This Week on Galileo - September 1-7, 1997
Galileo spends the first week of September observing the Great Red Spot and returning a variety of data to Earth, ranging from the Callisto multi-ringed area Valhalla to some of Jupiter's "minor" moons to Jupiter's large magnetic "tail."
This week Galileo's standard cruise activities are interrupted by plans to turn the spacecraft and allow for a series of Great Red Spot observations. These observations are taken as a part of the Great Red Spot observation campaign of the Callisto-9 encounter. They were delayed until this part of the orbit to allow the observations to occur at high-solar phase angles, i.e. when the spacecraft is on the dark side of Jupiter and only a small part of Jupiter is lit by the sun. This geometry allows sunlight to be scattered by the high layers of Jupiter's atmosphere. The observations taken during this opportunity will permit scientists to determine the particle size distribution of Jupiter's atmosphere at high altitudes. In other words, scientists will be able to tell the size and quantity of whatever particles exist in Jupiter's upper atmosphere.
With last week's late update to the playback schedule, planners decided to increase the amount of data returned from high-resolution observations of Callisto. As a result, this week's playback schedule includes some of the same data we thought we might have seen on last week's schedule, but which ended up not being sent back to Earth last week.
The first part of this week's playback schedule, up through the pause for the Great Red Spot observations, includes observations of Callisto's multi-ringed Valhalla region taken by the Near Infrared Mapping Spectrometer (NIMS) and the Solid State Imaging (SSI) camera. A polarimetry map of Callisto is also returned by the Photopolarimeter Radiometer (PPR). Observations of the Great Red Spot and a "plume head" cloud region are returned by SSI. Images of the minor moons Metis and Adrastea are also returned by SSI. Ganymede observations are added to the schedule by NIMS which returns a global map of the satellite and an observation of a region of Ganymede's surface where the terrain color changes from dark to light.
When playback resumes after the Great Red Spot observations, the playback schedule returns to observations of Jupiter's magnetotail (the region of the planet's magnetic field that has been stretched-out by the solar wind) taken earlier in this orbit. The observation returned this week was taken by the fields and particles insturments when the spacecraft was on the inbound (moving toward Jupiter) leg of this orbit at a distance of 130 Jupiter Radii or 9.3 million kilometers (5.8 million miles) from Jupiter. Completing this week's playback schedule are observations by NIMS of the Great Red Spot and regions of Jupiter's northern and southern hemispheres.