The Hubble Space Telescope, seen here after its last servicing mission in 2002, is an excellent spacecraft, but is it worth the cost and risk of another servicing mission? (credit: NASA)

Life after Hubble

by Jeff Foust
Monday, February 2, 2004

On January 14, it seemed likely that President Bush’s announcement of plans to send humans back to the Moon would be the biggest space story of the month, if not the year. Yet, within a few days it was in danger of being overshadowed by another, largely unrelated announcement. NASA’s decision to cancel the last shuttle servicing mission to the Hubble Space Telescope has received as much media attention of late as the new initiative. And, unlike the mixed reviews that the Bush plan received, the public and media reaction to the cancellation has been overwhelmingly negative.

NASA may have anticipated this. The agency never issued a press release about the Servicing Mission 4 (SM4) cancellation: the media initially relied on word that leaked out after NASA officials briefed the Space Telescope Science Institute (STScI) on the decision on the afternoon of Friday, January 16. In the two weeks since then, the decision, and NASA’s leadership, have been criticized by astronomers, politicians, and the general public, claiming that NASA had, in effect, sentenced the telescope to an early death. To some degree NASA brought this criticism down upon itself based on how it publicized, and even hyped, the Hubble over the last decade. However, that doesn’t mean NASA made the wrong decision when it cancelled SM4, nor does it mean that the end of Hubble means the end of quality astronomical research.

Hyping Hubble

There is little doubt that Hubble has been one of the most productive astronomical instruments in human history, a claim NASA willingly endorses. “Not since Galileo turned his telescope towards the heavens in 1610 has any event so changed our understanding of the universe as the deployment of the Hubble Space Telescope,” states a web page for the Hubble project at NASA’s Goddard Space Flight Center. An independent team of astronomers, asked by NASA to evaluate the future of the telescope last year, concluded that Hubble is “one of the most remarkable facilities in the entire history of science.”

There is certainly a lot of evidence to justify those lofty claims. Astronomers have used Hubble to peer into the distant, early Universe. They have also used it to confirm the existence of black holes and study other aspects of the birth and death of stars. Hubble also provided some of the best images of the 1994 collision of Comet Shoemaker-Levy 9 with Jupiter, revealing the dark impact scars left in the planet’s atmosphere by the colliding fragments.

NASA and STScI have not shied away from publicizing those or lesser discoveries made with the telescope. In the last ten years—since the telescope’s optics problem was corrected during the first shuttle servicing mission in late 1993—STScI has published, on average, nearly 40 press releases a year, nearly all featuring new results, and new images, from Hubble. In 2003, those releases included “Close-up of M27, the Dumbbell Nebula”, “Hubble Captures a Perfect Storm of Turbulent Gases”, and “Giant Radio Jet Coming from Wrong Kind of Galaxy”. Interesting to some astronomers, perhaps, and sometimes with attractive images, but often rather esoteric to the general public.

Why put so much effort into publicizing nebulae and radio jets? Part of it, certainly, is a genuine desire to share scientific results with the general public. Another aspect of this steady stream of press releases, though, is to keep Hubble in the mind of the public, to remind them that the veteran telescope is still making discoveries. Hubble is, after all, one of the cornerstone missions for NASA, a position it held long before its launch in 1990. The agency’s perception in the press has risen and fallen based on Hubble’s triumphs and tribulations.

Hubble also, ironically, has served as a rationale for human spaceflight. Hubble was designed to be launched and serviced by the shuttle back when the shuttle was going to provide inexpensive, routine access to space. While the shuttle failed to fulfill those promises, it has served its role to Hubble, launching the telescope and servicing it on four occasions, including the critical 1993 repair mission. However, this is something of an anomaly: other than Solar Max, a spacecraft repaired in orbit by the shuttle in 1984, Hubble is the only major astronomy mission to rely on the shuttle for servicing. The trend now is to launch major observatories—Chandra X-Ray Observatory, Spitzer Space Telescope, and the forthcoming James Webb Space Telescope—that not only aren’t designed to be serviced by the shuttle, but also are placed in inaccessible orbits. The Compton Gamma Ray Observatory, which like Hubble was designed to be serviced by the shuttle, never was, and was deorbited in 2000 after suffering gyro problems; NASA elected not to repair the spacecraft because it had operated for nearly twice its original five-year mission. Yet, speaking before the Senate Commerce Committee last week—after the agency decided to cancel SM4—NASA Administrator Sean O’Keefe used the Hubble as a reason why it was important to have humans in space.

Hubble alternatives

While NASA might be accused of trying to squeeze as much publicity out of Hubble as possible, it is an excellent telescope, and in an ideal world would continue to operate for as long as possible. However, this is far from an ideal world. In the post-Columbia environment, NASA has become understandably hypersensitive about safety. Any mission that cannot take advantage of the “safe haven” of the International Space Station in the event of problems will be viewed skeptically by the agency.

There are some alternatives to simply deorbiting Hubble being debated. In an article last August, when a NASA-commissioned panel of astronomers debated the future of Hubble, Dennis Wingo, CTO of Orbital Recovery Corporation, offered a different approach. His company has been developing a space tug that would be able to extend the life of communications satellites; a version of this, he argued, could be used to either boost the telescope into a higher orbit (thus eliminating the threat of reentry for decades to come), or even move it to the vicinity of the ISS, where astronauts there could service the spacecraft. It’s an intriguing idea, but others have noted that since the ISS is in a lower orbit that Hubble currently, the additional drag could pose an operational problem. Moreover, the ISS doesn’t have the facilities to do satellite servicing of any kind now: at the very least, the station would need some kind of mount that Hubble would dock with so that spacewalking astronauts and the station’s robot arm could work on it.

In a commentary in the January 31 issue of the New York Times, author Michael Benson offers another alternative. Instead of launching a deorbit propulsion module on an expendable rocket, as currently planned, have the shuttle carry the module to Hubble, where astronauts could attach it as well as service the spacecraft. The problem here is that the deorbit module doesn’t exist yet, and may take some time to develop: it appears that there are no good off-the-shelf stages that could be easily adapted. This could delay SM4 by several years, pushing it closer to the shuttle’s retirement date and increasing the odds that Hubble will shut down before the mission arrives. (Astronauts could always revive the telescope, though, as they did during the SM3A mission in late 1999.) It also assumes that there would be enough room in the shuttle’s cargo bay for the deorbit module.

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