single pass stereo, and four to six nadir 
spectral bands in the spectral range 400 to 
1000 nm. The spectral band widths are to be 
less than 10 nm with a dynamic range of 
4000:1. The major advances in technology of 
such a system compared to existing imagers are 
related to the much wider field-of-view 
(comparable to that of aerial cameras) and the 
improved spatial resolution, which together 
provide improved economic viability. In 
addition, there are advances in the 
digitization rate and signal processing on 
board as well as enhanced ground processing 
and interpretation optimized for the 
application requirements. The conceptual 
design of the MEIS FM system has now been 
completed and comprises airborne sensor, 
ground processor and workstation to provide an 
end-to-end system from data acquisition to 
product. 
WHiRL, airborne Wide-angle High Resolution 
Line-imager 
As part of the MEIS FM development project at 
CCRS, the critical components were identified, 
designed and tested. A prototype, WHiRL 191, 
comprising these test components was assembled 
and was flown first in December, 1989. The 
sensor uses a state-of-the-art 6000 element 
charge-coupled-device from Loral Fairchild. 
In order to obtain a lens of sufficiently 
large aperture with an acceptable modulation 
transfer function to obtain the required image 
uality, a custom lens was designed and 
abricated by the National Research Council of 
Canada. The signal output is digitized to 12 
bit, and recorded on high density digital 
tape. By using a data format similar to that 
of the MEIS II, existing hardware and software 
systems are used to display the imagery and to 
transcribe the data on the ground to computer 
compatible tapes. Flown at an altitude of 12 
km, the sensor has a pixel size of 2.8 m and 
a swath of 16.8 km. At an altitude of 1000 m, 
the pixel size is .23 m, with a swath of 1.4 
km. The details of the sensor and its 
performance are published elsewhere (Neville 
et al, 1990), but the test flights have shown 
the success of this approach, with excellent 
image quality and high spatial resolution 
obtained across the full field-of-view. The 
WHiRL sensor has demonstrated the feasibility 
of the high resolution, wide swath digital 
imager and has provided some very exciting 
imagery. It is an important step in the 
measurement of target signatures and in the 
development of fully commercial digital 
imagers for aerial survey and resource 
monitoring. 
MEIS calibration 
The advances in sensor technology require 
parallel advances in calibration and 
correction procedures for the data, to allow 
the sensor's full capability for signature 
measurement to be realized. The multispectral 
imager developments at CCRS have been 
accompanied by the design and implementation 
of an automated calibration facility for the 
precision geometric and radiometric 
calibration of multi-element array imagers 
such as MEIS II (Neville et al, 1990). The 
facility, which includes precision optics and 
micro-processor based software for control and 
data processing, 1s used for the "routine" 
annual calibration of the MEIS II. It is also 
used in the development of new sensors, to 
measure and evaluate the performance of 
components such as linear detectors. It was 
used extensively in the design and 
implementation of the wide-angle imager WHiRL, 
both in the alignment of the optical 
components and in the characterisation of the 
system. 
In addition to the development of calibration 
procedures, CCRS has ongoing research studies 
into the effects of atmospheric conditions and 
latform motions on electro-optical imagery, 
oth airborne and satellite. The atmospheric 
correction algorithms have been developed and 
refined over several years, using radiative 
transfer modelling, multi-sensor and multi 
temporal data acquisition, and validation 
procedures (Gauthier at al, 1989). Analytic 
algorithms have been specified for image 
processing systems, and additional effects, 
such as polarization and aerosol optical 
depths, are being considered. The improved 
understanding of the many processes involved 
in image formation, and the ability to correct 
for the atmospheric effects, are critical for 
the measurement of target signatures on a 
quantitative basis. 
Geometric corrections, to remove the effects 
of platform motion, and particularly aircraft 
motion, are also critical for many remote 
sensing applications. Georeferenced products 
are required for mapping and survey related 
activities, and for the increasing 
number of resource managers using geographic 
information systems. Rigorous photogrammetric 
adjustment and geometric correction algorithms 
for airborne line imager data have been 
developed by Gibson (1986), and have been in 
use on the VAX computer system at CCRS to 
correct MEIS II and airborne scanner data. 
Current activities follow pilot projects to 
evaluate the use of MEIS for topographic 
mapping, and include the refinement and 
transfer of the existing software to operate 
on a stand-alone workstation, and the 
implementation of algorithms to derive terrain 
height from stereo image data and to produce 
digital elevation models (Gibson and Bucheit, 
1990). 
SWIR SPECTRAL IMAGING 
Inspired in part by the two relatively broad 
short wave infra-red (SWIR) bands on the 
Thematic Mapper, there is growing interest in 
the SWIR spectral region and spectral 
signatures in this region. The remote sensing 
interest is concentrated in two resource 
areas: vegetation, including forestry, and 
geology. While SWIR detector technology has 
been under development for at least a decade, 
it is within the past 18 months that detectors 
with a reasonably large number of elements 
have become more readily available. CCRS has 
a research project underway to develop a 
prototype SWIR sensor and laboratory facility 
that will provide signature measurements for 
research in the spectral range of 1 to 2.5 urn. 
This region has not yet been extensively 
researched but offers a number of potential 
new applications. 
LASER SYSTEM DEVELOPMENTS 
The laser systems for remote sensing that were 
developed in the past under the research 
program of CCRS have now been largely 
transferred to the user agencies and 
industries. CCRS continues to provide 
technical assistance as required to help in 
their continuing development and use.