Hubble's End - or a New Beginning?

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Recently Sean O'Keefe decided not to proceed with SM4 - the fifth, and last scheduled Space Shuttle Servicing Mission to the Hubble Space Telescope. This mission would have installed new gyroscopes, and added several new instruments to the aging telescope allowing it to operate until the end of the decade. The plan had been that this would allow the research community to continue to utilize Hubble as NASA's next space telescope, the Webb Space Telescope, came online roughly around the time Hubble would be going offline.

News of this decision began to filter out within moments of the end of a meeting held at NASA GSFC with O'Keefe and Hubble managers. Internal memos arrived at NASA Watch followed by emails to NASA Watch from NASA headquarters. A few hours later, a hastily arranged telephone press briefing was held between reporters and NASA Chief Scientist John Grunsfeld. Grunsfeld, also an astronomer, had flown on the previous two Hubble serving missions and was slated to fly on SM4.

Clearly this did not look good. To date NASA has not even issued a formal press release on the issue. Many took the suddenness of this announcement personally. NASA sources tell NASA Watch that there had been a plan to do this more formally, but that word had already gotten out to Capitol Hill and that NASA Headquarters wanted the Hubble team to hear the news from O'Keefe, not some reporter.

None the less, this decision has quickly morphed formal decision not to send SM4 to Hubble (which still has a number of years left) to a decision for outright cancellation and shutdown of the Hubble. Indeed, a petition website has inevitably appeared. The speculation continues further with reporters and critics stating that the cancellation of Hubble (actually the cancellation of the SM4 mission) is part of Bush's new space policy.

Even Science magazine, one of the most respected scientific journals in the world, got it wrong. They said "Astronomers were stunned to learn that the president's plan precludes any more servicing missions to the Hubble Space Telescope". In reality the space policy makes no mention whatsoever about Hubble Servicing missions - or Hubble itself. It simply says "Focus use of the Space Shuttle to complete assembly of the International Space Station".

It also says "NASA will return the Space Shuttle to flight consistent with safety concerns and the recommendations of the Columbia Accident Investigation Board." The decision not to fly SM4 was made by NASA on safety grounds based on CAIB (Columbia Accident Investigation Board) recommendations and, to some extent, Stafford/Covey Return to Flight Task Force observations. Had O'Keefe decided to fly the mission it is doubtful the White House would have said or done anything.

Why this decision?

So - Let's be clear about what has been decided - and why. NASA has a number of recommendations it has sworn to adhere to with regard to flying the shuttle in the future. Most come from the CAIB. Some are now coming from the Return to Flight Task Force. The CAIB felt strongly about several things as the Shuttle fleet was prepared for flying again: first, the ability to have shuttle crews find a "safe haven" if, for whatever reason, their orbiter cannot return to Earth. A damaged orbiter is not necessarily a "safe haven" - and the only other pressurized habitable volume in space is the ISS.

Second, that there be an ability to inspect the shuttle in orbit and, if damage is found on any of the thermal protection surfaces, to have an ability to attempt a repair - and that this be available regardless of whether the mission is heading for the ISS or not. In the case of Hubble, it is in a different inclination and any shuttle visiting it would be as unable to visit the ISS as was Columbia. As such, some way for the crew to be rescued would need to be provided. According to Grunsfeld, this would have required that another shuttle be on the pad ready to go and that it be equipped with the ability to mount an exceptionally risky shuttle-to-shuttle crew transfer in the event that the first orbiter was damaged.

Of course, it is possible that a flight to the Hubble - or one to the ISS for that matter - could suffer from problem sand make it to a less than optimal orbit - and possibly be unable to do much maneuvering after that. In such cases some sort of external inspection and repair capability would be needed that does not rely on the ISS. Moreover, some capability must be in place wherein the shuttle could survive long enough until another mission could come and get to it should repairs not make it possible to return home.

Last year NASA announced that it would not pursue a shuttle mission to either retrieve the Hubble or attached a propulsion stage to return it to earth via destructive reentry. The time frame set for this disposal assumed the launch of SM4 and was pegged at being somewhere between 2010 and 2012.

In early December 2003 Hubble Program Executive Mike Moore told me that they could not justify the risk to the human crew and that automated means to safely deorbit the Hubble was now NASA's preference. When pressed, on the other hand, as to why the risk to a human crew was acceptable to fly SM4 he said that the only way to do the upgrades was by humans and that the risk to benefit ratio supported the use of a shuttle mission (with humans).

How to Bring it Back

In announcing the decision to cancel the SM4 mission NASA headquarters has said that the decision had nothing to do with budget, but that safety was the only driver. NASA Watch has learned that the cost of this servicing mission had long been anticipated and that it had been grandfathered into space shuttle budget estimates. As such, Code S would not have to pay for the mission. However these accommodations within the budget were made before the Columbia accident and did not take into account the need for having a second shuttle on the pad and the effect this would have, in a reduced shuttle fleet, upon ISS assembly.

However, with regard to a subsequent, post-SM4 disposal or retrieval flight, the issue is different. In December Moore said "Another shuttle mission would not be free in this time of full cost accounting. Code S [NASA's Office of Space Science] has to pay for the ride." In other words, costs on the order of $500 million would have had to be found.

Regardless of whether SM4 mission was flown or not, Hubble would be coming home without the aid of a Space Shuttle mission. This is whether this will happen sooner rather than later- and what NASA needs to do in order to allow this to happen safely.

When I asked Moore in December about options that might involve sending up an autonomous vehicle capable of not only docking with Hubble and deorbiting it he said that he'd like to use something "as close to off the shelf as possible". When I asked if he had looked into other options including the development of vehicles that could also extend the life of the Hubble he said that he was "adverse to spending Hubble money on technology demonstrations" and that he was "interested in keeping the risk down."

Last fall word of various systems to de-orbit the Hubble using expendable launch vehicles and a propulsion stage circulated - with a price tag of around $300 million (not counting the launch vehicle). Moore said that Code S had done a preliminary, high-level look at what options might be out there for such a mission. Among the potential solutions considered was NRL's ICM - Interim Control Module - a project NASA spent a lot of money on - and then abandoned a few years back as an alternative to relying on Russia for all ISS reboost propulsion.

According to Moore "we did not find any existing stages to be attractive. It is not that difficult to construct a stage to do this." He noted that there were some things that would have to be invented to some extent. "Autonomous rendezvous and capture is something we have not done."

Why are there only two choices?

NASA has always been rather binary about the Hubble's fate: either you service it or you destroy it. Other options never seem to enter the picture. When I asked Moore if anyone had looked at the notions of deeding the telescope over to some organization or consortium provided they found a safe way to operate and then dispose of it, Moore said "that has not occurred to me." He then quickly said that that sort of discussion is not something he'd normally be worried about and that I should talk with Ann Kinney, Director of the Astronomy and Physics Division at NASA Headquarters.

He said "one of the problems that I have personally with unproven methods is that we run a risk in terms of investment and accomplishment. We want something that we understand very well. We do not want to have to have inventions in order to come up with a solution. Right now we have a policy position in Code S that we are not going to leave the problem for future generations. This comes directly from [NASA Associate Administrator for Space Science] Ed Weiler." As for how one might operate Hubble with a new propulsion and control stage Moor said "driving the telescope with a booster to do science is a lot more complex than what we do today."

In his telecon with reporters, Grunsfeld spoke of a variety of potential solutions under development that would allow the useful life of Hubble to be extended. Right now three of its 6 gyroscopes are offline. Several of those online have given indications that they are getting close to the end of their lifetime. The orthodox rule for Hubble has been that three gyros are needed for full fledged science operations. Last summer the chance that there would be three operational gyros by Summer 2006 was rated at only 30%.

Grunsfeld spoke of software solutions that would allow Hubble to continue operating with only two gyros and he speculated that it might even be possible to continue to do some science with only one. However, there is still no plan (or any apparent interest) to try and extend Hubble's life through automated means - just to dispose of it.

When I asked Moore when the decision to bring Hubble back would be made he said that this would likely depend on whether the telescope was still able to do science. AS for when they'd need to have the disposal solution in place, Moore (who was then speaking under the assumption that SM4 could extend Hubble's life until the end of the decade) said that NASA would like to have the solution (propulsion stage) in place and ready to go. If this stage simply serves the function of deorbiting the telescope then it is just a matter of waiting until the telescope no longer worth operating. However, according to Moore, if such a stage is designed to extend science, then the issue becomes more complex.

In a press briefing in Pasadena on the eve of Opportunity's arrival on Mars, O'Keefe said that looking into such options might"raise the risk even higher". He continued "That would overcome one element but raise a whole other set of risks." Of course, the automated rendezvous an docking required to attach to and then deorbit the Hubble would be required regardless of whether the interest was to operate it or deorbit it.

According to Moore, new gyros would allow Hubble to continue operating until the end of the decade, perhaps a bit beyond and that disposal would be likely between 2010-2012. Now, with the prospect of a partially functional - potentially inoperable vehicle years earlier, it would seem that NASA needs to get started on a solution much faster. In December Moore spoke of possibly issuing a RFI for soliciting concepts in early 2004. There has been no word yet as to whether NASA will still be issuing that RFI with ground rules amend to reflect the cancellation of SM4.

We've been here before

NASA has faced this end of life dilemma before. In 2000 NASA made the decision to deorbit the Compton Gamma Ray Observatory when its complement of gyros needed to continue safe and productive operation failed. Compton was launched by Space Shuttle mission STS-37 in 1991 for a 5 year mission. It had operated for more than 9 years and had more than met all of its primary science objectives. CGRO had made many scientific discoveries, some of them "fundamental" according to Ed Weiler.

While CGRO was launch by a shuttle mission and was designed to be captured and repaired, Weiler decided that the spacecraft had more than accomplished what it was designed to do and that the prime issue was how to make certain that this spacecraft, which, at 33,000 lbs was one of the largest NASA had lofted, would land in a location far from where it could do any damage.

Of course, there is also the issue of what to do with the International Space Station when its mission is accomplished. I can recall a phrase in the high level requirements document used during the Space Station Freedom program that said that nothing could be launched that could not be safely returned to Earth. While NASA has been somewhat shy on this looming issue some thought has been given to it.

Of course, this was also a controversial issue with regard to Russia's venerable Mir.

Other options?

While the architecture that will eventually unfold to support the implementation of the President's new space policy has yet to appear, many, many attempts at coming up with architectures to support activity in earth orbit and cis-lunar space have been envisioned over the years. Almost without exception, such scenarios involve in-space propulsion- the moving of things from one place to another. One of the most common ways to do this is with a vehicle often referred to as a "space tug".

A space tug would have the ability to dock with, move, and then deposit another spacecraft in a new location. Some tug concepts rely upon traditional chemical propulsion, Other concepts envision the use of electric propulsion. Still other notions accomplish the task of moving things around with solar sails, momentum exchange tethers, and other more exotic means.

Regardless of which modalities are considered, it is almost a certainty that they vision embraced by the new space policy is gong to reuse this sort of capability. Why not use the Hubble predicament as a means to leverage an opportunity to come up with a solution with the need to develop such new capabilities? Indeed, NASA still needs to solicit ideas for Hubble's destruction - why not ask for ideas on how to save it as well?

Related Links

  • 16 January 2004: Internal STScI memo
  • 16 January 2004: Servicing Mission 4 Cancelled, Space Telescope Science Institute
  • 20 August 2003: Space Tug to NASA's Hubble Space Telescope's Rescue?
  • Hubble Servicing Mission 4 (SM4), NASA GSFC
  • 31 July 2003: Expected Hubble Space Telescope Science Lifetime After SM4
  • 31 July 2003: NASA Hubble Space Telescope End of Mission (EOM) Options
  • 31 July 2003: NASA Office of Space Science HST-JWST Transition Plan
  • 31 July 2003: NASA Hubble Space Telescope Servicing Missions: An Astronaut's Perspective
  • 31 July 2003: Increasing Hubble's Capability with New Instruments
  • Background Information

  • 14 Janaury 2000 NASA Preparing Plans for Destructive Reentry to End Compton Gamma Ray Observatory's Mission
  • 4 Jun 2000 Compton Gamma Ray Observatory Crashes on Earth
  • 7 Apr 1999: ISS end of life Disposal

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