[1] Univ Maryland, Dept Phys, Baltimore, MD 21201 USA
[2] NASA, Goddard Space Flight Ctr, Hydrospher & Biospher Sci Lab, Greenbelt, MD 20771 USA
[3] NASA, Goddard Space Flight Ctr, Wallops Flight Facil, Wallops Isl, VA 23337 USA
[4] Univ Colorado, Dept Elect & Comp Engn, Boulder, CO 80309 USA
[5] NASA, Goddard Space Flight Ctr, Wallops Flight Facil, EG&G Tech Serv, Wallops Isl, VA USA