When the Galileo spacecraft drifted out of Atlantis’ payload bay on the evening of 18 October 1989, on the first leg of its six-year voyage to Jupiter, the sight was a moving one for Shannon Lucid. As STS-34’s lead mission specialist, she was primarily responsible for the deployment of one of the most important payloads ever launched by NASA. For almost a dozen years, Lucid had lived and worked with the reality that her job was an overwhelmingly technical one, drawing from its roots in engineering and pure science…but as Galileo and its IUS booster floated silently into the inky void, she beheld a new reality: the romance of adventure. Emblazoned across the base of the spacecraft which would one day circle Jupiter and deposit an instrumented probe into its atmosphere were two names: ‘Galileo’ in script and ‘NASA’ in worm-like block capitals. To Lucid, those two words symbolised exactly what the mission stood for: the script represented the romance of adventure and exploration, whilst the worm was indicative of the outstanding engineering and scientific talent which had brought this awesome project from the drawing board to fruition.
Yet Galileo’s journey to the launch pad had been a long and tortured one and its voyage to Jupiter would be longer and harder still. The mission traced its genesis back to the mid-1970s. Named in honour of the Italian scientist, Galileo Galilei, whose endeavours in the early 17th century included the discovery of Jupiter’s four large moons, Ganymede, Callisto, Europa and Io. Originally known as ‘Jupiter Orbiter and Probe’ (JOP), the name ‘Galileo’ seemed an obvious one and the project received Congressional approval on the first day of October 1977, with a planned launch four years later. However, delays to the first flight of the Shuttle and the limited capability of Boeing’s Inertial Upper Stage (IUS) to boost Galileo on its way to Jupiter raised concerns. In 1979, Washington Post journalist Thomas O’Toole highlighted that problems with certifying the Shuttle’s main engines to operate at the 109-percent performance level needed to lift Galileo posed additional obstacles. By now, the launch had slipped until 1982 at the earliest. O’Toole noted that if the 109-percent-capable engines were not ready for this date, Galileo could slip even further. Timing was critical, since a 1982 launch depended upon a Mars gravity assist and if it was delayed much further, the potential existed to halve the scientific mission at Jupiter, from 11 to only five orbits of the giant planet.
At length, in late 1980, under pressure from Representative Edward Boland, a Democrat from Massachusetts, NASA was obliged to abandon the IUS plan and initiate planning for a launch on General Dynamics’ liquid-propelled Centaur-G Prime, which Administrator Robert Frosch had earlier opposed. The situation for Galileo’s future dimmed substantially for much of 1981, with Congressional mutterings of closing down the California Institute of Technology’s Jet Propulsion Laboratory, which managed many of NASA’s planetary projects. A massive letter-writing campaign to George Keyworth, head of the White House’s Office of Science and Technology Policy, was spearheaded by Galileo investigator and famed physicist James van Allen. In a speech to the National Academy of Sciences, van Allen identified Galileo as one of the most exciting missions of exploration ever undertaken and that its cancellation would prove devastating. Thankfully, in December 1981 the Office of Management and Budget relented, reinstated Galileo and it was rescheduled for 1983. There was a caveat, however: Galileo would not use the powerful Centaur-G Prime. In January 1982, NASA rescoped the mission, returned to the less powerful IUS fitted with a third, ‘injection stage’ to provide increased propulsion. As a consequence, Galileo’s launch was rescheduled for August 1985, but the absence of the powerful Centaur meant that it would take five years, instead of two, and the spacecraft would be injected into a two-year-long elliptical solar orbit, would require a gravity assisted boost from Earth in June 1987 and would finally reach Jupiter in January 1990.
By the summer of 1982, some members of Congress – led by New Mexico Senator Harrison ‘Jack’ Schmitt, a former Moonwalker and chair of the Senate Space Subcommittee of the Science, Commerce and Transportation Committee – were pushing vigorously for a return to the Centaur and a reduced journey time. Despite worries about additional expense in changing boosters again, coupled with concerns about further delays to the mission, in July President Reagan approved the move and NASA was forced to replan. The Centaur would be used to boost Galileo, but launch would be unavoidably postponed until May 1986, with a two-year flight time to the giant planet. At this stage, the mission truly entered the phase of equipment testing. In the early summer of 1983, the parachute for the instrumented probe, which would descend into Jupiter’s atmosphere, successfully passed full-scale tests, and by September of that year the main spacecraft and probe were integrated. A model of the Centaur passed its own tests in September 1984 and the actual flight model was rolled out of General Dynamics’ plant in San Diego in August of the following year.
By this time, NASA Administrator Jim Beggs had endorsed other possible tasks for Galileo, most notably a flyby of the asteroid Amphitrite, which it was hoped might unlock secrets of the primordial solar nebula from which the Sun and planets formed. An Amphitrite flyby would delay the Jupiter arrival from August to December 1988, however, and it was decided to make a final decision after launch. In December 1985, only weeks before the loss of Challenger, Galileo was transported, cross-country by truck, guarded by police, state troopers and other guards, and arrived safely at the Kennedy Space Center for launch the following May.
When Challenger exploded in the skies above Florida, Galileo was undergoing final checkout and preparation for attachment to its Centaur-G Prime. In the weeks after the accident, NASA Acting Administrator William Graham spoke of the possibility of a return to flight in the spring of 1987, which kept alive the option to launch Galileo in the next Jovian ‘window’ in June of that year. Eventually, the modifications to the SRBs and the orbiters themselves inevitably pushed the return to flight further to the right. On 19 June 1986, newly-reappointed NASA Administrator Jim Fletcher formally cancelled Centaur-G Prime and new options had to be found. One of these was an ‘enlargement’ of the IUS, possibly coupled with an additional booster, such as a Special Payload Assist Module (PAM-S).
However, as already noted, the IUS was insufficient to send Galileo directly to Jupiter and alternate trajectories, involving planetary gravity assists, were explored. Even before NASA settled on October-November 1989 as the most appropriate ‘window’ for Jupiter, Galileo’s planners were already working towards this date, creating a complex flight profile, known as the Venus-Earth-Earth Gravity Assist (VEEGA), in which the spacecraft would perform a flyby of Venus in February 1990, return to Earth in December and be placed into a two-year elliptical solar orbit. Returning a second time to Earth in December 1992, it would pick up sufficient energy to reach Jupiter in December 1995. The VEEGA technique was highly conservative and efficient of Galileo’s on-board propellant.
The trajectory also permitted possible rendezvous with up to three asteroids – Ausonia, Gaspra and Ida – and eventually the latter two were selected. However, since the spacecraft would fly much closer to the Sun than had been planned, additional thermal shielding was added in the three-year down time after Challenger. It is unsurprising that Galileo also ‘leapfrogged’ Ulysses in the launch pecking order. “NASA based its decision on optimising data return from the two missions,” wrote Michael Meltzer in Mission to Jupiter. “Launching Ulysses first would have resulted in too long a wait before Galileo reached Jupiter and began transmitting prime data from the Jovian system.”
As launch neared, with an opening of the Jupiter window at 1:29 pm EST on 12 October 1989, there were still last-minute concerns about Galileo…although these were not focused upon its mission, but upon its power system. Since the spacecraft would be travelling more than half a billion kilometres further from the Sun than Earth, the use of solar cells for electrical provision was impractical. Therefore, General Electric supplied a pair of Radioisotope Thermoelectric Generators (RTGs), fuelled by fracture-resistant ‘pellets’ of plutonium-238, whose decay produced heat which was in turn converted into electricity. To keep them at a safe distance from the sensitive scientific instruments, the RTGs were mounted on a boom, which extended them 15 feet away from the main body of the spacecraft. Both produced 570 watts of electricity at launch, which steadily decreased by around half a watt per month and reached around 493 watts by the time Galileo reached Jupiter. Atlantis also required modification to incorporate an RTG coolant line and purging system in her payload bay.
In the late 1980s, of course, ‘nuclear’ was a dirty word; a word which conjured images of military superpowers, the faceless Department of Defense and greedy power corporations. Peace marches were undertaken and representatives of several anti-nuclear groups gathered at the gates of the Kennedy Space Center to express their fear that a Challenger-like explosion could spread radioactive plutonium across the United States’ eastern seaboard. The allegation that NASA was playing “ecological roulette” with the lives of Floridians was not groundless. Memories of the ‘messy’ crash of the Soviet Union’s nuclear-fuelled Cosmos 954 satellite in Canada, a decade earlier, were fresh in many minds, and even the noted physicist Carl Sagan remarked that “there is nothing absurd about either side of this argument”.
Final approval to proceed with the Galileo launch came from President George H.W. Bush himself in September 1989. Three days before the scheduled launch, outraged protestors staged a mock ‘death scene’ at the Cape and even threatened to sit on Pad 39B itself to prevent Atlantis from launching into orbit. Franklin Chang-Díaz, one of the STS-34 mission specialists, was astonished by the controversy surrounding a mission which was a scientific odyssey. “It was striking to drive through the gates…and see all these demonstrators, trying to stop the launch,” he told a Smithsonian interviewer, years later. “The topic of nuclear power is going to come up over and over again as we move into space. It’s a key issue we are going to have to resolve, because the survival of people in space, far away from Earth, will totally depend on the use of nuclear power.”
The launch window for Jupiter would close on 21 November, after which the next opportunity would not arise until 1991, so there existed a very real risk that the mission might be cancelled. Security was increased at the Kennedy Space Center, as guards armed with M-16 assault rifles and 9 mm semi-automatic pistols patrolled the launch site. A faulty main engine controller put paid to the 12 October attempt and launch was rescheduled for the 17th, then the 18th when rain showers drifted within 20 miles of the Shuttle Landing Facility. During these few days, final efforts to stop the launch were rejected by the Circuit Court of Appeals in Washington, DC. In her summary, Chief Justice Patricia Wald declared that she could find no evidence that NASA had improperly compiled its environmental assessment reports for Galileo and on 16 October a number of activists were arrested at the Cape for trespassing. Launch on the 18th was postponed by about three and a half minutes in order to update Atlantis’ computers for a change in the Transoceanic Abort Landing site, which had moved from Ben Guerir in Morocco to Zaragoza in Spain, due to heavy rain at the former. At 12:53 pm EST, Atlantis and her crew of five – Don Williams, Mike McCulley, Shannon Lucid, Franklin Chang-Díaz and Ellen Baker – roared into the clear Florida skies.
Six hours into the mission, at 7:15 pm, Galileo and the IUS were tilted to their deployment position and set free. “Galileo is on its way to another world,” exulted Williams. “It’s in the hands of the best flight controllers in the world. Fly safely!” Chang-Díaz felt a very personal affinity with Galileo. To him, it was a memorable occasion, because it represented his childhood desire to leave Earth and travel to other planets. Shortly thereafter, Williams and McCulley manoeuvred Atlantis to a safe separation distance and the IUS fired to boost Galileo onto a course for Venus, which it would reach in a little over three months’ time. An hour after deployment, the IUS fired to commence Galileo’s six-year odyssey, kicking off a romantic adventure to explore a distant planet.
The spacecraft proved itself to be a remarkable example of triumph over adversity. A little more than a year into its cruise, and several months after its first flyby of Earth, its high-gain antenna only partially unfurled, threatening to ruin the mission. ‘Workaround’ techniques were devised to use the low-gain antenna in its stead and the spacecraft returned remarkable images from the asteroids Gaspra (in October 1991) and Ida (in August 1993) and, far from conducting two years of scientific exploration at Jupiter, Galileo spent almost eight years in operation. During that time, it measured the chemical composition of the giant planet’s atmosphere, directly observed its ammonia clouds and mysterious Great Red Spot, analysed the causes and effects of volcanism on Io and yielded tantalising clues for liquid oceans beneath the frozen surfaces of Europa and Ganymede and the extent of Jupiter’s gigantic magnetosphere was mapped and modelled for the first time. On its way to the planet, in July 1994, Galileo also observed the impact of Comet Shoemaker-Levy 9 into the Jovian clouds. Not until the end of 2003 was the mission finally terminated by having the spacecraft dive into the planet’s atmosphere.
Having set Galileo on its way, for all intents and purposes, the primary mission of STS-34 was over. A problem with one of Atlantis’ Auxiliary Power Units triggered an alarm which woke the crew on 22 October, and other minor glitches centred on the flash evaporator system and cryogenic oxygen manifolds. Predicted high winds at Edwards Air Force Base on the 23rd prompted a decision to bring the Shuttle home two orbits earlier than planned and Williams and McCulley brought their ship to a smooth touchdown at 6:33 am PST (12:33 pm in Florida), just 20 minutes short of five full days after launch. In hindsight, Williams regarded STS-34 as having achieved something remarkable for science. “We knew that Galileo was going to be a lasting programme,” he said. “The Galileo mission, we knew, if it was successful, the spacecraft was going to end up in orbit around Jupiter several years later and then there were going to be several years of data and images sent back. It was going to be a living, ongoing programme and we got to be a part of it.”
Tomorrow’s article will focus on STS-41, another October mission, which launched the Ulysses spacecraft on an odyssey to explore the Sun’s poles.