Mr. James E. Gill Profile

James E. Gill

Optical Engineer

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Author

Publications (4)

Proceedings Article | 10 September 2013 Paper

Optical alignment of the Global Precipitation Measurements (GPM) star trackers

Samuel Hetherington, Dean Osgood, Joe McMann, Viki Roberts, James Gill, Kyle McLean

Proceedings Volume 8844, 884406 (2013) https://doi.org/10.1117/12.2024558

KEYWORDS: Optical alignment, Stars, Mirrors, Relays, Optical tracking, Autocollimation, Space operations, Data analysis, Neodymium, Magnetorheological finishing

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Proceedings Article | 22 August 2009 Paper

Trades for ambient non-contact metrology

R. Ohl, B. Hoffmann Eegholm, M. Casas, B. Frey, M. Dominguez, J. Gill, J. Hayden, P. Morken, K. Redman, V. Roberts, B. Saif, T. Scirpo

Proceedings Volume 7433, 743306 (2009) https://doi.org/10.1117/12.831303

KEYWORDS: Mirrors, Lawrencium, James Webb Space Telescope, Metrology, LIDAR, Cryogenics, Space telescopes, Glasses, Composites, Optical testing

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Proceedings Article | 1 October 2007 Paper

Photogrammetric metrology for the James Webb Space Telescope integrated science instrument module

Maria Nowak, Allen Crane, Pamela Davila, William Eichhorn, James Gill, Acey Herrera, Michael Hill, Jason Hylan, Mark Jetten, James Marsh, Raymond Ohl, Robert Quigley, Kevin Redman, Henry Sampler, Geraldine Wright, Philip Young

Proceedings Volume 6692, 66920P (2007) https://doi.org/10.1117/12.733896

KEYWORDS: Photogrammetry, Nondestructive evaluation, Cameras, Metrology, James Webb Space Telescope, Cryogenics, Temperature metrology, Optical alignment, Space telescopes, Interfaces

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Proceedings Article | 7 July 2006 Paper

Methods for correlating autocollimation of theodolites and coordinate metrology in spacecraft systems

Carlos Aviado, James Gill, Kevin Redman, Raymond Ohl

Proceedings Volume 6273, 62733H (2006) https://doi.org/10.1117/12.670043

KEYWORDS: Space operations, Autocollimation, Metrology, Photogrammetry, Calibration, Transform theory, Aerospace engineering, Cameras, Laser metrology, Optical testing

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This paper will discuss the details of the metrology associated with the integration and testing of spacecraft systems and scientific instruments at the NASA Goddard Space Flight Center (NASA GSFC). Specifically, this paper will outline the process for correlating theodolite autocollimation measurements with theodolite coordinate triangulation measurements, laser tracker coordinate measurements, photogrammetry camera system, and other coordinate measurement techniques. For theodolite autocollimation data, NASA GSFC developed a Microsoft Excel-based spreadsheet program to calculate the transformation matrices from reference cube pointing directions into spacecraft coordinates defined by physical features. The autocollimated image return from the mirrored faces of the reference cubes are measured relative to each other and define unit vectors that point in the direction perpendicular to the cube face surface. The roll, zenith, pitch, and yaw are calculated from the direction cosines of the unit vectors that define the directional pointing rotations around coordinate axes. The theodolite-based pointing vectors are then transformed to the spacecraft coordinate system. The Brunson Spatial Analyzer^TM coordinate measuring software program is used to analyze data from theodolites using triangulation on target positions, a laser tracker coordinate measuring system, a photogrammetry system or any other coordinate measuring system. All the coordinate data is tied into theodolite coordinate data by measuring common targets. To correlate theodolite autocollimation on cube faces to the point coordinate location data, one must first measure the test object with the Spatial Analyzer^TM theodolite triangulation coordinate system. From coordinate features, a spacecraft coordinate system is defined by the blueprint design. One of the Spatial Analyzer^TM theodolites is used as the primary reference for the auto-collimation measurements. This ties together the coordinate target point locations to the pointing directions of mirrored surfaces of cubes.

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