Method and apparatus for maintaining the integrity of spacecraft based time and position using GPS
First Claim
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1. A method for maintaining the integrity of spacecraft based time and position using the Global Positioning System (GPS) comprising the steps of:
- providing a GPS receiver coupled to a Receiver Autonomous Integrity Monitor (RAIM) processor and a Kalman filter;
receiving GPS signals from GPS satellites and processing the GPS signals in the GPS receiver to provide time and position information;
periodically forming an extended fault vector in the Kalman filter with propagated open-loop position and velocity measurements;
the step of periodically forming the extended fault vector includes inputting a spacecraft acceleration model into the Kalman filter; and
using the extended fault vector to isolate and remove failing GPS satellites.
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Abstract
A method and apparatus for maintaining the integrity of spacecraft based time and position using GPS (11) is disclosed. A GPS receiver is provided with a Receiver Autonomous Integrity Monitor (RAIM) processor (12) and a Kalman filter (14). GPS signals are received from at least four GPS satellites and processed in the GPS receiver to provide time and position information. Periodically, an extended fault vector is formed in the Kalman filter with propagated open-loop position and velocity measurements. The extended fault vector is used to isolate and remove failing GPS satellites.
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10 Claims
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1. A method for maintaining the integrity of spacecraft based time and position using the Global Positioning System (GPS) comprising the steps of:
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providing a GPS receiver coupled to a Receiver Autonomous Integrity Monitor (RAIM) processor and a Kalman filter; receiving GPS signals from GPS satellites and processing the GPS signals in the GPS receiver to provide time and position information; periodically forming an extended fault vector in the Kalman filter with propagated open-loop position and velocity measurements; the step of periodically forming the extended fault vector includes inputting a spacecraft acceleration model into the Kalman filter; and using the extended fault vector to isolate and remove failing GPS satellites. - View Dependent Claims (2, 3)
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4. A method for maintaining the integrity of spacecraft based time and position using the Global Positioning System (GPS) comprising the steps of:
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providing a GPS receiver coupled to a Receiver Autonomous Integrity Monitor (RAIM) processor and a Kalman filter; receiving GPS signals from GPS satellites and processing the GPS signals in the GPS receiver to provide time and position information; computing unit variance in the RAIM processor and using the unit variance to desensitize the Kalman filter to off-nominal conditions; periodically forming an extended fault vector in the Kalman filter with propagated open-loop position and velocity measurements; the step of periodically forming the extended fault vector includes inputting a spacecraft acceleration model into the Kalman filter; and using the extended fault vector to isolate failures of GPS satellites and failing GPS satellites. - View Dependent Claims (5, 6, 7, 8)
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9. An apparatus for maintaining the integrity of spacecraft based time and position using the Global Positioning System (GPS) comprising:
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a GPS receiver; a Receiver Autonomous Integrity Monitor (RAIM) processor coupled to receive signals from the GPS receiver; a Kalman filter coupled to receive signals from the RAIM processor; a spacecraft acceleration model coupled to provide information to the Kalman filter to generate an extended fault vector; an open loop propagator coupled to receive extended fault vector information from the Kalman filter and supplying open-loop position and velocity measurements to the RAIM processor; and the RAIM processor, Kalman filter, spacecraft acceleration model, and open loop propagator are all functions performed in a single processor embedded in the GPS receiver. - View Dependent Claims (10)
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Specification