OPINION: A UNIQUE SPACE ODYSSEY WITH NO END From The Times, 21 August 2002 http://www.timesonline.co.uk/article/0,,482-390005,00.html By Nigel Hawkes Great journeys have inspired storytellers ever since Homer, but even he might have paused for breath at the odyssey of the Voyager spacecraft. Conceived when Richard Nixon was in the White House and launched in the Carter years, the two Voyagers slipped away without ceremony or fuss, bound for the outer reaches of the solar system. And then they went on going. Today, a quarter of a century later, they are by far the remotest spacecraft man has ever built, spreading human culture outwards like a gigantic tidemark in the cosmos. They have long since left the planets behind, cruising towards interstellar space where the influence of the Sun finally begins to peter out. They are so far away that their signals now reach the Earth with a power twenty billion times feebler than a digital watch. So long has their journey been that, despite being launched by an obsolete ballistic missile designed for impact rather than economy, they have averaged a miserly 30,000 miles per gallon. They have passed through radiation belts strong enough to wither a living creature, and returned enough data to encode 6,000 sets of Encyclopaedia Britannica. Nor is their mission over: they may yet send us, in a whisper, the first information we have ever had about the heliopause, the place where the solar system ends and interstellar space begins. They carry messages redolent of the 1970s - recordings of a kiss, a mother's lullaby, wind and water - as well as words from Carter and Kurt Waldheim, the former UN Secretary-General, and greetings in languages ranging from ancient Akkadian to modern Wu. The records, made of gold, also contain music by Mozart, Bach and Chuck Berry, whose version of Johnny B Goode may one day be played by a bewildered alien on an unimaginably distant planet. That is, if he can devise anything as old-fashioned as a turntable to play it on. The Voyagers were never planned to live so long, but the 1970s were not a cheeseparing decade for the National Aeronautics and Space Administration (Nasa) and when it did things, it did them well. And, like some Victorian bridge that still carries modern traffic because its engineers were not quite sure of themselves, the Voyagers were probably overdesigned for the task they had to perform. The first to be launched, oddly, was Voyager 2. It set off on August 20, 1977, and is now 6.3 billion miles away, dipping below the plane in which the planets lie. Voyager 1, launched a fortnight later on a different trajectory designed to get it to Jupiter first, is now 7.9 billion miles from Earth, twice as far as Pluto, and climbing at 38,500 mph above the ecliptic plane. The plan was for the two spacecraft to make a quick four-year tour of Jupiter and Saturn, and then retire. "We were on a mission of discovery," said Dr Edward Stone, the Voyager chief scientist, whose entire career has been caught up with the Voyagers. "But we didn't appreciate how much discovery there would be." Voyager 2 went on to make the first visits to Uranus and Neptune and then, since both spacecraft were still working after a dozen years, a new mission was devised - the exploration of the boundary between the solar system and interstellar space. The Sun pours out a constant flood of charged particles, the solar wind. They bathe the Earth and the other planets, blowing at millions of miles an hour. But ultimately, in a region known as the termination shock, the energy of the particles finally flags. This is the solar system's outer shore, a place where the particles slacken to a subsonic pace, and turbulent magnetic fields hold sway. Here interstellar particles begin to outnumber those from the Sun. But where exactly is here? That is the final question the Voyagers may be able to answer. The influence of the Sun waxes and wanes along with its 11-year cycle of activity, so the termination shock is further away at times of high solar activity, closer when the Sun is in a quiet mood. The peak of the current cycle was two years ago, so the termination shock is now shrinking even as the spacecraft hurtle towards it. The guess is that it will be reached within the next year or two, and then it will take a few more years - perhaps ten - for Voyager 1 to reach the very edge of the heliosphere. A new kind of race has now been joined: to make the first observations of the edge of the heliosphere and the entry into interstellar space before the two antique spacecraft run out of power in about 2020. Given the project's past history, nobody is betting against this being achieved. Earlier this year the Nasa team responsible for Voyager 1 feared that its navigation system, which guides the spacecraft by locking on to the Sun and the star Sirius, was beginning to show signs of age. But the spacecraft had a spare on board, which had been sitting unused for 25 years. Activating it, when it takes more than 12 hours for a signal from Earth to reach the spacecraft, and just as long for a reply to come back, took special precautions. The back-up equipment had not even been tested since 1980, when Voyager 1 was approaching Saturn. The danger was that the back-up would fail and Voyager 1 would begin to drift. The already tenuous connection to Earth would be lost and the spacecraft would then fall silent. So the team, with true ingenuity, arranged to switch briefly to the back-up system, and then revert automatically to the original. The switch would last long enough to see if the back-up worked, without running the risk of losing the spacecraft. It did work, and the permanent switch was made nine days later. Sometimes Nasa must wish its newer spacecraft worked as well as these old classics. Last week it lost yet another of its "faster, better, cheaper" generation of satellites when the $159 million Contour spacecraft disappeared. Contour was designed to study comets by completing a rendezvous with three of them in the next five years. It was successfully put into Earth orbit, but disappeared as it fired its rockets to begin the mission proper. The loss of Contour focused attention once again on Nasa's strategy. Critics say that it has lost its way, spending too much on manned missions to the International Space Station which achieve little of lasting value, while neglecting the unmanned missions to the planets which - the Apollo Moon landings apart - have proved its greatest glory. The Bush Administration stamped on the idea of a mission to Pluto and its moon, Charon - the only planet never to have been visited. Losing this mission means that it will be 2012 before it becomes possible again, because of Pluto's orbit. Nor has the current Nasa administrator, Sean O'Keefe, inspired the space buffs. His predecessor Dan Goldin, who originated "faster, better, cheaper", could at least count some successes for his strategy, even if there were also some embarrassing failures. But so far, O'Keefe has been more concerned with sorting out Nasa's financial accounting systems and trying to make its different centres work more co-operatively with one another. "As important as these matters are," urged Aviation Week and Space Technology in a recent editorial, "there is more to leading this space agency than simply managing it better. Nasa's lifeblood is exploration. Without objectives that expand horizons and results that inspire awe, Nasa becomes an expensive technical tangent for the American commonwealth." The critics also charge that under Goldin, Nasa downsized to become leaner and meaner, but in practice became weaker and less experienced. The administration is left with an ageing workforce, fewer skilled people than it had in its heyday, and a lack of fresh talent and leadership. True, it also costs a lot less. In the 1960s, during the race to the Moon, Nasa swallowed a thumping 3.8 per cent of the federal budget, while now it is down to less than 1 per cent. But nobody now remembers that the Voyager missions cost the better part of a billion dollars - they just remember the extraordinary success of the spacecraft, and marvel at the fact that 25 years later they are still sailing through the ether ticking like a well-oiled clock. Copyright 2002 Times Newspapers Ltd. |
