Abstract
In the recent years, China pays much
attention into microwave remote sensing
application. Synthetic Aperture Radar (SAR)
sensor is being developed as a key geomatics
data source. This paper presents the main
R&D activities of SAR systems. It includes 4
parts of work on airborne SAR, spaceborne
SAR, ground SAR processor and new
generation's SAR technologies. Some good
results are described.
1. Introduction
Synthetic Aperture Radar (SAR) is used
to acquire high-resolution large-scale
images of earth surface. The advantages
of a SAR device are operations in all
weather condition during the day and
night circles of an orbit in order to
complement the existing optical sensors.
At present SAR becomes an important
tool of active microwave remote
sensors for environment monitoring and
resource survey, military application in
the world.
Since the end of 70’s, institute of
Electronics, Chinese Academy of
Sciences (IECAS) started to study on
imaging radar technology for radar
system design and signal processing
methods as the main unit in China. As
technological progresses are rapidly
extended, SAR systems both airborne
and spaceborne platforms form the
major subjects in IECAS, not only to
demonstrate its technological feasibility,
but also to develop SAR engineering
projects and exploit some of the new
generation's SAR technology. Technical
researchers have developed hardware
and software dealing with data
processing of high data rate. The
applied researches on a variety of fields
are widely extended such as Institute of
Remote Sensing Application and users
etc. Work on cartography, crop
monitoring, disaster detection and
monitoring, desertification assessment
and new geographical information
systems are increasingly involved.
2. The Airborne SAR System
Chinese organizations have bought
several plans devoted to airborne SAR
system. IECAS completed the first
operational X-band airborne SAR with
mono-polarization in early 80’s. Then
we produced the first multi-polarization
and multi-swath airborne SAR imaging
system, which got radar images
successfully, used for flood monitoring
in the early 90’s. In above system, SAR
raw data are gathered on-board the
aircraft and stored on optical film
recorder for subsequent data processing
using optical correlator on the ground.
The first real-time on-board SAR
imaging processor has been developed
in 1994 in order to meet time urgent
applications. It does SAR images
processing on board the aircraft. The
produced images can be displayed and
recorded immediately to verify the SAR
data acquired. In the same time a data
downlink communication system is
used, the produced images can be also
displayed on ground monitoring system
in time.
The radar system has worked very well
under severe service conditions and
produced a great number of mapping
area images. An example of the digital
images is shown in fig. 1. The
boundaries between water and land are
displayed very clearly. The river course,
bridges and other prevention
engineering works are also shown
clearly. By use of these images and
other known information, the scientists
on geology and water conservancy can
efficiently evaluate the effects of
flooding to agriculture and properties.
Fig. 1 Flooded Yangtze River. The Jiu-Jiang Area, 1998.
