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  • 1
    Publication Date: 2003-04-28
    Print ISSN: 0264-9381
    Electronic ISSN: 1361-6382
    Topics: Physics
    Published by Institute of Physics
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  • 2
    Publication Date: 2017-05-01
    Print ISSN: 0196-2892
    Electronic ISSN: 1558-0644
    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 3
    Publication Date: 2018-06-06
    Description: Grazing incidence x-ray telescopes consist of surfaces which are nearly cylindrical in shape. The abrasive figuring of these surfaces is accomplished by moving a grinding tool along a helical path on this almost cylindrical surface. The measurement of the surface is, however, performed along "axial" scan lines which intercept this helical path. This approach to figuring and measuring permits a relatively simple scheme to be implemented for the determination of the optimal dwell times of the figuring tool. These optimal dwell times are determined by a deconvolution which approaches the problem in a linear programming context and uses the Simplex Method. The approach maximizes the amount of material removed at any point subject to inequality constraints. The effect of using these ''optimum" dwell times is to significantly improve the tools effectiveness at removing the higher spatial frequencies while staying (strictly) within the bounds and constraints imposed by the hardware. In addition, the ringing at the edges of the optic, frequently present in deconvolution problems, is completely eliminated.
    Keywords: Optics
    Format: application/pdf
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  • 4
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    In:  Other Sources
    Publication Date: 2019-07-18
    Description: The Laser Interferometer Space Antenna (LISA) optics model is used to generate a synthetic data stream in the absence of gravitational waves. The simulation has the spacecraft in moving in their respective Keplerian orbits. The pointing of the spacecraft and station keeping about the proof masses is accomplished using a control scheme, which minimizes the disturbance on the proof masses in the sensitive direction. The resulting data stream gives an indication of the magnitude of instrumental noise due to pointing jitter and motions of the spacecraft with respect to the proof masses. Computational details are presented and the results discussed.
    Keywords: Instrumentation and Photography
    Type: SPIE Conference; Aug 03, 2003 - Aug 08, 2003; San Diego, CA; United States
    Format: text
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  • 5
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    In:  Other Sources
    Publication Date: 2019-07-18
    Description: The Laser Interferometer Space Antenna (LISA) for the detection of Gravitational Waves is a very long baseline interferometer which will measure the changes in the distance of a five million kilometer arm to picometer accuracies. As with any optical system, even one with such very large separations between the transmitting and receiving, telescopes, a sensitivity analysis should be performed to see how, in this case, the far field phase varies when the telescope parameters change as a result of small temperature changes.
    Keywords: Optics
    Type: Jul 07, 2002 - Jul 11, 2002; Seattle, WA; United States
    Format: text
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  • 6
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    In:  Other Sources
    Publication Date: 2019-07-18
    Description: The LISA experiment has six telescopes, in three spacecraft, in orbit about the sun. There is a continuous laser link between all of the spacecraft. Because of the large, 5 million kilometer distances, between the spacecraft and the need to perform picometer level interferometry and the fact that the optical system is dynamic precludes the use of standard optical codes in the design and analysis of this optical system. A detailed description of the approach used to model all of the optics, in the spacecraft in orbit, is presented and the ability of this model to analyze requirements is discussed. A dynamic computer simulation will be shown to illustrate the laser link and the effects of this dynamic environment on the interferometry.
    Keywords: Space Sciences (General)
    Type: SPIE 2002; Aug 22, 2002 - Aug 28, 2002; Waikoloa, HI; United States
    Format: text
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  • 7
    Publication Date: 2019-07-17
    Description: In support of Goddard's Constellation-X mandrel manufacturing effort a series of fabrication experiments are being performed to determine a best approach. Currently, polishing immediately after diamond turning, produces a RMS surface roughness of 0.31 nm, on a nickel plated aluminum mandrel. Studies currently under way will incorporate an abrasive figuring step followed by a polishing operation. The current diamond turning, figuring and polishing procedures will be described and the results presented.
    Keywords: Optics
    Type: SPIE Conference; Jul 29, 2001 - Aug 03, 2001; San Diego, CA; United States
    Format: text
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  • 8
    Publication Date: 2019-07-17
    Description: The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument's solar diffuser is used in its radiometric calibration for the reflective solar bands (VIS, NTR, and SWIR) ranging from 0.41 to 2.1 micron. The sun illuminates the solar diffuser either directly or through a attenuation screen. The attenuation screen consists of a regular array of pin holes. The attenuated illumination pattern on the solar diffuser is not uniform, but consists of a multitude of pin-hole images of the sun. This non-uniform illumination produces small, but noticeable radiometric effects. A description of the computer model used to simulate the effects of the attenuation screen is given and the predictions of the model are compared with actual, on-orbit, calibration measurements.
    Keywords: Solar Physics
    Type: Jul 29, 2001 - Aug 03, 2001; San Diego, CA; United States
    Format: text
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  • 9
    Publication Date: 2019-07-18
    Description: A detailed optical radiometric model has been created of the MODIS instruments solar calibration process. This model takes into account the orientation and distance of the spacecraft with respect to the sun, the correlated motions of the scan mirror and the sun, all of the optical elements, the detector locations on the visible and near IR focal planes, the solar diffuser and the attenuation screen with all of its hundreds of pinholes. An efficient computational scheme, takes into account all of these factors and has produced results which reproduce the observed time dependent intensity variations on the two focal planes with considerable fidelity. This agreement between predictions and observations, has given insight to the causes of some small time dependent variations and how to incorporate them into the overall calibration scheme. The radiometric model is described and modeled and actual measurements are presented and compared.
    Keywords: Earth Resources and Remote Sensing
    Type: SPIE Conference; Nov 08, 2004 - Nov 12, 2004; Honolulu, HI; United States
    Format: text
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  • 10
    Publication Date: 2019-07-18
    Description: On-orbit calibration of the reflected solar bands on the EOS Moderate Resolution Imaging Spectroradiometer (MODIS) is accomplished by have the instrument view a high reflectance diffuse surface illuminated by the sun. For some of the spectral bands this proves to be much too bright a signal that results in the saturation of detectors designed for measuring low reflectance (ocean) surfaces signals. A mechanical attenuation device in the form of a pin hole screen is used to reduce the signals to calibrate these bands. The sensor response to solar illumination of the SD with and without the attenuation screen in place will be presented. The MODIS detector response to the solar diffuser is smooth when the attenuation screen is absent, but has structures up to a few percent when the attenuation screen is present. This structure corresponds to non-uniform illumination from the solar diffuser. Each pin hole produces a pin-hole image of the sun on the solar diffuser, and there are very many pin hole images of the sun on the solar diffuser for each MODIS detector. Even though there are very many pin-hole images of the sun on the solar diffuser, it is no longer perfectly uniformly illuminated. This non-uniformly illuminated solar diffuser produces intensity variation on the focal planes. The results of a very detailed simulation will be discussed which show how the illumination of the focal plane changes as a result of the attenuation, and the impacts on the calibration will be discussed.
    Keywords: Instrumentation and Photography
    Type: Washington Academy of Science; Mar 20, 2004 - Mar 21, 2004; Washington, DC; United States
    Format: text
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