Carolyn Tewksbury-Christle

Carolyn Tewksbury-Christle
Fort Lewis College · Geosciences

Doctorate of Science

About

25
Publications
1,277
Reads
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145
Citations
Additional affiliations
June 2016 - May 2019
United States Air Force
Position
  • Staff Officer (Reservist)
Description
  • The US Air Force Scientific Advisory Board (SAB) is an independent Federal Advisory Council that consists of STEM subject matter experts from industry, academic, and national laboratories. As a staff officer, I organized annual science and technology reviews of the Air Force Research Laboratories and assisted with Secretary of the Air Force-directed scientific studies.
May 2013 - June 2016
United States Air Force Academy
Position
  • Instructor
Description
  • I taught introductory, calculus-based physics and advanced physics and managed 3 team-taught courses. I also created a partnership between three US Air Force Academy (USAFA) departments and Colorado College involving students in geophysics research, developed and executed a USAFA-wide seminar series, and designed 100+ diagrams for introductory physics in support of a $348K NSF grant. As executive officer, I managed evaluations, awards, and promotions for department.
May 2007 - August 2011
United States Air Force
Position
  • Research Physicist
Description
  • I conducted basic research in optical physics for the Directed Energy Directorate, Air Force Research Labs, Kirtland Air Force Base.
Education
July 2018 - July 2021
ETH Zurich
Field of study
  • Geology
July 2016 - July 2018
University of Texas at Austin
Field of study
  • Geology
August 2011 - May 2013
University of Tennessee
Field of study
  • Geology

Publications

Publications (25)
Article
Full-text available
Low Velocity Zones (LVZs) with anomalously high Vp-Vs ratios occur along the downdip extents of subduction megathrusts in most modern subduction zones and are collocated with complex seismic and transient deformation patterns. LVZs are attributed to high pore fluid pressures, but the spatial correlation between the LVZ and the subduction interface,...
Article
Full-text available
The architecture and mechanical properties of the subduction interface impact large-scale subduction processes, including mass and volatile recycling, upper-plate orogenesis, and seismic behavior. The nature of the deep subduction interface, where a dominantly frictional megathrust likely transitions to a distributed ductile shear zone, is poorly u...
Article
Atmospheric turbulence imparts phase distortions on propagating optical waves. These distortions couple into amplitude fluctuations at the pupil of a telescope, which, for strong enough phase distortions, produce zeros in the amplitude called branch points. In our earlier work, we presented the case that branch points can be utilized as a source of...
Article
Branch points form from interference within a propagating wave due to phase differences imparted by atmospheric turbulence. In the companion paper, we demonstrated that the characteristics of density and separation found in our experimental work are reproducible in an independent wave optical simulation. In this paper, we expand on this demonstrati...
Article
Atmospheric turbulence imparts phase distortions on propagating optical waves. These distortions couple into amplitude uctuations at the pupil of a telescope, which, for strong enough phase distortions, produce branch points (zeros in the amplitude). In our earlier work we have presented the case that branch points can be utilized as a source of in...
Article
The 2011 Desert RATS tested delayed communications and several combinations of hardware and crew assignments for microgravity targets. We discuss the strengths and weaknesses with respect to conducting planetary field geology.
Article
Light propagating through atmospheric turbulence acquires spatial and temporal phase variations. For strong enough turbulence conditions, interference from these phase variations within the optical wave can produce branch points; positions of zero amplitude. Under the assumption of a layered turbulence model, our previous work has shown that these...
Article
Desert Research and Technology Studies (Desert RATS) is a multi-year series of hardware and operations tests carried out annually in the high desert of Arizona on the San Francisco Volcanic Field. These activities are designed to exercise planetary surface hardware and operations in conditions where long-distance, multi-day roving is achievable, an...
Conference Paper
This paper continues a series discussing branch points. In creating a wave optical model of our experiments, we found unexpected dependencies in the branch point distributions. This paper discusses these dependencies.
Conference Paper
High resolution satellite imagery reveals previously unstudied structures in Cretaceous chalk of the Khoman Formation where it is exposed in the broad regional Farafra anticline. The oldest units of the Khoman chalk display a complex network of low, narrow (1-2 m) ridges that outline roughly polygonal areas 500-1000 m across. Offsets of bedding ind...
Article
The ASALT lab has been investigating the use of a segmented MEMS DM in adaptive optics systems. One of the anticipated benefits of a segmented device is that in monochromatic light the throw is essentially infinite due to the modulo 2Pi nature of the device. Earlier work demonstrated how this modulo 2Pi behavior interacts unexpectedly with a standa...
Article
We propose a sensor that measures the number, strength, altitude and velocity of atmospheric turbulence layers. Recent research has shown that pupil plane branch points contain four independent and measureable parameters and that these four parameters can be used to estimate four independent turbulence layer parameters--number, strength, altitude a...
Article
In earlier work we have shown that pupil plane branch points carry information about the conditions of the atmospheric turbulence. Experiments in the Atmospheric Simulation and Adaptive-optic Laboratory Test-bed (ASALT) at the Air Force Research Laboratory. Directed Energy Directorate's Starfire Optical Range have shown that branch points can provi...
Article
Full-text available
One of the problems associated with the use of the sodium laser guide star as a beacon for an adaptive optics system is the changes in the sensitivity of the wavefront sensor caused by the extended nature of the sodium layer. Shack-Hartmann wavefront sensors use quad cell detectors to estimate the amount of x- and y- gradients in each sub-aperture....
Article
Micro-Electro-Machined Systems (MEMS) have been increasingly used as mirrors in place of conventional continuous face sheet deformable mirrors (DM) in adaptive optics (AO) systems. Here we study the diffraction effects introduced into the optical path when a segmented MEMS DM is used to correct for the wavefront aberrations. Diffraction effects are...
Article
Recent research has shown that branch points, as they appear in astronomical applications, have a rich collective behavior, showing, in particular, that branch point pairs have a well-defined, non-stoichastic velocity, and that once a branch point pairs location is measured, it can be tracked in open-loop adaptive optics operation. The research pre...
Article
The conventional adaptive-optics (AO) system configuration consisting of a Shack-Hartmann wavefront sensor using the Fried geometry is prone to an unsensed waffle mode because of an inability to have discrete point reconstruction of the phase at the actuator positions. Techniques that involve filtering and/or projecting out the waffle mode in the r...
Article
Full-text available
This paper is the 3rd in a series of papers discussing characterization of a Micro-Electrical-Mechanical-System (MEMS) deformable mirror in adaptive optics. Here we present a comparison between a conventional adaptive optics system using a Xinetics continuous face sheet deformable mirror with that of segmented MEMS deformable mirror. We intentional...
Article
The atmospheric turbulence simulator used in testing in the atmospheric simulation and adaptive-optic laboratory test-bed at Starfire Optical Range is configured based on three characteristics: Fried's parameter, the Rytov number and the Greenwood Frequency. All three may be estimated from open loop data as a means of verifying the simulated turbul...
Article
Full-text available
The use of a laser guidestar (LGS) for the purpose of a beacon in an adaptive-optics (AO) system is prone to perspective elongation effects on the spots of a Shack-Hartmann wavefront sensor. The elongated spots can vary in size over the subapertures and affect the gradient sensitivity of the sensor. The Air Force Research Laboratory (AFRL) has deve...

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Projects

Project (1)
Project
On-Ramps are available both as 2-page pdfs and as web pages. You can download the current On-Ramp pdfs at serc.carleton.edu/onramps/downloads.html or by clicking the "Project Log" tab and choosing the On-Ramps Presentaton. You can also visit our On-Ramps web site at serc.carleton.edu/onramps/index.html for a web version of the pdfs plus additional resources.