Operational aspects of the TanDEM-X Science Phase

Abstract

In the years 2010-2014 the satellites TSX and TDX collected all the Synthetic Aperture Radar (SAR) data necessary to fulfill the primary TanDEM-X mission objective: the generation of a global digital elevation model with unprecedented accuracy. In September 2014, when the necessary data set was almost complete, a transition to the so-called science phase took place. Its focus was the implementation of the TanDEM-X secondary mission objectives. TSX and TDX fly in close formation in low Earth orbit in order to form a SAR interferometer in space with adjustable interferometric baselines. Due to the diversity of scientific applications, the science phase was marked by several baseline and hence formation changes and, in addition, by unusual formation geometries. Modifications to the proven operational handling of SAR payloads and the data downlink became necessary as well as the adaptation of existing safety concepts. Furthermore, the transition from one baseline setting to the other had to be managed operationally safe and in such a way that downtimes were minimal. Nomenclature SAR= Synthetic Aperture Radar TanDEM-X Mission =

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“…In the analysis above it was assumed that the vertical ice motion is zero. As Mahoney et al (2016) demonstrated, already small vertical displacements of a few millimeters (as observed, for example, when infra-gravity waves propagate in sea ice covered areas) may cause significant phase shifts. However, in their investigation the temporal baseline was 10 s. They reported wave amplitudes between 1.2 and 1.8 mm with periods between 30 and 50 s. For topographic mapping, very short temporal baselines are required, at X band, e.g., optimally less than 0.5 s and even much less if the line-ofsight velocities are high (see Table 5).…”

Evaluating Landfast Sea Ice Ridging near UtqiaġVik Alaska Using TanDEM-X Interferometry

“…In bistatic mode, the temporal lag is in the order of roughly 10 ms, but with a substantial perpendicular baseline (the projection of the cross-track baseline perpendicular to the slant range). The baseline of this configuration changes over time depending on priorities [40]. The primary goal of the TanDEM-X mission is to acquire a digital elevation model (DEM) over land.…”

Sea ice local surface topography from single-pass satellite InSAR measurements: a feasibility study

“…The ascending node is the intersection of the equatorial plane and the satellite orbit on the leg from the Southern to the Northern Hemisphere. The TanDEM-X satellite is controlled with respect to TerraSAR-X (Maurer et al, 2016). The maximum baseline varies along the orbit; its length is expressed as a function of the geographical latitude (AO TanDEM-X Science Phase manual, https://tandemx-science.dlr.de/).…”

“…Optimal conditions for retrieving sea ice topography and movement are given when two satellites fly as a tandem in close formation ("single-pass InSAR"). The opportunity to study the potential of single-pass satellite InSAR for mapping of sea ice topography arose during the TanDEM-X Science Phase, which started in September 2014 and lasted for 17 months (Maurer et al, 2016). The TanDEM-X mission (TerraSAR-X add-on for Digital Elevation Measurements) has primarily been designed for topographic mapping of the Earth's land masses (Krieger et al, 2007).…”