78 
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. 
ELECTRO-OPTICAL SENSORS FOR SIGNATURE 
MEASUREMENTS 
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. 
MEIS SENSOR DEVELOPMENTS 
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. 
MEIS FM 
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