You are using an outdated browser that does not fully support the intranda viewer.
As a result, some pages may not be displayed correctly.

We recommend you use one of the following browsers:

Full text

Mesures physiques et signatures en télédétection

H. Otti and K.H. Zeller
DLR, German Aerospace Research Establishment
Institute of Radio Frequency Technology
82234 Oberpfaffenhofen, Germany
Tel.: +49-8153-28-2365, FAX: +49-8153-28-1449
For more than 10 years spaceborne SAR systems have been considered as indispensable sensors in
the scenario of EOS.
Unfortunately, due to funding problems, the EOS programme has been delayed. Further
more, the idea of large multisensor-platforms has been dropped in favour of smaller units carrying
only a few sensors, which also eases the problem of data links.
Discussions held at JPL in January 1993 were focussed on international cooperation con
cerning the use of SAR satellites and the adoption of mission goads. It was emphasized that ESA
continues with C-band SAR sensors on board ENVISAT as does Canada with RADARSAT in the
same frequency band.
Japan is expected to keep L-band in future JERS type satellites, while NASA is planning a
polarimetric L-band SAR satellite which would carry an X-band sensor provided by Germany and
eventually other European countries.
The purpose of the paper is to outline the main characteristics of the envisaged X-band
sensor, based on modern technology and an active phased array concept. Emphasis is being put on
a good efficiency at the conversion from DC into radiated RF power, and vice versa on low losses
between the antenna surface and low noise amplifiers, in order to achieve a low noise figure and to
keep the demand on satellite power low. The required technology is presently under study within
the German and Swedish electronic and space industry. Potential solutions will be indicated.
The required sensitivity (noise floor) of the system with respect to land applications will
be discussed as well as electronic beam steering (off-nadir angle range) and the achievable revisit
cycle for a specific near polar orbit altitude. The studied X-band SAR allows principally polarimet
ric measurements, but satellite power constrains those measurements (for the backscattered cross
polarized signals) to certain off-nadir angle ranges only. Therefore, the baseline is dual polariza
tion. The operational modes of the X-band SAR will include high resolution capability. However,
the L-band SAR of NASA/JPL will most likely be a fully polarimetric system optimized for wide
swath coverage and medium resolution, (of course with the possibility to change the operational
modes). The combination of a polarimetric L-band SAR and a dual polarized X-band SAR, both
with variable modes (SCANSAR, SPOTLIGHT), is a promising idea for global observations from