METHOD AND APPARATUS FOR DETERMINING THE ORIENTATION OF AN OBJECT RELATIVE TO AN ELLIPTIC OBJECT

• US 3,576,999 A
• Filed: 01/16/1965
• Issued: 05/04/1971
• Est. Priority Date: 01/16/1965
• Status: Expired due to Term

• Current Assignee: Blythe Richard, Donald S. Lowe, Edgar A. Work Jr, Gerald C. Scott, Philip G. Hasell Jr
• Original Assignee: Blythe Richard, Donald S. Lowe, Edgar A. Work Jr, Gerald C. Scott, Philip G. Hasell Jr
• Inventors: BLYTHE RICHARD, Scott, Gerald C., Work, Edgar A. Jr., Lowe, Donald S., Hasell, Philip G. Jr.
• Application Number:
  US04/609,520
• Time in Patent Office: 2,299 Days
• US Class Current: 701/514
• CPC Class Codes: G01S 3/7868 using horizon sensors

Abstract

Method and apparatus for maintaining the orientation of an object, such as a satellite or spacecraft, with respect to a primary object, such as the earth, by sensing points of interception of the primary object'"'"''"'"'s horizon with two scan lines and correlating the sensed information.

Claims

1. In the method of maintaining an object in predetermined relation to an elliptic body presenting its horizon to said object the steps of scanning for radiation along a first scan line which crosses the horizon, scanning for radiation along a second scan line which crosses said horizon at another point, detecting a first horizon position on said first scan line by detecting a radiation change as the scan crosses said horizon, detecting a second horizon position on said second scan line by detecting a radiation change as the scan crosses said horizon, and then correlating said first position with said second position to obtain an error indication representing a deviation by the object from a predetermined relation to the body.

2. The method set forth in claim 1 wherein said step of scanning for radiation along a second scan line comprises scanning along a line displaced laterally from said first scan line, and wherein said first and said second positions are correlated to obtain an error indication representing a rotational deviation by said object about an axis parallel to at least portions of said first and said second scan lines.

3. The method set forth in claim 1 wherein said step of scanning for radiation along a second scan line comprises scanning along a line axially aligned with said first scan line, and said first and said second positions are correlated to obtain an error indication representing a rotational deviation by said object about an axis perpendicular to at least portions of said scan lines.

4. An apparatus for maintaining an object in a predetermined orientation relative to a radiating body which presents a generally circular horizon to said device comprising first and second infrared detectors, optical means for projecting a first image of said first detector and a second image of said second detector in a direction generally toward said radiating body, said optical means including scanning means for moving said first image along a first rectilinear scanning line and for moving said second image along a second rectilinear scanning line generally parallel and in spaced relation to said first scanning line, said first detector being responsive to radiation from said first scanning line to develop an electrical signal representing radiation level variations along said first scanning line, said second detector means being responsive to radiation from said second scanning line to develop a second electrical signal representing radiation level variations along said second scanning line, first level detection means responsive to said first signal to provide first indications when said first image crosses said horizon and second level detection means responsive to said second electrical signal to provide second indications when said second image crosses said horizon, and comparison means responsive to selected ones of said first and said second indications to provide an error indication representing deviation of said object from said predetermined orientation relative to said body.

5. The apparatus set forth in claim 4 wherein said scanning means comprises a reflector, and drive means for oscillating said reflector, said optical means and said detectors being arranged so that oscillation of said reflector causes said first image and said second image to reciprocate along said first and said second lines in synchronism.

6. The apparatus set forth in claim 4 wherein said comparison means comprises means responsive to one of said first indications when said first beam crosses said horizon in one direction and responsive to another of said first indications when said first beam crosses an opposite horizon in the opposite direction and operable in response to said one and said other of said first indications to provide a difference signal representing a rotational deviation of said object relative to said body about an axis generally transverse to said first and second scan lines.

7. The apparatus set forth in claim 4 wherein said comparison means comprises means responsive to one of said first indications when said first beam crosses said horizon in a first direction and responsive to one of said second indications when said second beam crosses said horizon in said one direction and operable to provide an error signal representing a scanning displacement between said one of said first indications and said one of said second indications, said displacement being proportional to a rotational deviation by said object relative to said body about an axis generally parallel to scan lines.

8. The apparatus set forth in claim 4 wherein said comparison means comprises reference means to provide a reference signal when said beams cross the center of said scanning lines and said comparison means is responsive to said reference signal and said selected ones of said indications to provide said error indication.

9. Apparatus for determining the orientation of an object with respect to an elliptic body presenting its horizon to said object comprising:

radiation-receiving means constructed to receive radiation along a first line path which crosses the horizon of an elliptic body at two points, and to receive radiation from along a second line path which also crosses said horizon;

detecting means constructed to detect first and second horizon positions on said first line path and to detect a third horizon position on said second line path by detecting a radiation change at points where said line paths intercept said horizon;

means for correlating said first position with said second position and for correlating one of said positions on said first line path with said third position to obtain a complete determination of orientation with respect to said elliptic body.

10. The apparatus set forth in claim 9 wherein said means for receiving radiation include a reflector and means for oscillating said reflector to scan along said first and second line paths in synchronism.

11. The apparatus set forth in claim 9 wherein said radiation-receiving means is constructed to scan for radiation along said paths and said correlator means is constructed to compare the displacement of said first horizon position from the center of said first path with the displacement of said second horizon position from the center of said first path to obtain an indication or orientation.

12. The apparatus set forth in claim 9 wherein said radiaton-receiving means is constructed to scan for radiation along two generally parallel, rectilinear line paths, and said correlator means is constructed to compare the displacement of said first horizon position from the center of said first scan line with the displacement of said third horizon position from the center of said second scan line to obtain an orientation indication representing the degree of rotation about an axis perpendicular to said scan lines.

13. The apparatus set forth in claim 9 wherein:

said means for receiving radiation is constructed to scan for radiation along two generally parallel, rectilinear line paths;

said apparatus for receiving radiation along said line paths includes means for scanning for radiation across and beyonD said body along said first and second paths so that each scan traverses said horizon twice at each opposite side of said body during one scanning cycle;

said detecting means is constructed such that said first position is detected on said first path when scanning in one direction across said horizon at one side of said body, said second position is detected on said first path when scanning in an opposite direction across said horizon at an opposite side of said body, said third position is detected on said second path when scanning in said one direction across said horizon at said one side of said body, and a fourth position is detected on said second path when scanning in said opposite direction across said horizon at said opposite side of said body; and

said correlator means is constructed to provide one indication representing a difference between said first and said third positions detected while scanning in said one scanning direction and to provide a second indication representing a difference between said second and said fourth positions detected while scanning in said opposite scan direction.

14. The apparatus set forth in claim 9 wherein said detecting means is constructed to determine the points of interception of said paths and said horizon when scanning in a direction from space to body.