Satellite attitude acquisition by momentum transfer-the controlled wheel speed method

Abstract

Abstract. An implementation of the momentum transfer method for spacecraft attitude acquisition of momentum wheel stabilized geostationary satellites is presented, in which the wheel speed is varied in a predeterminable manner to reduce the nutation usually associated with the method. The implementation is found to be capable of achieving the transfer to the desired zero nutation end point with 5 ~ to 20 ~ of residual nutation in practical situations without additional nutation damping. The transfer time is typically 10-30 min. The implementation is described in terms of the momentum sphere and energy ellipsoid. The detailed functional dynamics and parametric relationships are given in terms of phase planes and elliptic integral solutions. Feasibility of the implementation is shown to be dependent on the moment of inertia configuration and the degree to which tolerances on moments of inertia, satellite spin rate, and wheel speed are predeterminable. A,B,C NomenclaturePrincipal moments of inertia of the total spacecraft. Unit vectors parallel to principal axes. Energy of the spacecraft body (excludes the spin energy of momentum wheel). Initial energy of the spacecraft (wheel not spinning). A constant arbitrary value of E(t). Energy after an impulse which causes ~ to equal zero, Equation (13). The constant value of E during Stage 2. Energy at the end of Stage 3. The separatrix value of E, i.e. E when e = 0. Angular momentum vector of the total spacecraft. Variable components of H 0 resolved with respect to bl, b2, and b 3. Moment of inertia of the momentum wheel. The slope of the wheel speed profile, Equation (31). Momentum wheel torque. Direction cosine of the angle, 0, between H 0 and b 2. Constant values of m. The centre of the momentum sphere. Spacecraft coordinate axes. Represents a state on the momentum sphere and energy ellipsoid. Momentum wheel speed. Constant value of s during Stage 2. Wheel speed after an impulse which causes e to be zero. Time. Elapsed time for Stages 1, 2, and 3 respectively. Roots of Equation (19)

NEOSSat Recovery Following Magnetometer and Torque Rod Failure

“…[13,14]) or after attitude stabilization using momentum transfer algorithms (as described in Ref. [15,16]). Another innovative approach considered was to estimate the magnetic field vector in the satellite's Extended Kalman Filter (EKF) for attitude determination by measuring the dynamic effects of torque rods on the satellite's body rates.…”

Momentum Transfer in Torque-Free Gyrostats

“…in the all-spun condition, defined by Eq. (20). Note that a constraint torque on the rotor is required since ii as = 0 only if the gyrostat is in equilibrium.…”