IEEE Geoscience and Remote Sensing Magazine - March 2013 - 38

of radar satellites will play a major
role in this task, since spaceborne
radar is the only sensor that has allweather, day-and-night, high-resolution imaging capability. Examples
of applications for such a constellation are environmental remote sensing, road traffic, hazard and disaster
(a)
(b)
(c)
monitoring, geoscience and climate
research, 3-D and 4-D mapping as
FIGURE 30. Concepts for a future constellation of radar satellites for quasi-continuous
well as reconnaissance and security
monitoring of the Earth. (a) Low Earth Orbit (LEO) satellites, (b) Geostationary Earth Orbit
related tasks.
(GEO) transmitter with a large reflector and LEO receivers, and (c) Medium Earth Orbit
The vision for spaceborne SAR
(MEO) satellites using a large reflector.
remote sensing looks exciting. A
space-based sensor web will provide
a view of our planet like we are used to see with Google
means including the use of time series, space diversity
Earth, but with high-resolution images and relevant geo(interferometry, tomography), multi-channel acquisition
spatial information being updated every few minutes.
(polarimetry, multi-frequency) and signal bandwidth
Future SAR mission concepts with digital beamforming
(resolution) as well as a combination of those. Each applitechnology in combination with large reflector antennas
cation poses however a different requirement on the senare being developed which will outperform the imaging
sor characteristics and observation scenario. The forward
capacity of current SAR systems by at least one order of
modeling followed by an inversion and regularization is
magnitude [168]-[196]. These highly innovative concepts
a key procedure to help defining the sensor characteriswill allow the global observation of dynamic processes
tics and observation scenario for each application. Fig. 29
on the Earth's surface with hitherto unknown qualshows a clear example of the increase in the information
ity and resolution. New spaceborne radar technologies
content provided by SAR images with 1 meter resolution
will also allow the implementation of a constellation of
(state of the art) compared to 25 cm resolution (next genradar satellites for reliable and systematic monitoring of
eration of spaceborne X-band SAR systems to be launched
the Earth's surface (cf. Fig. 30). It will open the door to a
within the next years) using a single-channel and a polarifuture global remote sensing system for the continuous
metric SAR sensor. Last but
observation of dynamic processes over the Earth, as it
not least, data fusion with
currently exists for weather prediction, where a network
different sensor types can be
A space-based sensor
of geostationary satellites is used.
further explored towards the
web will provide a
use of complementary information in the multi-dimennew view of our planet
References
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38

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Table of Contents for the Digital Edition of IEEE Geoscience and Remote Sensing Magazine - March 2013