Space Systems/loral, LLC

John Scott Higham

Gordon C Wu

Thomas J Holmes

Scott W Tilley

Keith J Reckdahl

Peter Y Chu

Tung Y Liu

Daniel Andrew Fluitt

Jude Zils

Elijah Zebadiah Gurnee

Yat Fai Leung

Donald W Gamble

Sun Hur-Diaz

Michel B Baylocq

David J Wirthman

Rhys Kevin Adsit

Lee Charles Rotlisberger

Birgit Sauer

Fatima Kazimi

Peter Timothy Gauthier

A spacecraft includes an additive manufacturing (A/M) subsystem and one or both of a thermal control arrangement and a contamination control arrangement. The A/M subsystem includes an A/M tool, feedstock and a workpiece and is configured to additively manufacture the workpiece using material from the feedstock. The thermal control arrangement is operable, in an on-orbit space environment characterized by near vacuum pressure and near zero-g force, to maintain temperature of at least one of the A/M tool, the feedstock, and the workpiece within respective specified ranges. The contamination control arrangement is operable, in the on-orbit space environment, to control outgassing of volatile organic compounds (VOCs).

Additive manufacturing on-orbit

Spacecraft transfer orbit operations include separating a spacecraft from a launch vehicle, while in a launch vehicle transfer orbit. The spacecraft includes a propulsion subsystem and a spacecraft controller that controls the spacecraft in a three-axis stabilized mode. With the spacecraft continuously in the three-axis stabilized mode, one or more orbit raising maneuvers are performed by firing either or both of a chemical thruster and an electric thruster firing. Any two consecutive orbit raising maneuvers are separated by a respective intervening coast period. While in the three-axis stabilized mode, the spacecraft does not rotate about any axis at a rate greater than 0.1 degree/sec and dumping of momentum stored in a reaction wheel system is avoided.

Spacecraft transfer orbit techniques

A controller and control method that perform satellite orbit-keeping maneuvers and proportionally scale orbit-keeping pulses to automatically minimize disturbance torques on-board a satellite. The controller and control method may also be used to remove residual momentum stored in spinning momentum wheels.

Controller and control method for satellite orbit-keeping maneuvers

An automatic, on-board system for orbiting spacecraft that controls and reduces short-term transients caused by roll momentum unloads by manipulating the states of the nutation damper through resetting one of the states in the polynomial transfer function to a value in proportion to the magnitude of the expected roll momentum unload and creating a transient equal and opposite in magnitude to that expected by the roll unload. The compensator will, of its own accord, automatically damp out the resulting transient. Thus the short-term transient is reduced without biasing the spacecraft in roll. No angle bias need be changed or removed.

Pre-bias scheme for roll momentum unloads on pitch momentum bias/yaw reaction wheel spacecraft

A control system and method that keeps solar arrays on a satellite pointing toward the sun. Exemplary control systems and methods are implemented as follows. An orbit propagator computes satellite orbital location data and computes a sun vector referenced to an inertial reference frame. A coordinate transformation processor processes the sun vector in the inertial reference frame and a sensed satellite attitude signal to generate a sun vector referenced to a satellite body reference frame. A solar array position processor processes a step count derived from a solar array pointing control system and sensed solar array position to generate an estimate of the position of the solar array. A summing device sums the solar array position estimate output, the body frame gun vector, and a bias signal derived from a ground command, to produce a solar array position error signal. A filter filters the solar array position error signal. A current regulator processor processes a measured solar array current to produce another solar array position error signal based on current output. An eclipse processor processes the satellite orbital location data, the solar array position error output signal, and the low pass filtered solar array position error signal to generate a step command. The solar array pointing control system processes the step command to generate control signals that point the solar array at the sun.

Sun seeking solar array control system and method

A method for estimating motion of a dual-spin spacecraft having a gimballed momentum wheel. The method disengages the gimbal from its drive train in anticipation of a short disturbance. Then, the gimbal slip resulting from the disturbance is measured. The method may be used to stabilize any dual-spin spacecraft that uses a gimballed momentum wheel. To stabilize the dual-spin spacecraft, the gimbal angle and gimbal rate are measured during and after the disturbance to provide an indication of the inertial spacecraft motion along gimbal axes. The magnitude and direction of the disturbance are determined by comparing motion of the gimbal before and after the disturbance. Then, torques are applied to the gimbal to counteract the spacecraft motion resulting from the disturbance. Temporarily reducing torque on the gimbal may be accomplished by disengaging the gimbal drive train, disengaging a holding mechanism between motor stator and rotor, or disabling command and back-emf torques, whether the drive is a DC motor or a stepper motor.

Spacecraft motion estimation using a gimballed momentum wheel

An automated spacecraft orbit compensation system and method that maintains a spacecraft in a desired orbit. The spacecraft orbit compensation system and method is automated to minimize human intervention. The system includes apparatus for determining orbital errors (ranging data) and apparatus for determining the duration and orbital location of thruster firings to correct the orbit. Each of the apparatus are located at a ground station. The system and method generates ranging data indicative of the range of the spacecraft. The ranging data are processed to estimate the orbit of the spacecraft. The estimated orbit is used to compute a thruster burn plan for the following N days. The thruster burn plan is uploaded to the spacecraft. The above steps are repeated at regular intervals.

Automated orbit compensation system and method

A spacecraft having a body, one or more appendages coupled thereto, and a controller that implements methods that rotate the one or more flexible appendages to point it (them) towards the Sun to reduce spacecraft attitude pointing disturbances and improves spacecraft attitude pointing. The steps of the one or more appendages are timed to deadbeat the disturbance imparted to the spacecraft body. Timing of the appendage steps may be such that the periodic disturbances are phased to substantially cancel each other, or phased to decrease the magnitude of the net disturbance. The present invention also cancels solar array slew disturbances. The present invention cancels predictable disturbance torques before they produce a pointing error, improving the spacecraft pointing performance. The present invention predicts a disturbance torque exerted on the body due to the controller moving the one or more appendages, calculates a feedforward torque necessary for the controller to cancel the disturbance torque and includes the feedforward torque in the calculation of the total control torque applied to the body.

Spacecraft and appendage stepping methods that improve spacecraft attitude pointing and cancel solar array slew disturbances

An onboard star tracking system is used to provide continuous attitude data based on a fixed star catalog. An orbital position reference for the sensed star data is estimated from uploaded data. The attitude is calculated based solely on the star sensor data referenced to the estimated orbital position and compared to mission attitude to generate an attitude adjustment.

Simplified onboard attitude control based on star sensing

An automatic, on-board system for orbiting spacecraft that controls yaw excursions caused by solar torques and thruster firings, which system combines inputs indicative of roll and yaw momentum increases and inputs containing information comprising the unbiased roll error from the earth sensor, yaw momentum measured from the wheel speeds, and commanded yaw momentum output from the wheel controller, and produces therefrom output signals indicative of the yaw estimate and the yaw momentum estimate. These output signals are combined and processed in a controller with a mimimum yaw error and roll thrust yaw controller gain and a miminmum yaw error and roll thrust yaw momentum controller gain, and a signal is produced therefrom for commanding roll thruster firings to change roll momentum, and, in turn, control yaw attitude and yaw excursions.

Thruster control of yaw without yaw measurements

A low cost, fuel efficient solution to the problem of avoiding high yaw errors in communications satellites after station keeping maneuvers is achieved by adding a selectable function to the LTMM controller which allows it to calculate roll momentum based on measured yaw attitude error data from the yaw DIRA. The so calculated roll momentum is used to trigger roll unloads, which will reduce the yaw attitude error. This solution has the advantages that: it maintains yaw attitude error within the pointing budget; the fuel penalty is negligible; it can be made fully automatic; it can be disabled and not used; and, it requires only a very small addition to the firmware.

Post transition momentum management

A spacecraft (201) maintains its north-south positioning by using one of two pairs of single-gimballed throttled thrusters (221-224) on a face of the spacecraft (201). The throttles (118) and gimbals (116) of the thrusters (221-224) are controlled to produce torques on the spacecraft (201) that will maintain a desired attitude for the spacecraft (201) while simultaneously desaturating the momentum stabilizing wheels ( 120, 121 ) of the spacecraft (201).

Growing community of inventors

Mountain View, CA, United States of America

John Scott Higham