lossy waveguides and numerous geometries that were previously difficult to model accurately. Many currently commercially available EM analysis software tools cannot be applied to large volume multimoded waveguide structures due to the computationally intensive nature of the problem. Usually each mode is analysed separately and this leads to many parallel simulations. Modematching allows all modes to be analysed simultaneously and so leads to a naturally computationally efficient approach. As we develop the code all required parameters can be extracted as desired. We conducted THz measurements with out collaborating partners in SRON Groningen measuring the optical response of a waveguide structure feed with a blackbody aperture source and also modelled a multimoded optical system composing of an Offner optical relay configuration. To supplement the modelling and simulation tool development we completed a number of experimental verifications using our W Band Nearfield Scanning Facility based on a vector network analyser. We also describe a number of developed system innovations to ensure highly precise and repeatable high frequency antenna field pattern measurements (precise calibration model and modelling multiple reflections or standing waves). In parallel, we started to develop W Band planar antennas to be used with lenslets in an array and investigated geometries that minimised crosstalk between focal plane pixels.

Metal-Coated Additive Manufactured mm-Wave Antenna Feed Chains with Integrated Orthomode Transducers

• Alexandros Dimitriadis (SWISSto12 S.A.)

Additive manufacturing (AM) methods are nowadays considered as a promising alternative for the fabrication of complex RF components for space applications. Among all the AM technologies, selective laser sintering (SLS) is currently the most explored technique for space applications. This is mainly motivated by the characteristics of materials used (such as metals and ceramics), for which most of the mechanical and thermal requirements for space applications are known to be met. After several years of development in the field, SWISSto12 proposes an alternative by first creating component skeletons with AM of polymers (stereolitography - SLA) and subsequently metal coating these skeletons to enable the suitable RF functionality. The main advantages of this approach over SLS are its higher mechanical precision, increased design flexibility, and lower surface roughness. Moreover, for current SLA techniques, a large variety of polymers are commercialy available, some of which have good thermal propreties which can mitigate space compatibility issues. Today most remote sensing and radar applications systems employed in satellite and ground-based science missions or civil applications are formed by a primary feed (typically a horn or a planar antenna) illuminating a larger secondary antenna (typically a reflector or a lens). The signals generated by the feed are then properly transformed by the secondary antenna through reflection or transmission in order to achieve the desired radiation properties of the resulting electromagnetic waves. Though lenses and reflectors are frequently the most visible part of the antenna system, the performance of the system depends critically on the feeder. Ideally, these feeders must be intimately associated to other components, thus creating a specific subsystem called the antenna feed chain. A key component in this chain is the orthomode transducer (OMT) that separates or combines orthogonally polarized signals. For instance, in radar applications, the use of orthogonal polarized beams helps building contrast in images. In all cases OMTs reduce the number of required feeds, which leads to savings in terms of cost and weight. In this activity, SWISSto12 has developed and manufactured several feed-chain components for Ka-band and V-band science missions. The advantages and the limitations of stereolithography for such components have been extensively investigated and the design flexibility of AM has been exploited to propose innovative RF designs. Specifically, the following examples will be presented: a Ka-band feed chain composed of a turnstile junction OMT and a corrugated feed horn and a hexagonal array of smooth-walled, profiled horns operating in V-band.

A Study on Future Microwave Radiometers for Atmospheric Correction of Radar Altimeters in Coastal Regions

• Janet Charlton (JCR Systems)

Microwave radiometers have a long heritage of providing a dedicated wet tropospheric correction to the path delay of radar altimeter pulses and echo backscatter due to water vapour content within the troposphere. With the introduction of synthetic aperture processing in radar altimetry, more accurate altimetry data is anticipated for coastal and inland waters. Therefore, the objective of this study was to address MWR instrument design for future operational radar altimetry missions such as next Generation Sentinel-3 and Jason-CS+.. Such a design was to be compact and to include the classical, current MWR channels for ensuring observation continuity, augmented by a set of high frequency channels for enabling accurate altimetry over coastal and inland waters. As a secondary objective, the selection of the high frequency channels was also to consider the retrieval of wet tropospheric delay over sea ice and ice-sheets. In order to meet the objectives, the study was divided into three major tasks. Each task generated a task report, the final versions of which are contained within the Final Report. • Task 1 to be concerned with the selection of an optimum set of high frequency channels based upon a scientific review and analysis. • Task 2 to be concerned with the derivation of an instrument suite of requirements, from which alternative MWR design concepts were to be developed using the frequency sets established in Task 1, followed by a trade-off of the concepts with a baseline MWR instrument concept to be proposed for the Agency’s approval. • Task 3 was concerned with the preliminary design of the MWR instrument and assessment of the accuracy of the wet tropospheric delay retrieval under representative atmospheric conditions and over different surface types (water, sea ice, ice-sheets) for the baseline design. The study has undertaken a fully consistent approach in an iterative process relating instrument design and retrieval, such that an instrument design has been proposed addressing the most up-to-date requirements on sensitivity, spatial resolution, spatial discrimination, stability and by physical considerations (radiative transfer) assessed in other studies. The instrument concept is based upon a multi-frequency quasi-optic feed and draws upon experience gained from MetOp-SG MWS developments, whilst addressing the additional challenges of operating an accurate and stable radiometer in non sun-synchronous orbits. Two dedicated retrieval algorithms, (i) a classical robust Empirical Neural Network and (ii) a promising flexible and performing 1DVAR have been developed, and have demonstrated that high frequency channels do improve the performances: over open ocean, over coastal regions, over ice/sea ice. It was not possible to ensure obtaining the goal of 1cm rm. error everywhere, due to limitations in the data processing capabilities and to unknown issues (clouds, rain, etc.) as the retrieval algorithms do not yet include this and further development of the 1DVAR algorithm is recommended.

A Radiometer Antenna for Accurate Coastal Altimetry

• Janet Charlton (JCR Systems)

The wet tropospheric correction (WTC) is a major source of uncertainty in a radar altimetry budget error, due to its large spatial and temporal variability: this is why the most altimetry missions include a microwave radiometer. With the introduction of the along-track synthetic aperture processing, first implemented in CryoSat-2, and now in the upcoming operational altimetry missions such as Sentinel-3 and Jason-CS, more accurate altimetry data is anticipated for coastal and inland waters. Yet the WTC in coastal areas is degraded with respect to that of the open oceans due to the wide field of view of the current microwave radiometers which are also subject to contamination by land brightness temperatures which fall within the radiometer footprint. The objective of this study was to build upon an earlier TRP study, to design a multi-frequency radiometer antenna and feed system that could provide such accurate atmospheric corrections. In order to meet this objective the study was divided into four major tasks. Each task generated a Task Report, a summary of which can be found in the Final Report. Task 1 completed a review of relevant state of the art technologies for antenna concepts operating in multiple frequency bands. Mission characteristics and radiometer instrument requirements were critically reviewed and a preliminary requirements specification for the radiometer antenna derived. Task 2 established a wide range of antenna configurations utilising the most promising of the identified technologies. Each antenna concept was assessed for critical performance and accommodation factors and traded off to identify a preferred configuration. Task 3 undertook detailed RF design and analysis of the selected antenna architecture. This included a preliminary evaluation of a typical thermal and structural environment and the associated thermo-elastic deformation of the antenna on the overall performance. Task 4 provided a development plan and a technology roadmap for the critical elements of the radiometer antenna including verification requirements. Recommendations included a number of areas for further study including further definition of user requirements as well as further refinement of the thermal design for non sun synchronous mission. Technical Development Programmes were also proposed that covered components as well as development of on-ground verification techniques for large aperture radiometers.

Focal Plane Array Bread-Board for Advanced Multiple Beam Radiometer Antenna

• Cecilia Cappellin (TICRA)

Spaceborne imaging microwave radiometers for Earth observations can determine a multitude of properties of land and oceans, by measuring the brightness temperature emitted by the Earth. For ocean observations, ocean surface wind vector, sea surface temperature and sea ice characteristics are important parameters, normally measured in C band, at 6.9 GHz. The above instruments are defined by specific radiometric requirements on spatial resolution (also known as footprint), radiometric resolution and accuracy. An important characteristic for radiometers for ocean observation is additionally the so-called distance to coast, which quantifies how close to land and sea ice the radiometer can accurately measure. Radiometric requirements can be converted into antenna requirements: the spatial resolution determines the reflector antenna projected aperture, while the radiometric resolution determines the number of beams generated by the antenna in the along track and across track direction. Accuracy and distance to coast set a limit on the maximum cross-polar power that can be received by the antenna, and on the sidelobes of the antenna beams illuminating the land, respectively. An accuracy of 0.25 K implies a maximum value of cross-polar power on the Earth smaller than 0.29% of the total power. An accuracy of 0.25 K and a distance to coast of maximum 20 km at 6.9 GHz, as required by future missions, cannot immediately be satisfied by traditional conical-scan or wide-scan push-broom reflector antennas in single-feed-per-beam configuration, due to the non-negligible cross-polar power of the antenna beams and unless the footprint is sacrificed and accepted being larger than 20 km. The challenging requirements can however be met in a multi-feed-per-beam configuration, where more feed array elements take part in the formation of each beam, and the same element takes part in the formation of multiple beams. This is realized in practice by a feed array with elements placed less than one wavelength from each other, properly excited in amplitude and phase, and connected to a digital beamformer. In this work, we have focused on a 5 m conical scan radiometer working at 6.9 GHz, and designed its feed array in a multi-feed-per-beam configuration, in order to achieve 20 km of spatial resolution, 0.3 K of radiometric resolution, 0.25 K of accuracy and less than 20 km of distance to coast. The feed array is analyzed in detail in two commercial software, i.e. the MoM add-on to GRASP and CST, including mutual coupling between the array elements and the effect of a finite ground plane, and is later manufactured and tested. The work constitutes the proof of concept and generalization of a previous TRP activity “Study on advanced multiple beam radiometers” ESA contract 4000107369/12INL/MH, where the electrical model of the feed array did not include mutual coupling and edge truncation effects, and the optimization algorithm used to find the proper array excitation thus considered identical element beams as input.

Multifunctional antennas for future navigation payloads

• Fernando Monjas (RF engineer)

The main objective of this project (performed by Airbus Defence and Space Spain) is to perform an exhaustive trade-off for multi-functional antennas, mainly focused on the combination of NAVANT L-band and Search and Rescue antennas (RX UHF antenna and TX L-band antennas), which are the biggest antennas in the GALILEO satellites antenna farm. The trade-off covers a broad range of possibilities ranging from planar patch antenna technologies to reflector antennas, helixes and PEC (patch excited cup) technologies. The work has been performed under ESA contract AO/1-8404/15/NL/MH (“Multifunctional antennas for future navigation payloads”). Second generation GALILEO (G2G) missions will embark several additional payloads and antennas apart from the main navigation antenna. Actual IOV/FOC satellites have the following antennas and payloads in the Earth deck panel: Search and Rescue UHF/L-Band antennas, C-band mission antenna and Laser Retro Reflector. For future G2G satellites additional antennas and payloads are also considered such as SBAS antennas, inter satellite links antennas and other navigation antennas. Embarking all these various functions on the same platform is generating issues of accommodation so new antenna architectures and configurations aimed at maximizing the use of real state (combining antennas on the same physical aperture) will be required while keeping required performance in terms of power handling (multipaction, corona and PIM), antenna gain and EIRP, signal quality (phase centre, phase pattern linearity, stability in temperature and in coverage), EIRP and isolation between the different antennas. Antenna architectures will have to limit possible interference between payloads and take antenna coupling into careful consideration for performance optimisation.

WAVEMILL ANTENNA CONCEPT AND CRITICAL BREADBOARDING.

• Fernando Monjas (AIRBUS Defence and Space)
• Ana Olea (Airbus Defence & Space España)

The Wavemill is an RF instrument which follows a pure along-track interferometer concept, the 'Javelin’ one. In the Javelin architecture, master and slave phase centres should be perfectly aligned in the along track direction, and the resulting interferogram, co-located, is only sensitive to surface motion. The objective of the Wavemill instrument is to combine along and across track radar interferometry to provide high accuracy 2D measurements of ocean current velocity, ocean current direction and ocean topology, over a wide swath of 2 x 100 km. Earlier studies resulted in an instrument design based on four separate antenna structures. This concept, whilst having good predicted performance potentially experienced differential heating across the antennas which required compensation and complicated the instrument calibration. An alternative design called 'Javelin' based on two in-line antenna structures was therefore developed which would experience a more uniform thermal environment and simplify in-orbit calibration. In the frame of the Wavemill program an antenna capable of generating up to four squinted beams with a swath of around 100km is being studied. The Wavemill instrument is composed of two subsystems, each subsystem includes two antennas and both fore and aft subsystem are separated by a baseline distance of more than 12 meters in the along-track direction. One single antenna shall transmit a dual linear polarized pulsed signal in one beam at a time. Each antenna of the two subsystems shall receive in a dual linear polarized mode the reflected signal within this beam. This operation shall be repeated successively 4 times, for the 4 different beams. The Javelin Wavemill instrument operation provides the required along-track interferometric baselines with a compact spacecraft at launch. Each antenna subsystem shall be able to produce 4 transmit beams in dual linear polarization, and for each transmitted beam, the 2 antenna subsystems separated in along track shall be able to produce at the same time the same beam footprint to receive the reflected radar signal in the same polarization. The antenna subsystem is defined as the antenna radiating aperture(s), the feeding network, the single antenna structure, the deployment arm interconnecting the antenna to the host spacecraft, the relevant hold-down and release system, and the deployment and pointing mechanism. The orientation of the vertical polarization shall be perpendicular to the flight direction at mid footprint incidence angle, horizontal polarization shall be orthogonal to the vertical one. A Leaky wave antenna concept has been chosen as the most suitable one for Wavemill mission. A representative antenna breadboard has been manufactured and tested in Airbus Defence & Space España. RF measurements and assessment of the results are included in this project obtaining very good agreements with the predictions.

Low Side Lobe Level Image Reconstruction in Microwave Interferometry.

• Albert Zurita (Airbus Defence& Space España)
• Ana Olea (Airbus Defence & Space España)
• Josep Closa (Airbus Defence & Space España)

SMOS has been in orbit for more than 8 years, which has allowed to learn significantly on the reconstruction process of the synthetic aperture radiometer and the influence of the correspondent calibration parameters. One of the remaining artefacts to be corrected is the spatial ripple that can be observed in the brightness temperature images even if in perfect calibration conditions and perfect knowledge of the antenna patterns. Its origin is due to the fact that in the reconstruction process there are more unknowns than observables and is basically affected by the spacing between the antennas and the similarity between them. It has been demonstrated that closer antennas, would, first, enlarge the alias-free region, and, second, would reduce the level of the undesired spatial modulation that affects the images. In the same way, more similar antenna patters will also significantly reduce the level of reconstruction errors and hence of this modulations. In the first case, there is a clear limitation on the distance that the L band antennas can be located due to the physical sizes. An improvement from the current SMOS design could be achieved if located from the current 0.875 lambdas separation in SMOS to the closer 0.767 lambdas proposed for the follow-on SMOS-Ops instrument. Regarding antenna similarity, it has been seen that there is a clear dependency of the patterns on the electromagnetic environment that affects the antennas once mounted on the arms of the instrument, which have a strong shape dependency on the geometry of the arm, and hence on boundary conditions imposed by the geometry itself and the coupling between antennas located in different positions with respect to the polarization axis for each of the arms. The objective of this project is to experimentally demonstrate the improvement on image quality reconstruction by reducing the distance between the antennas and minimizing the pattern dissimilarity. This last goal is achieved surrounding the antennas by other ones identical (dummies), properly arranged on the hexagonal instrument structure, which is the one proposed for a future SMOSops follow on. Three different array configurations have been considered to characterize the embedded antennas: 1) a reference array, where 13 antennas are located in two contiguous segments of a hexagonal array following the SMOSops geometry surrounded by a ground plane. 2) An array, where the previous 13 antennas are surrounded by dummy matched antenna elements separated 0.767 lambdas. A total number of 87 radiating elements is considered, since the experience gained during the antenna ground characterization of MIRAS showed that the radius of the scattering area of one particular element, and hence the mutual coupling, spans up to 3 times the element spacing, which sets the amount of dummy antennas that is needed to surround every active element to have the same boundary conditions. 3) An extended target array, a modification of configuration 2 by adding and extra element, to confirm the size of the scattering region.

Ka-Band Interferometric SAR Antenna: active breadboard

• Rens Baggen (IMST GmbH)

The objective of this activity is to realise an active breadboard for integration with an existing feed horn-array, populated with COTS LNA MMIC’s, waveguide interfaces, and SMP- and DC-connectors consisting of 7 RF-channels in total. The frequency band is 35.5-36 GHz. Each channel has one LNA that can be switched on or off via an external control line, and a coupler for calibration purposes. The complete circuitry is noise optimised, and representative of a front-end for the later flight implementation. The knowledge on noise figure to be gained is highly relevant for all Ka-band instruments as e.g. ocean wide swath altimeter, SAR for cryosphere research and high resolution 3D imaging of the earth environment.

Medium-to-high gain X-band antenna with customisable pattern and polarisation

• Francesco Caminita (Wave Up srl)

The proposed activity aims at bringing to TRL 5 an X-band medium-to-high gain antenna system based on the modulated MTS concept. This concept has been the subject of a number of projects financed by the European Space Agency and the Italian Space Agency, which have demonstrated up to TRL 4 the unique flexibility of MTS antennas in the choice of radiation pattern and polarization using the same overall structure. This is a fundamental property for a number of space applications, including data transmission for Earth observation missions and telemetry and tele-command links for near-Earth and deep-space science and exploration missions. In fact, it allows one to reduce antenna costs, while ensuring the best fit to mission requirements. The activity involved the design, development and testing, up to TRL 5, of the antenna system. Two baseline sets of requirements were specifically addressed in the design phase: - Tx-Rx spot beam antenna system for asteroid exploration mission; - Tx-only isoflux beam antenna for data transmission from LEO. The work comprised electrical design optimization, mechanical and thermal design as well as the handling of technological issues for the two solutions. This activity concluded with the fabrication and testing to TRL 5 of the E(Q)M of the isoflux beam antenna.

Design and Analysis of X-Band TT&C and K-Band Low Gain Antennas for Future Low Earth Orbit (LEO) Missions

• Paolo Campana (Thales Alenia Space)
• Rodolfo Ravanelli (Thales Alenia Space)

The study has been devoted to the design of X-band TTC antenna on enlarged bandwidth (7.19-7.25 GHz and 8.025-8.400 GHz) and K-band DDL antenna (25.5-27.0 GHz) for Future Low Earth Orbit missions. An innovative TTC antenna has been defined with a compact envelope and good RF performance. The TTC antenna design is based on aperture surface impedence control over wide frequency bandwidth to minimize the crosspolarization up to large scan angles. This RF performance has been achieved placing a corrugated dielectric surface on the top of metallic aperture. In this contest the dielectric material and gluing process have been characterized. An EM model of TTC antenna has been manufactured and tested with a good agreement between experimental and theoretical results. The main features of K-band DDL antenna are: good copolar directivity between 59°and 70° of angular coverage and a very low level of XPD (below -18 dB).

Development of a Radiating Demonstrator of a 26GHz Band Electrical Scanning Data Downlink Antenna for Earth Observation Satellites

• Franco Perrini (Thales Alenia Space Italy)

This paper describes a Ka band antenna S/S for downloading data from Low Earth Orbit satellites (LEO’s) with costant power flux density (PFD) on earth, as requested in typical Low Earth Orbit satellites (LEO’s) orbiting at 500 Km attitude. The antenna consists of a small electronically steerable planar phased array magnified by a rotationally symmetric double reflector system. The passive radiating antenna S/S has been experimentally validated through an RF demonstrator. A satisfactory correlation of the RF model to the experimental results has been obtained. The whole antenna S/S has been conceived for operation with centralized amplification and ferrite phase shifters. However a potential active DRA evolution using GaN technology is possible in medium term.

Ka-Band Payload Data Downlink Electronically Steerable Antenna for Earth Observation Critical Breadboarding (ferrite phase shifter)

• OLIVIER PERRIN (THALES ALENIA SPACE)

In parallel to KABESA project (Ka Band Payload Data Downlink Electronically steerable Antenna), Thales Alenia Space in France was awarded by ESA for the development of a Ka band ferrite phase shifter (ESA Contract No 4000111738). Indeed, this ferrite phase shifter is the key device which provides the electrical beam scanning functionality while allowing a high efficient solution thanks to the low loss properties of the ferrite technology. In the frame of this contract, 2 Demonstrators have been developed, based on Exxelia-Temex European ferrite supplier. The measured performances are comparable to published state of the art and good enough to validate the design of the ferrite phase shifter and respond to KABESA needs. The presentation will address the following topics : • Context and objectives of the study • Recall of the ferrite phase shifter concept • Design description • Demonstrator Test plan and Test results • Recommendations for the development plan of the ferrite phase shifter Flight model

Novel Investigation in Multipactor Effect in Ferrite and other Dielectrics used in High Power RF Space Hardware

• Vicente Carlos (AURORASAT (CST/3DS))

Within the frame of this activity we have investigated the multipactor effect when dielectric and ferrite materials are present in a component. To do so, specific designs have been implemented in order to evaluate the breakdown power level. In addition to that, simulations have been performed in order to determine the ability of numerical techniques to predict the multipactor breakdown levels in such type of components. This has been done in a large bandwidth in order to be able to generate multipactor susceptibility charts of the different dielectric materials investigated (six in total).

Multipactor Analysis of 3D Structures Under Modulated Signals

• Vicente Carlos (AURORASAT (CST/3DS))

Within the frame of this activity we have investigated the impact of different modulation schemes in the multipactor breakdown power levels in different passive components. Simulations ans tests have been compared in order to demonstrate the ability of current tools to analyse multipactor under such conditions. In particular, SPARK3D and CST Particle Studio have been used for such a purpose.

Design, production and tests of an Engineering Model of S-band diplexer for CubeSat nanosatellites

• Robert Stefanski (WiRan Sp. z o. o.)

The design and development of low cost planar S-band diplexers for CubeSats is presented. Technology and topology considerations are discussed in detail. Electrical and mechanical design is presented. Results of BB measurements are presented and discussed. Manufacturing aspects are discussed with reference to final performance. Eventually, CubeSat compatible low cost planar S band diplexer with low losses and high isolation is presented.

NPI - Design techniques for low-cost filters

• Fernando Teberio (Public University of Navarre)

In this Thesis, several novel design techniques for waveguide low-pass filters (LPFs) and band-pass filters (BPFs) are proposed. Firstly, a quasi-analytical technique for classical corrugated waveguide LPFs is presented. It allows to reduce the design-times and its associated costs, since the final dimensions of the final prototype are computed by closed-form expressions. This technique has been extended to include the inherent rounded corners due to the fabrication by milling and a new method to embed routing capability in these filters is also proposed. After that, an accurate and simple design procedure for classical waffle-iron filters is also proposed. With this technique, waffle-iron filters with and without transmission zeros can be designed in a matter of minutes. Besides, a new type of waffle-iron filter is also presented. This novel structure is more compact and has lower insertion loss than its classical counterpart. The main issue of the previous classical filters is that it is not possible to achieve a wide rejected band and a high-power behavior simultaneously. This issue has been surpassed with the novel LPFs with smooth profile presented in this Thesis. Specifically, a synthesis technique has been developed, which permits to obtain larger gaps and very wide rejected bands at the same time. These new structures allow their use in high-power applications such as the output stage of satellite payloads. However, although their fabrication following space-compatible procedures has been demonstrated, it is quite difficult and expensive to be utilized in mass-production. Therefore, a new design method which accomplishes easy-to-manufacture LPFs with the same performance in terms of frequency and high-power behavior has been proposed. The objective is to reduce the fabrication costs and to develop a fully-customized technique that opens the range of potential applications. Indeed, its feasibility to be utilized as output filter in broadband satellite payloads, between the amplifiers and the diplexers in multi-beam payloads, and in diplexers is demonstrated. Furthermore, a combination between the latter low-pass filtering structure and a classical high-pass filtering function is utilized to develop a new class of BPF which can be used in high-performance compact satellite diplexers. Finally, novel BPFs with reduced sensitivity to manufacturing tolerances are also proposed. This structure finds its niche market in the upcoming Q/V-band satellite payloads. Indeed, the fabrication yield of a novel BPF intended for Q-band payloads has been dramatically improved in comparison with the one obtained from its classical counterpart. Last but not least, the size of the previous structures can be reduced with the new meandered topology developed in this Thesis. This technique permits to reduce the size of the previous BPFs (and also in classical LPFs) along with embedding routing capabilities, opening the door to more complex and compact terminals due to their adaptable and flexible layout. Additionally, it also allows to include several transmission zeros to enhance the out-of-band rejection of the LPFs.

Miniature Timing Source (mTS)

• Christian Schori (Orolia Switzerland)

The goal of this project is to demonstrate a miniature Timing Source (mTS) with low power consumption and frequency drift at least one order of magnitude better than more bulky Oven Controlled X-tal Oscillators (OCXO). The latters are currently considered the best available option in Space for timekeeping applications. The mTS technology is based on Orolia’s commercial rubidium clock adapted for low power and volume. For example, the power demanding rubidium plasma-lamp has been replaced with a low power VCSEL (Vertical Cavity Surface Emitting Laser). In addition, the size of the glass-blown rubidium vapor cell has been reduced to fit the complete physics package inside a commercial DIL-14 hermetic package. The complete mTS clock is shown in the picture below. The clock volume is 51x51x18 mm3 with a maximum (worst case) power consumption of 500 mW in cold conditions. For space usage evaluation, the mTS clock has been tested in vacuum for a period of 3 months. The measured short-term frequency stability is shown in the graph below, together with the project specifications (green line). In addition, the measured long-term drift of 2E-12/day is within the specified requirement. Besides vacuum testing, the mTS clock has been submitted to radiation tests, taking advantage of the Co-60 facility at ESTEC. The radiation test showed that the physic package is insensitive (within retrace error) up to 100 kRAD of Total Ionizing Dose (TID). Work is still needed to reduce the thermal and magnetic sensitivity of the mTS clock down to the target values.

Single GaN HPA/LNA for Radar Applications

• Jim Mayock (VIPER RF Limited)

This report focuses on the critical design of the key T/R functions of high power amplification, low noise amplification and switching for the design of a C-Band GaN single chip front end (SCFE) for radar applications. The designs are performed on a commercial European 0.25um GaN process technology. Circuit architectures for the HPA, LNA and T/R switch are considered in order to meet a target output power of 40W within a monolithically integrated solution. A set of HPA designs, LNA/switch designs and full T/R MMIC solutions are presented with a full set of layouts and simulations.

Development of a novel Transverse Schottky Diode and related membrane circuitry.

• Liam Floyd (Tyndall National Institute)

**Introduction** Schottky components are required for future space instruments and for emerging terrestrial applications in millimetre-wave imaging employed in the generation of the local oscillator signal and/or downconversion of the signal. This activity aimed at the development of a novel Transverse diode. **Objectives** The main objectives of the activity were: (1) To develop discrete Schottky diodes with good electrical and mechanical characteristics, both for mixers and frequency multipliers, and (2) To demonstrate their good performance by designing, fabricating and testing of mixer and multiplier Demonstrators for a receiver operating around 300 GHz. **Experimental** Tyndall National Institute was contracted with Farran Technology to develop the Tyndall Transverse diode. Techniques developed at Tyndall enable the thinning of the semiconductor substrate to micron thicknesses to minimise losses. This same technology is compatible with integration of the transverse diode to fabricate millimetre wave membrane circuits. Several models evolved in the design of the transverse Schottky mixer and varactor diodes. Data from these studies was then used for the design of a mixer with a centre operating frequency of 340 GHz and a doubler at 170 GHz. Development of the transverse diode fabrication process was undertaken by going through many process runs to produce diodes that when DC tested achieved the target requirements. However RF testing both at Tyndall and Millilab showed a drop-off of impedance below around 4 GHz due to inflated capacitances. This effect was also present on simple transmission lines deposited on the semiconductor substrate. In parallel to the diode fabrication, process development was extended to fabricate the mixer and multiplier membrane circuits. Mixer and doubler circuits were assembled into RF blocks and tested to measure conversion loss, noise, and efficiency. While some process runs showed good RF results others had indifferent performance. A study was undertaken to identify and remedy the source of the variability. It was found that a thin charge layer existed at the interface of one of the etchstop layers and the GaAs membrane. An alternative etchstop material was substituted and experiments then showed that no charge layer now existed. A new substrate structure was specified and wafers were grown in house. However this modified substrate unexpectedly exhibits hugely elevated localised etch rates (cheese hole formations on the membranes) leading to high series resistances in the doubler diodes and high capacitances of the mixer diodes. **Conclusion** The goal of this activity was to produce mixers and multipliers that employ a complete circuit on a semiconductor membrane as opposed to using discrete diodes mounted in a quartz substrate circuit. It was demonstrated that this is feasible. Any future development work should concentrate on the MOVPE overgrowth step where a thin layer of n-GaAs is epitaxially overgrown on the mesa sidewall. Effort should also be spent on the epi-structure and growth of the wafer substrate. The other process steps are at this stage well understood and mature.

Time efficient satellite antenna testing technique based on NF measurement and simulation with controlled accuracy

• Lars Foged (Microwave Vision Italy)
• Maria Saporetti (Microwave Vision Italy)

The increasing complexity and stringent performances required in RF instruments and payloads demand more and more that functional verification be performed on the integrated satellite under the most realistic operational conditions. Due to accuracy and testing speed, Near field methods are very attractive techniques for such testing. However, in standard Near field testing of small antennas on large platforms, the minimum number of samples is determined by the size of the entire satellite. This requirement leads to very long testing times even for smaller antennas. During the frame of this activity, an advanced RF test methodology that aims at minimizing the duration and the cost of both preliminary preparation and test campaigns has been developed and validated with actual measurements. The time efficiency with respect to traditional measurements is achieved through the exploitation of measurements and simulations combined together. The developed methodology allows to perform fast antenna measurements in the target environment applicable to Antenna Integration and Test Verification (AIT/AIV). The methodology is an add-on to standard near field measurements ranges and is the best choice for fast analysis, like verification testing, while maintaining a reasonable level of accuracy. Two methodologies have been developed and validated: • Stand-alone measurements methodology. This approach is based on reconstruction, by Equivalent Currents, using INSIGHT, of the measured antenna by itself. Standard numerical computational tools are used to include the effect of the surrounding environment. • Embedded measurements methodology. The antenna and platform is measured using a reduced number of measurement points. The expansion base is derived from numerical simulation of the platform. This approach is particularly efficient when applied to small antennas in big scenarios. Stand-alone measurements methodology has been validated with actual measurements of a GNSS antenna on ESA Sentinel Satellite. The embedded measurements methodology has been validated with small X-band antenna on a large satellite mock-up. The number of samples is reduced with a factor close to 9, while maintaining a reasonable level of accuracy with respect to standard measurement, making this technique suitable for verification testing. No electromagnetic (EM) or mechanical information about the design of the antenna is needed (no intellectual property issues): the radiating source is modelled using a small number of EM sources placed on a volume enclosing it. The number of EM sources is equal to the number of unknowns. The scattering part is analyzed with raytracing (Satsim software) and Full Wave methods on an approximate CAD model of the satellite obtained through 3D model reconstruction by multiple images. The reduced number of measured points are used to compute the weighting coefficients to reconstruct the complete field. The methodology can be employed for all missions embarking an antenna and can be applicable to any standard NF or FF measurements systems. The minimization of duration and cost of test campaigns is useful to reduce time-to-flight of any new space missions, with a very wide field of applications.

Invited Presentation - ESA Patent Porfolio Presentation

• de Clercq Aude (European Space Agency)
• Bierbuesse Franziska (European Space Agency)
• Hernandez Alfageme Nuria (European Space Agency)
• Martin-Iglesias Petronilo (European Space Agency)
• Sanchez Alvarez Mercedes (European Space Agency)

This talk aims to shortly present the ESA Patent Porfolio and explain the way to request a license for the use of the patents listed in the Portfolio. Several recent patents in the domain of microwave parts will be briefly also presented.

Development and validation of generic libraries for radiometric and geometric image processing (GRL)

• Luca Galli (Advanced Computer Systems S.r.L.)

The objective of GRL project is to build a Level 1 processing module as a series of standalone processing building blocks for radiometric and geometric image processing for Earth Observation space-born sensors. Starting from raw data (Level 0), orbit/attitude and sensor auxiliary info, GRL Level 1 Processing Module is able to generate Level-1 products applying radiometric and geometric corrections in a fully configurable and modular way. GRL is part of E2E Mission Performance simulations for Earth Observation missions. These tools are useful to assess the mission performance and support the consolidation of the technical requirements and conceptual design, as well as to allow end-users assessing the fulfillment of requirements of a future mission. A wide range of instrument types are covered by GRL, including: - optical passive Multi-band imagers (also called multi-spectral imagers, i,e, with spectral separation achieved by individual filters for each spectral band); - Spectro-imager (also called spectrometers, i.e. with spectral separation achieved by a dispersive element, such as a prism or a grating); - radiometers (passive optical instruments that rely on a very accurate measurement of the radiance, usually with lower spatial and/or spectral resolution than the two previous types of instruments). The L1 processing module and the associated building blocks cover all the spectral range from UV (ultra-violet) to TIR (Thermal Infra Red). In addition, GRL covers all types of image acquisition concepts, in particular: pushbroom, whiskbroom and matrix. A complete overview of the GRL radiometric and geometric functionalities will be given including processing results obtained by using real data acquired by ESA Missions (i.e. Sentinel-2, PROBA-V) and by Third Part Missions (i.e. Landsat ETM+).

Prototyping a vicarious calibration system for GEOSS in the frame of the CEOS a.k.a RadCalNet

• Béatrice Berthelot (Magellium)

Optical space sensors and their optionally supporting calibration devices are generally characterised pre-flight and calibrated against an on-ground traceable radiometric reference. However, both instruments and calibration devices are then exposed to space environment and susceptible to radiometric degradations once in operation. This results in a loss of traceability as soon as optical instruments are in operation in space, as they cannot be brought back to the calibration lab to be re-calibrated with respect to a ground reference. RadCalNet is an initiative of the Working on Calibration and Validation under the Committee on Earth Observation Satellites. RadCalNet provides satellite operators with SI-traceable Top-of-Atmosphere (TOA) spectrally-resolved reflectances to aid in the post-launch radiometric calibration and validation of optical imaging sensors from a coordinated network of instrumented land-based sites. The free and open access service provides a continuously updated archive of TOA reflectances and associated uncertainties at 10 nm intervals spanning the spectral range 380 nm to 2500 nm at 30 minute intervals from each of its member sites together with guidelines to support in its use. RadCalNet is currently used by more than users and space opeators world wide.

Estimation of LAI and Chlorophyll Content using Full or Reduced Hyperspectral Observation

• Béatrice Berthelot (Magellium)

The objectives of the HYPOS project (ESA ITT AO/1-8345/15/NL/LvH ) are to assess the accuracy of the biophysical parameters using full hyperspectral information or reduced hyperspectral information assess the potential of the red edge spectral bands to estimate mainly the two vegetation biophysical variables, leaf area index (LAI) and leaf or canopy chlorophyll content. To achieve this goal, the project has been split in four main tasks : 1) Build a database containing hyperspectral data and biophysical parameters. 2) Develop and evaluate method for hyperspectral data reduction 3) Develop, test and compare retrieval algorithms making use of reduced hyperspectral information (OSA) against retrieval algorithms receiving as input the full hyperspectral wavelength information (WSA). 4) Provide guidelines and recommendation for future hyperspectral optical missions and in-situ campaigns.

Closing Remarks