Design and implementation of a Synthetic Aperture Radar for Open Skies (SAROS) aboard a C-135 aircraft Page: 3 of 9
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DESIGN AND IMPLEMENTATION OF A
SYNTHETIC APERTURE RADAR FOR OPEN SKIES (SAROS)
ABOARD A C-135 AIRCRAFT
Dale W. Cooper
Sandia National Laboratories (SNL)
P O Box 5800; MS 0312
Albuquerque, NM 87185-5800
Loral Defense Systems-Arizona
PO Box 85
Litchfield Park, AZ 85340-0085
Michael Murphy and the
Special Radars Dept. of SNL
PO Box 5800, MS 0529
Albuquerque, NM 87185-5800
NATO and former Warsaw Pact nations have
agreed to allow overflights of their countries in
the interest of easing world tension. The United
States has decided to implement two C-135
aircraft with a Synthetic Aperture Radar (SAR)
that has a 3-meter resolution. This work is being
sponsored by the Defense Nuclear Agency
(DNA) and will be operational in Fall 1995.
Since the SAR equipment must be exportable to
foreign nations, a 20-year-old UPD-8 analog
SAR system was selected as the front-end and
refurbished for this application by Loral Defense
Systems. Data processing is being upgraded to a
currently exportable digital design by Sandia
National Laboratories. Amplitude and phase
histories will be collected during these over-
flights and digitized on VHS cassettes. Ground
stations will use reduction algorithms to process
the data and convert it to magnitude-detected
images for member nations. System Planning
Corporation is presently developing a portable
ground station for use on the demonstration
flights. Aircraft integration into the C-135
aircraft is being done by the Air Force at
Wright-Patterson AFB, Ohio.
Key Words: Systems, Synthetic Aperture Radar,
Treaty, Open Skies.
Synthetic Aperture Radar (SAR) is one of the
imaging technologies identified for use under the
Open Skies Treaty. Synthetic Aperture Radar for
Open Skies (SAROS) will provide an all-
weather, day and night imaging capability.
SAROS is unique among Open Skies sensors in
that complex signal processing is necessary to
form a SAR image from the raw radar signal.
Prior to April 1, 1994, the U.S. could not export
modern digital SAR technology to any country
that was not one of the 17 countries in tpe
Coordinating Committee for Multilateral Export
Controls (COCOM). In addition, exportable
technology must pass the Defense Technology
Security Administration's (DTSA) guidelines.
In order to meet these requirements, a hybrid
SAR system is being designed using a 20-year-
old UPD-8 analog radar, which is being refur-
bished to eliminate sunset and nonexportable
technologies. This work is being done by Loral
Defense Systems in Phoenix, Arizona.
Digital SARs, particularly those employing digi-
tal waveform generation and analog-to-digital
(AID) converters with speeds above 100
Megasamples per second, are nonexportable
technologies. Sandias digital design was re-
quired to meet these exportation standards.
By treaty, it was necessary to restrict the SAROS
resolution to no more than 3 meters. To do this.
it was necessary to incorporate an azimuth filter
and a Litton 92 Inertial Navigation System with
Global Positioning System (GPS) updates to
correct for aircraft/antenna movement.
2.0 SAR IMAGING GEOMETRY
In an Open Skies mission, the C-135 aircraft will
fly a straight trajectory that projects the ground
track as shown in Figure 1. The SAR transmits
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Cooper, D. W.; Murphy, M. & Rimmel, G. Design and implementation of a Synthetic Aperture Radar for Open Skies (SAROS) aboard a C-135 aircraft, article, August 1, 1994; Albuquerque, New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc1339348/m1/3/: accessed April 19, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.