Gary E. Galica,* B. David Green, and Mark T. Boies* Physical Sciences, Inc., Andover, Massachusetts 01810 O. Manuel Uy, David M. Silver, Richard C. Benson,**and Robert E. Erlandson Johns Hopkins University, Applied Physics Laboratory, Laurel, Maryland 20723 Bob E. Wood** Sverdrup Technology, Inc., Arnold Air Force Base, Tennessee 37389 and David F. Hall The Aerospace Corporation, El Segundo, California 90245