Spaceflight Now: Breaking News

This week on Galileo
Posted: Dec. 29, 1999

Galileo continues to playback data acquired during the spacecraft's November 24 flyby of Io. The November encounter also afforded the spacecraft a unique view of Jupiter's icy moon Europa. Data playback is interrupted twice this week. On Friday, the spacecraft performs a flight path adjustment, if necessary. On Saturday, the spacecraft performs standard maintenance on its onboard tape recorder, just prior to starting its next encounter late Saturday evening (Pacific Time).

The spacecraft continues to return data from a second pass through the observations stored on the tape recorder. This additional pass allows replay of data lost in transmission to Earth, reprocessing of data using different parameters, or return of new additional data. The Solid-State Imaging camera (SSI) returns three observations this week, the Photopolarimeter Radiometer (PPR) returns two, and the Near-Infrared Mapping Spectrometer returns four.

SSI first returns an observation of Amalthea, one of Jupiter's minor moons. The observation provides the best resolution ever of the moon at 3.7 kilometers (2.3 miles) per picture element.

PPR then takes to the schedule with the return of two observations. The first contains a thermal map of Europa's dark side. The observation will be compared to previous dayside observations of the same regions, with the goal of identifying heat sources or thermal anomalies on the moon. The second observation contains polarimetry measurements of Europa's surface, which will allow scientists to study Europa's surface texture and thermal properties.

NIMS returns to the playback schedule with an observation of Europa's north polar region. The observation is expected to contain the highest resolution view of the polar region to date. NIMS then returns a spectral map of Europa's surface designed to look for evidence of plate tectonics on Europa's surface. This is followed by portions of a 12-image global mosaic of Europa taken by SSI. The final two observations of this week are returned by NIMS. One captures part of the equatorial region of Europa, while the other is global in scale.

Encounter commands for Galileo's next encounter begin to execute late Saturday night (Pacific Time). The encounter features a close flyby of Europa set to occur on Monday, January 3, 2000. The start of the encounter brings with it the resumption of the magnetospheric survey conducted from orbit to orbit by the Fields and Particles instruments. During the survey, the instruments obtain measurements of plasma, dust, and electric and magnetic fields. These measurements are not recorded on board, but rather are processed and returned to Earth in near real time. This survey allows scientists to study the long term variations within the inner portions of Jupiter's magnetosphere.

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