Galileo's first flyby of Ganymede on 27 June was the first of the satellite flybys to have all the instruments taking observations. (During the Io flyby in December 1995, no images were taken to ensure that all the probe data were captured.) During this encounter, the Energetic Particles Detector (EPD) went into a safe mode and did not make any observations close to Ganymede. In addition, following the flyby, the Near Infrared Mapping Spectrometer (NIMS) experienced some difficulties in playing back some of its data. Both problems have been fixed by ground engineers and are not expected to reoccur.
At the same time the NIMS experienced its anomalous behaviour, the Photopolarimeter-Radiometer (PPR) experienced a problem with its filter wheel, which engineers discovered after the encounter had become stuck. Attempts to free the stuck filter wheel will not occur until after the Ganymede 2 encounter, therefore no observations will be made with the PPR during that encounter.
The flyby of Ganymede made by Galileo was the first of several close encounters of the Galilean satellites and the second closest flyby Galileo will make to Ganymede. The distance Galileo came to Ganymede during this flyby was about 835 km altitude above the satellite (or about 1.3 Ganymede radii from Ganymede's center), some 17 times closer than Voyager 2. Some tentative science results from some of the instruments are available in a JPL press release dated 10 July 1996.
The following timeline is a list of different events which occurred beginning with the official start of the Ganymede encounter and proceding until the last data from the encounter were played back. The times are given in Universal Time (UTC) of the event at the spacecraft.
Date/Time Instrument Event
________ __________ _____
23 June 16:00 Start of Ganymede encounter
16:02 F&P Real-time survey (Ganymede-1)
24 June 02:54 UVS Jupiter auroral map, Io footprint
18:30 Orbital Trim Maneuver (OTM) 6
25 June 17:36 SSI First Io monitoring observation (See NSSDCA Photo Gallery.)
26 June 08:45 SSI Ganymede Global color image
12:40 NIMS Callisto Global composition map
20:29 RS Ganymede gravity field measurement
21:23 UVS Io torus observation
21:30 NIMS/UVS Ganymede global surface map
27 June 03:24 PPR Ganymede dayside thermal map
04:18 SSI First Great Red Spot (GRS) observation (See NSSDCA Photo Gallery.)
06:07 F&P Ganymede wake crossing recording
06:08 SSI Mosaic of Uruk Sulcus (Ganymede) (See NSSDCA Photo Gallery.)
06:09 SSI Mosaic of Galileo Regio (Ganymede) (See NSSDCA Photo Gallery.)
06:29 Ganymede closest approach (3,480 km)
13:13 Callisto closest approach (1,040,000 km)
28 June 00:01 NIMS Europa north high-latitude observation (See NSSDCA Photo Gallery.)
00:31 Jupiter closest approach (789,000 km)
01:22 Europa closest approach (156,000 km)
01:43 NIMS/SSI Europa global observation
18:22 PPR Io full disk map (See NSSDCA Photo Gallery.)
18:28 Io closest approach (697,000 km)
22:30 Science turn (high-phase Io, Jupiter)
29 June 03:37 PPR
03:46 SSI
06:38 Science turn (high-phase Io, Jupiter)
11:32 NIMS Last Io monitoring observation
14:45 NIMS Last GRS observation
30 June 02:00 F&P Plasma sheet crossing recording
04:30 Start of data playback (Ganymede-1)
07:42 Orbital Trim Maneuver (OTM) 7
01 July 00:45 Turn to return to Earth point
03 July 00:00 F&P End of real-time survey (Ganymede-1)
05 Aug 08:00 Orbital Trim Maneuver (OTM) 8
10 Aug 01:49 Ganymede OPNAV (for Ganymede-2)
15 Aug 00:00 F&P Start of first magnetosphere mini-tour
19 Aug 01:49 Turn for attitude maintenance
27 Aug 06:36 EUV/UVS First Io torus observation (Ganymede-2)
17:30 Orbital Trim Maneuver (OTM) 8
01 Sep 16:00 End of data playback (Ganymede-1)
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