Advanced Concepts for Ultra-Wide-Swath SAR Imaging

This paper reviews advanced multi-channel SAR system concepts for the imaging of ultra-wide swaths with high azimuth resolution. Novel system architectures and operational modes are introduced and compared to each other with regard to their performance

Digital Beamforming Architecture and Techniques for a Spaceborne Interferometric Ka-Band Mission

The paper presents the instrument concept and performance of a Ka-band single-pass interferemetric mission proposed for measuring topography and topographic changes. A formation flying constellation of two compact synthetic aperture radars (SAR) satellites equipped with innovative digital beamforming hardware and advanced operation modes is described

Measurements of a Multi Feed Reflector Antenna for SAR Systems Based on Digital Beam Forming

In the last years, the Synthetic Aperture Radar (SAR) systems evolution migrates toward the use of multi-channel systems based on Digital Beam Forming (DBF) techniques [1]. This tendendy allows fulfilling stringent SAR requirements, providing high spatial resolution within a wide swath. Moreover, the combination of DBF techniques with parabolic reflector antennas merges both flexibility and high antenna gain ending up in a high versatile system [2]. One of the main parts in a Digital Beam Forming (DBF) Synthetic Aperture Radar system is constituted by the antenna. An accurate characterization of the antenna radiation pattern is of high interest for the calibration of the system which guarantees the performance and versatility of the DBF network. This paper describes the measurements of a multi- feed single offset reflector antenna designed in X-band. The antenna is part of an on ground multi-channel radar system used to demonstrate ind investigate DBF techniques at HR/DL

X/Ka-Band Dual-Polarized Digital Beamforming Synthetic Aperture Radar

This paper presents a digital beamforming (DBF) synthetic aperture radar (SAR) for future spaceborne earth observation systems. The objective of the DBF-SAR system is to achieve a low cost, lightweight, low-power consumption, and dual-band (X/Ka) dual-polarized module for the next-generation spaceborne SAR system in Europe. The architectures and modules of the proposed DBF-SAR system are designed according to a realistic mission scenario, which is compatible with the future small/microsatellites platforms. This system fills an important gap in the conception of the future DBF-SAR, facilitating a high level of integration and complexity reduction. The proposed system is considered not only the first demonstrator of a receive-only spaceborne DBF system, but also the first X/Ka-band dual-polarized SAR system with shared aperture. This paper presents a description of the proposed instrument hardware and first experimental validations. The concept and design of the DBF multistatic SAR system are discussed and presented first, followed by the design of subsystems such as DBF networks, microwave integrated circuit, and antennas. Simulated and measured results of the subsystems are presented, demonstrating that the proposed SAR instrument architecture is well-suited for the future SAR applications

Orbit Determination Error Analysis for a future Space Debris Tracking Radar

Independent of light and weather conditions radar systems provide observations of space debris in low and medium earth orbits. In general two operational principles can be distinguished - in survey mode all objects passing through the radar instrument’s field of view and above a certain size threshold are detected; subject to the tracking mode is the task to collect positional information on an already detected object. A recently proposed radar concept balances survey and tracking performance in a novel way by combining a mechanical steerable reflector antenna with digital beam-forming techniques. The utilization of multiple digital feed elements allows illumination of a larger survey zone, compared to the relative narrow pencil beam of conventional tracking radars. Signal processing from independent digital channels preserves a high antenna gain on the reception path. It is also a prerequisite for the implementation of an advanced Track While Scan operational mode. During design phase an optimal combination of surveillance and tracking functionality will have to be found. As the number of simultaneously observable space debris is directly linked to the angular extension of the survey zone plus the amount of transmitted/received power, it is straightforward to define system requirements to meet an envisaged survey performance. Moreover, it is less obvious to characterize tracking data that lead to reliable and accurate orbit determination results. Variables of influence are the type of involved measurement data, their temporal and geometrical distribution as well as systematic measurement errors, e.g. measurement bias and noise, or erroneous measurement correction and force modelling. The amount of error introduced by each variable can be quantized in a so called Consider Covariance Analysis. This paper presents the outcomes of this kind of orbit determination error analysis. Qualitative simulations for a small set of tracking scenarios serve as a starting point for the establishment of tracking requirements for a possible future space debris radar located at DLR ground station in Weilheim. The analyzed tracking scenarios are representative for three satellite missions currently operated at German Space Operation Centre (GSOC) and take into account the timeliness constrains inhered from a tracking request for refined orbit determination in case of a conjunction warning. Based on analysis findings the number of station passes, space debris can be tracked on, is investigated in more detail and an analytical formula is given for the optimization of minimum elevation angle