A simple analytical model for the signal acquisition range for a laser guided mortar is presented. The signal consists of a
repetitively pulsed laser of fixed pulse duration and fixed pulse repetition frequency. The pulses are detected by a seeker
consisting of a quadrant photodiode and a trans-impedance amplifier. Noise is introduced from solar irradiance and
from the detector/amplifier electronics. The model maximizes the acquisition range by optimizing trans-impedance
amplifier circuit components. A comparison of integrating multiple low energy pulses (MPLD) versus detecting each
pulse individually (conventional) is made.
An analysis of the parametric interaction and the initial fiber geometry to achieve wavelength conversion
from common laser sources operating in the 1030-1064nm spectral band into the 900-950nm wavelength range has
been performed. The preliminary analysis shows that new fiber designs involving fibers with cores engineered with
crystal-like shapes and also pulsed fiber sources operating at wavelengths in the 1030-1064nm will be required to
achieve efficient emission within the desired wavelength range. Both the fiber required for phase-matching the
parametric nonlinear process and the pulsed fiber laser pump source are within reach of current technology. They both
require engineering efforts to produce a packaged, rugged and compact source.
Analytical results and tradeoffs are reported for an aerosol lidar system that is intended to serve as a referee during testing of standoff bio-aerosol detection systems. The lidar system is still under development by Dugway Proving Grounds -- results from the operational system are not included in this paper. The recommended configuration of the lidar system is to use a 1064 nm lidar in elastic mode to measure the concentration of the aerosol, and a 355 nm excitation to measure the fluorescence of the bio-aerosol. Both of these measurements are important in scoring the performance of the systems that will be tested at DPG. Performance tradeoffs and predictions are presented primarily for the elastic mode lidar. The elastic mode lidar is designed to make measurements out to ranges of approximately 15 km. The UV fluorescence mode of operation is intended to support discrimination of bio-aerosols from non-biological aerosols, and is only required to operate at a range of 1 km. The optical design of the proposed telescope supports dual wavelength operation, allows for effective TV camera imaging for test and alignment support, and tailors the optical overlap function for the UV and near IR lidar to optimize the performance of both subsystems.
The CONTOUR Remote Imager and Spectrometer (CRISP) was a multi-function optical instrument developed for the Comet Nucleus Tour Spacecraft (CONTOUR). CONTOUR was a NASA Discovery class mission launched on July 3, 2002. This paper describes the design, fabrication, and testing of CRISP. Unfortunately, the CONTOUR spacecraft was destroyed on August 15, 2002 during the firing of the solid rocket motor that injected it into heliocentric orbit. CRISP was designed to return high quality science data from the solid nucleus at the heart of a comet. To do this during close range (order 100 km) and high speed (order 30 km/sec) flybys, it had an autonomous nucleus acquisition and tracking system which included a one axis tracking mirror mechanism and the ability to control the rotation of the spacecraft through a closed loop interface to the guidance and control system. The track loop was closed using the same images obtained for scientific investigations. A filter imaging system was designed to obtain multispectral and broadband images at resolutions as good as 4 meters per pixel. A near IR imaging
spectrometer (or hyperspectral imager) was designed to obtain spectral signatures out to 2.5 micrometers with resolution of better than 100 meters spatially. Because of the high flyby speeds, CRISP was designed as a highly automated instrument with close coupling to the spacecraft, and was intended to obtain its best data in a very short period around closest approach. CRISP was accompanied in the CONTOUR science payload by CFI, the CONTOUR Forward Imager. CFI was optimized for highly sensitive observations at greater ranges. The two instruments provided highly complementary optical capabilities, while providing some degree of functional redundancy.
A filtered imager, the CONTOUR Forward Imager (CFI), was designed, fabricated, and qualified for the Comet Nucleus Tour (CONTOUR) Discovery class mission. The CONTOUR spacecraft was launched July 3, 2002, and failed during injection to heliocentric orbit on August 15, 2002. This paper provides an overview of the efforts to produce CFI.
The CFI imager was designed to perform optical navigation, comet nucleus imaging, and comet coma imaging. CFI was complemented in the CONTOUR payload by the CONTOUR Remote Imager and Spectrometer (CRISP). The emphasis in the CFI design was on high sensitivity at moderate to long ranges from the comet nucleus, while CRISP was designed for high-speed observations in close to the nucleus. A unique aspect of CFI was the requirement to image multiple comets after being exposed to high-velocity cometary dust on the
previous comet flybys (which damages and contaminates the forward looking optics). The first optical surface was replaceable between comet encounters, using a mirror "cube" mechanism, to alleviate the dust damage. Another challenging aspect of the design is that the spacecraft was thruster stabilized (no reaction wheels), placing limits on the available exposure time to accomplish the high sensitivity observations required.
CFI utilized ten filters covering from 300 to 920 nm to image onto a backthinned 1024 by 1024 element CCD. The Ritchie-Chrietien telescope provided a clear aperture of 62 mm, a full field of view of 2.5 degrees, and a pixel field of view of 43 microradians. CFI was designed and fabricated by a combined effort of the Johns Hopkins University Applied Physics Laboratory and SSG Precision Optronics. The CONTOUR mission was lost prior to CFI being powered on in flight.
Proc. SPIE. 3692, Acquisition, Tracking, and Pointing XIII
KEYWORDS: Navigation systems, Global Positioning System, Cameras, Control systems, Receivers, Commercial off the shelf technology, Fourier transforms, Control systems design, Image registration, Digital cameras
A pointing and stabilization system has been developed and flight tested which permits an optical payload to be operated for an extended time period from a nearly stationary point in the air aboard a hovering helicopter. The system is assembled primarily from commercial 'off the shelf' components and is capable of pointing the payload as desired to image geo-referenced aim points on the earth's surface. The payload contains two digital cameras and laser illuminator. The payload is mounted in a 20-inch diameter, two axis stabilized ball gimbal available form a previous program. The payload also contains a dynamically tuned gyro- based inertial measurement unit, which with GPS-aiding provides ball gimbal position and pointing information. The processed data is used to accurately register images in ground coordinates. The inertial measurement data is also used in real time to control pointing of the ball gimbal and to generate a hover display for the pilots of the SH-60 helicopter. The system has been successfully flight tested. The longest test sequence to data is a 30 minute long hover at 7000 ft altitude during which the payload was staring at a fixed aim point. During this half-hour period, pilots maintained the helicopter at its hover point within a circle of approximately 150 meters radius. Similar hover accuracy is routinely obtained. This system provides a unique research capability to observe ground phenomena from a fixed airborne perspective and to register the resulting data into fixed ground coordinates.