1939
Dr. Greenhall is born in New York City, New York to A. Frank Greenhall and Miriam Housman.
1961
Dr. Greenhall receives a Bachelor of Arts from Pomona College in Claremont, California.
1966
Dr. Greenhall receives a Doctor of Philosophy from the California Institute of Technology in Pasadena, California.
1968
Dr. Greenhall becomes an assistant professor of mathematics at the University of Southern California in Los Angeles, California.
1977
Dr. Greenhall becomes a senior member of the technical staff of the Jet Propulsion Laboratory in Pasadena, California.