meetings - Space Flight Mechanics Committee

This paper describes the development of an approximate method for propagating
uncertainty through stochastic dynamical systems using a quadrature rule integration based
method. The development of quadrature rules for Gaussian mixture distributions is
discussed. A numerical solution to this problem is considered that uses a Gram-Schmidt
process. The new approach is applied to the attitude estimation problem where a quadrature
expansion is considered on SO(3). The proposed method outperforms the unscented kalman
filter for attitude estimation while providing an expansion that maintains the attitude
parameterizations on SO(3).
9:20 AAS Cubesat Attitude Control Systems with Magnetic Torquers and Flywheel
13-210 Junquan Li, York University; Mark Post, York University; Regina Lee, York
University
9:40 Break
The accuracy of nanosatellite attitude control using pure magnetic actuators only is low and
on the order less than 5 degrees. The main reason is that the magnetic torque is only
orthogonal to the instantaneous direction of the Earth's magnetic field. In this paper, the
pure magnetic control and hybird magnetic control numerical simulations are presented for
nadir pointing and limb pointing. The results show that precise attitude tracking can be
reached using hybrid magnetic control. The attitude control accuracy of hybrid nonlinear
sliding mode control method is less that 0.5 degree.
10:05 AAS Nanosatellite Sun Sensor Attitude Determination using Low-Cost Hardware
13-481 Mark Post, York University; Junquan Li, York University; Regina Lee, York
University
This paper outlines the development of two coarse sun sensor methodologies that are
compact and efficient enough for a CubeSat-class nanosatellite: direct measurement of the
solar angle using a photodiode array sensor, and estimation of the solar angle using current
measurements from an array of solar cells. An overview of the technology and hardware
designs used is provided in the context of a university nanosatellite development program.
Testing results from the sun sensors on a laboratory attitude control system are used to
validate and compare the performance of the two methodologies for nanosatellite attitude
control.
10:25 AAS Optimization of Directional Sensor Orientation with Application to
13-479 Photodiodes for Spacecraft Attitude Determination
John Springmann, University of Michigan; James Cutler, University of Michigan
We present a method to optimize the orientation of body-mounted directional sensors and
instruments. The optimization formulation consists of using the attitude sphere to create
directions over which to optimize, and deriving an objective function that uses these
directions along with their weights. The optimization method demonstrated by application
to photodiodes for spacecraft attitude determination, in which the orientation of the
photodiodes are optimized to provide the most accurate sun vector estimates with the given
23 rd AAS / AIAA Space Flight Mechanics Meeting Page 95