IEEE Geoscience and Remote Sensing Magazine - March 2014 - 46

data download and re-tasking of satellites is possible. Satellite operators are thus increasingly leveraging the use of various ground station locations distributed across the globe.
Polar stations can offer access to (almost) all orbits of polar
orbiting LEO satellites, thus enabling the data download
after completion of each orbit and also the timely re-tasking
of the space systems. In addition mid-latitude stations offer
complementary capacities for operators to improve data
latency and coverage.

Furthermore, multi-polarization capability will enable new
applications and services in a variety of domains.
Another trend is the combination of SAR data with AIS
data for maritime monitoring applications. AIS receivers
as secondary payload on SAR satellites (as foreseen for
TerraSAR-X Next Generation) will enable a synchronised
acquisition and matching of SAR data and AIS information facilitating a rapid provision of information for Open
Ocean Surveillance.

c) Space-baSed data tranSfer SyStemS
In the future space-based data transfer systems will complement conventional data transmission functionalities.
Such data transmission systems are able to extend the
NRT product delivery capabilities from areas of interest with
a direct receiving station to a
DEmanDs anD
truly global scale.
REquiREmEnts fRom
The first commercial data
novEl applications
transfer
system, the SpaceDaanD incREasED upDatE
taHighway3, is currently under
of saR imaGERy aRE
implementation and will comthE kEy DRivERs of
mence service provision in
tEchnoloGy anD
2015. A system of geostationsERvicE DEvElopmEnts.
ary satellites will enable satellites to immediately transfer
data to the ground instead of
waiting until they pass over a ground station. The key
technology of the SpaceDataHighway is its novel Laser
Communication Terminal (LCT), which facilitates data
transmission at up to 1.8 Gigabits per second. Routing
data over the SpaceDataHighway will enable unprecedented performance options for satellite payload tasking
and data downlinking-bringing a true meaning to the
term near-real-time data. Actionable information can be
made available within 10-15 minutes on a global scale.
Thus applications such as Open Ocean Surveillance and
defence missions will be able to benefit from enhanced
reactivity and high volume surveillance capabilities outside of ground station vicinity.

thE terrasaR-X nEXt GEnERation pRoGRam
A second generation of TerraSAR-X is currently under
preparation. The development of the next generation mission is based on the experiences and lessons learned from
more than five years of commercial SAR operations with
TerraSAR-X/TanDEM-X and related user feedback.
This TerraSAR-X Next Generation mission will benefit
from an advanced SAR sensor technology allowing a spatial resolution of 0.5 m by utilizing the current ITU allowance for 600 MHz chirp bandwidth, and down to 0.25 m
with a total sweep (chirp) bandwidth of 1,200 MHz,
as will be considered under an agenda item 1.12 at the
World Radio Conference in 2015.
Services based on TerraSAR-X Next Generation will
comprise heritage modes and products from the first generation as well as enhanced products and services, featuring improved signal to noise ratio, larger swaths and submeter resolution, polarimetry, and synchronous AIS data
collection. The data dissemination concept of TerraSAR-X
Next Generation will continue to support registered TerraSAR-X receiving stations.
The TerraSAR-X Next Generation mission is intended to
take TerraSAR-X data and service continuity well beyond
2025. The Space Segment, initially a single spacecraft, will
be launched into the TerraSAR-X reference orbit while first
generation TerraSAR-X systems will still be operational.
A constellation concept called WorldSAR is envisaged
for TerraSAR-X Next Generation. The objective of WorldSAR is to provide Near-Real-Time (NRT) remote sensing
information-at a global scale. This will be achieved
through a network of three to five TerraSAR-X Next Generation type satellites operated by entities in regulated
partner nations in the frame of a Coordinated Constellation Concept (CCC). This establishes a weather independent high quality SAR satellite constellation with
unrivalled NRT data access and high speed workflow/
processing capability for the benefit of the users.
The WorldSAR constellation will use a network of
main and external ground stations including polar stations to minimise the information latency at the regional
levels. Complementing the conventional data transmission functionality with a Laser Communication Terminal
(LCT) would enable the bi-directional optical communication via relay satellites (EDRS-SpaceDataHighway
with potential extensions) and extend the NRT product
delivery capabilities to a global scale.
GRS

EnhancEmEnt of applications
The technological advancements and enhancement of service capabilities as described in the previous chapters will
enable the improvement of various SAR-based applications.
Sophisticated future systems will be able to provide a
geolocation accuracy of even less than 20 cm. This facilitates
enhanced 3D applications in urban areas and surface motion
monitoring of small infrastructures. Particularly, very high
resolution will increase the number of persistent scatters
significantly, which will open the floor for highly precise
interferometric and satellite based geodesy applications.
3The SpaceDataHighway Service is based on the European Data Relay System (EDRS) developed and implemented within a Public Private Partnership (PPP) between the European Space Agency (ESA) and Airbus Defence
and Space.

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march 2014

Table of Contents for the Digital Edition of IEEE Geoscience and Remote Sensing Magazine - March 2014