An artist's concept of NASA's Galileo spacecraft in orbit around Jupiter. Photo: NASA/JPL

With two weeks to go before the next flyby, activities on the spacecraft are relatively quiet, while activities on the ground are heating up. The flight team of scientists and engineers are busy putting the final touches on the series of commands that will govern Galileo as it skims past Io on August 5. On Friday, the spacecraft performs routine maintenance on the propulsion system.

The Extreme Ultraviolet Spectrometer (EUV) is continuing its two-month-long study of interplanetary hydrogen gas. This activity will conclude just before the start of encounter operations.

During the past two weeks, the Dust Detector instrument (DDS) has seen a dramatic increase in the number of dust impacts that it measures. During this cruise period the normal interval between data read-outs from the DDS instrument is 20 days. The spacecraft team has sent commands to read out DDS data approximately once every three days during this period of high activity, which is expected to last one more week.

Playback of the data recorded during Galileo's May flyby of Callisto is nearly 60% complete. This week, playback data are expected from the Solid State Imaging camera (SSI), the Near Infrared Mapping spectrometer (NIMS), and the suite of Fields and Particles instruments that measure the magnetic field environment of Jupiter. These instruments are the Energetic Particle Detector (EPD), Heavy Ion Counter (HIC), Magnetometer (MAG), Plasma instrument (PLS), and Plasma Wave Subsystem (PWS).

The SSI data are from Callisto global color images and stereo images taken near closest approach. For the most part, these are samples of the frames, and the imaging team will use these samples to determine the best choice of processing and compression parameters to use on the next pass through the data.

NIMS data return includes global color observations of Io, observations of a hot spot in Jupiter's atmosphere and of an area in the wake of the Great Red Spot, and an observation of the Asgard impact basin region on Callisto. In addition, earlier data sampled from the NIMS Io eclipse observation revealed new, high-temperature volcanic activity at a location in high southern latitudes where no volcanic activity had been detected before. NIMS is replaying about 1 minute of data from this observation with a greater data density (larger number of spectral samples) in order to better resolve both the location and the temperature of the new eruption.

The Fields and Particles playback data were taken at the closest approach to Callisto.