Editing Galileo project (section)

===Reconsideration===
On January 28, 1986, {{OV|Challenger|full=nolink}} lifted off on the [[STS-51-L]] mission. A failure of the solid rocket booster 73 seconds into flight tore the spacecraft apart, resulting in the deaths of all seven crew members.{{sfn|Meltzer|2007|pp=72–77}} The [[Space Shuttle Challenger disaster|Space Shuttle ''Challenger'' disaster]] was America's worst space disaster up to that time.{{sfn|Dawson|Bowles|2004|pp=206–207}} The immediate impact on the ''Galileo'' project was that the May launch date could not be met because the Space Shuttles were grounded while the cause of the disaster was investigated. When they did fly again, ''Galileo'' would have to compete with high-priority [[United States Department of Defense|Department of Defense]] launches, the [[tracking and data relay satellite]] system, and the Hubble Space Telescope. By April 1986, it was expected that the Space Shuttles would not fly again before July 1987 at the earliest, and ''Galileo'' could not be launched before December 1987.{{sfn|Meltzer|2007|p=78}}

[[File:Animation of Galileo trajectory.gif|thumb|right|Animation of ''Galileo''{{'s}} trajectory from October 19, 1989, to September 30, 2003 <br/>{{legend2|magenta|''Galileo''}}{{·}}{{legend2|lime|
[[Jupiter]]}}{{·}}{{legend2|royalblue|[[Earth]]}}{{·}}{{legend2|PaleGreen|[[Venus]]}}{{·}}{{legend2|Gold|[[951 Gaspra]]}}{{·}}{{legend2|Cyan|[[243 Ida]]}} |alt=Depicts slingshot maneuvers around Venus and Earth.]]
The [[Rogers Commission]] into the ''Challenger'' disaster handed down its report on June 6, 1986.{{sfn|Meltzer|2007|p=78}} It was critical of NASA's safety protocols and risk management.{{sfn|Rogers|1986|pp=160–162}} In particular, it noted the hazards of a Centaur-G stage.{{sfn|Meltzer|2007|pp=176–177}} On June 19, 1986, NASA Administrator [[James C. Fletcher]] canceled the Shuttle-Centaur project.{{sfn|Meltzer|2007|p=79}} This was only partly due to the NASA management's increased aversion to risk in the wake of the ''Challenger'' disaster; NASA management also considered the money and manpower required to get the Space Shuttle flying again, and decided that there were insufficient resources to resolve lingering issues with Shuttle-Centaur as well.{{sfn|Dawson|Bowles|2004|pp=216–218}} The changes to the Space Shuttle proved more extensive than anticipated, and in April 1987, JPL was informed that ''Galileo'' could not be launched before October 1989.{{sfn|Meltzer|2007|p=93}} The ''Galileo'' spacecraft was shipped back to JPL.{{sfn|Meltzer|2007|p=177}}

Without Centaur, it looked like there was no means of getting ''Galileo'' to Jupiter. For a time, ''[[Los Angeles Times]]'' science reporter [[Usha Lee McFarling]] noted, "it looked like ''Galileo''{{'}}s only trip would be to the [[Smithsonian Institution]]."<ref name="McFarling">{{cite news |first=Usha Lee |last=McFarling |author-link=Usha Lee McFarling |date=September 22, 2003 |title=Stalwart Galileo Is Vaporized Near Jupiter |newspaper=[[Los Angeles Times]] |url=https://www.latimes.com/archives/la-xpm-2003-sep-22-me-galileo22-story.html |access-date=May 19, 2024 |archive-date=May 19, 2024 |archive-url=https://web.archive.org/web/20240519195233/https://www.latimes.com/archives/la-xpm-2003-sep-22-me-galileo22-story.html |url-status=live }}</ref> The cost of keeping it ready to fly in space was reckoned at $40 to $50 million per year (equivalent to ${{Inflation|US-GDP|40|1986}} to ${{Inflation|US-GDP|50|1986}} million in {{Inflation/year|US-GDP}}), and the estimated cost of the whole project had blown out to $1.4 billion (equivalent to ${{Inflation|US-GDP|1.4|1986}} billion in {{Inflation/year|US-GDP}}).<ref>{{cite web |title=NASA's Galileo mission clears hurdles for Jupiter voyage. In flying past Venus, probe could learn much about 'greenhouse effect' |newspaper=Christian Science Monitor |date=December 3, 1987 |first=Peter N. |last=Spotts |url=https://www.csmonitor.com/1987/1203/agal.html |access-date=November 7, 2020 |archive-date=December 7, 2021 |archive-url=https://web.archive.org/web/20211207041458/https://www.csmonitor.com/1987/1203/agal.html |url-status=live }}</ref>

At JPL, the ''Galileo'' Mission Design Manager and Navigation Team Chief, Robert Mitchell, assembled a team that consisted of Dennis Byrnes, Louis D'Amario, Roger Diehl and himself, to see if they could find a trajectory that would get ''Galileo'' to Jupiter using only a two-stage IUS. Roger Diehl came up with the idea of using a series of gravity assists to provide the additional velocity required to reach Jupiter. This would require ''Galileo'' to fly past Venus, and then past Earth twice. This was referred to as the Venus-Earth-Earth Gravity Assist (VEEGA) trajectory.{{sfn|Meltzer|2007|pp=293–294}}

[[File:Galileo probe deployed (large).jpg|thumb|left|''Galileo'' is prepared for release from {{OV|Atlantis}}. The [[Inertial Upper Stage]] (white) is attached.|alt=refer to caption]]
The reason no one had considered the VEEGA trajectory before was that the second encounter with Earth would not give the spacecraft any extra energy. Diehl realised that this was not necessary; the second encounter would merely change its direction to put it on a course for Jupiter.{{sfn|Meltzer|2007|pp=293–294}} In addition to increasing the flight time, the VEEGA trajectory had another drawback from the point of view of [[NASA Deep Space Network]] (DSN): ''Galileo'' would arrive at Jupiter when it was at the maximum range from Earth, and maximum range meant minimum signal strength. It would have a [[declination]] of 23 degrees south instead of 18 degrees north, so the tracking station would be the [[Canberra Deep Space Communication Complex]] in Australia, with its two 34-meter and one 70-meter antennae. A northerly declination could have been supported by two sites, at [[Goldstone Deep Space Communications Complex|Goldstone]] and [[Madrid Deep Space Communications Complex|Madrid]]. The Canberra antennae were supplemented by the 64-meter antenna at the [[Parkes Observatory]].{{sfn|Mudgway|2001|p=301}}{{sfn|Taylor|Cheung|Seo|2002|p=23}}

Initially it was thought that the VEEGA trajectory demanded a November launch, but D'Amario and Byrnes calculated that a mid-course correction between Venus and Earth would permit an October launch as well.{{sfn|Meltzer|2007|p=157}} Taking such a roundabout route meant that ''Galileo'' would require sixty months to reach Jupiter instead of just thirty, but it would get there.<ref name="McFarling" /> Consideration was given to using the USAF's [[Titan IV]] launch system with its Centaur G Prime upper stage.{{sfn|Dawson|Bowles|2004|p=215}} This was retained as a backup for a time, but in November 1988 the USAF informed NASA that it could not provide a Titan IV in time for the May 1991 launch opportunity, owing to the backlog of high priority Department of Defense missions.{{sfn|Office of Space Science and Applications|1989|p=2{{hyphen}}19}} However, the USAF supplied IUS-19, which had originally been earmarked for a Department of Defense mission, for use by the ''Galileo'' mission.{{sfn|Bangsund|Knutson|1988|p=10{{hyphen}}12}}