University of Minnesota
Aerospace Engineering and Mechanics
Winter 1999 Seminar Series
MAP Stability, Design and Analysis
Abstract The Microwave Anisotropy Probe (MAP) is a follow-on to the
Differential Microwave Radiometer (DMR) instrument on the Cosmic Background
Explorer (COBE) spacecraft. The full spacecraft and instrument flexible model
was developed in NASTRAN, and the resulting flexible modes were plotted and
reduced with the Modal Significance Analysis Package (MSAP). The reduced-order
model was used to perform the linear stability analysis for each control mode,
the results of which are presented in this paper. Although MAP is going to a
relatively disturbance-free Lissajous orbit around the Earth-Sun L2 Lagrange
point, a detailed disturbance-torque analysis is required because there are
only a small number of opportunities for momentum unloading each year.
Environmental torques, including solar pressure at L2, and aerodynamic and
gravity gradient during phasing-loop orbits, were calculated and simulated. A
simple model of fuel slosh was derived to model its effect on the motion of the
spacecraft. In addition, a thruster mode linear impulse controller was
developed to meet the accuracy requirements of the phasing loop burns. A
dynamic attitude error limiter was added to improve the performance of the ACS
during large attitude slews. The result of this analysis is a stable ACS
subsystem that meets all of the mission's requirements.
Friday, March 5, 1999
Refreshments served after the seminar in
227 Akerman Hall.
Disability accomodations provided upon request.
Contact Kristal Belisle, Senior