1. a CESF, State University of New York , 308 Bray Hall, Syracuse, New York, 13210, U.S.A
2. b Northeastern Forest Experiment Station, U.S. Forest Service, State University of New York , Syracuse, New York, 13210, U.S.A
3. c Space Department , Royal Aircraft Establishment , Farnborough, Hampshire, GU14 6TD, England