Sandia National Laboratories currently utilizes two laser tracking systems to provide time-space-position-information
(TSPI) and high speed digital imaging of test units under flight. These laser trackers have been in operation for decades
under the premise of theoretical accuracies based on system design and operator estimates. Advances in optical imaging
and atmospheric tracking technology have enabled opportunities to provide more precise six degree of freedom
measurements from these trackers. Applying these technologies to the laser trackers requires quantified understanding of
their current errors and uncertainty. It was well understood that an assortment of variables contributed to laser tracker
uncertainty but the magnitude of these contributions was not quantified and documented.
A series of experiments was performed at Sandia National Laboratories large centrifuge complex to quantify TSPI
uncertainties of Sandia National Laboratories laser tracker III. The centrifuge was used to provide repeatable and
economical test unit trajectories of a test-unit to use for TSPI comparison and uncertainty analysis. On a centrifuge, testunits
undergo a known trajectory continuously with a known angular velocity. Each revolution may represent an
independent test, which may be repeated many times over for magnitudes of data practical for statistical analysis.
Previously these tests were performed at Sandia's rocket sled track facility but were found to be costly with challenges in
the measurement ground truth TSPI. The centrifuge along with on-board measurement equipment was used to provide
known ground truth position of test units. This paper discusses the experimental design and techniques used to arrive at
measures of laser tracker error and uncertainty.
Conventional tracking systems measure time-space-position data and collect imagery to quantify the flight dynamics of
tracked targets. A major obstacle that severely impacts the accuracy of the target characterization is atmospheric
turbulence induced distortion of the tracking laser beam and imagery degradations. Tracking occurs in a continuously
changing atmosphere resulting in rapid variations in the tracking laser beam and distorted imagery. These atmospheric
effects, combined with other degradation effects such as measurement system motion, defocus blur, and spatially varying
noise, severely limit the viability and accuracy of many tracking and imagery-based analysis methods. In 2007, using a
high speed sled test, the feasibility of quantifying flight dynamics with stereo laser tracking and multi-video imagery was
demonstrated. The technique acquires stereo views (two or more) of a moving test article that has an applied random
speckle (dot) pattern painted on the surface to provide unique tracking points. The stereo views are reconciled via
coordinate transformations and correlation of the transformed images. The 2007 results demonstrated that dual laser
tracker data can be used to update camera calibration data for stereo imaging to extend the image correlation approach to
moving field of view applications such as missile tracking and missile performance characterization, e.g., attitude
measurements. However, these results were predominantly qualitative in nature, focusing on the degree of correlation.
This paper will present quantitative results from 2008 outdoor centrifuge tests and assess the digital image correlation
accuracy for time varying attitude and position measurements.
Conventional tracking systems measure time-space-position data and collect imagery to quantify the flight dynamics of
tracked targets. One of the major obstacles that severely impacts the accuracy and fidelity of the target characterization is
atmospheric turbulence induced distortions of the tracking laser beam at the target surface and imagery degradations.
Tracking occurs in a continuously changing atmosphere resulting in rapid variations in the tracking laser beam and
distorted imagery. These atmospheric effects, in combination with other sources of degradation, such as measurement
system motions (e.g. vibration/jitter), defocus blur, and spatially varying noise, severely limit the useful and accuracy of
many tracking and analysis methods.
This paper discusses the viability of employing stereo image correlation methods for high speed moving target
characterization through atmospheric turbulence. Stereo imaging methods have proven effective in the laboratory for
quantifying temporally and spatially resolved 3D motions across a target surface. This technique acquires stereo views
(two or more) of a test article that has an applied random speckled (dot) pattern painted on the surface to provide
trackable features on the entire target surface. The stereo views are reconciled via coordinate transformations and
correlation of the transformed images. The principle limitations of this method have been the need for clean imagery and
fixed camera positions and orientations. However, recent field tests have demonstrated that these limitations can be
overcome to provide a new method for quantifying flight dynamics with stereo laser tracking and multi-video imagery in
the presence of atmospheric turbulence.
The current and future laser tracking mission requirements of Sandia National Laboratories are discussed. The capabilities of Sandia's existing laser trackers are summarized. The deficiencies of the current laser trackers are identified with respect to future mission requirements. Candidate commercial technologies are addressed to correct the identified deficiencies. Technology gap areas are identified where additional research needs to be conducted prior to developing an effective next generation laser tracking system
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.