NASA Administrator Sean O’Keefe caused an uproar in January when he announced that, because of safety concerns after the Columbia accident, any further space shuttle service missions to the Hubble Space Telescope would be too risky for astronauts (see Physics Today, Physics Today 0031-9228 57 3 2004 29 https://doi.org/10.1063/1.1712491 March 2004, page 29 ). Professional societies—the American Association for the Advancement of Science, the American Astronomical Society, the American Physical Society, and the Royal Astronomical Society, to name a few—issued statements in support of servicing the telescope. Congress introduced resolutions in favor of future service missions. Astronauts complained and the public swamped NASA with letters protesting the telescope’s demise. But O’Keefe insisted that the only mission heading to the HST was a one-way trip by an unmanned propulsion module to help the telescope burn up in a controlled reentry into the atmosphere. Service missions were off the table.
Eventually, though, the agency buckled and requested that the National Research Council investigate options for extending the telescope’s life. The resulting report is due out later this year, but in a letter in July, the NRC advised NASA to keep the HST ’s options open. The NRC recommended that NASA replace the batteries and gyroscopes, add two new instruments to the telescope, build expertise for a potential robotic service mission, and “take no actions that would preclude a space shuttle servicing mission.”
While the NRC was debating the merits of various HST options, NASA was quietly evaluating just one approach: a robotic rescue mission. Since March, NASA has been testing the Canadian-built special purpose dexterous manipulator (Dextre)—a plug-in device for a robotic arm on the International Space Station.
NASA’s Goddard Space Flight Center, which is carrying out the tests, gave Dextre high marks. On a mock-up of the HST , the robot was able to disconnect and reconnect power cables and remove and replace science instruments—albeit 10 times slower than an astronaut. The servicing would be the most complex space mission yet given to a robot. With new batteries, gyroscopes, and a pair of new science instruments, the 14-year-old telescope could remain functional to 2013.
Robotic surprise
On 9 August, O’Keefe announced to Goddard staff that NASA would ask Congress for additional resources in the 2005 budget to pay for a robotic service mission to the HST . It was his strongest endorsement to date for keeping the telescope alive, and it caught many by surprise—including Al Diaz, newly appointed NASA associate administrator for science, who hastily organized a telephone conference with reporters.
“I would feel more comfortable if NASA were actively keeping open both options—a shuttle servicing mission and a robotic servicing mission—as recommended by the NRC committee,” says John Bahcall of the Institute for Advanced Study in Princeton, New Jersey. But, adds Bahcall, who served last year on a NASA committee on extending the HST ’s life, “if successful, [a robotic mission] would be very good for the nation, providing not only servicing of the Hubble but also giving the US an important technology that has many other potential important applications.”
While NASA’s plans for a rescue mission were progressing, the HST was showing signs of old age. Most of the gyroscopes for positioning the telescope are already dead. The space telescope imaging spectrograph died on 3 August, and engineers are becoming increasingly concerned that the HST ’s batteries may fail in 2007. STIS had unique spectroscopic capabilities for studying supermassive black holes and was one of the few space-borne instruments sensitive to UV light.
Robotic compromise
Under time pressure to service the HST , NASA approached industry for off-the-shelf ideas, says Paul Cooper, vice president for R&D at MD Robotics, the Brampton, Ontario, builders of Dextre. Of the 26 proposals sent to NASA over the past year, two close contenders—Robonaut by the Johnson Space Center and the University of Maryland’s Ranger system—were ruled out because they are several years away from being flight-ready.
NASA will have to solve many problems if a mission using Dextre is to succeed. One unknown is how Dextre would rendezvous with and dock to the HST . But the greatest challenge for the robot is one of the simplest tasks for an astronaut: closing the instrument bay doors on the telescope after installing new equipment.
Congress has given no indication that NASA’s funding request will be approved during this, an election year. The final tab, estimated at $1 billion to $1.6 billion for a robotic service mission, is higher than the cost for a space shuttle flight. Only $300 million, for the HST de-orbiting module, is currently in NASA’s budget—which is being increasingly squeezed because of the president’s plan to send manned missions to the Moon and Mars.
Although it’s a compromise, astronomers are relieved that NASA is considering a robotic servicing mission rather than letting the HST die. “It’s technically feasible but more risky [in terms of fixing unexpected problems during the service mission] than using the shuttle,” says Steven Beckwith, director of the Space Telescope Science Institute in Baltimore, Maryland, which schedules observing time on the HST .
Bahcall is confident that the telescope can be rescued. “We have had more near-fatal situations than a department full of hospital heart patients, but somehow the ingenuity of the engineers, the originality of the scientists, and the strong backing of Congress and the general public have kept [the HST ] alive. I hope it will continue to bring us beautiful and inspiring pictures of the universe for another 10 years.”
Despite the request by a National Research Council committee that NASA keep open the option of a shuttle visit to Hubble, no money has been set aside for it.
Despite the request by a National Research Council committee that NASA keep open the option of a shuttle visit to Hubble, no money has been set aside for it.
