76 
ADVANCES IN SIGNATURE MEASUREMENTS - RECENT SENSOR 
DEVELOPMENTS AT THE CANADA CENTRE FOR REMOTE SENSING 
Susan M. Till 
Canada Centre for Remote Sensing 
2464 Sheffield Road, Ottawa, Ontario, Canada K1A 0Y7 
ISPRS Commission VII Symposium 
Victoria, Canada, September 1990 
ABSTRACT 
The sensor research and development program at the Canada Centre for Remote Sensing (CCRS) covers 
the development and evaluation of new systems and new techniques for remotely sensing the earth's 
resources and environment. The airborne sensor developments nave been accompanied by the parallel 
development of data processing and analysis systems, by advances in calibration and correction 
procedures for signature measurements, and by extensive data acquisition for remote sensing 
application development. An overview of the sensor developments will be presented, including the 
high performance CCRS synthetic aperture radar, with the implementation of polarimetrie and 
interferometric SAR modes, and the high resolution electro-optical spectral imagers including the 
new wide angle system WHiRL. 
KEY WORDS: Synthetic aperture radar, multispectral imager, remote sensing, airborne. 
INTRODUCTION 
Recent sensor developments at the Canada 
Centre for Remote Sensing are leading to 
advances in signature measurements, both in 
the microwave area and in the visible and 
infrared regions. 
In the area of microwave signature 
measurement, the CCRS Convair-580 provides an 
airborne radar research facility that is used 
to establish synthetic aperture radar 
technology for remote sensing, to conduct 
research in imaging radar, and to develop new 
remote sensing applications and new sensor 
properties for remote sensing. It has flown 
extensively for research projects across 
Canada as part of the Radar Data Development 
Program (RDDP), to prepare for the new range 
of radar satellites including Radarsat and 
ERS-1. It has, as well, participated in major 
international missions in Canada and Europe, 
such as LIMEX/LEWEX (1987), BEPERS (1988), 
SISEX (1989), and LIMEX (1989). 
In the electro-optical area, continuing sensor 
developments are underway in the 
implementation and use of high resolution 
digital imagers for signature measurements in 
the visible and infra red regions. These have 
included the development and test flights of 
the Wide-angle High Resolution Line-imager, 
WHiRL, with high radiometric and spatial 
resolution across a 70 degree field-of-view, 
and the development, now in the integration 
stage, of an airborne multi-spectral short 
wave infra red imager for research studies of 
infra red signatures. Other activities include 
the development of an automated laboratory 
calibration facility for radiometric, 
geometric and spectral calibration of array 
imagers, and advances in algorithms and 
methodology for atmospheric and geometric 
corrections to allow for enhanced thematic and 
mapping applications. 
RADAR SIGNATURE MEASUREMENTS 
The CCRS airborne synthetic aperture radar 
(SAR) has acquired a unique and extensive set 
of radar data from oceans, ice and land, and 
these have led to improved understanding of 
microwave-target interactions. The SAR, which 
is the primary sensor in the Convair-580, is 
an extremely versatile system for remote 
sensing research, with many options for flight 
and radar configurations and image products. 
The CCRS C-/X-Band SAR system, which was 
developed under contract to CCRS by MacDonald, 
Dettwiler and Associates as prime contractor, 
has been designed to operate in a large number 
of well-defined discrete states. Parameters 
are accurately resettable and automatically 
logged during operation of the radar, while a 
small number of key radar system parameters 
such as range delay are continuously variable. 
The system has proved not only a versatile 
state-of-the-art research facility but a 
reliable and stable system that can be well 
calibrated. 
The C-Band portion of the radar was 
commissioned in the CCRS Convair-580 aircraft 
in 1987, and the X-Band portion was installed 
in January 1988. Since then, the two radars 
have flown more than 200 research missions for 
a range of remote sensing disciplines and for 
many research groups and user agencies in the 
remote sensing community. These missions have 
ranged from multi-temporal studies of 
agricultural targets, during the growing 
season and under different environmental 
conditions, to studies of ice and oceans with 
dedicated survey vessels and participants from 
international groups, to forestry signature 
investigations coordinated with ground data 
measurements and multi-sensor acquisition. 
These missions have been complemented by 
continuing development and evaluation of the 
system, its calibration, and the processing 
methods. 
Results from the Convair-580 research missions 
were presented at the first RDDP Workshop held 
in January 1990, and a comprehensive list of 
publications resulting from the C-/X-Band SAR 
developments and the RDDP are provided in the 
Workshop Report (1990). Some specific 
developments include improved understanding of 
ice and ocean interaction (for example, refer 
to: Special Issue on Labrador Ice Margin 
Experiment LIMEX and the Labrador Extreme 
Waves Experiment (LEWEX), 1989; and Vachon and 
Bhogal, 1990), advances in agricultural 
signature measurements (for example, Brisco et