Ship heading and pitch using satellite ephemerides and radar range measurement of satellite
First Claim
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1. A method for determining at least one of heading and pitch of a movable platform, said method comprising the steps of:
- operating a radar system in communication with a computer, and having receivers mounted at forward and aft positions on said moveable platform, and having a transmitter mounted on at least one of said forward and aft positions on said movable platform, where said forward and aft positions define a baseline, to measure the ranges of at least two satellites, operating said radar system comprising;
transmitting a radar signal from an active radar and receiving said first radar signal at said active radar when said radar signal is reflected off of one of said at least two satellites, said active radar mounted at said forward location; and
receiving by a passive radar receiver said radar signal transmitted by said active radar, wherein said passive radar receiver is mounted at said aft location;
obtaining from a memory coupled to said computer, pre-stored ephemerides for said satellites; and
using said computer and said satellite ephemerides, setting up delta-range equations in said computer expressing a baseline vector in terms of range measurements from said forward and aft positions and said at least two satellites, and determining a least squares solution for the at least one of heading and pitch using the delta-range equations and the range measurements from said forward and aft locations,wherein said solution for at least one of heading and pitch is determined independently of any off-platform sensors or transmissions.
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Abstract
There may be situations in which a ship at sea is lost and GPS is not available due to jamming, and neither a position fix nor GPS is available, or the heading and attitude sensors are degraded. A system and method allow estimating a ship'"'"'s heading and pitch using radar range measurements, multiple antennas and satellite ephemeris data.
28 Citations
18 Claims
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1. A method for determining at least one of heading and pitch of a movable platform, said method comprising the steps of:
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operating a radar system in communication with a computer, and having receivers mounted at forward and aft positions on said moveable platform, and having a transmitter mounted on at least one of said forward and aft positions on said movable platform, where said forward and aft positions define a baseline, to measure the ranges of at least two satellites, operating said radar system comprising; transmitting a radar signal from an active radar and receiving said first radar signal at said active radar when said radar signal is reflected off of one of said at least two satellites, said active radar mounted at said forward location; and receiving by a passive radar receiver said radar signal transmitted by said active radar, wherein said passive radar receiver is mounted at said aft location; obtaining from a memory coupled to said computer, pre-stored ephemerides for said satellites; and using said computer and said satellite ephemerides, setting up delta-range equations in said computer expressing a baseline vector in terms of range measurements from said forward and aft positions and said at least two satellites, and determining a least squares solution for the at least one of heading and pitch using the delta-range equations and the range measurements from said forward and aft locations, wherein said solution for at least one of heading and pitch is determined independently of any off-platform sensors or transmissions. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9)
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2. A method for determining heading and pitch of a movable platform carrying a first radar arrangement including an antenna located at one of a forward-located and an aft-located position and also carrying a second radar arrangement including an antenna located at the other one of said forward-located and aft-located positions, said method comprising the steps of;
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transmitting a radar signal from said first radar arrangement at an active radar mounted at a first of said forward-located and said aft-located positions and receiving said radar signal transmitted from said active radar at said first position; receiving said radar signal transmitted from said active radar at said second radar arrangement at a passive radar mounted at the other one of said forward-located and aft-located positions; measuring by said first and second radar arrangements, the range to at least two Earth satellites from said first and second radar arrangements, to form measured ranges; obtaining from a memory in communication with said computer, ephemeris data for said satellites pre-stored in said memory; obtaining from a second memory in communication with said computer, an initial estimate of heading and pitch pre-stored in said second memory; in a computer process, calculating an estimated vector representing a baseline extending between said forward- and aft-located positions independently of any off-platform sensors or transmissions; in said computer process, calculating estimated range differences between said satellites and said forward and aft locations; in said computer process, forming a geometry matrix from said ship-satellite geometry; in said computer process, forming a Jacobian matrix representing variation in the baseline vector; in said computer process, forming an incremental solution for heading and pitch; and updating said estimated heading and pitch with said incremental solution. - View Dependent Claims (12, 13, 14, 15)
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10. A system for determining at least one of heading and pitch of a movable platform, said system comprising:
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a radar arrangement mounted at forward and aft positions on said movable platform, where said forward and aft positions define a baseline, said radar arrangement being operable to measure the ranges of at least two satellites, said radar arrangement comprising; an active radar including a first radar antenna configured to transmit a radar signal and to receive said first radar signal when said radar signal is reflected off of one of said at least two satellites, said first radar antenna mounted at said forward location; and a passive radar receiver including a radar antenna configured to receive said radar signal transmitted by said active radar, wherein said passive radar receiver antenna is mounted at said aft location; a computer coupled to said radar arrangement; a memory having pre-stored therein ephemerides for said satellites, said memory coupled to said computer; and a second memory containing estimates of heading and pitch of said moveable platform, wherein said computer is configured to set UP delta-range equations expressing a baseline vector in terms of range measurements from said forward and aft positions and said at least two satellites independently of any off-platform sensors or transmissions, and for obtaining a least squares solution for the at least one of heading and pitch using the delta-range equations and the range measurements from said forward and aft locations.
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11. A system for determining at least one of heading and pitch of a movable platform, said system comprising:
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a radar arrangement mounted at forward and aft positions on said movable platform, where said forward and aft positions define a baseline, said radar arrangement being operable to measure the ranges of at least two satellites, said radar arrangement comprising; a first active radar including a first radar antenna configured to transmit a first radar signal and to receive said first radar signal when said first radar signal is reflected off of one of said at least two satellites, said first active radar antenna mounted at said forward location; and a second active radar including a second radar antenna configured to transmit a second radar signal and to receive said second radar signal when said second radar signal is reflected off of one of said at least two satellites, wherein said second active radar antenna is mounted at said aft location; a computer coupled to said radar arrangement; a memory having pre-stored therein ephemerides for said satellites, said memory coupled to said computer; and a second memory containing estimates of heading and pitch of said moveable platform, wherein said computer is configured to set UP delta-range equations expressing a baseline vector in terms of range measurements from said forward and aft positions and said at least two satellites independently of any off-platform sensors or transmissions, and for obtaining a least squares solution for the at least one of heading and pitch using the delta-range equations and the range measurements from said forward and aft locations.
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16. A system for determining heading and pitch of a movable platform, said system comprising:
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a radar system located on said movable platform at one of a forward-located and an aft-located position, and also carrying a radar receiver located at the other one of said forward-located and aft-located positions, said radar system and receiver measuring the ranges to at least two Earth satellites from said radar and receiver, respectively, to form measured ranges independently of any off-platform sensors or transmissions, said radar system comprising; an active radar including a first radar antenna configured to transmit a radar signal and to receive said radar signal when said radar signal is reflected off of one of said at least two satellites, said active radar antenna mounted at said forward location; and a passive radar receiver including a radar antenna configured to receive said radar signal transmitted by said active radar, wherein said passive radar receiver antenna is mounted at said aft location; a computer coupled to said radar system and said radar receiver; a memory having pre-stored therein satellite ephemeris data for said at least two Earth satellites, said memory coupled to said computer; and a second memory having pre-stored therein an initial estimate of heading and pitch coupled to said computer; wherein, said computer is configured to calculate estimated range differences between said satellites and said forward and aft locations, to form a geometry matrix from said ship-satellite geometry, to form a Jacobian matrix representing variation in said baseline vector as a function of said estimated range, to form an incremental solution for heading and pitch, and to update said estimated heading and pitch with said incremental solution. - View Dependent Claims (18)
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17. A system for determining heading and pitch of a movable platform, said system comprising:
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a radar system located on said movable platform at one of a forward-located and an aft-located position, and also carrying a radar receiver located at the other one of said forward-located and aft-located positions, said radar system and receiver measuring the ranges to at least two Earth satellites from said radar and receiver, respectively, to form measured ranges independently of any off-platform sensors or transmissions, said radar system comprising; a first active radar including a first radar antenna configured to transmit a first radar signal and to receive said first radar signal when said first radar signal is reflected off of one of said at least two satellites, said first active radar antenna mounted at said forward location; a second active radar including a second radar antenna configured to transmit a second radar signal and to receive said second radar signal when said second radar signal is reflected off of one of said at least two satellites, said second active radar antenna mounted at said aft location; a computer coupled to said radar system and said radar receiver; a memory having pre-stored therein satellite ephemeris data for said at least two Earth satellites, said memory coupled to said computer; and a second memory having pre-stored therein an initial estimate of heading and pitch coupled to said computer; wherein, said computer is configured to calculate estimated range differences between said satellites and said forward and aft locations, to form a geometry matrix from said ship-satellite geometry, to form a Jacobian matrix representing variation in said baseline vector as a function of said estimated range, to form an incremental solution for heading and pitch, and to update said estimated heading and pitch with said incremental solution.
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Specification