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Leader, F.

Publications and source records attributed to Leader, F..

13 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

Active Volcanism on IO: Global Distribution and Variations in Activity

Io's volcanic activity has been monitored by instruments aboard the Galileo spacecraft since June 28, 1996. We present results from observations by the Near-Infrared Mapping Spectrometer (NIM) for the first ten orbits of Galileo, correlate them with results from the Solid State Imaging System (SSI)and from ground-based observations, and compare them to what was known about Io's volcanic activity from observations made during the two Voyager fly-bys in 1979.

near-infrared mapping spectrometry solid state ima↗
NASA NTRS1995

Galileo NIMS Direct Observations of the SL-9 Fireballs

The Galileo spacecraft was situated 1.8 AU from Jupiter, at a phase angle of 51 deg, providing a direct view of the impacts of the comet fragments with the planet. Low resolution infrared spectra in the 1 to 5 micron range were recorded for several of the events, which can be used to study the early evolution of the fireballs. Preliminary analysis of the data received for the G event show an initial fireball temperature of greater than 5000 K and an effective source diameter of less than 10 km. These spectra show absorption by molecular hydrogen and methane which place the upper emitting surface in the stratosphere, above the ammonia cloud level. As time progresses, the fireball cools and the effective diameter of the radiating area increases at roughly 2 km/sec. In 30 seconds, the fireball cools to approximately 1000 k and exhibits a diameter of about 100 km.

NIMS↗
NASA NTRS1995

Galileo Infrared Observations of the Shoemaker Levy 9 G and R Fireballs and Splash

The Galileo spacecraft was fortuitously situated for a direct view of the impacts of comet Shoemaker(ka)evy 9 in Jupiter's atmosphere and measurements were recorded by the Near Infrared Mapping Spectrometer (NIMS) instrument for several of the impact events. Seventeen discrete wavelength channels were used between 0.7 to 5.0 microns, obtained with a time resolution of 5 seconds. Two phases of the impact phenomena are found in the data: the initial fireball, which was evident for one minute, and subsequent fallback of impact ejecta onto the atmosphere, starting six minutes after fireball initiation.

Shoemaker Levy↗