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Raumfahrt - NASA Is Studying a Private Mission to Boost Hubble’s Orbit. Is It Worth the Risk?

6.11.2022

SpaceX and the entrepreneur Jared Isaacman are pursuing a plan to rescue the iconic Hubble Space Telescope from a fiery plunge into Earth’s atmosphere

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The Hubble Space Telescope hovers at the boundary of Earth and space in this picture, taken after Hubble's second servicing mission in 1997. Credit: NASA

For more than three decades, the Hubble Space Telescope has been breaking new ground in astronomy, cosmology and planetary science, delivering results that few if any other facilities can match—let alone exceed. No other orbital observatory has managed such consistent high performance for so many years, thanks to a series of repair and servicing missions by NASA astronauts.

NASA staged five space shuttle missions to Hubble in low-Earth orbit between 1993 and 2009 to upgrade science instruments, replace failed systems and boost Hubble’s orbit, which naturally decays over time because of friction against the tenuous outer reaches of Earth’s atmosphere. Servicing missions ceased with the end of the space shuttle program, leaving Hubble in a slow but steady descent toward Earth. Without further intervention, NASA officials say the telescope has a 50 percent chance of falling back into the atmosphere in 2037.

Now, however, a new hope for Hubble is emerging from the realm of commercial spaceflight. Entrepreneur and private astronaut Jared Isaacman, who is preparing for his second of four flights purchased from SpaceX, wants to pilot one of the company’s Dragon capsules to Hubble to boost its orbit—at little-to-no cost to taxpayers. “I think it would be a great thing to do for science and research across the world,” Isaacman tells Scientific American.

The proposed rendezvous would be part of the Isaacman-funded and -led Polaris Program, which is expected to culminate with the first crewed voyage aboard Starship, a gigantic multipurpose and reusable space transportation system now being developed by SpaceX. For the Polaris kickoff mission, slated to launch in March of 2023 aboard a Dragon spacecraft, Isaacman and three crewmates plan to conduct a spacewalk—a first by private astronauts—and to break the high-altitude record for a crewed spacecraft in Earth orbit, set in 1966 by Gemini 11.

NASA already is deeply invested with SpaceX, a company that has rapidly come to dominate the global spaceflight industry. When the agency staged its fifth and final space-shuttle servicing call to Hubble in May 2009, SpaceX was still a year away from the first flight of its Falcon 9 rocket, and three years away from the first docking of a Dragon capsule at the International Space Station. Today, SpaceX is approaching its 200th launch—70 percent of which were on rockets that had been recovered and reflown. Dragon capsules have docked at the station 33 times with cargo and crews, including a private charter for Houston-based Axiom Space. And in 2021, SpaceX also completed one free-flying crewed Dragon mission—Isaacman’s first spaceflight, named Inspiration4.

After the California Institute of Technology, which operates the Jet Propulsion Laboratory for NASA, the U.S. space agency now annually spends more money with SpaceX—upwards of $2 billion in fiscal 2022 alone—than on any other organization. In addition to station cargo runs and crew ferry flights, SpaceX, which is headed by tech entrepreneur Elon Musk, holds NASA contracts to launch high-priority science projects, including the multibillion-dollar Europa Clipper mission; cargo flights to cislunar space; and a demonstration of Starship-based transportation services for landing astronauts on the surface of the moon as part of the agency’s Artemis program.

Beyond NASA, SpaceX provides launch services to the U.S. military, commercial customers and foreign governments. The company also manufactures, launches and operates its own space-based broadband service, Starlink, which already is the world’s largest satellite constellation. More than 3,000 Starlink satellites are now in low-Earth orbit, and SpaceX has approval from the Federal Communications Commission to expand the network with nearly 9,000 more.

All of which is why when SpaceX and Isaacman pitched a Dragon mission to Hubble, NASA took the proposal seriously. As a first step, the space agency on September 22 signed an unfunded Space Act Agreement with SpaceX to launch a six-month feasibility study. “We’re working on crazy ideas all the time,” NASA’s science chief Thomas Zurbuchen told reporters during a September 29 conference call. “We’re always supposed to push the envelope, and this is really compelling.”

NASA hoped that its final shuttle-servicing mission to Hubble would extend the observatory’s life to at least 2014, by which time its successor, the James Webb Space Telescope (JWST), was expected to launch. Although JWST ended up not flying until December 2021, Hubble held on. NASA now expects Hubble to remain operational into the 2030s without any further servicing missions. “We’re able to forecast what [the] problems are most likely going to be, and start working on those issues ahead of time,” says Patrick Crouse, Hubble’s project manager at NASA’s Goddard Space Flight Center in Greenbelt, Md.

For example, engineers have developed techniques to point Hubble and lock on targets even if additional onboard guidance hardware fails. The observatory currently has three of six spacecraft-orienting gyroscopes operational, although all of those remaining are of an upgraded, more robust design than those that have shut down.

“We have a lot of components that are past their expected life for radiation dosage or various issues that can cause them to fail. We have a fair amount of redundancy … and we project that, due to radiation, we might see some degradation, but it would be a graceful—not sudden—failure of systems,” Crouse says. “I think it’ll be a horse race, if we’re able to make it out to the 2030s, between the gyros and the fine guidance sensors,” he added.

Hubble’s degrading orbit is another matter. The telescope has drifted downward by more than 30 kilometers since its last boost in 2009, when NASA’s final servicing mission lifted it to an altitude of 564 kilometers.

SpaceX proposes to boost Hubble into a significantly higher orbit somewhere between 600 and 610 kilometers above Earth. The study, which will be overseen by Barbara Grofic, program manager of NASA Goddard’s Astrophysics Projects Division, will assess Dragon’s technical capabilities and the potential risks to Hubble.

Quelle: Scientific American

 

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