Direct Trajectory Optimization and Costate Estimation via an Orthogonal Collocation Method Benson, David A. ; Huntington, Geoffrey T. ; Thorvaldsen, Tom P. ; Rao, Anil V. Abstract Publication: Journal of Guidance Control Dynamics Pub Date: November 2006 DOI: 10.2514/1.20478 Bibcode: 2006JGCD...29.1435B