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.
This image from April 24, 2021, shows the SpaceX Crew Dragon Endeavour as it approached the International Space Station. Credit: NASA
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.
The six-member, all-Goddard study team, appointed on October 19, also will consider potential additional services Dragon could provide beyond raising Hubble’s orbit. “We haven’t looked at anything specifically at this time,” Crouse says.
Dragon is not the only U.S. spacecraft capable of reaching Hubble. Northrop Grumman, Boeing and Sierra Space all have or are developing suitable spacecraft for missions in low-Earth orbit. Years ago, NASA studied flying one of its own Orion capsules to Hubble. “We will look at any and all options that are in the interest of the taxpayer,” Zurbuchen said during the September 29 briefing.
Without knowing what the future would bring, as NASA wound down the shuttle program it also laid the groundwork for other spacecraft to visit Hubble. The last servicing crew outfitted the telescope with a docking ring and navigation targets so that a vehicle without a robot arm could attach itself directly onto Hubble. (Shuttle missions grappled the telescope with a 15-meter-long arm, then mounted the observatory on a work platform in the orbiter’s cargo bay for servicing by spacewalking astronauts.)
At the very least, NASA figured that at the end of its life Hubble would need to be visited once more—though not necessarily by astronauts. The purpose of another rendezvous would be to install a propulsion module for guiding the telescope’s plunge into the atmosphere or boosting it into a stable, high-altitude graveyard orbit. Whether Hubble would fall to Earth or linger on high, such a mission would minimize the chances of any collateral damage from the telescope’s demise.
“We’re going to need to go to Hubble in the next 15 years or so because you would like to have either a controlled entry or a boost up,” says Scott Altman, a former astronaut who commanded the last two Hubble servicing missions.
“Bottom line is, first do no harm. We’ve got a great observatory up there now,” says Altman, who is now president of Beltsville, Md.-based ASRC Federal, a technical consultancy and service provider. “The thing I learned more than anything going to Hubble is: Don’t rush. Slow and steady wins the race.”
NASA may decide to pass on SpaceX’s proposal. Hubble is operating well and its orbital decay is not a particularly pressing concern. Even if a Dragon mission to Hubble proves technically feasible and relatively low-risk, the observatory could run into a problem that bumps the flight outside of the Polaris Program’s schedule.
Former astronaut and NASA science chief John Grunsfeld, an astronomer who served on Hubble’s last three servicing missions, says a reasonable program might be for NASA to use a Dragon reboost flight to collect data for a future servicing call by Dragon, Starship or another vehicle.
“One of the discussions I had with SpaceX a long time ago was to use Starship—it has such capability, you can add airlocks, new instruments and other big stuff—to grab Hubble, bring it back, refurbish it and put it back up again,” Grunsfeld says.
“I’ve not dug into the low-level details, but I think that a Dragon reboost would be relatively low-risk—if that’s all they do,” he adds. “There is a risk that is you dock too hard you could break something, like a solar array. Hubble wasn’t designed to be as robust as the International Space Station.”
Adds Isaacman, “There are a lot of things that will need to be figured out. I think the primary objective is going to be how can you safely leave Hubble in a healthier state than it is today.”