APL Colloquium

February 23, 2001

Colloquium Topic: Microwave Anisotropy Probe: Stability, Design, and Analysis

Microwave Anisotropy Probe: Stability, Design and Analysis is a follow-on to the Differential Microwave Radiometer (DMR) instrument on the Cosmic Background Explorer (COBE) spacecraft. The design and analysis of the MAP attitude control system (ACS) have been refined since work previously reported. 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, aerodynamic and gravity gradient during phasing-loop orbits, were calculated and simulated. Thruster plume impingement torques that could affect the performance of the thruster modes were estimated and simulated, and 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 mission¹s requirements.

Colloquium Speaker: Aprille Ericsson-Jackson

Dr. Aprille Ericsson-Jackson graduated from M.I.T with a B.S. in Aeronautical/Astronoutical Engineering and received her M.E. and Ph.D. from Howard University (HU). She is the first African-American female to receive a Ph.D. in Mechanical Engineering with Aerospace option from HU. Dr. Ericsson-Jackson is currently an aerospace engineer in the Guidance, Navigation & Control Center with NASA/GSFC. Her primary job is to design, analyze and maintain the spacecraft¹s stability, orientation and position during all phases of the mission. She has worked on several different satellite projects: MAP-Microwave Anisotropy Probe, XTE-X-Ray Timing Explorer, TRMM-Tropical Rain Forest Measurement Mission and TRACE-Transition Region & Coronal Explorer. Dr. Ericsson-Jackson is a member of the NASA GSFC Speakers Bureau and the Women of NASA Group (WON) and has been Aerospace-Rocketry-Mechanical-Engineering-Professor-Computer Instructor-Career Advisor-Mentor and Friend for many students. In the past, she has been an Adjunct Professor at Bowie State University and Howard University. In 1996 and 1997, Dr. Ericsson-Jackson was acknowledged by the National Technical Association, for being amongst the Top 50 minority women in Science and Engineering. In 1997, she received the Women in Science and Engineering award for the best female engineer in the Federal Government that year. In 1998, she received a Special Recognition Award at the Black Engineers Award Conference. During 1999, she was awarded two NASA awards: 1998 NASA Goddard Honor Award for Excellence in Outreach and Center of Excellence Award for the TRMM Project. She also received a 1999 Federal Career Award from The Federal Executive Board of Excellence of Maryland, a Topp¹s Africa-Centered Award from Bowie State University, and a Centurion of Technology Award at the Women¹s of Color Technology Awards Conference. In February 2000, She received a Giant in Science Award from The Quality Education for Minorities Network: Mathematics, Science and Engineering and a NASA Customer Service Excellence Award for MAP Flight Software. She was also featured by: NBC Nightly News in their series, Women to Watch; iVillage.com as Women Who Rule; ScienceMaster.com; Essence in the You done good girl article; Yahoo Internet Life in their America Uses the Net article; Howard University Magazine in their Alumni feature; and Emerging Markets Magazine in their Leading the Way section.