![]() However, bidirectionalĭistributions observed at nearly perpendicular shocks cannot beĮxplained in the framework of the single shock encounter mechanism. The predictions of the gradient drift acceleration model, showing a Reflections of particlesįrom the shock were clearly identificable by the loss cone in the Spacecraft at several shock associated events. Ion spectrometer aboard the International Sun Earth Explorer (ISEE) 3 The energy range 35 keV to 1 MeV has been. Predictions of the gradient drift acceleration model concerning theĮnergy, time, and angular dependence of the particle flux caused by a Scatter-free acceleration of energetic particles by quasi-perpendicular Thank you for your interest, and I'm happy to respond to any non-proprietary questions. I've also continued work on definitive attitude and calibration products for the MMS mission and occasional consultation and slew planning for the LRO mission. My projects this past year have been launch support and calibrations of the attitude sensors on the NICER and JPSS-1 missions. We are now able to estimate where the breakage occurred as a function of the change in coning angle. We recently completed an analysis of how the inertia tensor and the coning angle would change on one of the MMS spacecraft (these are four spinners flying in formation) if one of the long (60 m) wire booms breaks. Our team will soon begin work on developing an Attitude Ground System (AGS) for NASA's PACE mission. The gyro parameter covariance will be estimated from a combination of the smoother and least-squares covariances arising from the IRU and attitude sensor noise. The difference will be minimized using an iterated least-squares method. This utility will be based on a direct comparison between data from each gyro channel and the best estimate of the true rate from an opt imal smoother. My most recent work involves a new gyro calibration utility. Sensor can be accurately estimated as long as its boresight is not too Gyro biases are independently known, the timetag error for a single Even with bad geometry and constant rates, if Performs well when the rate is either varying or noncoplanar with the Observability is much improved and the filter The EUVE geometry, though, is a degenerate case having coplanar sensorsĪnd rotation vector. TheĮstimates are particularly sensitive to filter mistuning in this case. In the absence of attitude maneuvers, the state elementsĪre highly correlated, and the state estimate is unreliable. The state vector is severely limited when the spacecraft rotation rate Due to EUVE's sensor geometry, the observability of Or two sensors, both constant and time-varying, and with and without The tests include cases with timetag errors on one The flight data come from times when EUVE had aĬonstant rotation rate, while the simulated data feature large angleĪttitude maneuvers. Use both simulated and actual flight data from the Extreme UltravioletĮxplorer (EUVE). Several examples with simulated star tracker timing errors. The observability of the state vector is studied first throughĪn examination of the algebraic observability condition and then through ![]() Thus, this filter isĪpplicable to cases where the true timing errors are constant or slowly Random walk processes: their expectation values propagate as constantsĪnd white noise contributes to their covariance. ![]() Vector here consists of the attitude quaternion, timetag biases, and, Rotating or the reference vectors themselves vary with time. The observations can lead to attitude errors if either the spacecraft is Mean rotation from a set of reference vectors in inertial space to theĬorresponding observed vectors in the body frame. Spacecraft attitude is determined by finding the This paper presents an extended Kalman filter for estimating attitude
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