According to an aspect of the present invention, there is provided a method comprising: propelling a servicing spacecraft to an object; deploying one or more counter mass(es) away from a servicing spacecraft bus to offset the center of mass of the servicing spacecraft into an empty volume; approaching the object, by the servicing spacecraft; positioning the center of mass of the servicing spacecraft in approximately the same location as the center of mass of the object; imparting angular momentum to the servicing spacecraft to match the tumble rate of the object; and contacting the object with one or more mechanical attachments to the servicing spacecraft.

A shell rotor assembly for use in a control moment gyroscope herein. The shell rotor assembly includes, but is not limited to, a first shell member having a first wall portion and a first rim portion formed integrally with one another and a second shell member having a second wall portion and a second rim portion formed integrally with one another. The first rim portion and the second rim portion are attached to one another.

A satellite in orbit around a planetary body includes a bus and a drag flap coupled to the bus. The drag flap is used to increase the drag torque applied to the satellite. The bus may house sensors and actuators, such as a star tracker, a gyroscope, a reaction wheel, and a global position system (GPS) receiver to monitor the attitude of the satellite in response to the applied drag torque. The measurements from the sensors and actuators may be used to determine the drag torque applied to the satellite. An estimate of the atmospheric density may be then be determined based on the drag torque. Compared to conventional approaches, the satellite and methods described herein estimates the atmospheric density at comparable, if not better, resolution and bandwidth. The atmospheric density estimates may also be acquired in real-time using a cheaper, lighter, and smaller satellite.

Feedback control circuitry includes rate limiter circuitry configured to generate a rate limited position command based on a position command for a controlled component and based on a speed command for the controlled component. The feedback control circuitry also includes error adjustment circuitry configured to apply a control gain to an error signal to generate an adjusted error signal. The error signal is based on position feedback and the rate limited position command, and the position feedback indicates a position of the controlled component. The feedback control circuitry further includes an output terminal configured to output a current command generated based on the adjusted error signal.

Dither circuitry includes harmonic signal generation circuitry configured generate a high order even harmonic of a base excitation signal. The dither circuitry also includes a combiner configured to generate a dithered excitation signal based on the high order even harmonic and the base excitation signal. The dither circuitry further includes an output terminal configured to output the dithered excitation signal to a sensor device.

A spacecraft including a spacecraft bus and a set of thrusters for changing a pose of the spacecraft. Wherein at least two thrusters are mounted on a gimbaled boom assembly connecting the two thrusters with the spacecraft bus, such that the two thrusters are coupled thrusters sharing the same gimbal angle. A model predictive controller to produce a solution for controlling thrusters of the spacecraft by optimizing a cost function over multiple receding horizons. The cost function is composed of a cost accumulated over the multiple receding horizons, including a cost accumulated over a first horizon using a dynamics governing a north-south position of the spacecraft, and a cost accumulated over a second horizon using a model of dynamics of the spacecraft governing an east-west position. A thruster controller to operate the thrusters according to their corresponding signals.

Dither circuitry includes harmonic signal generation circuitry configured generate a high order even harmonic of a base excitation signal. The dither circuitry also includes a combiner configured to generate a dithered excitation signal based on the high order even harmonic and the base excitation signal. The dither circuitry further includes an output terminal configured to output the dithered excitation signal to a sensor device.

A method of controlling the attitude of a spacecraft in spinning around itself with a non-zero total angular momentum H.sub.TOT. The spacecraft includes a set of inertia flywheels configured to form an internal angular momentum H.sub.ACT. The axis of the total angular momentum H.sub.TOT is aligned with a principal axis of inertia of the spacecraft, in the course of which the inertia flywheels are controlled to form an internal angular momentum H.sub.ACT. The following expression, in which J is the inertia matrix of the spacecraft:
H.sub.actJ.sup.1(H.sub.tot.Math.J.sup.1H.sub.tot)
is negative if the principal axis of inertia targeted is the axis of maximum inertia of the spacecraft and is positive if the principal axis inertia targeted is the axis of minimum inertia of the spacecraft.

When the number of CMGs is represented by n (n is an integer of 4 or more), (n3) gimbal angles out of n gimbal angles corresponding to the n CMGs are set as free parameters, and an algebraic equation representing a relationship among three gimbal angles out of the n gimbal angles, the free parameters, and an angular momentum of all the CMGs is used to solve the algebraic equation while changing the free parameters within set ranges, to thereby obtain solutions of the gimbal angles of the plurality of CMGs required for achieving a given angular momentum.

A launch lock system includes a first portion rigidly coupled to the second portion in a first state and the first portion movable in all directions relative to the second portion in a second state. The launch lock system includes a fastener subassembly coupled to the second portion, and the fastener subassembly is movable relative to the second portion from a first position to a second position. The launch lock system includes at least one pivot arm subassembly having a pivot arm movable between a first position and a second position. The pivot arm is coupled to the first portion in the first position. In the first state, the pivot arm is in the first position and cooperates with the fastener subassembly in the first position, and in the second state, the pivot arm is uncoupled from the first portion and the fastener subassembly.