Editing Galileo project (section)

==Voyage to Jupiter==
=== Comet Shoemaker–Levy 9 ===
{{main|Comet Shoemaker–Levy 9}}
[[File:SL9ImpactGalileo.jpg|thumb|right|Four images of Jupiter and [[Comet Shoemaker–Levy 9]] in visible light taken by ''Galileo'' at {{frac|2|1|3}}-second intervals from a distance of {{convert|238|e6km|e6mi|sp=us|abbr=off}} |alt=refer to caption]]
''Galileo''{{'s}} prime mission was a two-year study of the Jovian system, but on March 26, 1993, while it was en route, astronomers [[Carolyn S. Shoemaker]], [[Eugene Merle Shoemaker|Eugene M. Shoemaker]] and [[David H. Levy]] discovered fragments of a comet orbiting Jupiter, the remains of a comet that had passed within Jupiter's [[Roche limit]] and had been torn apart by [[tidal force]]s. It was named [[Comet Shoemaker–Levy 9]]. Calculations indicated that it would crash into the planet sometime between July 16 and 24, 1994. Although ''Galileo'' was still {{convert|238|e6km|sp=us|abbr=off}} away, Jupiter was 66 pixels wide in its camera, and it was perfectly positioned to observe this event. Terrestrial telescopes had to wait to see the [[impact event]] sites as they rotated into view because it would occur on Jupiter's night side.{{sfn|Meltzer|2007|pp=188–189}}{{sfn|Harland|2000|p=80}}

Instead of burning up in Jupiter's atmosphere as expected, the first of the 21 comet fragments struck the planet at around {{convert|320000|km/h|sp=us}} and exploded with a fireball {{convert|3000|km|sp=us}} high, easily discernible to Earth-based telescopes even though it was on the night side of the planet. The impact left a series of dark scars on the planet, some two or three times as large as the Earth, that persisted for weeks. When ''Galileo'' observed an impact in ultraviolet light, the fireballs lasted for about ten seconds, but in the infrared they persisted for 90 seconds or more. When a fragment hit the planet, it increased Jupiter's overall brightness by about 20 percent. The NIMS observed one fragment create a fireball {{convert|7|km|sp=us}} in diameter that burned with a temperature of {{convert|8000|K|C F|sigfig=2}}, which was hotter than the surface of the Sun.{{sfn|Meltzer|2007|pp=190–191}}{{sfn|Harland|2000|pp=82–83}}

===Probe deployment===
The ''Galileo'' probe separated from the orbiter at 03:07&nbsp;UTC on July 13, 1995,<ref name="galileo-arrival" /> five months before its rendezvous with the planet on December 7.{{sfn|D'Amario|Bright|Wolf|1992|p=24}} At this point, the spacecraft was {{convert|83|e6km|e6mi|sp=us|abbr=off}} from Jupiter, but {{convert|664|e6km|e6mi|sp=us}} from Earth, and telemetry from the spacecraft, transmitted at the [[speed of light]], took 37 minutes to reach JPL. A tiny frequency change in the radio signal indicated that the separation had been accomplished. The ''Galileo'' orbiter was still on a collision course with Jupiter. Previously, course corrections had been made using the twelve {{convert|10|N|adj=on}} thrusters, but with the probe on its way, the ''Galileo'' orbiter could now fire its {{convert|400|N|adj=on}} [[Messerschmitt-Bölkow-Blohm]] main engine which had been covered by the probe until then. At 07:38 UTC on July 27, it was fired for the first time to place the ''Galileo'' orbiter on course to enter orbit around Jupiter, whence it would act as a communications relay for the ''Galileo'' probe. The ''Galileo'' probe's project manager, Marcie Smith at the [[Ames Research Center]], was confident that the LGAs could be used as relays. The burn lasted for five minutes and eight seconds, and changed the velocity of the ''Galileo'' orbiter by {{convert|61.9|m/s|sp=us}}.<ref>{{cite press release |title=Critical Engine Firing Successful for Jupiter-Bound Galileo |publisher=NASA/Jet Propulsion Laboratory |url=https://www.jpl.nasa.gov/news/critical-engine-firing-successful-for-jupiter-bound-galileo/ |access-date=19 January 2021 |archive-date=February 1, 2021 |archive-url=https://web.archive.org/web/20210201000728/https://www.jpl.nasa.gov/news/critical-engine-firing-successful-for-jupiter-bound-galileo/ |url-status=live }}</ref>{{sfn|Meltzer|2007|pp=194–195}}

===Dust storms===
In August 1995, the ''Galileo'' orbiter encountered a severe dust storm {{convert|63|e6km|e6mi|sp=us}} from Jupiter that took several months to traverse. Normally the spacecraft's dust detector picked up a dust particle every three days; now it detected up to 20,000 particles a day. Interplanetary dust storms had previously been encountered by the ''[[Ulysses (spacecraft)|Ulysses]]'' probe, which had passed by Jupiter three years before on its mission to study the Sun's polar regions, but those encountered by ''Galileo'' were more intense. The dust particles were 5 to 10&nbsp;nm in size, about the same as those in cigarette smoke, and had speeds ranging from {{convert|90,000|to|450,000|mi/h|km/h|order=flip|sp=us}} depending on their size. The existence of the dust storms had come as a complete surprise to scientists when ''Ulysses'' encountered them. While data from both ''Ulysses'' and ''Galileo'' hinted that they originated somewhere in the Jovian system, it was a mystery how they had been created and how they had escaped from Jupiter's strong [[gravitational field|gravitational]] and [[electromagnetic field]]s.<ref>{{cite press release |title=Galileo Flying Through Intense Dust Storm |publisher=NASA/Jet Propulsion Laboratory |first1=Douglas |last1=Isbel |first2=James H. |last2=Wilson |id=95-147 |url=https://www.jpl.nasa.gov/news/galileo-flying-through-intense-dust-storm-on-way-to-jupiter |access-date=15 April 2024}}</ref>{{sfn|Meltzer|2007|pp=195–196}}{{sfn|Graps|Grün|Svedhem|Krüger|2000|p=49}}

===Tape recorder anomaly===
The failure of ''Galileo''{{'s}} high-gain antenna meant that data storage to the tape recorder for later compression and playback was crucial in order to obtain any substantial information from the flybys of Jupiter and its moons. The four-track, 114-[[megabyte]] digital tape recorder was manufactured by [[Iteris|Odetics Corporation]].<ref>{{cite web |url=http://www2.jpl.nasa.gov/galileo/faqtape.html |archive-url=https://web.archive.org/web/20090403160253/http://www2.jpl.nasa.gov/galileo/faqtape.html |archive-date=April 3, 2009 |title=''Galileo'' FAQ – Tape Recorder |publisher=NASA/Jet Propulsion Laboratory |url-status=dead |access-date=May 15, 2011}}</ref> On October 11, it was stuck in rewind mode for 15 hours before engineers learned what had happened and were able to send commands to shut it off. Although the recorder itself was still in working order, the malfunction had possibly damaged a length of tape at the end of the reel. This section of tape was declared "off limits" to any future data recording, and was covered with 25 more turns of tape to secure the section and reduce any further stresses, which could tear it. Because it happened only weeks before ''Galileo'' entered orbit around Jupiter, the anomaly prompted engineers to sacrifice data acquisition of almost all of the [[Io (moon)|Io]] and [[Europa (moon)|Europa]] observations during the orbit insertion phase in order to focus on recording data sent from the atmospheric probe during its descent.<ref>{{cite press release |url=https://www.jpl.nasa.gov/news/galileo-on-track-after-tape-recorder-recovery/ |title=Galileo on Track After Tape Recorder Recovery |publisher=NASA/Jet Propulsion Laboratory |date=October 26, 1995 |access-date=January 19, 2021 |archive-date=November 30, 2021 |archive-url=https://web.archive.org/web/20211130055714/https://www.jpl.nasa.gov/news/galileo-on-track-after-tape-recorder-recovery |url-status=live }}</ref>