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Satellite motion included in gyro output disturbs the estimation of Allan variance coefficients of fiber optic gyro on board. Moreover, as a standard method for noise analysis of fiber optic gyro, Allan variance has too large offline computational effort and data storages to be applied to online estimation. In addition, with the development of deep space exploration, it is urged that satellite requires more autonomy including autonomous fault diagnosis and reconfiguration. To overcome the barriers and meet satellite autonomy, we present a new autonomous method for estimation of Allan variance coefficients including rate ramp, rate random walk, bias instability, angular random walk and quantization noise coefficients. In the method, we calculate differences between angle increments of star sensor and gyro to remove satellite motion from gyro output, and propose a state-space model using nonlinear adaptive filter technique for quantities previously measured from offline data techniques such as the Allan variance method. Simulations show the method correctly estimates Allan variance coefficients, R = 2.7965exp − 4and tracks degradation of gyro performance from initail values, R = 0.651 • /h 2 , K = 0.801 • /h 1.5 , B = 0.385 • /h, N = 0.0874 • /h 0.5 and Q = 8.085exp − 5 • , to final estimations, R = 9.548 • /h 2 , K = 9.524 • /h 1.5 , B = 2.234 • /h, N = 0.5594 • /h 0.5 and Q = 5.113exp−4 • , due to gamma radiation in space. The technique proposed here effectively isolates satellite motion, and requires no data storage and any supports from the ground.

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We present a method for the trajectory and the velocity measurement of a particle in spray by digital holography. Based on multiple exposure digital in-line holography, a sequence of digital holograms of a dynamic spray particle field at different times are recorded with a CW laser and a high-speed CCD. The time evolution of the serial positions of particles, i.e., the motion trajectories of the particles, is obtained by numerically reconstructing the synthetic hologram of a sequence of digital holograms. The center coordinate (x,y) of each particle image can be extracted using a Hough transform and subpixel precision computing, and the velocity of an individual particle can also be obtained, which is then applied to measuring the velocity of diesel spray and alcohol spray. The research shows that the method presented in this paper for measuring spray field is feasible.

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