Orbital Mechanics

Motion of  spacecraft in highly perturbed systems using analytical, semi-analytical, and numerical methods.

Spacecraft formation flight dynamics and solution of formation boundary value problems

Spacecraft dynamics in unstable orbital environments

Orbit mechanics about planetary satellites

Orbital motion about and on asteroids and comets, asteroid threat mitigation issues

Solar sail dynamics and modeling

Celestial Mechanics of translational and rotational coupling

Navigation, Control and Estimation

Investigation of nonlinear navigation and control of spacecraft in challenging environments.

Orbit determination and statistical control of spacecraft in unstable orbital environments

Optimal nonlinear feedback trajectory control of low-thrust space vehicles

Dynamics and control of uncertainty distributions in Hamiltonian systems

Space Situational Awareness

Application of astrodynamics and optimal control theory to problems in SSA.

Short-arc orbit determination using optical sensors

Uncorrelated satellite tracking and correlation

Reachability analysis of thrusting satellites in orbit

Estimation and reconstruction of thrusting satellite trajectories and thrust profiles

Asteroid and Comet Science

Modeling and dynamical evolution of comets and asteroids

Member of the science team on the NASA Near Earth Asteroid Rendezvous (NEAR) mission and the Japanese Hayabusa mission to asteroid Itokawa. 

NASA-OSS funded investigations into the basic mechanics and dynamics of the asteroid and comet environment. 

Co-I on several proposed NASA missions.