Robert H. Tolson

Learn More
The Mars Global Surveyor spacecraft was initially placed into a high eccentricity, nearly polar orbit about Mars with a 45-hour period. To accomplish the science objectives of the mission, a 2-hour, circular orbit was required. Using a method known as aerobraking, numerous passes through the upper atmosphere slowed the spacecraft, thereby reducing the(More)
The Mars Atmosphere and Volatile Evolution (MAVEN) mission, during the second of its Deep Dip campaigns, made comprehensive measurements of martian thermosphere and ionosphere composition, structure, and variability at altitudes down to ~130 kilometers in the subsolar region. This altitude range contains the diffusively separated upper atmosphere just above(More)
R. H. Tolson∗ North Carolina State University, Hampton, Virginia 23666-6147 G. M. Keating George Washington University, Newport News, Virginia 23602 R. W. Zurek Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109-8099 S. W. Bougher University of Michigan, Ann Arbor, Michigan 48109-2143 C. G. Justus Morgan Research(More)
Data collection during the aerobraking period. The atmospheric density of Mars at the aerobraking altitude showed significant variation over time as well as large orbit-toorbit differences. On each orbit the density must be predicted to determine the appropriate and safe depth within the atmosphere for the aerobraking passage sufficiently in advance to(More)
During the last 2 weeks of February 1977, an intensive scientific investigation of the martian satellite Phobos was conducted by the Viking Orbiter-1 (VO-1) spacecraft. More than 125 television pictures were obtained during this period and infrared observations were made. About 80 percent of the illuminated hemisphere was imaged at a resolution of about 30(More)
Coupling between the lower and upper atmosphere, combined with loss of gas from the upper atmosphere to space, likely contributed to the thin, cold, dry atmosphere of modern Mars. To help understand ongoing ion loss to space, the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft made comprehensive measurements of the Mars upper atmosphere,(More)
Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. The NASA Scientific and Technical Information (STI) Program Office plays a key part in helping NASA maintain this important role. The NASA STI Program Office is operated by Langley Research Center, the lead center for NASAÕs scientific and technical information.(More)
Atmospheric drag measurements obtained from the study of the orbital decay of Pioneer Venus 1 indicate that atomic oxygen predominates in the Venus atmosphere above 160 kilometers. Drag measurements give evidence that conditions characteristic of a planetary thermosphere disappear near sundown, with inferred exospheric temperatures sharply dropping from(More)
Three missions have successfully used aerobraking to reduce the spacecraft orbit period and achieve the desired orbit geometry. A fourth, Mars Reconnaissance Orbiter, will employ aerobraking following its orbit insertion in March, 2006. The propellant mass reductions enabled by the aerobraking technique allow the use of smaller launch systems, which(More)