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Proceedings of the Symposium on Global and Environmental Monitoring

and image phase information. This in turn
will provide relative pixel elevation which
with a few ground control points will lead to
digital elevation. Following the aircraft
modification, airborne testing is planned for
early 1991.
SAR Processing
In addition to the research and development of
new radar sensor technology, new data
processing methods are being studied,
specifically phase preserving SAR processing.
Using algorithms to preserve image phase
(which in the past was routinely discarded
during processing), software has been
developed and used to process airborne SAR
data and SEASAT data. The work was motivated
by that of Rocca but the approach used is
different. The first order processing is
implemented in the two dimensional wavenumber
domain and then second and higher order
processing are implemented in the new range-
Doppler domain.
The new remote sensing technologies of
interferometric SAR and polarimetric SAR,
together with the advances in SAR data
processing, hold great promise for significant
advances in application of radar remote
sensing, through improved and expanded
measurements of microwave target signatures.
The new modes of the CCRS airborne SAR and the
imagery data acquired through the Convair-580
airborne program provide a unique target
signature data set, to demonstrate the
enhanced target and terrain differentiation
possibilities, and to develop multi
disciplinary remote sensing applications in
resource and environmental monitoring.
SAR Calibration
The CCRS airborne SAR is one of the leading
remote sensing systems available to conduct
research in microwave signatures, with its
ability to produce high quality data
(resolution and radiometry) and images in
real-time over a large swath. Calibration is
an important aspect of the system, with
requirements related to its radiometric,
eometric and phase performance, and the need
or intercomparison of data, from scenes
imaged at different times or under different
environmental conditions. In addition, there
is the role that calibrated airborne systems
can play in the calibration of future
satellite radars.
The calibration project for the C-/X- Band SAR
has been a major activity, covering
theoretical analysis, system characterization
including antenna pattern measurements,
fabrication of a calibration test site, and
acquisition of imagery over six test areas.
The airborne missions and field trials were in
conjunction with projects in agriculture as
well as some in hydrology, forestry and ice
studies; they used a combination of active
radar calibrators and corner reflectors, to
aid in the calibration, and ground-based and
airborne scatterometers for verifying the
calibration methodology and results. These
have resulted in the development of a software
package for radiometric calibration of the
imaqery, and the development of calibration
methodology that is already being used in the
multidisciplinary application projects.
Further improvements are underway,
specifically related to motion compensation
and advances in the use of ground-based
calibration targets, and are expected to lead
to refinements in the radiometric corrections.
The CCRS SAR has been found to be very stable,
and it is hoped that this will permit eventual
radiometric calibration even without the use
of point targets in every scene. While the
results of the airborne SAR calibration
project have substantially increased the
understanding of the correction requirements
and hence the ability to measure microwave
signatures and to interpret the airborne
imagery in terms of quantitative geophysical
parameters, these results will also be of
importance in interpreting the imagery from
the new satellite-borne radars.
At CCRS, the Multi-detector Electro-optical
Imaging Sensor, MEIS II, has been operating
since 1983. This is a pushbroom line-imager,
with fore-aft stereo, and high spectral,
spatial and radiometric resolution. It has
flown well over 400 missions installed as the
primary sensor in the Falcon electro-optical
airborne facility, with the data being used
primarily for research purposes in remote
sensing (Till et al, 1986). Since 1987, the
airborne facility has been operated by
industry on a commercial basis, and has
participated in pilot projects related to
forestry survey, bathymetry, urban studies,
and mapping etc. In 1989, the MEIS
demonstrated its potential for environmental
monitoring when it acquired extensive multi
temporal data after the Valdez oilspill in
Alaska, monitoring coastlines and inland
waters during the clean-up exercise. The
electro-optical facility is an integrated
package which includes, as well as the MEIS,
a multi-spectral scanner with visible and
thermal infra-red response, a real-time image
display with image enhancement capability, and
associated navigation and digital data
recording systems. This facility also helped
monitor the forest fires that occurred in the
Western States in 1988 and 1989.
As a result of the MEIS research and
development program, a number of applications
have emerged as prime candidates for
operational implementation using a MEIS-based
airborne system. Two of these are forestry
resource surveying and topographic mapping.
The sensor offers the advantages of high
spatial and radiometric sensitivity (necessary
in forestry applications for signature
measurements related to inventory or insect
damage), stereo information for derivation of
terrain elevation, and digital output for ease
of processing and ready compatibility with
geographic information systems. CCRS, with the
Canadian Department of Forestry, completed a
study into the functional requirements for a
sensor tailored to these specific
applications, and initiated a project with
industry to develop a system, MEIS FM (MEIS
for Forestry and Mapping), for commercial
resource survey.
Under the MEIS research program at CCRS, the
functional specifications were determined for
such a sensor (Neville and Till, 1989). The
multispectral imager is specified to have a
field-of-view of 70 degrees, high resolution
and wide swath, fore-nadir-aft continuous