By Richard Stone on Science 29 June 2012: 1630-1637 Full Text (PDF)
China's crewed space program has won admiration for the engineering prowess on display earlier this week in the Shenzhou 9 mission. Upcoming science missions hope to steal some of the spotlight.
In the hot seat. The crew of Shenzhou 9 prepares for China's first mission to dock spacecraft with astronauts aboard.
CREDIT: QIN XIANAN/COLOR CHINA PHOTO/AP IMAGES
BEIJING—When Shenzhou 9 gently fired its thrusters to pull to within several centimeters of the orbiting Tiangong module on 24 June, mission managers were on edge. For a fleeting moment, a question hung in the air: Would the astronauts succeed in China's first attempt to manually dock the two spacecraft, circling Earth at 7.8 kilometers per second? They'd performed the maneuver on the ground, in a simulator, hundreds of times before. This was the real test. The slightest miscalculation could have spelled disaster for Shenzhou's three-person crew, including the country's first female astronaut. No country had lost someone in space—and China didn't want to be the first.
One person with a big stake in the mission says he was not sweating out that tense moment: Shenzhou's former chief designer, Qi Faren. “I wasn't nervous,” he claims. Shenzhou's first flight in 1999, Qi says, was a far riskier roll of the dice. That landmark mission went well, as did the Shenzhou 9 docking maneuvers, completing a milestone on China's road to a sustained human presence in space. “It's a huge step,” says Dean Cheng, an expert on China's space program with the Heritage Foundation in Washington, D.C. “Docking is essential to doing just about anything in space,” he says, including China's plan to build a space station by 2020.
CREDIT: BETTMANN/CORBIS/AP IMAGES; R. STONE/SCIENCE; AP PHOTO/EUGENE HOSHIKO; (INSET) IGNAT SOLOVEY/WIKIMEDIA COMMONS; AP PHOTO/ZHA CHUNMING; NASA IMAGES; IMAGINECHINA VIA AP IMAGES; SPACEBABE/WIKIMEDIA COMMONS; MAGINECHINA VIA AP IMAGES; AP PHOTO/RUSSIAN ROSCOSMOC SPACE AGENCY, HO; SUN ZIFA/COLOR CHINA PHOTO/AP IMAGES
China's leaders had a lot riding on Shenzhou 9, too. The Communist Party, which is expected to begin a leadership transition this autumn, spent the first half of 2012 in damage-control mode over the fall of former governor Bo Xilai and the high-profile flight of blind activist Chen Guangcheng. For the party, the elegant pas de deux at 343 kilometers above Earth's surface was a timely propaganda triumph. “China's space program gives the party legitimacy,” Cheng says. “The leaders can say, ‘Look what we have done for the country.’”
The engineering feat is indisputable. “China is emerging as a world leader in space,” says Mark Stokes, executive director of the Project 2049 Institute, a think tank in Arlington, Virginia, that produced an analysis of China's space program last April for the U.S.-China Economic and Security Review Commission.
Soon, China's basic researchers will take a star turn. Over the next several years, the country plans to launch five scientific missions, including a dark-matter probe and an attempt at long-distance quantum communication. Four more innovative missions are in the design stage, Science has learned: an x-ray telescope to study black holes, a solar imager that would swing high above and far below the line of sight between Earth and the sun, a space-based very-long-baseline interferometer (VLBI) tuned to long-millimeter wavelengths, and a four-satellite cluster to study coupling of the magnetosphere, ionosphere, and thermosphere. Scientific payloads are being assembled for Tiangong 1 and for two more Tiangong modules, including a crewed space laboratory, which China plans to launch in the next 3 years. And scientists are designing experiments for the future space station.
It's a new dawn for China's space scientists. For decades, they have been left in the shadows by the generals and engineers who run China's space program. China's sole dedicated science missions to date were Double Star, in which it teamed up with the European Space Agency (ESA) from 2003 to 2007 to study magnetic storms, and the ill-fated Mars probe Yinghuo-1, which failed to leave Earth orbit.
“When I look at astronomy textbooks, none of the discoveries were made by people working in China. I don't see a single photo taken by a Chinese telescope. It's very frustrating,” says Zhang Shuang-Nan, an astrophysicist here at the Institute of High Energy Physics of the Chinese Academy of Sciences (CAS). “We feel more and more pressure, not just from the top, but also from the bottom, to produce knowledge,” adds Wu Ji, director general of CAS's National Space Science Center (NSSC). With the raft of missions now in the works, they may end up not just revising but rewriting textbooks.
Rags to riches
The visionary who set China's sights on space also played a key role in the early days of the U.S. program. In the 1940s, Chinese-born aeronautical engineer Qian Xuesen was one of the founders of the Jet Propulsion Laboratory in Pasadena, California. Considered a genius by his peers, Qian, known in the United States by the older spelling of his name, Hsue-Shen Tsien, fell victim to the Red Scare and in 1950 was accused of being a Communist. The United States revoked his security clearance and—after 5 years of house arrest—exiled him to China. Qian returned home to a hero's welcome and soon proposed that the young nation start a missile program.
A year after a small team set to work, the Soviet Union shocked the world on 4 October 1957 with the launch of Sputnik 1, the world's first artificial satellite. China wanted one, too. “However, we didn't even have a rocket at that time,” says Qi, now a dean at Beijing University of Aeronautics and Astronautics. China turned to the Soviet Union for help; hundreds of engineers poured in. Key facilities were set up across the hinterlands to avoid offering fat targets. But several months after embarking on this vast enterprise, China, strapped for cash, aborted its space program to focus on guided missiles.
Qian bided his time working on weapons. Then, in a report to top leaders in 1965, Qian argued that China needed to reboot its space program because satellites were indispensable for military surveillance and communication. The government concurred and revived its space program. By then, though, the Sino-Soviet split meant that China had to go it alone. “They weren't talking to anyone, not the Soviets, certainly not the Americans,” Cheng says. That's why, he says, “much of China's space program is domestically produced.”
After a failed attempt in 1969, China on 24 April 1970 put its first satellite in orbit, becoming only the fifth country to do so. For 1 month, Dongfanghong 1 took readings of the ionosphere and transmitted data back to Earth. In a patriotic touch, it broadcast the song “The East is Red,” for which it was named. “It was a simple satellite,” says Qi, who served on the engineering team. But the 1-meter-wide debutante, heavier than the first satellites of the Soviet Union, United States, France, and Japan combined, made a powerful statement.
China then set its sights on a crewed program—but didn't get very far. “There were some key technical problems beyond our ability at that time,” Qi says. In 1975, he recalls, “Premier Zhou Enlai convinced us to not try to match the Soviet Union and U.S., and first develop more satellites.”
China hatched plans for a new crewed program in 1986. Work began in earnest in 1992, the year that Qi succeeded Qian as China's general spacecraft designer. Sanctions on high-tech exports to China forced Qi's team to toil in isolation. As a result, he says, China “spent too much time and resources” developing the Shenzhou spacecraft, the workhorse of the crewed program. “On one hand, we felt uncomfortable about the restrictions. On the other hand, those restrictions helped us a lot,” Qi says. “Although our spacecraft may not be the best, we successfully made it by ourselves.” The second watershed event of China's space program came in 2003, when Shenzhou 5 carried astronaut Yang Liwei into orbit. China became the third country to independently send a person into space.
While other spacefaring nations have set up civilian agencies for peaceful exploration of space, in China the army has always run the show. For that reason, China's ultimate intentions are debated (see p. 1634). One concern is that China's space-industrial complex is bigger than any other country's. Two state-owned space enterprises together employ more than 267,000 people. Add in staff at space-related R&D institutes and university-based researchers, and the number of Chinese involved in the space program may top 300,000. This gargantuan ground force has propelled China into the upper echelon of spacefaring nations. China “is one of the elite,” Cheng says.
China's space science community hasn't gotten there quite yet.
Rising from the ashes
On 9 November 2011, China thought it was on its way to the Red Planet. Early that morning, Russia launched the Fobos-Grunt spacecraft on a Proton rocket with the aim of landing on Mars and returning 200 grams of soil to Earth in 2014. China was hitching a ride. A small probe called Yinghuo-1, built by CAS's Center for Space Science and Applied Research, would separate from Fobos-Grunt before the spacecraft entered Mars orbit. Its aim was to take the most detailed measurements yet of the planet's magnetic field. “It really was our dream to go with the Russians,” says Wu, who led the Yinghuo-1 design team.
Seconds after Fobos-Grunt had separated from the rocket, the spacecraft's thrusters failed to execute a burn properly, stranding it and its piggybacked companion in low Earth orbit. Over the next several days, controllers at the Lavochkin Association in Moscow, which designed Fobos-Grunt, attempted to communicate with the spacecraft to set it back on course, but to no avail. Fobos-Grunt plunged back through the atmosphere on 15 January, broke apart, and disappeared over the Pacific Ocean. “It was very disappointing. A really big blow for our science,” Wu says.
Wu's chagrin may prove short-lived. In the months before the Fobos-Grunt disaster, China had already begun drafting blueprints for a space science program that, it hopes, will make the country stand out not just for aeronautical engineering but for discoveries in space science, as well.
Until now, most other science missions have languished as mere proposals. Although the first two spacecraft launched under China's lunar exploration program—Chang'e 1 in 2007 and Chang'e 2 in 2010—carried scientific instruments, they “were more for prestige and engineering than for science,” Wu says. After mapping future landing sites, Chang'e 2 is now en route for a flyby of 4179 Toutatis, a potentially hazardous asteroid that will whiz close to Earth at the end of the year. Chang'e 3, scheduled for launch in 2013, will be the first spacecraft to make a soft landing on the moon since the Soviet Union's Luna mission in 1976. It will roll out a rover that will analyze soil samples and set up an extreme ultraviolet telescope—the first astronomical observatory on the moon. Some officials have talked of a crewed lunar landing after 2020, but that adventure is not set in stone. The rationale for such a mission, Qi says, “is being hotly debated.”
Heralding a new era for space science, on 3 May 2011, Wu announced that CAS will undertake five scientific missions in the coming years (Science, 20 May 2011, p. 904). CAS has budgeted $554 million over 5 years for the missions and established NSSC last year to oversee the burgeoning program.
Astrophysics is set to take center stage. First off the blocks should be the Hard X-ray Modulation Telescope (HXMT), conceived nearly 20 years ago to observe black holes, neutron stars, and other objects based on their x-ray and gamma ray emissions. HXMT, China's first astronomy satellite, could be launched as early as 2014 and will be the first of three instruments in China's Black Hole Probe Program. Another mission incubating for years that now has a green light is KuaFu, a Sino-Canadian mission to study the sun's influence on space weather. Russia may join KuaFu, pegged for a 2015 launch along with Shijian 10, a spacecraft that will study the effects of strong radiation and microgravity on organisms and materials.
Work is also progressing on two later launches. One is the lead probe in China's Dark Matter Detection Program. The spacecraft, being designed by CAS's Purple Mountain Observatory in Nanjing, aims to register gamma rays generated when dark-matter particles annihilate each other. The fifth mission in the works, the Quantum Science Satellite, is designed to transmit entangled photons between a spacecraft and receiving stations on Earth (see p. 1632). Success would mark a first step in secure intercontinental quantum communication.
Four more missions that have passed preliminary reviews would considerably build up China's clout in spaceborne astrophysics. The goal is to get them launched in the next 5-year plan, beginning in 2016. One is the X-ray Timing and Polarization (XTP) telescope, conceived by CAS's Institute of High Energy Physics. As the lead facility in the planned Diagnostics of Astro-Oscillations Program, XTP would be “a much more powerful mission that goes far beyond HXMT,” says Zhang, the project's leader. XTP would have a larger collection area and powerful mirrors to collect more photons—and thus observe fainter objects and scrutinize them in greater detail, he says. Astrophysicists around the world have been clamoring for just such a telescope, but early last year NASA and ESA canceled plans for an International X-ray Observatory, and a scaled-down version called Athena lost out to a Jupiter probe in an ESA competition which concluded last month.
XTP would study x-ray emissions from matter spiraling into a black hole, or x-ray signatures of frame-dragging generated, for instance, as a spinning black hole tugs at spacetime. “We'll look at the physics of extreme conditions,” Zhang says. For now, XTP is a purely Chinese mission. But China is exploring teaming up with Germany, which is contemplating a scaled-down Athena called Gravitas. A big attraction for China is that Germany could equip a joint probe with a much more advanced mirror; restrictions on the sale of high-tech equipment to China would force Zhang's team to commission an inferior Chinese-made mirror.
As the centerpiece of the Portraits of Astrophysical Objects Program, China intends to invest its long-standing expertise in VLBI in new space radio telescopes. Its current VLBI network consists of four large, ground-based dishes; three times a year, two of its dishes team up with the European VLBI Network for monthlong observation runs. China's plan calls for spacecraft that would operate in tandem or as arrays with ground dishes, mimicking a huge radio telescope whose effective diameter is the maximum distance between the instruments. They would follow in the footsteps of Japan, which operated a space-based array from 1997 to 2002, and Russia, which is now testing its Spektr-R radio telescope launched last year.
China's proposed array would initially consist of two long-millimeter-wavelength antennas, each 10 meters wide. Key challenges include getting the space antennas to work with high pointing accuracy and having enough bandwidth to transmit scientific data, says Hong Xiaoyu, director of the Shanghai Astronomical Observatory, which is designing the system and is open to international collaboration. The top priority would be to map the fine structure of supermassive black holes that inhabit the center of galaxies and their accretion disks, which are believed to be the power source for active galactic nuclei. Ten years after the first array, Hong says, his team hopes to launch millimeter-wave antennas. Longer baselines and shorter wavelengths produce a higher resolution of radio sources.
China also hopes to blaze a trail in interplanetary physics. NSSC is designing a solar probe that would receive a gravity assist from Jupiter, which would send it into a highly inclined orbit above and below the ecliptic plane, the line of sight between Earth and the sun. Only one previous satellite has followed a similar orbit: Ulysses, an ESA-U.S. probe launched in 1990 that measured a steady weakening of the solar wind and helped pinpoint sources of gamma ray bursts. NSSC's Solar Polar Orbit Radio Telescope (SPORT) would be the first to gaze down or up at coronal mass ejections streaming from the sun. Besides probing the properties of the solar wind and coronal mass ejections, Wu says, SPORT's spectacular bird's-eye view should improve forecasts of space weather.
The fourth new mission to pass muster is MIT, named for the magnetosphere, ionosphere, and thermosphere. The four-spacecraft cluster, another NSSC brainchild, would attempt to shed light on how electrons and other energetic particles flow between those regions of space.
To maintain the momentum of China's suddenly vibrant space science program, NSSC is about to call for proposals for another slate of missions—up to three more, Wu says—that would be funded after 2015. Unlike in Europe or the United States, the price tag won't be a showstopper. “In China, the decision process may be slow, but once a mission is approved, it will go,” Zhang says. “We haven't had a mission canceled because of the budget.”
They do face one big impediment: limited interactions with colleagues abroad, especially those from the United States. “If scientists from NASA come to China for a conference, they cannot talk with Chinese scientists one-to-one,” Wu says. “It reminds me of our Cultural Revolution,” he says, when science in China was largely suppressed. The NSSC and the U.S. National Academies are discussing ways to catalyze discussions between space scientists in the two countries. One tantalizing conversation starter may be China's long-term space astronomy plan, which envisions putting telescope arrays on the moon after 2035.
Dark sentinel. From its perch in low Earth orbit, China's dark-matter-detection satellite will use a stack of scintillators (inset) to look for gamma rays generated when dark-matter particles annihilate each other.
CREDITS: JIN CHANG
A lasting legacy
Shenzhou 9's success opens a new realm for Chinese scientists. The ability to perform docking maneuvers in space will allow China to ferry equipment to Tiangong 1 and add up to two more modules. Research on Tiangong involves closer coordination with the space program's military masters. Two years ago, CAS founded the Technology and Engineering Center for Space Utilization here to manage scientific payloads for Tiangong and the planned space station. The army-run China Manned Space Engineering Office has barred foreign correspondents from interviewing center staff. However, scientists elsewhere in CAS and at universities who are designing the experiments were able to speak with Science.
A bevy of experiments are now being readied for Tiangong, including an atomic clock, a materials science furnace, and a plant tissue culture apparatus. Astrophysicists also have reason to cheer. Among the approved projects, China and Switzerland are teaming up on POLAR, a gamma ray burst detector slated to fly on Tiangong 2 in 2014 as part of the Black Hole Probe Program. It will be the only dedicated instrument in space for measuring gamma ray polarization, which should help scientists determine the structure of a gamma ray jet's magnetic field, Zhang says. That, in turn, may shed light on the origin of gamma ray bursts. One hypothesis is that they are unleashed when a massive star collapses at the end of its life; another is that they are generated when neutron stars or black holes merge. “Each model predicts a different structure of the magnetic field,” Zhang says.
Scientists here may never have had such a wealth of opportunities if China had been invited to join the 16-nation International Space Station. “China didn't have to make Tiangong if we could participate. But we were blocked out,” Qi says. Tiangong is a steppingstone to a 60-ton space station that China announced last December that it would build by 2020.
Although a pipsqueak compared with the 450-ton International Space Station, China's space station should host high-powered science. China Manned Space Engineering Office is expected to approve the first payloads from among dozens of contenders early next year. Among those vying for space are a suite of astronomy experiments called the Cosmic Lighthouse Program. One of two proposed large instruments is the High Energy Cosmic Radiation Detection Facility to study dark matter and cosmic rays.
The other instrument would allow China to play a major role in the coming era of large-scale astronomical surveys—and possibly help unravel the nature of dark energy. China's wide-field optical telescope would complement planned instruments elsewhere, such as the Large Synoptic Survey Telescope (LSST), an 8.4-meter dish to be built in Chile that could see first light in 2018. But LSST will not be able to detect infrared or near-ultraviolet waves from cosmic sources, which are absorbed in the upper atmosphere, and its resolution, despite Chile's superb conditions, will be limited by atmospheric turbulence.
China's as-yet-unnamed mission also won't look in the infrared, as it is not possible to import astronomy-grade infrared detectors. Chinese industrial-grade detectors “don't have the needed performance,” says team member Zhan Hu, a cosmologist here at the National Astronomical Observatory of China. But China's space station survey, he says, will complement other efforts with its high angular resolution and multiple bands covering optical and near-ultraviolet wavelengths. One challenge to mounting any telescope on a space station is that the station will rotate as it orbits. To keep a fixed gaze, the telescope must counterrotate. That job will be farmed out to optomechanical engineers. “They'll do the heavy lifting,” Zhan says.
If the survey mission passes muster, Zhan is confident that Chinese scientists will have new knowledge to contribute to science. “With surveys, you always find something unexpected,” he says. “Current physics cannot explain dark energy. We have an opportunity to discover some revolutionary physics.”
