US4912475A
Expired / Lapsed
US
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Techniques for determining orbital data
Assignee: Massachusetts Institute of Technology
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Filing: 1989-03-29
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Granted: 1990-03-27
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Expires: 2009-03-29
Abstract
Abstract Techniques are disclosed for determining orbital data of space borne vehicles including earth satellites such as those of the NAVSTAR Global Positioning System. Each of a set of such satellites transmits signals which include carrier waves which may be suppressed, or only implicity present. The signals are received from the observable satellites concurrently by means of an antenna at each of at least three ground stations forming a network of baselines. The stations are arrayed such that the ratio of the maximum to the minimum baseline length is much greater than one. From the signals received at a station pair forming each baseline a time series of doubly-differenced phase measurement data is formed which is biased by an integer number of cycles of phase. The data series for different satellite and station pairs are processed together to determine the orbits of the satellites and the doubly-differenced phase biases. Unique determination of the integer values of at least some of the biases is facilitated by the above noted spatial arrangement of the stations such that the ratio of the maximum to the minimum baseline length is much greater than one. This integer bias determination enhances the accuracy of the related orbit determination. Unique determination of the integer values of at least some of the doubly-differenced carrier phase biases may also be facilitated by the use of a plurality of carrier frequencies with the ratio of the maximum to the minimum frequency being much greater than one.
Inventors
- 👤 Charles C. Counselman, III
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 13:43
CPC Classifications
G; G01; G01S; G01S3/00; G01S3/02; G01S3/14; G01S3/46; G01S3/48; G01S19/00; G01S19/01; G01S19/02; G01S19/38; G01S19/39; G01S19/42; G01S19/43; G01S19/44
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
98 words
A method of determining orbital data from doubly differenced phase observations of satellites derived from stations defining a network of baselines, comprising: (a) arranging the stations to provide a wide ranging progression of baseline lengths, from short to long; (b) applying observations from a long baseline to enhance observations from a substantially shorter baseline by resolving ambiguity in said short baseline observations; (c) applying the enhanced observations from the short baseline to enhance observations from a longer baseline by resolving ambiguity in said longer baseline observations; and (d) applying the enhanced observations to enhance the orbital data determination.
Claim 2
Independent Claim
98 words
A method of determining orbital data from doubly differenced phase observations of satellites derived from stations defining a network of baselines, comprising: (a) arranging the stations to provide a wide ranging progression of baseline lengths, from short to long; (b) applying observations from a long baseline to enhance observations from a substantially shorter baseline by resolving ambiguity in said short baseline observations; (c) applying the enhanced observations from the short baseline to enhance observations from a longer baseline by resolving ambiguity in said longer baseline observations; and (d) applying the enhanced observations to enhance the orbital data determination.
Claim 3
Dependent Claim
62 words
The method of claim 1, wherein: a plurality of said satellites transmit code-modulated, spread-spectrum, suppressed-carrier signals simultaneously on the same frequencies; and the phase observations are related to a plurality of carrier waves implicit in the signals received at each station and are derived from these signals independently of externally derived knowledge of the information content of the codes modulating these carriers.
Claim 4
Dependent Claim
92 words
The method of claim 2, further comprising: using an upward looking omnidirectional antenna at a station to collect a first composite signal simultaneously including overlapping spread-spectrum signals received from a plurality of satellites; reconstructing the first composite signal to form a second composite signal simultaneously including a discrete reconstructed carrier component from each of the plurality of satellites; using Doppler differences to separate reconstructed carrier components corresponding to the same implicit frequency transmitted by different satellites; and measuring the phases of the separated reconstructed carrier components of a plurality of satellites simultaneously.
Claim 5
Dependent Claim
68 words
The method of claim 2, further comprising: deriving phase observations related to a plurality of implicit carriers having a first frequency and a substantially different second frequency in the transmissions of each satellite, said first and second frequencies being the same for different satellites; and using phase observations related to the second frequency to enhance observations related to the first frequency by resolving ambiguity in the latter observations.
Claim 6
Dependent Claim
23 words
The method of claim 1, further comprising: arranging the stations to provide a wide ranging progression of baseline projections on two orthogonal axes.
Claim 7
Dependent Claim
17 words
The method of claim 1, further comprising: arranging the stations to provide a geometric progression of baselines.
Claim 8
Dependent Claim
16 words
The method of claim 5 or 6, further comprising: arranging the stations to provide redundant baselines.
Claim 9
Dependent Claim
20 words
The method of claim 1, further comprising: applying modulation delay observations of the satellites to enhance the orbital data determination.
Claim 10
Dependent Claim
18 words
The method of claim 8, further comprising: applying modulation delay observations of the satellites to enhance ambiguity resolution.
Claim 11
Dependent Claim
106 words
An improved method of determining orbital data from doubly differenced phase observations of satellites derived from stations defining a network of baselines, wherein the improvement comprises: (a) arranging the stations to provide a wide ranging progression of baseline lengths, from short to long; (b) applying observations from a long baseline to enhance observations from a substantially shorter baseline by resolving ambiguity in said short baseline observations; (c) applying the enhanced observations from the short baseline to enhance observations from a longer baseline by resolving ambiguity in said longer baseline observations; and (d) applying the enhanced observations from the longer baseline to enhance the orbital data determination.
Claim 12
Dependent Claim
106 words
An improved method of determining orbital data from doubly differenced phase observations of satellites derived from stations defining a network of baselines, wherein the improvement comprises: (a) arranging the stations to provide a wide ranging progression of baseline lengths, from short to long; (b) applying observations from a long baseline to enhance observations from a substantially shorter baseline by resolving ambiguity in said short baseline observations; (c) applying the enhanced observations from the short baseline to enhance observations from a longer baseline by resolving ambiguity in said longer baseline observations; and (d) applying the enhanced observations from the longer baseline to enhance the orbital data determination.
Claim 13
Dependent Claim
62 words
The method of claim 10, wherein: a plurality of said satellites transmit code-modulated, spread-spectrum, suppressed-carrier signals simultaneously on the same frequencies; and the phase observations are related to a plurality of carrier waves implicit in the signals received at each station and are derived from these signals independently of externally derived knowledge of the information content of the codes modulating these carriers.
Claim 14
Dependent Claim
92 words
The method of claim 11, further comprising: using an upward looking omnidirectional antenna at a station to collect a first composite signal simultaneously including overlapping spread-spectrum signals received from a plurality of satellites; reconstructing the first composite signal to form a second composite signal simultaneously including a discrete reconstructed carrier component from each of the plurality of satellites; using Doppler differences to separate reconstructed carrier components corresponding to the same implicit frequency transmitted by different satellites; and measuring the phases of the separated reconstructed carrier components of a plurality of satellites simultaneously.
Claim 15
Dependent Claim
68 words
The method of claim 11, additionally comprising: deriving phase observations related to a plurality of implicit carriers having a first frequency and a substantially different second frequency in the transmissions of each satellite, said first and second frequencies being the same for different satellites; and using phase observations related to the second frequency to enhance observations related to the first frequency by resolving ambiguity in the latter observations.
Claim 16
Dependent Claim
23 words
The method of claim 10, further comprising: arranging the stations to provide a wide ranging progression of baseline projections on two orthogonal axes.
Claim 17
Dependent Claim
17 words
The method of claim 10, further comprising: arranging the stations to provide a geometric progression of baselines.
Claim 18
Dependent Claim
16 words
The method of claim 14 or 15, further comprising: arranging the stations to provide redundant baselines.
Claim 19
Dependent Claim
20 words
The method of claim 10, further comprising: applying modulation delay observations of the satellites to enhance the orbital data determination.
Claim 20
Dependent Claim
18 words
The method of claim 17, further comprising: applying modulation delay observations of the satellites to enhance ambiguity resolution.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-03-26 | 1993-09-25 | 1994-03-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-03-26 | 1997-09-25 | 1998-03-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-03-26 | 2001-09-25 | 2002-03-27 | $7700.00 | Window Closed / Lapsed |