Abstract: The present system and methods enable simultaneous momentum dumping and orbit control of a spacecraft, such as a geostationary satellite. Control equations according to the present system and methods generate accurate station-keeping commands quickly and efficiently, reducing the number of maneuvers needed to maintain station and allowing station-keeping maneuvers to be performed with a single burn. Additional benefits include increased efficiency in propellant usage, and extension of the satellite's lifespan. The present system and methods also enable tighter orbit control, reduction in transients and number of station-keeping thrusters aboard the satellite. The present methods also eliminate the need for the thrusters to point through the center of mass of the satellite, which in turn reduces the need for dedicated station-keeping thrusters. The present methods also facilitate completely autonomous orbit control and angular momentum control using.

Abstract: The present system and methods enable simultaneous momentum dumping and orbit control of a spacecraft, such as a geostationary satellite. Control equations according to the present system and methods generate accurate station-keeping commands quickly and efficiently, reducing the number of maneuvers needed to maintain station and allowing station-keeping maneuvers to be performed with a single burn. Additional benefits include increased efficiency in propellant usage, and extension of the satellite's lifespan. The present system and methods also enable tighter orbit control, reduction in transients and number of station-keeping thrusters aboard the satellite. The present methods also eliminate the need for the thrusters to point through the center of mass of the satellite, which in turn reduces the need for dedicated station-keeping thrusters. The present methods also facilitate completely autonomous orbit control and angular momentum control using.

Abstract: Methods and structures are provided that enhance attitude control during gyroscope substitutions by insuring that a spacecraft's attitude control system does not drive its absolute-attitude sensors out of their capture ranges. In a method embodiment, an operational process-noise covariance Q of a Kalman filter is temporarily replaced with a substantially greater interim process-noise covariance Q. This replacement increases the weight given to the most recent attitude measurements and hastens the reduction of attitude errors and gyroscope bias errors. The error effect of the substituted gyroscopes is reduced and the absolute-attitude sensors are not driven out of their capture range. In another method embodiment, this replacement is preceded by the temporary replacement of an operational measurement-noise variance R with a substantially larger interim measurement-noise variance R to reduce transients during the gyroscope substitutions.

Abstract: Methods and structures are provided that enhance attitude control during gyroscope substitutions by insuring that a spacecraft's attitude control system does not drive its absolute-attitude sensors out of their capture ranges. In a method embodiment, an operational process-noise covariance Q of a Kalman filter is temporarily replaced with a substantially greater interim process-noise covariance Q. This replacement increases the weight given to the most recent attitude measurements and hastens the reduction of attitude errors and gyroscope bias errors. The error effect of the substituted gyroscopes is reduced and the absolute-attitude sensors are not driven out of their capture range. In another method embodiment, this replacement is preceded by the temporary replacement of an operational measurement-noise variance R with a substantially larger interim measurement-noise variance R to reduce transients during the gyroscope substitutions.

Abstract: A momentum control system for driving the momentum of a spinning spacecraft to zero while it spins around a sunline. The system includes a sun sensor for determining the position of the sun, a suite of tachometers for determining the momentum stored in the spacecraft, and a stored movement sensor. Each of the readings from these sensors is fed to a controller. The controller also monitors the magnitude of the spacecraft overturning momentum and the windmill momentum. If the overturning momentum is outside acceptable limits then the rotation rate of the spacecraft is modulated to drive the overturning momentum towards zero. If the windmill momentum exceeds acceptable limits, the angle of the solar panel is adjusted to drive the windmill momentum towards zero.

Abstract: A star tracker coupled to the spacecraft having a star catalog associated therewith. A sun sensor is coupled to the spacecraft. A control processor is coupled to the star tracker and the sun sensor. The processor obtains star data using a star tracker and an on-board star catalog. The processor generates a coarse attitude of the spacecraft as a function of the star data, and establishes a track on at least one star in the on-board star catalog. The processor calculates a sun tracking rate, and obtains a normal phase attitude as a function of the star data and the coarse attitude. The information is used to slew the spacecraft to a desired attitude.

Abstract: A recreational game for two or more participants is disclosed which employs an aerodynamically designed, multiwinged airfoil projectile, together with at least one hand-held shield. The shield has a front face with a generally flat projectile receiving surface, a rear generally convex face generally configured to be supported by the natural form of a user's generally relaxed hand, and shock-absorbing chamber-defining means between the two faces to effectively cushion the user's hand against impact of the projectile. The shield includes a strap spaced from the back face by a hand-accommodating distance whereby a participant's hand is removably retained in the space by the pressure exerted against the hand by the disk and strap.The projectile is thrown by one participant, and captured on the shield by a second participant via a suction device on the projectile.

Abstract: A recreational game for two or more participants is disclosed which employs an aerodynamically designed, multiwinged airfoil projectile, together with at least one hand-held shield. The shield has a front face with a generally flat projectile receiving surface, a rear generally convex face generally configured to be supported by the natural form of a user's generally relaxed hand, and shock-absorbing chamber-defining means between the two faces to effectively cushion the user's hand against impact of the projectile. The shield includes a strap spaced from the back face by a hand-accommodating distance whereby a participant's hand is removably retained in the space by the pressure exerted against the hand by the disk and strap.The projectile is thrown by one participant, and captured on the shield by a second participant via a suction device on the projectile.