Lockheed Martin Corporation

Honeywell International Inc.

Lockheed Martin Corpora Tion

Emergent Space Technologies, Inc.

Harald Juergen Weigl

Neil Evan Goodzeit

Santosh Ratan

Matthew Henry Rosenbrock

Joseph F Eder

Timothy Hindle

Michael Brett McMickell

Xipu Li

David Gaylor

William Bamford

Provided herein are various enhanced systems, apparatuses, and techniques for optical communication among a constellation of satellites. One example includes establishing an initial cross-connect configuration comprising optical communication links among a constellation of satellites. In the initial cross-connect configuration, the satellites can optically communicate with both adjacently positioned and non-adjacently positioned satellites in the constellation. The satellites obtain angular states of the optical communication links resultant from orbital motion of the satellites. When angular states of a portion of the optical communication links reach an exclusion range, the satellites establish a subsequent cross-connect configuration to avoid optically communicating within the exclusion range.

Solar irradiance mitigation in satellite optical communication

Optical communication satellite cross-connect

The present invention addresses performance limitation of gyros (e.g., MEMS gyros) by significantly reducing common-mode noise and bias effects. In one embodiment, an array of gyros, which may comprise four or more gyros, is configured so that common-mode error effects can be separated from the sensed rotational motion of the gyros and therefore removed. Removing the common-mode effects increases attitude estimation and spacecraft pointing accuracy, particularly during periods when the gyros must solely provide the attitude reference.

System and method for improved accuracy gyro rate sensing

The present disclosure provides systems and methods that improve the pointing accuracy of a spacecraft using temperature-sensitive gyros (e.g., MEMS gyros) by using a temperature bias model to compensate for temperature biases of the gyros and using attitude data (e.g., star tracker data) to automatically and continuously calibrate the temperature bias model over the life of the spacecraft. When star tracker data is unavailable (e.g., due to sun interference), the most recently updated temperature bias model is used in open-loop to provide improved estimation of the gyro biases and improved attitude estimation.

Autonomous gyro temperature calibration

A system for isolating vibration among a plurality of instruments on a spacecraft includes at least two platforms, each of which is configured to couple to and isolate vibration for a single one of the plurality of instruments. Each of the at least two platforms is configured to mount to the spacecraft. A device is also provided for isolating vibration for one instrument among a plurality of instruments on a spacecraft.

System for isolating vibration among a plurality of instruments

A spacecraft includes a plurality of thrusters, a thruster firing logic, an actuator assembly, an attitude control system, and a torque calibration system. The plurality of thrusters is configured to apply torque to the spacecraft. The thruster firing logic is configured to control firing of the plurality of thrusters. The actuator assembly is configured to apply torque to the spacecraft. The attitude control system is configured to sense an attitude of the spacecraft and to provide an attitude control torque. The torque calibration system is configured to provide a thruster feedforward torque. A machine-readable medium includes instructions for a method for providing torque calibration to a spacecraft.

Spacecraft thruster torque feedforward calibration system

An active vibration damping (AVD) control system for spacecraft provides a simple-to-implement and robust formulation that provides a novel damping control method for reducing spacecraft structural vibrations and improving antenna and instrument pointing. The AVD control system comprises an excitation signal generator configured to generate excitation input signals, and a damping model identification unit configured to receive system identification data and configured to produce control model parameters, the system identification data comprising the excitation input signals and information associated with motion of the spacecraft. The AVD control system further comprises an AVD control unit configured to receive the control model parameters, the AVD control unit configured to produce AVD control signals to control one or more actuators of the spacecraft.

Active vibration damping (AVD) system for precision pointing spacecraft

A spacecraft system is provided, including a measurement device configured to measure information associated with position of a spacecraft, a filter configured to process the measured information and to provide estimated pre-maneuver information associated with position of the spacecraft and estimated post-maneuver information associated with position of the spacecraft, a propagator configured to predict post-maneuver information associated with position of the spacecraft based upon the estimated pre-maneuver information associated with position of the spacecraft and a model of a maneuver of the spacecraft, an error calculator configured to calculate an acceleration error based upon the estimated post-maneuver information associated with position of the spacecraft and the predicted post-maneuver information associated with position of the spacecraft, and a maneuver archive configured to store the acceleration error for updating the model of the maneuver. The filter, the propagator, the error calculator and the maneuver archive may be implemented in software and/or onboard the spacecraft.

Geosynchronous spacecraft autonomous navigation

An attitude determination system is provided for determining attitude values of a yaw-steering spacecraft, and includes a rate sensor, at least one attitude sensor, and a processor operable to receive measured spacecraft body rates from the rate sensor, to receive measured spacecraft attitude values from the at least one attitude sensor, and to calculate estimated spacecraft attitude values based on the measured spacecraft body rates and the measured spacecraft attitude values by using a Kalman filter that includes a plurality of attitude estimate error states, a plurality of gyro bias states, and a plurality of commanded rate dependent gyro error states.

Attitude determination system for yaw-steering spacecraft

The present invention provides a system and a method for improving spacecraft antenna pointing accuracy utilizing feedforward estimation. The present invention takes advantage of the fact that spacecraft antenna pointing error has periodic behavior with a period of 24 hours. Thus, unlike the prior art feedback systems which blindly correct antenna pointing error continuously reacting only to presently sensed error, the present invention takes an intelligent approach and learns the periodic behavior of spacecraft antenna pointing error. Then, an estimate of antenna pointing error at a particular time going forward is predicted based on the learned model of the periodic behavior of the antenna pointing error. The predicted estimate is then used to correct or cancel out the antenna pointing error at a particular time in the future. The result is more accurate correction of spacecraft antenna pointing error by more than a factor of two.

Antenna autotrack control system for precision spot beam pointing control

Momentum control is maintained in a geosynchronous orbiting spacecraft that uses a plurality of reaction wheel assemblies and a plurality of magnetic torquers to control the spacecraft momentum, each orbit of the spacecraft being comprised of a set of time steps, by determining a current momentum error for a current time step of a current orbit by adding a system momentum change determined for an immediately preceding orbit to an average system momentum determined for the immediately preceding orbit, and then subtracting a magnetic control torque momentum change determined for the immediately preceding orbit, determining a current duty cycle for each of the magnetic torquers based on the current momentum error and on a torque value applied by each magnetic torquer at each time step of the immediately preceding orbit, and commanding each magnetic torquer to operate at the current time step in accordance with its respective determined current duty cycle, wherein the magnetic torquers apply a magnetic momentum control torque to the spacecraft to offset the current momentum error.

Spacecraft magnetic momentum control system

A velocity change (&#x394;V) thruster is operated on a spacecraft, which unavoidably causes attitude error. A reaction wheel (RWA) corrects the attitude. At the beginning of the thruster maneuver, the total attitude control momentum required to at least correct for the &#x394;V thruster attitude errors over the duration of the entire maneuver is determined, and the RWA momentum may also be determined. Attitude control thrusters (REAs) are operated. The REAs are operated to correct at least the net &#x394;V thruster induced attitude error, and preferably also to reset the RWA to its nominal momentum. The maneuver may be stationkeeping.

High-efficiency REA optimized stationkeeping

A method for correcting spacecraft pointing errors. An orbit frequency distortion angle between a rate sensor and at least one attitude sensor is estimated. An estimated attitude of the spacecraft is adjusted to correct for the distortion angle.

System for on-orbit correction of spacecraft payload pointing errors

A method for maintaining three axis control of a geosynchronous spacecraft without body rate measurements using reaction wheel assemblies. Earth sensor assembly angle measurements are utilized for high-bandwidth roll and pitch control. A positive pitch momentum bias is stored in the reaction wheel assemblies. A gyroscopic feedforward torque is applied to rotate reaction wheel assembly momentum in a yaw/roll plane of the spacecraft at orbit rate. A dynamic mode that couples yaw and roll axes and that results from applying the gyroscopic feedforward torque and the high-bandwidth roll control is damped based on earth sensor assembly roll measurements.

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Doylestown, PA, United States of America

Harald Juergen Weigl