Cassini-Huygens

It is clear that Europe cannot allow itself to be reduced to a subordinate or subsid­iary role in space ventures if it is to maintain its current hard-won position [. . .] The need for international collaboration on major space undertakings is not disputed, but Europe wishes to enter such undertakings on an “equal partnership” basis, this concept applying at all levels, including operational control.

—Reimar Lust, 198790

The new determination by ESA to be taken seriously as an international partner by the United States required a change of approach in Europe. More resources were needed for space science along with a coherent plan that could be used to win the broad support of the multidisciplinary space science community and of potentially reluctant member states. Existing procedures for selecting experi­ments were creating some resentment in the United States and also had to be revised. The Cassini-Huygens spacecraft, whose launch in October 1997 by a Titan IV-Centaur vehicle was “regarded as a miracle by some people involved in the mission,” not only promised to be of immense scientific importance, it also benefited from these institutional reforms, along with the possibility of levering the Clinton administration’s commitment to international space collaboration in the mid-1990s.91

The Cassini mission extended the avenues opened up by the data from the Voyager 1 and Voyager 2 flybys of Saturn in 1980 and 1981. The mother craft that would approach Saturn was provided by NASA, and the probe that would land on Saturn’s moon, Titan, was provided by ESA. The Italian Space Agency provided telecommunications and microwave systems. US-European cost­sharing on Cassini-Huygens was about 70 : 30. Eighteen instruments would “conduct orbital remote sensing of Saturn’s atmosphere, icy satellites and rings; in situ orbital measurements of charged particles, dust particles, and magnetic fields; and detailed measurements [would be made] with six instruments on the Huygens probe during descent though Titan’s dense, nitrogen atmosphere to the surface.”92 The probe would also make surface science measurements if it survived impact. The range of questions addressed by the mission was such as to attract broad-based support in the planetary science community.

The intricacies of the decision-making processes and funding battles that accompanied the acceptance and development of the Cassini mission on both sides of the Atlantic have been adequately described elsewhere.93 This brief account will focus on those features of the mission—be they scientific, institutional, or political—that provide insight into the international aspect of the cooperation.94

When Roger Bonnet was nominated ESA’s director of the scientific program in 1983 he was determined to place it on a stable base. He believed that ESA required a long-term science plan that was ambitious enough to demand regional collaboration, and broad enough to satisfy the diverse needs of the European space science community. It also had to be challenging enough to attract inter­national cooperation with leading space powers, notably NASA, without being vulnerable to the kinds of setback that had bedeviled ISPM. Bonnet’s solution was Horizon 2000.95

Horizon 2000 emerged after intensive and extensive consultation with the European space science community. It comprised four costly, long-term “corner­stones.” Two were in the field of solar system exploration (solar-terrestrial phys­ics and cometary science), and two were in the field of astronomy/astrophysics (X-ray spectroscopy and a far-infrared telescope). These cornerstones were to be under ESA’s leadership and to be consistent with Europe’s own technical and financial means “in order for ESA to be master of its own future and not to be dependent upon decisions taken outside its own control.”96 The cornerstones were complemented by small – and medium-sized satellites with no a priori exclu­sion of disciplines, and were to be selected one by one. This introduced the flex­ibility needed to respond to changing scientific demand and to take advantage of opportunities for international cooperation.

The broad scientific support for Horizon 2000, the lucidity of its logic, and the scope that it gave national administrations to plan their financial appropria­tions in advance had an immediate effect. Meeting in Rome in January 1985, the ESA member states agreed to increase the science budget by 5 percent annually in real terms (i. e., after adjustment for inflation) for ten years. This was the first time that the science budget had been increased for fifteen years, and it made it possible not only to rationalize coordination between ESA and national science programs, but also to coordinate the agency’s initiatives more effectively with its international partners. With more money available for space science, and with a protective wall around the major ESA-led cornerstones, Horizon 2000 enabled the European community to engage with NASA from a position of strength that combined competition with cooperation.

Another important source of friction between ESA and NASA was removed in 198 3.97 In line with the announcement at COSPAR in March 1959, NASA had a policy of allowing any interested party to respond to an Announcement of Opportunity (AO) on its space science satellites. This caused little difficulty when other programs were in their infancy. But as they matured, and more and better foreign proposals were received, some American scientists began to feel that the agency preferred payloads submitted from abroad because they were free of charge to the US, as opposed to US entities having to pay the cost of their experiments. This frustration was heightened by ESA’s restriction of its AO to proposals from

member state scientists, as required by its charter. Nor did ESA feel that it should be called upon to reciprocate each individual agreement that a member state had negotiated bilaterally with NASA without involving the European agency.

Bonnet was called upon to resolve this thorny issue as soon as he took up his new position at ESA in 198 3.98 The matter was resolved after a spirited discus­sion thanks to the previous progress made by a committee of “wise men” that ESA had set up to tackle the problem and make recommendations. To defuse the obvious ill-will that the European policy was causing it was agreed that ESA, like NASA, would open flight opportunities to foreign investigators.99

In November 1988 ESA’s Science Program Committee selected the Titan probe as the first medium-sized mission in the new Horizon 2000 paradigm, and baptized it Huygens to emphasize its European provenance. A year later the US Congress approved start-up funds for the Cassini and CRAF (Comet Rendezvous Asteroid Flyby) missions, the latter a joint venture with Germany. ESA and NASA issued separate but coordinated AOs for their respective contri­butions to Cassini. Sixteen European countries and the United States provided 18 instruments distributed over both mother craft and probe, with two-ten countries providing parts of each instrument. The overall management of the program was based at NASA Headquarters. Project managers for the Cassini mother craft and the Huygens probe established offices at the Jet Propulsion Laboratory (JPL) and at ESTEC (the European Space Research and Technology Centre), respectively. They were advised by Project Science Groups that gathered together all principal investigators, scientists, and team leaders that had instru­ments on the parts of the spacecraft that they managed. These groups served as a valuable forum “to optimize scientific return and to resolve the usual conflicts between the engineering and science sides of the mission.”100

In fall 1991 the trajectory of the joint project hit a bump that threatened to sour the good relationships that had been established between the partners. A House-Senate committee cut the budget allocation to Cassini/CRAF for 1992 by $117 million, which NASA absorbed by deciding to delay the launch of Cassini from 1995 to 1997. The chairman of ESA’s Space Science Advisory Committee, David Southwood, immediately contacted Berrien Moore, the chairman of NASA’s Space Science and Applications Advisory Committee. Southwood emphasized that the increase in the cost of the Huygens probe caused by the delay would create an “intolerable stress” on ESA’s program. It had not been easy to get the member states to agree on funding for the probe and for instrumentation for Huygens and Cassini. Their delegates had been “dragooned, cajoled and otherwise persuaded” to do so, “by emphasizing the importance of not delaying the NASA timetable.” A launch delay imposed by NASA “within a year of the selection” would increase costs by about 15 percent, and could seriously undermine the “climate of cooperation.”101 Southwood’s letter was quickly followed by one from ESA director general Jean Marie Luton to NASA administrator Richard H. Truly stressing that any delay in the launch date was “unacceptable” and would cost ESA a further $30 million.

In 1992 NASA and Germany agreed to cancel CRAF altogether. Responding to European objections, engineers at JPL in consultation with their European colleagues simplified the orbiter design to meet the domestic budget cut with­out delaying the launch. Instruments that were mounted on movable platforms that could be continuously pointed at their targets were bolted down so that the entire spacecraft had to be turned toward the target to take measurements. A separately steerable antenna intended to provide a communications link to the Huygens probe was removed, and just one antenna was used for the Cassini – Huygens link and for the Cassini-earth link. This meant that scientific data had to be stored in a buffer system until data-taking was suspended, whereupon the antenna could be turned toward the earth to transmit the stored information to ground stations. To absorb the increased operational costs of the program it was also decided to drop plans for the acquisition of scientific data in the journey through space to Saturn and its moon. While the scientific community was dis­tressed by the limitations imposed by these changes, they also realized that some “descoping” was imperative if there was going to be any mission at all.

Cassini almost suffered the axe again in preparation for the president’s budget request to Congress in January 1994, and the Congressional deliberations in the summer of that year. The threat-level was increased by the approach taken to satellite projects by a new NASA administrator collectively known as “faster, better, cheaper.” In 1992 the National Space Council, reestablished by President George H. W. Bush, engineered the removal of Richard Truly who they felt was too committed to NASA’s tradition of large and costly activities.102 He was replaced in April by Dan Goldin, then an executive of TRW who had the repu­tation of favoring small, inexpensive spacecraft. In his confirmation hearings Goldin did not suggest that “faster, better, cheaper” was necessarily the best way for NASA to operate, and he did not mention it at all in his first address to NASA employees. It was only when he got down to preparing the agency’s budget request for FY1994 that he felt that NASA had “unrealistic” expecta­tions. Goldin decided to “re-invent NASA” by miniaturizing technology and by streamlining project management. Let’s see, he said, how many satellites “we can build that weigh hundreds not thousands of pounds; that use cutting edge technology, not ten-year old technology that plays it safe; that cost tens and hundreds of millions, not billions; and take months and years, not decades, to build and arrive at their destination.” From henceforth larger spacecraft were to be the exception, not the rule for NASA projects.

Faced with pressure from the Senate to reduce the budget, Goldin cast a skep­tical eye over Cassini-Huygens in 1994. Indeed it was a prime example of the kind of mission that he wanted NASA to avoid. Howard McCurdy’s calculations of the cost and weight of the satellite and its probe from various NASA sources give one an idea of why Goldin was so concerned:

Cost Cassini. Launched 1997. Development, $1,422m; launch support, $422m; mission operations and data analysis, $755m; tracking and data support, $54m; foreign contribution, $660m; total, $3,313m (real-year dollars)

Weight Cassini. Orbiter, 4,685lbs; Huygens probe, 705lbs; launch vehicle adapter, 298lbs; propellant, 6,905lbs; total, 12,593lbs.103

Contrast the $3 billion plus for this mission that matured for fifteen years, and that needed another eight years after launch to begin taking data, with the cost and time of the satellites built by NASA respecting Goldin’s mantra. Beginning in 1992, the first sixteen missions flown under the new philosophy together cost less (in inflation-adjusted dollars) than did Cassini-Huygens alone. Nine of the first ten of these ventures were a success—though the initiative floundered in 1999 when four of the next five “faster, better, cheaper” missions failed.104

Given the inhospitable climate at NASA to a mission of this scale it is hardly surprising that a major effort was made on both sides of the Atlantic to save Cassini-Huygens from further damage. This time the scientific communities were united by their dependence on each other, as Roger Bonnet explained: “The Europeans wanted to put their probe on Cassini because they could not do the mission without it [. . .] For the Americans, the provision of the probe was a unique opportunity to do outstanding novel science.” In Bonnet’s view the Europeans also brought more, though: project stability. He remembers “Carl Sagan calling me on the phone from California asking for help because NASA was trying to stop the mission.” European ambassadors to Washington were asked to impress upon the State Department “that they could not stop Cassini, with such a big involvement of Europe, both on the payload of Cassini and with the Huygens probe.”105

European pressure over the satellite was given added leverage because the Clinton administration needed to make amends for its poor handling of the geopolitics of the International Space Station (ISS) that Canada, Europe, and Japan had joined in the 1980s. This is discussed in chapter 8 of this book and the thread is taken up again in chapter 13. For the present, suffice it to say that meet­ing in Vancouver in April 1993 the American and Russian presidents established the Gore-Chernomydin Commission comprising a number of working groups, including one on space, to advance bilateral cooperation. A year later, beginning around April 1994 stakeholders on both sides began to explore ways to integrate Russia into the ISS. This was formalized at a meeting in June 1994. NASA and the Russian Space Agency signed an interim agreement covering initial Russian participation in the ISS program. This included a $400-million contract with the new partner, 75 percent of the American money being for Russian space hardware, services, and data in support of the “Shuttle-Mir” project (a joint flight program leading to the development of the ISS). In doing so the agency not only suspended the principle of “no exchange of funds” that had been required of its traditional allies, but NASA also rode roughshod over their sentiments. As NASA official Lynn Cline put it to me, “This was another case where I don’t think we adequately consulted with our partners. People in charge at the time told Dan Goldin that we needed to consult with our partners. He didn’t want to hear it.”106

This attitude may well explain why the ESA director general, Jean Marie Luton, bypassed Goldin and wrote directly to the vice president ten days before the June 1994 meeting of the Gore-Chernomydin Commission to plead the case for Cassini. Luton upped the stakes by stressing that a negative deci­sion on Cassini could have implications far beyond this one case. As he put it, Europe “views any prospect of a unilateral withdrawal on the part of the United States as totally unacceptable. Such an action would call into question the reli­ability of the US as a partner in any future major scientific and technological collaboration.”107 A month later, in July 1994 President Clinton intervened to enable NASA to proceed with both the space station and its science program. All are agreed that in this case “the international aspect of the Cassini mission was an extremely important factor in reversing almost certain cancellation of the mission.”108 It must not be forgotten, though, that that “international aspect” coupled a satellite of predominantly scientific importance with a space station of immense technological and geopolitical significance. This strong coupling is probably what saved Cassini.

Goldin did not give up his reservations about the program even after the dra­matic crisis of 1994 was resolved. In 1995, much to the distress of the European participants, the NASA administrator demanded that the entire project, includ­ing the foreign contributions be subjected to an external review. This not only struck a blow to the fine cooperative spirit that had prevailed at the scientific level, it was doubly infuriating because technical findings of the review panel that were deemed to touch on matters of national defense could not be conveyed to partners abroad. In the event the mission overcame this hurdle, but was then confronted with another: the “Stop Cassini” campaign by the Florida Coalition for Peace and Justice. The coalition objected to the use of plutonium dioxide in three radio-isotopic thermoelectric generators and on heater units. This was a technological option that the designers of the spacecraft had invoked since solar power was not feasible for a deep-space mission. Rallies and demonstrations were held on both sides of the Atlantic, letters were sent to the US president for and against the mission, and protestors threatened a sit-in on the launch pad in Cape Canaveral to force a launch abort. Their objections were overruled by a safety evaluation made by the Department of Energy and the Interagency Nuclear Safety Review Panel.

Cassini-Huygens finally lifted into space on October 15, 1997. Its long journey was punctuated by difficulties that emerged in the radio relay link between the European probe and the American spacecraft. These were overcome by having Cassini fly by Titan at a far greater distance than foreseen, so that the Huygens probe had to travel 65,000 kilometers instead of just 1,200 kilometers to enter Titan’s atmosphere. Cassini went into orbit around Saturn on July 1, 2004. The probe was separated from the mother craft six months later on Christmas Day, reaching Titan’s outer atmosphere on January 14, 2005. The descent of Huygens was slowed when its parachutes were deployed about 150 kilometers above the surface. It survived the impact and it continued to transmit data for over three hours. The first results were relayed via NASA’s Deep Space Tracking Network to the European Space Operations Center in Darmstadt, Germany, where “sci­entists waiting anxiously for the data to arrive [. . .] hugged each other when the first signals arrived during the morning, showing that the mission, 20 years in the planning and execution, was functioning.”109

The joint development of the Cassini mission was a fine example of interna­tional collaboration. That success only makes sense, though, if placed in his­torical context. The scientific importance of the trip to Saturn and Titan was as crucial as the historically maturing institutional and political factors: the new cohesion of the European space science community provided by Roger Bonnet’s Horizon-2000 long-term plan, the “institutional learning” that structured the joint management of the project, the determination by scientists on both sides of the Atlantic not to let a repeat of the ISPM experience sour their cooperation, and the political backbone provided by the opportunity for ESA and its member states to escalate a threat to Cassini into a threat to US-European collaboration in any future major scientific and technological project.