Oscar Lucas Colombo

Oscar Lucas Colombo passed away on June 1, 2024. He was just shy of his 82nd birthday. Oscar was the senior geodesist in the Geodesy and Geophysics Laboratory at the NASA Goddard Space Flight Center. Oscar's home base had been at Goddard since 1983, although he had also been a visiting scientist at institutes in Japan, Australia and Europe. Oscar will be sorely missed by his colleagues at NASA and globally for his expertise and for his wit. Oscar was producing innovative ideas almost until the time of his death. The last few months of his life were burdened by a heavy illness. Over Oscar's career he had made important contributions in satellite altimetry, gravity determination and the use of Global Positioning System (GPS) technology.

 Oscar was born in the city of Pergamino, in the province of Buenos Aires, Argentina on July 16, 1942. He received his education in Argentina through his undergraduate degree at the Universidad Nacional de la Plata in 1967. Oscar then moved on to Australia and earned a PhD in Electrical Engineering in 1977 from the University of New South Wales (UNSW) in Sydney. His thesis was entitled “On the control of discrete-time systems with constrained input and state variables”. Oscar's geodetic career began soon thereafter when he began working with the prominent geodesist, Ron Mather, also at the UNSW. Oscar worked with Ron Mather until Mather's sudden death in September 1978. During the period 1977-1978 Ron Mather's geodesy team had strong collaborations with the Department of Geodetic Science at The Ohio State University (Columbus, Ohio) in the area of satellite ocean altimetry, and the NASA Goddard Space Flight Center. After Mather's death Oscar moved to The Ohio State University at the invitation of Professor Richard Rapp, where he completed several publications in the well-known Report series of the Department of Geodetic Science. During this time Richard Rapp's geodesy group was also working with scientists at the NASA Goddard Space Flight Center where Oscar would eventually find his home base. In 1982 Oscar left Ohio State for a fellowship at the Delft University of Technology (Delft, The Netherlands). This was an extremely productive period during which Oscar produced an important report published by the Netherlands Geodetic Commission, entitled “The Global Mapping of Gravity With Two Satellites”, in 1983. This was a blueprint for GRACE-like gravity missions. Furthermore, the report showed how the computations could be accomplished within the limits of the computers of that time. 

 In 1983 Oscar came to work at NASA Goddard where he worked in various capacities until his death. He was employed under various contracts and University grants while at NASA GSFC. In his first few years at Goddard Oscar worked on the TOPEX/Poseidon ocean altimetry mission. Oscar helped to make improvements in orbit determination which contributed to the unprecedented precision of the TOPEX orbits, ultimately allowing not only to synoptically map ocean surface topography, but also to map the global changes in Global Mean Sea Level. These contributions to orbit determination are still being used. In the late 1980’s Oscar focused his career on the Global Positioning System (GPS). Oscar eventually concentrated on kinematic GPS which became an important focus of his work, and led to many collaborations in Japan, Australia, and Europe. For example, Oscar worked with colleagues in Japan to combine kinematic GPS with acoustic observations to determine the position of seafloor stations off of the coast of Japan. He also maintained an interest in other applications of GNSS, including ionosphere mapping. He continued to contribute to precise orbit determination with GNSS with his GSFC colleagues, which led to improvements for the ICESat, ICESat-2 and GEDI missions. Late in his career he became interested in using anomalous ionosphere perturbations measured by GNSS to detect possible tsunami signatures. One of his last publications before his death was a NASA Technical Memorandum describing a tsunami early-warning system based on a global constellation of Cubesats that use GNSS.

 Oscar was devoted to geodesy and he lived very simply. He drove the same small car that he bought in the 1980s until the time of his death. Oscar was famously not a morning person. He did most of his work at night. He enjoyed dining out with friends and discussing music, literature and politics. We, his friends and colleagues, will miss his conversations, his wit, his company and, of course, his expertise in geodesy.