Goddard Space Flight Center, Greenbelt, Maryland 20771
ENGINEERING COLLOQUIUM
Monday, March 26, 2007 / 3:30 PM, Building 3 Auditorium
John Degnan
"Applications of High Precision Laser Ranging to Artificial Satellites, the Moon, and the Planets"
ABSTRACT -- The first successful laser tracking of an artificial satellite carrying an array of passive retroreflectors took place at the NASA Goddard Space Flight Center on October 31, 1964. Over the next four decades, international scientists and engineers developed a global network of almost 40 satellite laser ranging (SLR) stations which have provided precision tracking to over 60 international space missions. Over the same period, the ranging precision has improved approximately three orders of magnitude, from a few meters in 1964 to a few millimeters today. The scientific data gleaned from these experiments has contributed immensely, either directly or indirectly, to our understanding of the Earth’s gravity field, plate tectonics, regional crustal deformation, ocean circulation, global warming, etc.
In the late 1960’s and early 1970’s, the manned US Apollo and unmanned Soviet Lunakhod lunar missions placed a total of five optical retroreflectors on the Moon. Laser ranging data from a few select stations (notably in the US and France) to these reflectors has been used by analysts to study Earth-Moon and Solar System dynamics and to provide unique tests of General Relativity. Recent GSFC laser transponder experiments to the Messenger and Mars Global Surveyor spacecraft, carried out in 2005 at distances of 24 and 80 million Km respectively, have demonstrated the ability of lasers to make decimeter or better measurements throughout the inner solar system with potentially important applications to interplanetary navigation and communications, solar system science, and fundamental physics.
SPEAKER -- John J. Degnan received his BS in Physics from Drexel University in 1968 and his MS and Ph.D. degrees in Physics from the University of Maryland College Park in 1970 and 1979 respectively. Prior to joining Sigma Space Corporation as Chief Scientist in February 2003, he accumulated over 38 years of technical and 25 years of supervisory and project management experience at NASA’s Goddard Space Flight Center where he led the development of advanced lasers and electro-optical sensors and was instrumental in creating the International Laser Ranging Service (ILRS) in 1998. He has authored approximately 200 publications (including many invited review papers and book chapters) on laser theory and design, satellite laser ranging (SLR), laser altimetry, atmospheric lidar, free space optical communications, interplanetary laser transponders, receiver design for both direct detection and heterodyne/homodyne systems, and laser-related medical instrumentation. Dr. Degnan is a Fellow of the IAG, a Senior Member of the IEEE, a Charter Member of the International Laser Communications Society, and a Member of the Optical Society of America (OSA), the American Geophysical Union (AGU), and Sigma Pi Sigma National Physics Honor Society. He is the recipient of numerous NASA, international, and academic awards including GSFC’s Moe I. Schneebaum Memorial Award for Engineering in 1987, the Russian Space Agency’s Tsiolkovsky Medal in 2002, and Drexel University’s Alumni Circle of Distinction Award in 2005.