Measurement Modes

MeasurementModes
Tandem-L uses two complementary imaging modes in combination with a systematic imaging strategy to fulfill the mission requirements.
The Tandem-L mission concept relies on a systematic data acquisition strategy using a pair of co-operating L-band SAR satellites flying in close formation. The satellite system will be operated in two complementary measurement modes; the Deformation Mode and the 3-D Structure Mode. Both modes allow for a systematic and global imaging of the Earth with a spatial resolution of 7 m. While the Deformation Mode is designed for repeated observations every one to two weeks, the 3-D Structure Mode has a lower repeat cycle of one to two months, which is sufficient to observe the 3-D structure changes of volume scatterers like vegetation and ice.

 

Basic Modes Parameters Description
Deformation Mode 350 km swath, 7 m azimuth resolution, Single/Dual-pol. Staggered SAR
3-D Structure Mode 175 km swath, 7 m azimuth resolution, Quad-pol. Staggered SAR

 

The Deformation Mode employs repeat-pass interferometry to systematically monitor small and large-scale shifts on the Earth’s surface with accuracies down to centimetres or even millimetres.

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An innovative ultra-wide swath SAR imaging mode with 350 km cross-track coverage and a hitherto unparalleled azimuth resolution of 7 m will support the generation of consistent image stacks for large contiguous areas with frequent updates. This provides a solid data base to mitigate temporal decorrelation as well as tropospheric and ionospheric propagation errors. 3-D motion vectors are derived by combining data acquired from ascending and descending orbits with different incident angles as well as in right- and left-looking configurations. Important applications served by the Deformation Mode are the large-scale monitoring of tectonic shifts at plate boundaries, the regular observation of volcanos, the surveillance of urban subsidence, and systematic surveys of potential landslide areas.

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deformation-mode
Deformation Mode

The 3-D Structure Mode is especially designed for the three-dimensional surveying and tomographic imaging of volume scatterers, such as vegetation, ice, snow and dry soil. This imaging mode uses both satellites to collect interferometric and fully polarimetric SAR data with adjustable cross-track baselines.

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Thanks to the simultaneous data acquisition with two satellites, errors from temporal decorrelation and atmospheric disturbances can be minimized. This enables the generation of vertical and horizontal structure information with unprecedented resolution and accuracy on a global scale.
The repeated tomographic observations will provide a unique data base for the scientific monitoring of internal structure dynamics in vegetation, soil and ice. A further important application is the generation of both a digital surface and a digital terrain model, thereby complementing and updating the digital elevation data acquired by TanDEM-X. The 3-D Structure Mode therefore optimally fulfills the requirements of a large number of scientific applications pertaining to the biosphere, hydrosphere and cryosphere.

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3D-structure-mode
3-D Structure Mode