The TanDEM-X Mission Phases—Ten Years of Bistatic Acquisition and Formation Planning

Bachmann, Markus; Kraus, Thomas; Bojarski, Allan; Schandri, Maximilian; Böer, Johannes; Busche, Thomas; Bello, Jose-Luis Bueso; Grigorov, Christo; Steinbrecher, Ulrich; Buckreuss, Stefan; Krieger, Gerhard; Zink, Manfred

doi:10.1109/jstars.2021.3065446

Cited by 16 publications

(12 citation statements)

References 47 publications

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“…equator up to an incidence angle of 50°. This is comparable to high-resolution DEMs in the TanDEM-X mission [46]. Thus, the largest cross-track baseline between Rx1 and Rx3 was derived to be 1300 m at the equator.…”

Section: Baseline and Orbit Formationsupporting

confidence: 69%

“…For example, phase unwrapping is more difficult in case that the two baselines are not acquired at the same time due to, e.g., different depth of penetration in forested areas. A quantitative prediction of the phase unwrapping improvement when comparing two MirrorSAR satellites with three ones is difficult but TanDEM-X experience [46] clearly favored three MirrorSAR satellites.…”

Section: A Mirrorsar Satellite Number and Single-pass Baselinesmentioning

confidence: 99%

“…The interferometric height error is finally obtained from the smallest HoA (cf. The smaller baseline allows for a high-quality phase unwrapping [46]. Fig.…”

Section: Interferometric Height Errormentioning

confidence: 99%

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MirrorSAR: An HRWS Add-On for Single-Pass Multi-Baseline SAR Interferometry

Mittermayer

Krieger

Bojarski

et al. 2022

IEEE Trans. Geosci. Remote Sensing

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This paper reports the Phase A study results of the interferometric extension of the High-Resolution Wide-Swath (HRWS) mission with three MirrorSAR satellites. According to the MirrorSAR concept, small, low cost, transponder-like receiveonly satellites without radar signal demodulation, digitization, memory storage, downlink, and synchronization are added to the planned German X-band HRWS mission. The MirrorSAR satellites fly a triple helix orbit in close formation around the HRWS orbit and span multiple single-pass interferometric baselines. A comprehensive system engineering and performance analysis is provided that includes orbit formation, MirrorLink, Doppler steering, antenna pattern and swath design, multi-static echo window timing, SAR performance, height performance and coverage analysis. The overall interferometric system design analysis of Phase A is presented. The predicted performance of the global Digital Elevation Model (DEM) is improved by one order of magnitude compared to presently available global DEM products like the TanDEM-X DEM.

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Section: Baseline and Orbit Formationsupporting

confidence: 69%

Section: A Mirrorsar Satellite Number and Single-pass Baselinesmentioning

confidence: 99%

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MirrorSAR: An HRWS Add-On for Single-Pass Multi-Baseline SAR Interferometry

Mittermayer

Krieger

Bojarski

et al. 2022

IEEE Trans. Geosci. Remote Sensing

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“…Six global-scale DEMs were selected for evaluating their influences on ITIMs, based on popularity, data source, resolution and sensor type (optics or SAR) (Table 1). 2) TanDEM-X 90 m DEM (hereafter TanDEM-X) is a product derived from the first bistatic X band SAR mission of the world which took place from 2014 to 2016 (Bachmann et al 2021). It is a pixel-reduced product of the global TanDEM-X DEM with a pixel spacing of 0.4 arcseconds (12 m).…”

Section: Dems Evaluated (Aw3d30 Tandem-x Nasadem Srtm)mentioning

confidence: 99%

Towards ice thickness inversion: an evaluation of global DEMs by ICESat-2 in the glacierized Tibetan Plateau

Chen

Zhang

et al. 2021

Preprint

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Abstract. Accurate estimates of regional ice thickness, which are generally produced by ice-thickness inversion models, are crucial for assessments of available freshwater resources and sea level rise. Digital elevation model (DEM) derived surface topography of glaciers is a primary data source for such models. However, the scarce in-situ measurements of glacier surface elevation limit the evaluation of DEM uncertainty, and hence its influence on ice-thickness modelling over the glacierized area of the Tibetan Plateau (TP). Here, we examine the performance over the glacierized TP of six widely used and mainly global-scale DEMs: AW3D30 (30 m), SRTM-GL1 (30 m), NASADEM (30 m), TanDEM-X (90 m), SRTM v4.1 (90 m) and MERIT (90 m) by using ICESat-2 laser altimetry data while considering the effects of glacier dynamics, terrain, and DEM misregistration. The results reveal NASADEM as the best performer, with a small mean error (ME) of −1.0 and a root mean squared error (RMSE) of 12.6 m. A systematic vertical offset existed in AW3D30 (−35.3 ME and 34.9 m RMSE), although it had a similar relative accuracy to NASADEM (~ 13 m STD). TanDEM-X also performs well (−0.1 ME and 15.1 m RMSE), but suffers from serious errors and outliers on steep slopes. SRTM-based DEMs (SRTM-GL1, SRTM v4.1, and MERIT) (all ~ 36 m RMSE) had an inferior performance to NASADEM. However, their errors were reduced in the ablation zone when glacier variations were excluded. Errors in the six DEMs increased from the south-facing to the north-facing aspect and become larger with increasing slope. Misregistration of DEMs relative to ICESat-2 footprint in most glacier areas is small (less than one pixel). An intercomparison of four ice-thickness models: GlabTop2, Open Global Glacier Model (OGGM), Huss-Farinotti (HF), Ice Thickness Inversion Based on Velocity (ITIBOV), show that GlabTop2 is sensitive to the accuracy of both elevation and slope, while OGGM and HF are less sensitive to DEM quality, and ITIBOV is the most sensitive to slope accuracy. Considering the inconsistency of DEMs acquisition dates, NASADEM would be a best choice for ice-thickness estimates over the TP, followed by AW3D30, and TanDEM-X (if steep and high elevation terrain can be avoided). Our assessment figures out the performances of mainly global DEMs over the glacierized TP. This study not only avails the glacier thickness estimation with ice thickness inversion models, but also offered references for other cryosphere studies using DEM.

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“…The TanDEM-X mission is a partnership between the German Aerospace Centre (DLR) and Airbus Defence and Space. It is a constellation of two satellites (TerraSAR-X and TanDEM-X), orbiting in a close formation and acquiring high spatial resolution radar images of Earth's surface [12,13]. DLR is responsible for the operation of the satellites in the orbit, the collection of data during the mission, their interferometric processing, as well as the distribution of the final model to the scientific community.…”

Section: Introductionmentioning

confidence: 99%

Applicability of Data Acquisition Characteristics to the Identification of Local Artefacts in Global Digital Elevation Models: Comparison of the Copernicus and TanDEM-X DEMs

et al. 2021

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Several global digital elevation models (DEMs) have been developed in the last two decades. The most recent addition to the family of global DEMs is the TanDEM-X DEM. The original version of the TanDEM-X DEM is, however, a nonedited product (i.e., it contains local artefacts such as voids, spikes, and holes). Therefore, subsequent identification of local artefacts and their editing is necessary. In this study, we evaluated the accuracy of the original TanDEM-X DEM and its improved edited version, the Copernicus DEM, in three major European mountain ranges (the Alps, the Carpathians, and the Pyrenees) using a digital surface model derived from airborne laser scanning data as a reference. In addition, to evaluate the applicability of data acquisition characteristics (coverage map, consistency mask, and height error map) and terrain characteristics (slope, aspect, altitude) to the localization of problematic sites, we modeled their associations with the TanDEM-X DEM error. We revealed local occurrences of large errors in the TanDEM-X DEM that were typically found on steep ridges or in canyons, which were largely corrected in the Copernicus DEM. The editing procedure used for the Copernicus DEM construction was evidently successful as the RMSE for the TanDEM-X and Copernicus DEMs at the 90 m resolution improved from 45 m to 12 m, from 16 m to 6 m, and from 24 m to 9 m for the Alps, the Pyrenees, and the Carpathians, respectively. The Copernicus DEM at the 30 m resolution performed similarly well. The boosted regression trees showed that acquisition characteristics provided as auxiliary data are useful for locating problematic sites and explained 28–50% of deviance of the absolute vertical error. The absolute vertical error was strongly related to the height error map. Finally, up to 26% of cells in the Copernicus DEM were filled using DEMs from different time periods and, hence, users performing multitemporal analysis or requiring data from a specific time period in the mountain environment should be wary when using TanDEM-X and its derivations. We suggest that when filling problematic sites using alternative DEMs, more attention should be paid to the period of their collection to minimize the temporal displacement in the final products.

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The TanDEM-X Mission Phases—Ten Years of Bistatic Acquisition and Formation Planning

Cited by 16 publications

References 47 publications

MirrorSAR: An HRWS Add-On for Single-Pass Multi-Baseline SAR Interferometry

MirrorSAR: An HRWS Add-On for Single-Pass Multi-Baseline SAR Interferometry

Towards ice thickness inversion: an evaluation of global DEMs by ICESat-2 in the glacierized Tibetan Plateau

Applicability of Data Acquisition Characteristics to the Identification of Local Artefacts in Global Digital Elevation Models: Comparison of the Copernicus and TanDEM-X DEMs

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