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  • 1
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    APART/PADE analytical evaluation of the diffuse infrared background experiment for NASA's cosmic background explorer (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The stray light performance of NASA's Diffuse Infrared Background Experiment (DIRBE) has been calculated using the APART/PADE code. That code has been upgraded to handle off-axis optical systems such as DIRBE. Under observing conditions, sunlight is attenuated by 21 to 29 orders-of-magnitude; uniform diffuse illumination, by 6 to 9 orders of magnitude. The sunlight is attenuated by multiple diffraction at an external sun shield and by a forebaffle at the entrance to the DIRBE. Stray light is nearly a linear function of the Bidirectional Reflectance Distribution Function (BRDF) of the primary mirror at all wavelengths - or it can be made to be so by reducing the size of the field defining stop from 0.866 to 0.7 degrees square. For uniform diffuse illumination, half of the stray radiation comes from within 5 degrees of the center of the field-of-view. Particulate contamination of the primary mirror is expected to be a problem and special polishing and cleaning procedures are recommended - before mirror overcoating and again before flight.
    Keywords: SPACECRAFT INSTRUMENTATION
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Stray light in the Infrared Astronomical Satellite (IRAS) (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Changes made to the telescope and critical objects considered in modeling these changes into the APART program are described. The optical system was analyzed for scattered light, diffracted then scattered radiation, and thermally emitted radiation. The damaged area of the primary to mirror was also examined. Results are presented in tables and graphs.
    Keywords: ASTRONOMY
    Type: NASA-CR-166226
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Infrared Astronomical Satellite (IRAS) analysis of the transmittance of off-axis energy due to scattering and diffraction (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Stray light transmittance is analyzed. Mathematical models are evaluated. The results of scatter and diffraction are considered separately, and the combined transmittance values evaluated.
    Keywords: OPTICS
    Type: NASA-CR-166227
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Stray light analysis of the Diffuse Infrared Background Experiment (DIRBE) (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The straylight analysis of the diffuse infrared background experiment (DIRBE) on the cosmic background explorer (COBE) mission is discussed. From the statement of work (SOW), the purpose of DIRBE is to measure, or set upper limits on, the spectral and spatial character of the diffuse extra galactic infrared radiation. Diffuse infrared sources within our own galaxy are measured. The required reduction of the unwanted radiation imposes severe design and operating restrictions on the DIRBE instrument. To accomplish its missions, it will operate at a multitude of wavelengths ranging from 1.25 um out to 200 to 300 microns. The operating bands and the required point source normalized irradiance transmittance (PSNIT) are shown. The important straylight concepts in the DIRBE design are reviewed. The model and assumptions used in APART analysis are explained. The limitations due to the scalar theory used in the analysis are outlined.
    Keywords: ASTRONOMY
    Type: NASA-CR-175225 , NAS 1.26:175225
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Stray optical-radiation suppression (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Report describes five computer programs for study of scattered radiation.
    Keywords: PHYSICAL SCIENCES
    Type: MFS-23495 , NASA Tech Briefs (ISSN 0145-319X); 2; 1; P. 3
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    NASA TECHNICAL REPORTS
  • 6
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    User's manual for University of Arizona APART program (Analysis Program - Arizona Radiation Trace) (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A description and operating instructions for the Analysis Program Arizona Radiation Trace (APART) are given. This is a computer program that is able to efficiently and accurately predict the off-axis rejection characteristics of unwanted stray radiation for complex rotationally symmetric optical systems. The program first determines the critical objects or areas that scatter radiation to the image plane either directly or through imaging elements: this provides the opportunity to modify, if necessary, the design so that the number of critical areas seen by the image plane is reduced or the radiation to these critical areas is minimized. Next, the power distribution reaching the image plane and a sectional power map of all internal surfaces are computed. Angular information is also provided that relates the angle by which the radiation came into a surface to the angle by which the radiation is scattered out of the surface.
    Keywords: OPTICS
    Type: NASA-CR-143938
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    Comparison of stray light mechanisms and performance in the Infrared Astronomy Satellite /IRAS/ and Shuttle Infrared Telescope Facility /SIRTF/ telescopes (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: NASA is developing two large space-based infrared astronomy telescopes, IRAS and SIRTF. Both of these systems will be functioning in the environment of a bright thermal emitting earth and sun while concurrently having baffle surfaces radiating thermal photons which combine to produce a stray-radiation background. The APART program was used to analyze the stray radiation propagation paths of both the IRAS and SIRTF designs. The SIRTF design was found to be about 1000 times superior in its stray radiation transmission, because several design options were able to be incorporated through different mechanical and optical constraints that were different, while being generically of a similar optical design.
    Keywords: OPTICS
    Type: Seminar on Radiation scattering in optical systems; Sep 30, 1980 - Oct 01, 1980; Huntsville, AL
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    NASA TECHNICAL REPORTS
  • 8
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    Stray radiation and the Infrared Astronomical Satellite /IRAS/ telescope (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Stray light control is a major consideration in the design of infrared cryogenically cooled telescopes such as the Infrared Astronomical Satellite (IRAS). The basic design of the baffle system, and the placement, shape, and coating of the secondary support struts for the telescope subsystem are described. The intent of this paper is to highlight the stray light problems encountered while designing the system, and to illustrate how computer analysis can be a useful design aid. Scattering measurements of the primary mirror, and a full system level scatter measurement are presented. Comparisons of predicted performance with the measured results are also presented.
    Keywords: OPTICS
    Type: Seminar on Radiation scattering in optical systems; Sep 30, 1980 - Oct 01, 1980; Huntsville, AL
    Format: text
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    NASA TECHNICAL REPORTS
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