Sun sensor

• US 5,914,483 A
• Filed: 09/18/1997
• Issued: 06/22/1999
• Est. Priority Date: 03/27/1995
• Status: Expired due to Term

• Current Assignee: Ithaco Space Systems, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Ithaco Space Systems, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Falbel, Gerald, Fallon, James J.
• Primary Examiner(s): LE, QUE TAN
• Application Number:
  US08/932,650
• Time in Patent Office: 642 Days
• Field of Search: 250/203.4, 250/203.6, 250/203.1, 244/3.16, 244/3.21, 244/3.18, 244/164, 244/171, 356/141.1-141.3
• US Class Current: 250/203.4
• CPC Class Codes: B64G 1/281 Spin-stabilised spacecraft
• CPC Class Codes: B64G 1/36 using sensors, e.g. sun-sensors, horizon sensors
• CPC Class Codes: B64G 1/363 using sun sensors
• CPC Class Codes: G01J 1/04 Optical or mechanical part supplementary adjustable parts
• CPC Class Codes: G01J 1/0407 Optical elements not provided otherwise, e.g. manifolds, windows, holograms, gratings
• CPC Class Codes: G01J 1/0437 using masks, aperture plates, spatial light modulators, spatial filters, e.g. reflective filters
• CPC Class Codes: G01J 1/0462 Slit arrangements
• CPC Class Codes: G01J 1/4228 arrangements with two or more detectors, e.g. for sensitivity compensation
• CPC Class Codes: G01J 2001/4266 for measuring solar light
• CPC Class Codes: G01S 3/7861 Solar tracking systems

Abstract

A sun sensor for use in orbiting satellites provides accurate attitude control yet eliminates the use of complicated optical components. The improved accuracy results from adjustment of the relative positions of a slit or pinhole aperture and a cooperating linear array of photodetector elements to increase the operating range of the sun sensor. Enhanced accuracy is further achieved by the use of a relatively wide slit instead of complicated optical components, in conjunction with a processing procedure which uses the finite angular subtense of the sun to increase the accuracy of the attitude control of the satellite by the sun sensor. A further embodiment of the invention includes a sun sensor device having dual "pinhole" apertures which is particularly useful for attitude control of a spinning satellite.

Claims

1. A sun sensor for orbiting spacecraft, said sun sensor comprising:

an array of photodetectors,

an element defining an opening therein for directing irradiance of the sun onto said array of photodetectors, and

means for processing signals including means for generating a signal proportional to said irradiance by sampling said array and producing a pulse train having an envelope, means for demodulating said pulse train envelope, means for passing said demodulated pulse train through a low pass filter, and means for applying a threshold signal to said pulse train after it passes through said low pass filter.

2. The sun sensor as claimed in claim 1 wherein the output of said sensor representing the angular position of the sun along said array corresponds to the phase of the thresholded square pulse resulting from the application of said threshold signal to said pulse train envelope after it has passed through said low pass filter.

3. The sun sensor as claimed in claim 2 wherein said opening defined in said element is a slit, and said slit is sufficiently wide for directing the irradiance of the sun on said array of photodetectors such that the sun subtends several Least Significant Bit (LSB) optical elements.

4. The sun sensor as claimed in claim 3 wherein said slit is wider than the Least Significant Bit (LSB).