Hughes Aircraft Company

Other

Goodrich Corporation

Hughes Danbury Optical Systems, Inc.

Edward F Zalewski

William M Rappoport

Richard A Keller

Carlo F LaFiandra

Charles T Apel

Peter R Silverglate

Richard A Rockwell

Peter R Silvergate

Peter Silverglate

George R Huse

Calibration is provided for a diffuser panel ( ) on board a spacecraft ( ) employed in measuring the intensity of sunlight reflected from subjects on the earth. The calibration is accomplished by comparing the intensity of solar radiation reflected from the panel with the intensity of the solar radiation incident directly from the sun. The comparison is obtained by directing both radiation into an integrating sphere ( ) through separate ports ( ) which are sized to admit substantially equal amounts of power of the reflected and the direct radiations. A detector ( ) detects an average value of intensity of the reflected radiation while the direct rays are excluded by a shutter ( ). Upon an opening of the shutter and a deflecting of the diffuser panel from the calibrating position, the detector detects the average value of radiation intensity from the direct rays of the sun. The detected values of the radiation intensities may be transmitted back to earth, or are stored in memories and of a computer , and then applied to an arithmetic unit to produce the calibration ratio which is then made available for transmission with imaging data back to the earth.

Calibration of solar reflectance panel

A spacecraft telescope door (10) adapted for use with remote sensing devices requiring optical and infrared calibration. The door (10) includes a first calibration surface (24) disposed on a first panel (14) for providing a radiant temperature reference for infrared calibrations. A second calibration surface (26) is disposed on a second panel (12) for providing an absolute radiance reference for optical calibrations. A panel hinge (16) controls the relative position of the panels (12,14) with respect to each other, and an aperture hinge (20) controls the relative position of the panels with respect to the aperture (28). In a specific embodiment, the first surface (24) is painted with chemglaze Z306, a highly emissive paint with a low reflectance for facilitating infrared calibration. The second surface (26) is painted with YB71, a diffuse reflective paint for facilitating optical calibration. In the illustrative embodiment, the panel hinge (16) and the aperture hinge (20) are motorized for controlling the relative orientation of the panels (12,14) and the aperture (28). By controlling the orientation of the panels (12,14) and the aperture (28), the first surface (24) and the second surface (26) may be accurately positioned for infrared and optical calibrations respectively. In addition, the panels (12,14) may be positioned so as to protect the diffuse second surface (26) from ultraviolet degradation, as most white diffuse paints degrade with prolonged exposure to ultraviolet light. In addition, the first panel (24) may contain heaters and temperature sensors (25) for control of the radiant temperature.

Aperture door and calibration source for spacecraft remote sensing

A focal plane array employing a segmented multiplexer having differing unit cell capacitances and amplifiers in respective segments of the multiplexer. The segmented multiplexer accommodates and processes the maximum expected signal at differing illumination levels without saturation and provides for optimized noise levels in each of its segments. The focal plane array includes an array of detectors and an array of multiplexer cells respectively coupled thereto. The array of detectors comprises a plurality of groups of detector elements that each detect energy in a predetermined spectral region. The array of multiplexer cells comprise a plurality of groups of multiplexer cells that are respectively coupled to the plurality of groups of detector elements. Each multiplexer cell includes an integrating capacitor and an amplifier, and the integrating capacitor of each cell in a particular group has a predetermined capacitance whose charge integration capability corresponds to an expected maximum intensity level of radiation in the particular spectral region that is detected by the corresponding detector element in the detector array. The optimization of the characteristics of the integrating capacitor and amplifier provided for optimized detection of the radiation in that spectral region. By using more than one unit cell design, the response of each portion of the focal plane array is optimized to the range of expected intensities that will be incident on that portion of the focal plane array. In this manner, saturation is avoided in those portions of the focal plane that are expected to observe very high light intensities. In those portions of the focal plane that are expected to observe low light intensities, the cell amplifiers are designed to accommodate the lower intensity levels with decreased noise.

Segmented multiplexer for spectroscopy focal plane arrays having a

A light source (12) emits radiation which is maintained at a desired intensity by use of a photodetector which views the radiation and has a fixed relationship between incident radiation and output photodetector (18) current. Intensity of the radiation is established by varying electric current applied to the source, via a feedback loop (42, 24, 22, 34), to attain a reference value of the photodetector current, the photodetector current being representative of the desired value of radiation intensity. This procedure may be performed first in an air environment with a specific optical assembly of source and photodetector to establish the reference value of photodetector current for a desired value of radiation intensity. Thereupon, the optical system may be operated in a vacuum environment, and a monitoring of the photodetector current establishes the desired value of radiation intensity. Alternatively, the source is operated at a fixed value of excitation current, and an iris (44) or other radiation attenuator is operated to produce the reference value of photodetector current.

Polychromatic source calibration by one or more spectrally filtered

A method and system for calibrating color filters employed in polychromatic imaging of a subject includes a scanning mirror (28), telescope (30), filters (104), and a detector array (60) employed for both imaging and calibration processes. A bundle (44) of optical fibers is employed for producing a slit-shaped beam of solar rays which are collimated and applied to a diffraction grating plate (54) or prism (72) to produce a set of dispersed solar rays. The dispersion is based on color. In one position of the scanning mirror, rays from a subject (12) to provide an image are directed through the telescope and scanned across the filters (104) and detectors (102). In another position of the scanning mirror, the set of dispersed solar rays is scanned past the filters and the detectors. Imaging data outputted by the detectors is collected for producing an image (112) of the subject. Data of the dispersed rays is collected for calibrating the color filters. A stored reference color profile (92) of each filter is correlated with the calibration data ( 90) to obtain a set of correction terms which are employed for altering the image data to compensate for any drift in the color characteristics of the filters. A broad band detector detects Fraunhofer spectral lines to serve as a reference standard wavelength for alignment of the system.

Solar monochromator for filter calibration

The disclosure relates to an optogalvanic intracavity detector and method for its use. Measurement is made of the amount of light absorbed by atoms, small molecules and ions in a laser cavity utilizing laser-produced changes in plasmas containing the same atoms, molecules, or ions.

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Sandy Hook, CT, United States of America

Edward F Zalewski