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This Week on Galileo?
November 26 - 28, 1999

Galileo Wraps Up Encounter with Jupiter System on Friday

Galileo wraps up its encounter with the Jupiter system on Friday, just a few short hours after passing within a few hundred kilometers of Io's south pole. Friday's activities include one observation by the Solid-State Imaging camera (SSI), one by the Extreme Ultraviolet Spectrometer (EUV), and the continuation of the Fields and Particles low resolution survey of the Jovian magnetosphere.

Playback of the data stored on the spacecraft's onboard tape recorder during the last few days is initiated today at 4:30 pm PST-SCET (5:05 pm PST-ERT, see Note 1). The next few days see the return of observations performed by the Near-Infrared Mapping Spectrometer (NIMS) and Fields and Particles Instruments. Data return is interrupted once. On Sunday morning, the spacecraft performs a standard gyroscope performance test.

Friday's SSI observation captures Amalthea, one of Jupiter's minor moons. The observation will provide the best resolution ever of the moon at 3.7 kilometers (2.3 miles) per picture element. Later in the day, the Extreme Ultraviolet Spectrometer (EUV) obtains data by looking at the Io torus. The Io torus is a doughnut-shaped region with its inner edge bounded by Io's orbit. It is a region of intense plasma and radiation activity, in which there are strong magnetic and electric fields. Similar observations have been performed during Galileo's previous encounters, and the data set will allow scientists to examine long term variations in the torus' size and shape, with the goal of understanding energy transfer between the torus and the overal Jovian magnetosphere.

NIMS returns the first observation on the playback schedule. The observation was designed to capture information on surface properties near a hot spot called Tiermes. The remaining observation on this week's is the first portion of a 49 minute recording by the Fields and Particles instruments made as the spacecraft flew closest to Io. The recording contains measurements describing the plasma, dust, and electric and magnetic fields surrounding Io. The primary purpose of this observation is to determine if Io possesses its own internally-generated magnetic field, similar to both the Earth and to another Galilean satellite, Ganymede.

Come back on Monday, November 29, for the return of This Week on Galileo.

Note 1. Pacific Standard Time (PST) is 8 hours behind Greenwich Meridian Time (GMT). The time when an event occurs at the spacecraft is known as Spacecraft Event Time (SCET). The time at which radio signals reach Earth indicating that an event has occured is known as Earth Received Time (ERT). Currently, it takes Galileo's radio signals 35 minutes to travel between the spacecraft and Earth.

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