In recent years ARTEMIS, Inc. has developed a series of compact, versatile Synthetic Aperture Radar (SAR)
systems which have been operated on a variety of small manned and unmanned aircraft. The multi-frequency-band SlimSAR has demonstrated a variety of capabilities including maritime and littoral target detection, ground
moving target indication, polarimetry, interferometry, change detection, and foliage penetration. ARTEMIS also
continues to build upon the radar's capabilities through fusion with other sensors, such as electro-optical and
infrared camera gimbals and light detection and ranging (LIDAR) devices. In this paper we focus on experiments
and applications employing SAR and LIDAR fusion. LIDAR is similar to radar in that it transmits a signal
which, after being reflected or scattered by a target area, is recorded by the sensor. The differences are that
a LIDAR uses a laser as a transmitter and optical sensors as a receiver, and the wavelengths used exhibit a
very different scattering phenomenology than the microwaves used in radar, making SAR and LIDAR good
complementary technologies. LIDAR is used in many applications including agriculture, archeology, geo-science,
and surveying. Some typical data products include digital elevation maps of a target area and features and
shapes extracted from the data. A set of experiments conducted to demonstrate the fusion of SAR and LIDAR
data include a LIDAR DEM used in accurately processing the SAR data of a high relief area (mountainous,
urban). Also, feature extraction is used in improving geolocation accuracy of the SAR and LIDAR data.
This paper presents ARTEMIS, Inc.'s approach to development of end-to-end synthetic aperture radar systems
for multiple applications and platforms. The flexible design of the radar and the image processing tools facilitates
their inclusion in a variety of application-specific end-to-end systems. Any given application comes with certain
requirements that must be met in order to achieve success. A concept of operation is defined which states how
the technology is used to meet the requirements of the application. This drives the design decisions. Key to
adapting our system to multiple applications is the flexible SlimSAR radar system, which is programmable on-the-fly to meet the imaging requirements of a wide range of altitudes, swath-widths, and platform velocities. The
processing software can be used for real-time imagery production or post-flight processing. The ground station
is adaptable, and the radar controls can be run by an operator on the ground, on-board the aircraft, or even
automated as part of the aircraft autopilot controls. System integration takes the whole operation into account,
seeking to flawlessly work with data links and on-board data storage, aircraft and payload control systems,
mission planning, and image processing and exploitation. Examples of applications are presented including
using a small unmanned aircraft at low altitude with a line of sight data link, a long-endurance UAV maritime
surveillance mission with on-board processing, and a manned ground moving target indicator application with
the radar using multiple receive channels.
The MicroASAR is a flexible, robust SAR system built on the successful legacy of the BYU ìSAR. It is a compact
LFM-CW SAR system designed for low-power operation on small, manned aircraft or UAS. The NASA SIERRA
UAS was designed to test new instruments and support flight experiments. NASA used the MicroASAR on the
SIERRA during a science field campaign in 2009 to study sea ice roughness and break-up in the Arctic and high
northern latitudes. This mission is known as CASIE-09 (Characterization of Arctic Sea Ice Experiment 2009).
This paper describes the MicroASAR and its role on the SIERRA UAS platform as part of CASIE-09.
KEYWORDS: Synthetic aperture radar, Antennas, L band, X band, Doppler effect, Radar, Data storage, Signal to noise ratio, Imaging systems, Continuous wave operation
The SlimSAR is a small, low-cost, Synthetic Aperture Radar (SAR) and represents a new advancement in high-performance
SAR. ARTEMIS employed a unique design methodology in designing the SlimSAR that exploits
previous developments. The system is designed to be smaller, lighter, and more flexible while consuming less
power than typical SAR systems. The system consists of an L-band core and frequency block converters and
is very suitable for use on a number of small UAS's. Both linear-frequency-modulated continuous-wave (LFM-CW)
and pulsed modes have been tested. The LFM-CW operation achieves high signal-to-noise ratio while
transmitting with less peak power than a comparable pulsed system. The flexible control software allows us to
change the radar parameters in flight. The system has a built-in high quality GPS/IMU motion measurement
solution and can also be packaged with a small data link and a gimbal for high frequency antennas. Multi-frequency
SAR provides day and night imaging through smoke, dust, rain, and clouds with the advantages of
additional capabilities at different frequencies (i.e. dry ground and foliage penetration at low frequencies, and
change detection at high frequencies.)
The flight testing phase is vital in the development of an airborne SAR system, but can be time consuming
and expensive, especially for UAS based systems. As part of a SAR design methodology, we are using a small,
manned aircraft as a surrogate for UASs and other platforms. Prototypes of new systems can be easily installed
on the testbed in order to quickly and inexpensively obtain sensor and motion data. These data can be used to
aid in system-specific algorithm development, as well as further refinement of the system hardware as necessary.
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