Refractive aiming corrections for satellite observation of stars

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Description

Standard references describe how apparent zenith angles differ from true zenith angles for observers on the Earth. In fact, correction formulae are available for aiming Earth-based sensors at stars; some corrections give variations as a function of observer altitude. Such corrections have not been available for observers in space. This report develops formulae appropriate for proper aiming from space-based sensors toward the relatively few stars that are near the Earth`s limb at any given time. These formulae correct for refractive effects and may be critical for steerable space-borne sensors with fields of view less than one degree, tasked to observe ... continued below

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25 p.

Creation Information

Vittitoe, C. N. & Schmidt, R. L. March 1, 1997.

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This report is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided by UNT Libraries Government Documents Department to Digital Library, a digital repository hosted by the UNT Libraries. More information about this report can be viewed below.

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  • Sandia National Laboratories
    Publisher Info: Sandia National Labs., Albuquerque, NM (United States)
    Place of Publication: Albuquerque, New Mexico

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Description

Standard references describe how apparent zenith angles differ from true zenith angles for observers on the Earth. In fact, correction formulae are available for aiming Earth-based sensors at stars; some corrections give variations as a function of observer altitude. Such corrections have not been available for observers in space. This report develops formulae appropriate for proper aiming from space-based sensors toward the relatively few stars that are near the Earth`s limb at any given time. These formulae correct for refractive effects and may be critical for steerable space-borne sensors with fields of view less than one degree, tasked to observe starlight passing near the Earth`s surface. Ray tracing in the U.S. Standard Atmosphere, 1976 including H{sub 2}O effects, is used to determine relations between the refracted tangent height, the apparent tangent height resulting from observation at the sensor, and the angle through which the detected rays have deviated. Analytic fits of the ray deviation as a function of apparent tangent height allows quick determination of corrections needed for a space-borne sensor. Using those results that apply in the plane of incidence and using the necessary coordinate rotations, alterations in the star`s apparent right ascension and declination are evaluated to improve the aim. Examples illustrate that alterations can be larger than one degree, with effects lasting up to a few minutes.

Physical Description

25 p.

Notes

OSTI as DE97004244

Source

  • Other Information: PBD: Mar 1997

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  • Other: DE97004244
  • Report No.: SAND--97-0415
  • Grant Number: AC04-94AL85000
  • DOI: 10.2172/451209 | External Link
  • Office of Scientific & Technical Information Report Number: 451209
  • Archival Resource Key: ark:/67531/metadc678111

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  • March 1, 1997

Added to The UNT Digital Library

  • July 25, 2015, 2:21 a.m.

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  • June 13, 2016, 12:49 p.m.

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Vittitoe, C. N. & Schmidt, R. L. Refractive aiming corrections for satellite observation of stars, report, March 1, 1997; Albuquerque, New Mexico. (digital.library.unt.edu/ark:/67531/metadc678111/: accessed August 19, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.