IEEE Geoscience and Remote Sensing Magazine - June 2015 - 22

tabLe 4. uniqueness of tandem-L Products and aPPLications.
Product

tandem-L

3-D Forest Height
& Structure

◗ High spatial and vertical resolution
◗ BIOMASS (approved):
* Height: 10% @ 30 x 30 m2
* Lower vertical and horizontal resolution (voxel size worse by a factor of 40)
* Structure: 10 x 50 x 50 m3 voxel size
* No global coverage (SOTR restrictions in Europe, North America and parts
◗ Frequent monitoring for the assessof Asia)
ment of seasonal and annual dynamics
* No structure dynamics (single tomographic measurement dispersed over
(2 global coverages/year)
one year)
◗ GEDI (approved):
* No seamless coverage (only lidar tracks)
* No global coverage (lack of northern boreal forests)
* poor performance for the assessment of seasonal and annual dynamics
◗ SAOCOM-CS (planned):
* Mostly demonstration with reduced performance
* No global coverage and no dynamics

Digital Elevation
Model

◗ Terrain and surface models with high
accuracy and resolution
◗ Seasonal and yearly updates

◗ TanDEM-X (current):
* Provides only a digital surface model
* No updates

3-D Deformation

◗ High resolution deformation maps on
a global scale
◗ Systematic acquisition concept for the
measurement of 3-D vector movements
◗ Low temporal decorrelation in L-band

◗ Sentinel-1 (current):
* Increased susceptibility to temporal decorrelation due to four times
shorter wavelength in C-band
* Lower spatial resolution in TOPS mode
* No dedicated acquisition plan and processing for 3-D vector movements
◗ ALOS-2 (current):
* No systematic acquisition for large-scale deformations and no processing
of image stacks
* Conventional SAR with limited swath width and/or resolution
◗ TerraSAR-X/TanDEM-X (current):
* Can only acquire one global acquisition/year
* Strong temporal decorrelation in X-band

3-D Ice Structure

◗ High spatial and vertical resolution
◗ Monitoring of seasonal and annual
dynamics

◗ No comparable spaceborne data available yet (currently only small-scale airborne and ground-based sounder/GPR data available).

Soil Moisture

◗ High spatial resolution (30 x 30 m2)
◗ (Bi-)weekly acquisitions

◗ Spaceborne radiometers and scatterometers (SMOS, SMAP, ...) provide only
resolutions in the order of 10 km and more
◗ SAOCOM (approved) is a conventional SAR with significantly worse spatial
and temporal resolution

avaiLabLe Products (current, aPProved or PLanned missions)

spaceborne Earth observatory for continuous monitoring of
the Earth and its environment, analogous to the existing
network of weather satellites. Further studies include the investigation of a Tandem-L-based mission concept for daily
monitoring of geo/bio-environmental phenomena as well
as tectonic hazards prevalent within the inner tropical belt
by means of equator-orbiting satellites [34], [35].

figuRe 16. Artist's view of Tandem-L in a bistatic formation flight.

Acknowledgment
The authors would like to thank the JAXA team who jointly worked with the DLR team during the pre-phase-A study
as well as the science team of the HGF Alliance HA-310
"Remote Sensing and Earth System Dynamics" for their
valuable and extensive contribution to the definition of
the science requirements of the Tandem-L mission.

Presently, Tandem-L is undergoing a phase A study by
DLR. Figure 16 shows the artist's view of the satellite design
under investigation by the German space industries. The
goal is a launch by 2021. Due to the innovations in science,
methodology and technology, Tandem-L is predestined to
lay the foundation for future SAR missions towards a unique

[1] A. Moreira, G. Krieger, I. Hajnsek, K. Papathanassiou, M. Younis,
F. Lopez-Dekker, S. Huber, M. Eineder, M. Shimada, T. Motohka,
M. Watanabe, M. Ohki, A. Uematsu, and S. Ozawa, "TandemL/ALOS-Next: A highly innovative SAR mission for global observation of dynamic processes on the Earth's surface," in Proc.
IGARSS, Milan, Italy, July 2015.

RefeRences

ieee Geoscience and remote sensing magazine

june 2015

Table of Contents for the Digital Edition of IEEE Geoscience and Remote Sensing Magazine - June 2015