GNSS transpolar earth reflectometry exploriNg system (G-TERN): mission concept

The global navigation satellite system (GNSS) Transpolar Earth Reflectometry exploriNg system (G-TERN) was proposed in response to ESA's Earth Explorer 9 revised call by a team of 33 multi-disciplinary scientists. The primary objective of the mission is to quantify at high spatio-temporal resolution crucial characteristics, processes and interactions between sea ice, and other Earth system components in order to advance the understanding and prediction of climate change and its impacts on the environment and society. The objective is articulated through three key questions. 1) In a rapidly changing Arctic regime and under the resilient Antarctic sea ice trend, how will highly dynamic forcings and couplings between the various components of the ocean, atmosphere, and cryosphere modify or influence the processes governing the characteristics of the sea ice cover (ice production, growth, deformation, and melt)? 2) What are the impacts of extreme events and feedback mechanisms on sea ice evolution? 3) What are the effects of the cryosphere behaviors, either rapidly changing or resiliently stable, on the global oceanic and atmospheric circulation and mid-latitude extreme events? To contribute answering these questions, G-TERN will measure key parameters of the sea ice, the oceans, and the atmosphere with frequent and dense coverage over polar areas, becoming a “dynamic mapper”of the ice conditions, the ice production, and the loss in multiple time and space scales, and surrounding environment. Over polar areas, the G-TERN will measure sea ice surface elevation (<;10 cm precision), roughness, and polarimetry aspects at 30-km resolution and 3-days full coverage. G-TERN will implement the interferometric GNSS reflectometry concept, from a single satellite in near-polar orbit with capability for 12 simultaneous observations. Unlike currently orbiting GNSS reflectometry missions, the G-TERN uses the full GNSS available bandwidth to improve its ranging measurements. The lifetime would be 2025-2030 or optimally 2025-2035, covering key stages of the transition toward a nearly ice-free Arctic Ocean in summer. This paper describes the mission objectives, it reviews its measurement techniques, summarizes the suggested implementation, and finally, it estimates the expected performance.Peer ReviewedPostprint (published version

Development of a broadband and squint-free Ku-band phased array antenna system for airborne satellite communications

Novel avionic communication systems are required for various purposes, for example to increase the flight safety and operational integrity as well as to enhance the quality of service to passengers on board. To serve these purposes, a key technology that is essential to be developed is an antenna system that can provide broadband connectivity within aircraft cabins at an affordable price. Currently, in the European Commission (EC) 7th Framework Programme SANDRA project (SANDRA, 2011), a development of such an antenna system is being carried out. The system is an electronically-steered phased-array antenna (PAA) with a low aerodynamic profile. The reception of digital video broadcasting by satellite (DVB-S) signal which is in the frequency range of 10.7-12.75 GHz (Ku-band) is being considered. In order to ensure the quality of service provided to the passengers, the developed antenna should be able to receive the entire DVB-S band at once while complying with the requirements of the DVB-S system (Morello & Mignone, 2006). These requirements, as will be explained later, dictate a broadband antenna system where the beam is squint-free, i.e. no variation of beam pointing direction for all the frequencies in the desired band. Additionally, to track the satellite, the seamless tunability of the beam pointing direction of this antenna is also required. In this work, a concept of optical beamforming (Riza & Thompson, 1997) is implemented to provide a squint-free beam over the entire Ku-band for all the desired pointing directions. The optical beamformer itself consists of continuously tunable optical delay lines that enable seamless tunability of the beam pointing direction

Architectures for ku-band broadband airborne satellite communication antennas

This paper describes different architectures for a broadband antenna for satellite communication on aircraft. The antenna is a steerable (conformal) phased array antenna in Ku-band (receive-only). First the requirements for such a system are addressed. Subsequently a number of potential architectures are discussed in detail: a) an architecture with only optical true time delays, b) an architecture with optical phase shifters and optical true time delays and c) an architecture with optical true time delays and RF phase\ud shifters (or RF true time delays). The last two architectures use sub-arrays to reduce complexity of the antenna system. The advantages and disadvantages of the different architectures are evaluated and an optimal architecture is selected

City branding as economic necessity

Kvalitetno brendiranje grada je preduvjet za njihovu prepoznatljivost, kvalitetno pozicioniranje i stvaranje dodatne vrijednosti. Praksa i mnogobrojni primjeri potvrđuju ispravnost ove teze. Brendiranje gradova je nužno kako bi se pojačala konkurentnost, ostvarila veća dobit i osigurao razvoj mjesta. No ne radi se samo o ekonomskim kategorijama jer se pod razvojem mjesta podrazumijevaju i pozitivna demografska kretanja, obogaćivanje kulturnih sadržaja kao i drugih činitelja koji podižu ukupnu kvalitetu života. Izazov je to i nužnost i za gradove u Hrvatskoj kako bi bili konkurentni u oštroj tržišnoj konkurenciji.Quality city branding is a precondition for their recognazibility, quality positionig and creating of added value. Practice and numerous examples confirm correction of this theses. City branding is necessary to enhance concurence, gain bigger profit and ensure place development. But this is not only about economic categories because under place development it is understandable alsto positive demographic movement, enrichment of cultural contens as well as other factors which raise total quality of life. This is as well a challenge as it is a necessity for cities in Croatia so they could be concurente in harsh economy concurence

Towards structural integration of airborne Ku-band SatCom antenna

The paper describes research towards a fully structurally integrated Ku-band SatCom antenna. This antenna covers the complete receive band for aeronautical earth stations and DVB-S broadcast in Ku band (10.7 - 12.75 GHz). The antenna front-end consists of 32 tiles where each tile has 8×8 Ku-band stacked patch antenna elements. Optical True Time Delays (TTDs) in an Optical Beam Forming Network (OBFN) enable a squint free beam steering over the whole band to geostationary satellites. The Ku-band antenna itself covers the whole frequency band in input impedance matching and radiation pattern. The performance of a Ku-band antenna tile will be discussed. A design is presented for the structural integration of 32 tiles and the associated optical beam forming networks into a fuselage panel of an aircraft

A compact phased array for SatCom applications

This paper outlines the development of an electronically steerable receive-only array antenna realized within a project funded by the European Space Agency (ESA): the NATALIA project. The antenna has been designed for the reception of mobile satellite services in Ku-band and targets the European high-end automotive market. Based on an innovative polarization agile phased array concept, the antenna is highly compact in size, has a cost-effective buildup, and shows excellent RF-performance

GNSS transpolar earth reflectometry exploriNg system (G-TERN): mission concept

The global navigation satellite system (GNSS) Transpolar Earth Reflectometry exploriNg system (G-TERN) was proposed in response to ESA's Earth Explorer 9 revised call by a team of 33 multi-disciplinary scientists. The primary objective of the mission is to quantify at high spatio-temporal resolution crucial characteristics, processes and interactions between sea ice, and other Earth system components in order to advance the understanding and prediction of climate change and its impacts on the environment and society. The objective is articulated through three key questions. 1) In a rapidly changing Arctic regime and under the resilient Antarctic sea ice trend, how will highly dynamic forcings and couplings between the various components of the ocean, atmosphere, and cryosphere modify or influence the processes governing the characteristics of the sea ice cover (ice production, growth, deformation, and melt)? 2) What are the impacts of extreme events and feedback mechanisms on sea ice evolution? 3) What are the effects of the cryosphere behaviors, either rapidly changing or resiliently stable, on the global oceanic and atmospheric circulation and mid-latitude extreme events? To contribute answering these questions, G-TERN will measure key parameters of the sea ice, the oceans, and the atmosphere with frequent and dense coverage over polar areas, becoming a “dynamic mapper”of the ice conditions, the ice production, and the loss in multiple time and space scales, and surrounding environment. Over polar areas, the G-TERN will measure sea ice surface elevation (<;10 cm precision), roughness, and polarimetry aspects at 30-km resolution and 3-days full coverage. G-TERN will implement the interferometric GNSS reflectometry concept, from a single satellite in near-polar orbit with capability for 12 simultaneous observations. Unlike currently orbiting GNSS reflectometry missions, the G-TERN uses the full GNSS available bandwidth to improve its ranging measurements. The lifetime would be 2025-2030 or optimally 2025-2035, covering key stages of the transition toward a nearly ice-free Arctic Ocean in summer. This paper describes the mission objectives, it reviews its measurement techniques, summarizes the suggested implementation, and finally, it estimates the expected performance.Peer Reviewe