Bistatic spaceborne-airborne experiment TerraSAR-X/F-SAR: data processing and results

Abstract

Following an original proposal by the authors to the TerraSAR-X (TSX) scientific coordination board, a spaceborneairborne bistatic experiment was successfully performed early November 2007. TSX was used as transmitter and DLR's new airborne radar system, F-SAR, as receiver; due to the capability of the latter to acquire data quasi-continuously, no echo window synchronisation is needed. Monostatic data were also recorded during the acquisition. This paper includes description and results of the spaceborne-airborne bistatic experiment, with special focus on data processing and image comparison. Given the acquisition scenario, with two-channel sampling and transmitter and receiver clocks operating independently, data processing must necessarily follow a three-step strategy: 1) channel balancing, 2) data synchronisation and 3) bistatic SAR processing. Since neither absolute range nor Doppler references are available in the bistatic data set, synchronisation is done with the help of calibration targets on ground and based on the analysis of the acquired data compared to expected data. Due to the variant nature of the bistatic acquisition and the required precision for the processing, data are processed using a bistatic backprojection approach.

Bistatic TerraSAR-X/F-SAR Spaceborne–Airborne SAR Experiment: Description, Data Processing, and Results

“…Fig. 2) had to be switched alternately to enable quasi-continuous data recording [16], [17]. To avoid any hardware modification on the F-SAR X-band receiver chain, not only two different ADCs but also two different receiver chains were used.…”

“…Within the bounds of the approximation, the error introduced by (17) in the estimation of the degradation factor α res as a function of φ ant is shown in Fig. 24.…”

“…In addition, it delivers, for equivalent synthetic apertures, a better performance in terms of signal-to-noise ratio (SNR) and spatial resolution with respect to the monostatic spaceborne SAR. This paper presents the design, analysis, processing, and results of the first X-band spaceborne-airborne bistatic SAR experiment using TerraSAR-X as transmitter and the DLR's new airborne radar F-SAR as receiver [16], [17]. The experiment was proposed by the authors to the TerraSAR-X scientific coordination board in 2005 and was successfully conducted early November 2007.…”

Generic signal synchronisation algorithm for passive global navigation satellite system‐based synthetic aperture radar

“…This type of system is also referred to as hybrid SAR, and there has been a rising interest in this area over the past few years. The common factor in this general research is the use of radar satellites as transmitters, while the receiver is air-borne [3,4] or fixed on the ground [5][6][7]. To synthesise an aperture, motion of at least one platform (transmitter or receiver) is required.…”

First bistatic spaceborne SAR experiments with TanDEM-X

“…TanDEM-X extends the TerraSAR-X (TSX) mission by adding a second fully-active satellite with cooperative operation capabilities forming a single-pass interferometric system, and is therefore capable of providing very accurate 3D information. During the first years of the TerraSAR-X mission, DLR has benefitted from the flexibility of the system to perform some innovative SAR experiments in non-nominal configurations, i.e., spaceborne-airborne bistatic imaging [2] or the demonstration of new imaging modes [3]. The uniqueness and the increased operational possibilities of the new mission allow one to envisage a large amount of challenging and creative experiments to take advantage of the potential of the payloads.…”