Editing Galileo project (section)

===Initiation===
Following the approval of the ''[[Voyager program|Voyager]]'' missions, NASA's Scientific Advisory Group for Outer Solar System Missions considered the requirements for Jupiter orbiters and atmospheric probes. It noted that the technology to build a [[heat shield]] for an atmospheric probe did not yet exist, and indeed facilities to test one under the conditions found on Jupiter would not be available until 1980. There was also concern about the effects of radiation on spacecraft components, which would be better understood after ''Pioneer 10'' and ''Pioneer 11'' had conducted their flybys. ''Pioneer 10''{{'}}s flyby in December 1973 indicated that the effects were not as severe as had been feared.{{sfn|Meltzer|2007|pp=29–30}} NASA management designated JPL as the lead center for the Jupiter Orbiter Probe (JOP) Project.{{sfn|Meltzer|2007|pp=32–33}} [[John R. Casani]], who had headed the ''[[Mariner program|Mariner]]'' and ''Voyager'' projects, became the first project manager.<ref>{{cite web |publisher=NASA |title=NASA's 50 Year Men and Women |url=https://www.nasa.gov/50th/50th_magazine/50yearsEmployees.html |access-date=October 28, 2020 |archive-date=March 19, 2010 |archive-url=https://web.archive.org/web/20100319002842/https://www.nasa.gov/50th/50th_magazine/50yearsEmployees.html |url-status=dead }}</ref> The JOP would be the fifth spacecraft to visit Jupiter, but the first to orbit it, and the probe the first to enter its atmosphere.{{sfn|Dawson|Bowles|2004|pp=190–191}}

Ames and JPL decided to use a ''Mariner'' spacecraft for the Jupiter orbiter like the ones used for ''Voyager'' rather than a ''Pioneer'' spacecraft. ''Pioneer'' was stabilized by spinning the spacecraft at 60 [[rpm]], which gave a 360-degree view of the surroundings, and did not require an [[attitude control system]]. By contrast, ''Mariner'' had an attitude control system with three [[gyroscopes]] and two sets of six [[nitrogen]] jet thrusters. Attitude was determined with reference to the Sun and [[Canopus]], which were monitored with two primary and four secondary [[star tracker]] sensors. There was also an [[inertial reference unit]] and an [[accelerometer]]. The attitude control system allowed the spacecraft to take high-resolution images, but the functionality came at the cost of increased weight: a ''Mariner'' weighed {{convert|722|kg}} compared to just {{convert|146|kg}} for a ''Pioneer''.{{sfn|Meltzer|2007|pp=30–32}}

The increase in weight had implications. The Voyager spacecraft had been launched by [[Titan IIIE]] rockets with a ''[[Centaur (rocket stage)|Centaur]]'' upper stage, but Titan was retired afterwards. In the late 1970s, NASA was focused on the development of the reusable [[Space Shuttle]], which was expected to make expendable rockets obsolete.<ref>{{cite news |newspaper=[[The New York Times]] |title=Test Rocket for Planetary Exploration Rolled Out |first=John Noble |last=Wilford |author-link=John Noble Wilford |date=3 October 1973 |url=https://www.nytimes.com/1973/10/03/archives/test-rocket-for-planetary-exploration-rolled-out-forthcoming.html |access-date=8 October 2020 |archive-date=August 10, 2020 |archive-url=https://web.archive.org/web/20200810122304/https://www.nytimes.com/1973/10/03/archives/test-rocket-for-planetary-exploration-rolled-out-forthcoming.html |url-status=live }}</ref> In late 1975, NASA decreed that all future planetary missions would be launched by the Space Shuttle. The JOP would be the first to do so.{{sfn|Mudgway|2001|p=294}} The Space Shuttle was supposed to have the services of a [[space tug]] to launch payloads requiring something more than a [[low Earth orbit]], but this was never approved. The [[United States Air Force]] (USAF) instead developed the [[solid-fueled]] Interim Upper Stage (IUS), later renamed the [[Inertial Upper Stage]] (with the same acronym), for the purpose.{{sfn|Meltzer|2007|pp=32–33}}

The IUS was constructed in a modular fashion, with two stages, a large one with {{convert|21400|lb|order=flip}} of propellant, and a smaller one with {{convert|6000|lb|order=flip}}. This was sufficient for most satellites. It could also be configured with two large stages to launch multiple satellites.{{sfn|Heppenheimer|2002|pp=330–335}} A configuration with three stages, two large and one small, would be enough for a planetary mission, so NASA contracted with [[Boeing]] for the development of a three-stage IUS.{{sfn|Heppenheimer|2002|pp=368–370}} A two-stage IUS was not powerful enough to launch a payload to Jupiter without resorting to using a series of [[gravity-assist]] maneuvers around planets to garner additional speed. Most engineers regarded this solution as inelegant and planetary scientists at JPL disliked it because it meant that the mission would take months or even years longer to reach Jupiter.{{sfn|Bowles|2002|p=420}}{{sfn|Heppenheimer|2002|pp=368–370}} Longer travel times meant that the spacecraft's components would age and possibly fail, and the onboard power supply and propellant would be depleted. Some of the gravity assist options also involved flying closer to the Sun, which would induce thermal stresses that also might cause failures.{{sfn|Meltzer|2007|p=82}}

It was estimated that the JOP would cost $634 million (equivalent to ${{Inflation|US-GDP|0.634|1979|r=3}} billion in {{Inflation/year|US-GDP}}), and it had to compete for [[fiscal year]] 1978 funding with the Space Shuttle and the [[Hubble Space Telescope]]. A successful lobbying campaign secured funding for both JOP and Hubble over the objections of [[United States Senate|Senator]] [[William Proxmire]], the chairman of the Independent Agencies Appropriations Subcommittee.{{sfn|Meltzer|2007|p=38}} The [[United States Congress]] approved funding for the Jupiter Orbiter Probe on July 19, 1977,<ref>{{cite web |title=Congressional Record |publisher=United States Congress |url=https://www.congress.gov/95/crecb/1977/07/19/GPO-CRECB-1977-pt19-3-1.pdf |access-date=11 July 2024}}</ref> and JOP officially commenced on October 1, 1977, the start of the fiscal year.{{sfn|Meltzer|2007|pp=33–36}} Project manager Casani solicited suggestions for a more inspirational name for the project from people associated with it. The most votes went to "Galileo", after [[Galileo Galilei]], the first person to view Jupiter through a telescope, and the discoverer of what are now known as the [[Galilean moons]] in 1610. It was noted at the time that the name was also that of a [[Galileo (Star Trek)|spacecraft]] in the ''[[Star Trek: The Original Series|Star Trek]]'' television show. In February 1978, Casani officially announced the choice of the name "Galileo".{{sfn|Meltzer|2007|p=38}}