R. Horn | German Aerospace Center (DLR) (original) (raw)

Papers by R. Horn

2011 IEEE International Geoscience and Remote Sensing Symposium, 2011

ABSTRACT The F-SAR airborne SAR instrument represents the successor of the E-SAR system of the Ge... more ABSTRACT The F-SAR airborne SAR instrument represents the successor of the E-SAR system of the German Aerospace Center (DLR), which has been extensively used in the last three decades. Its development was triggered by the current demand for data being simultaneously acquired at different wavelengths and polarisations as well as by the demand for very high resolution in the order of decimetres. F-SAR is a modular development utilising the most modern hardware and commercial off the shelf components. As for E-SAR DLRs Dornier DO228-212 aircraft is the first choice as platform for the new system. Although the F-SAR system is still under development, it is already taking over some of the operational duties of the old E-SAR system. This paper will analyse the performance of the current system, based on the multi-frequency and fully polarimetric imagery acquired during several campaigns in the last two years. Since F-SAR is using a fixed antenna mount without gimbal, precise radiometric calibration is particularly challenging, especially in the shorter wavelengths. Therefore, special emphasis is placed on the system calibration and the associated quality control including the achieved spatial resolution and radiometric accuracy in the different bands. PT [kW] 2.5 2.2 2.2 0.9 0.9 Rg res. [m] 0.2 0.4 0.5 1.0 1.5 Az res. [m] 0.2 0.3 0.35 0.4 1.5 Rg cov. [km]

IGARSS '96. 1996 International Geoscience and Remote Sensing Symposium

Microwave remote sensing is a main area of research of the German Aerospace Research Establishmen... more Microwave remote sensing is a main area of research of the German Aerospace Research Establishment (DLR). Especially the Institut fuer Hochfrequenztechnik is engaged in this field by making use of synthetic aperture radar systems (S A R) on both air-and spacebome platforms. The institute's engagement in the international projects ERS-1 and SIR-C/X-S A R initiated the design and development work, which lead to the well-known Experimental airborne S A R , E-SAR. It is used for testing new technologies and signal processing algorithms. In recent years it has advanced to a main research tool for remote sensing applications in geology, agriculture, forestry and military reconnaissance.

Tropical forests are the most complex, heterogeneous, undiscovered and remote forest ecosystems a... more Tropical forests are the most complex, heterogeneous, undiscovered and remote forest ecosystems and represent therefore a big challenge for remote sensing. SAR systems operating at low frequencies seems to be one of the potential remote sensing techniques allowing estimation of vertical structure and surface ground information in such ecosystems. However, a suitable radar data base over tropical forest that allows the assessment of the performance of SAR techniques is today missing. In order to support the closing of this gap the European Space Agency (ESA) has conducted within the framework of its Earth Observation Envelope Programme an airborne radar campaign. The objective of the experiment is to build up a radar data base that will allow the investigation and validation of bio-/geophysical parameter estimation techniques from polarimetric SAR interferometry (Pol-InSAR) data at Land P-band and to provide first order data evaluation. The scientific feedback from the evaluation of the acquired data will allow ESA to draw conclusions about the optimal SAR sensor configuration for biomass retrieval and monitoring in tropical areas. In a first line this campaign should be able to provide answers about the feasibility of Land/or P-band SAR to estimate forest height; about the relation between forest height and forest biomass and about the feasibility of using empirical relations to relate radar backscatter to forest biomass. For this, repeat pass polarimetric SAR interferometry at Land Pband has been flown over several test sites in Indonesia with the Experimental Synthetic Aperture Radar (E-SAR) of the German Aerospace Centre (DLR) supplemented by extensive ground measurements performed for a wide range of forest types in the frame of the INDREX-II experiment in November 2004. In this paper the general framework of the INDREX-II campaign will be outlined and preliminary results are presented and discussed.

The F-SAR airborne SAR instrument represents the successor of the E-SAR system of the German Aero... more The F-SAR airborne SAR instrument represents the successor of the E-SAR system of the German Aerospace Center (DLR), which has been extensively used in the last three decades. Its development was triggered by the current demand for data being simultaneously acquired at different wavelengths and polarisations, as well as by the demand for very high resolution in the order of decimetres. F-SAR is a modular development utilising the most modern hardware and commercial off the shelf components. As for E-SAR DLR's Dornier DO228-212 aircraft is the first choice as platform for the new system. Although the F-SAR system is still under development, since some years it is already taking over some of the operational duties of the old E-SAR system. With the recently completed L-band and P-band subsystems, F-SAR is now ready for fully replacing the E-SAR. This paper presents the new L-band subsystems and analyses its performance based on fully polarimetric imagery acquired during recent system test and calibration campaigns. The maiden flight of the new F-SAR P-band system has been postponed to spring 2012, first results will be shown in the conference presentation. Special emphasis is placed on the system calibration and the associated quality control including the achieved spatial resolution and radiometric accuracy in the different bands.

emrsdtc.com

Page 1. 6th EMRS DTC Technical Conference Edinburgh 2009 A2 The SARTOM Project: Tomography and ... more Page 1. 6th EMRS DTC Technical Conference Edinburgh 2009 A2 The SARTOM Project: Tomography and polarimetry for enhanced target detection for foliage penetrating airborne SARNick Walker 1 , Ralf Horn 2 , Armando Marino 3 , Matteo Nannini 2 , Iain Woodhouse 3 ...

EUSAR 2008, 2008

A bistatic X-band experiment was successfully performed early November 2007. TerraSAR-X was used ... more A bistatic X-band experiment was successfully performed early November 2007. TerraSAR-X was used as transmitter and DLR's new airborne radar system F-SAR, which was programmed to acquire data in a quasi-continuous mode to avoid echo window synchronization ...

IEEE Transactions on Geoscience and Remote Sensing, 2008

Synthetic aperture radar (SAR) interferometric data offer the opportunity to measure temperate gl... more Synthetic aperture radar (SAR) interferometric data offer the opportunity to measure temperate glacier surface topography and displacement. The increase of the resolution provided by the most recent SAR systems has some critical implications. For instance, a reliable estimate of the phase gradient can only be achieved by using interferogram local frequencies. In this paper, an original two-step method for estimating local frequencies is proposed. The 2-D phase signal is considered to have two deterministic components corresponding to low-resolution (LR) fringes and high-resolution (HR) patterns due to the local microrelief, respectively. The first step of the proposed algorithm consists in the LR phase flattening. In the second step, the local HR frequencies are estimated from the phase 2-D autocorrelation function computed on adaptive neighborhoods. This neighborhood is the set of connected pixels belonging to the same HR spatial feature and respecting the "local stationarity" hypothesis. Results with both Manuscript

The design and test of a dual linear polarized C-Band antenna for the airborne Synthetic Aperture... more The design and test of a dual linear polarized C-Band antenna for the airborne Synthetic Aperture Radar (SAR) system of DLR is presented. Distinctive features are dual polarization, high bandwidth, high power handling and a modular construction.

IEEE Transactions on Geoscience and Remote Sensing, 2009

This paper presents a methodology to process airborne interferometric synthetic aperture radar (S... more This paper presents a methodology to process airborne interferometric synthetic aperture radar (SAR) data to measure surface velocity fields (SVFs) of temperate glaciers, and applies it to data acquired over the Aletsch glacier. The first part of this paper deals with the main limitation in airborne interferometric SAR to retrieve reliable interferometric products, namely, the existence of the so-called residual motion errors-inaccuracies on the order of a few centimeters in the navigation system. An extended multisquint approach is proposed for their estimation in the case of nonstationary scenes. The second part of this paper expounds an efficient methodology to derive SVFs with airborne systems, where the line-of-sight displacement is estimated using differential interferometry and the along-track component by estimating the azimuth coregistration offsets. The necessary steps to finally obtain the 3-D SVF are also presented, as well as the possibility of combining different acquisition geometries. Airborne interferometric SAR data acquired by the Experimental SAR system of the German Aerospace Center over the Aletsch glacier, located in the Swiss Alps, are used to evaluate the performance of the proposed approach. The motion of the corner reflectors deployed in the scene is retrieved with an accuracy between 1 and 5 cm/day using L-band data.

As a part of scientific collaboration between ISRO and DLR, a joint SAR campaign was conducted du... more As a part of scientific collaboration between ISRO and DLR, a joint SAR campaign was conducted during Sept- Oct 2004 using DLR-228-212 aircraft equipped with DLR E SAR having multi-parameter SAR imaging ability. This paper discusses the preliminary results including details of the mission.

2007 European Radar Conference, 2007

During recent years the Experimental SAR (E-SAR) system of the German Aerospace Center (DLR) has ... more During recent years the Experimental SAR (E-SAR) system of the German Aerospace Center (DLR) has continuously been operated to acquire data for different scientific applications in forestry, agriculture and glaciology. In this context, the data where mainly used to develop new scattering models in preparation of future space-borne missions posing increasing accuracy requirements especially for the processing of repeatpass interferometric data. Also direct model-free methods like differential SAR interferometry for measuring displacements in the order of the wavelength or SAR tomography for real 3D microwave imaging of scattering volumes determined the development of advanced and very accurate motion compensation techniques. This paper first gives an overview of the updates of the E-SAR system performed during the last couple of years and then focusses on the recently developed airborne interferometric processing methods and their applications.

2012 6th European Conference on Antennas and Propagation (EUCAP), 2012

ABSTRACT A Compact Test Range (CTR) facility extends the measurement capabilities at the Microwav... more ABSTRACT A Compact Test Range (CTR) facility extends the measurement capabilities at the Microwaves and Radar Institute of the German Aerospace Centre, in Oberpfaffenhofen. Increasing requirements in the precision of RF-component characterization was the main driving factor to establish the measurement facility. A new ‘TechLab’ building houses the CTR facility. The operations started at the end of 2009. An overview of the CTR facility is the objective of this paper.

This paper presents first the relevant parameters of the experimental E-SAR system for single-and... more This paper presents first the relevant parameters of the experimental E-SAR system for single-and repeat-pass SAR interferometry. The implementation of the different interferometric operation modes is described and special attention is paid to the problems posed by the unstable airborne platform. Each interferometric mode is described including the solution of its critical problems. The given examples prove the enormous information content one can obtain from the different imaging modes of airborne SAR interferometry. Finally, future developments concerning polarimetric SAR interferometry and tomography will be addressed.