Human Hubble mission wins support

By Molly Bentley

Hubble needs regular maintenance

Support is growing for a human mission to be sent to repair the Hubble space telescope instead of robots.

The American Astronomical Society (AAS) said it endorsed a National Research Council recommendation that Nasa pursue a manned mission to repair Hubble.

It said the mission should be launched as early as possible after the space shuttle is ready to fly again.

Scientists have been wrangling over how - or whether - to service the ageing telescope for some months now.

The debate over using a human or a robot has grown contentious.

A panel of the National Research Council (NRC), the operating agency of the National Academy of Sciences (NAS), recently recommended that astronauts make the repairs.

"[The NRC] came down very clearly saying that if you really care about the space telescope, then doing the shuttle mission is the best answer," said Robert Kirshner, Harvard University astronomer and AAS president.

Not in time

The NRC panel comprises a group of distinguished astronomers, engineers, former astronauts and Nobel laureates.

Its December report concluded that an unprecedented robotic mission might not be developed in time to save Hubble.

It might also be more technologically risky, and could critically damage the telescope.

We have probably as many questions as you have about what is the future of Hubble, what is the best way to maximise the future of Hubble and what are our options Colonel Mark Borkowski, Nasa project manager

It also found that the differences between the risks faced by a crew to service Hubble and those of a single shuttle mission to the International Space Station (ISS) were small.

US Congress had directed Nasa to request a study from the NRC to look into servicing options for Hubble, after Nasa cancelled what was to be the fifth, and final, shuttle-servicing mission to the telescope.

Nasa Administrator Sean O'Keefe, citing safety concerns, announced the decision to cancel the shuttle flight shortly after President George Bush announced his space initiative.

He said that shuttle flights would be used only to service the ISS, as a step towards putting humans on the moon and Mars.

Since then, the space agency has pursued robotic options to repair Hubble's fading gyroscopes and batteries.

The telescope is also slated to be fitted with a new camera and spectrograph.

The Cosmic Origins Spectrograph would be sensitive to very faint UV light, such as intergalactic gas from the early universe, and the Wide Field Camera 3 would be optimised for infrared, ultraviolet and visible wavelengths.

With repairs, Hubble's observing life could extend to 2013.

Although it recently signed a contract with a Canadian firm, MacDonald Dettwiler Robotics, to develop a servicing robot, Nasa has not fully committed to a robotic mission.

Colonel Mark Borkowski, Nasa project manager for Hubble Robotic Servicing, said at the AAS meeting last week that 2005 would be used to firm up a plan.

"We have probably as many questions as you have about what is the future of Hubble, what is the best way to maximise the future of Hubble and what are our options," he said.

Left in space?

Although the agency is investigating the feasibility a robotic mission, there is also the alternative of leaving Hubble to its fate.

While the robotic technology developed is encouraging, said Dr Borkowski, it may neither justify its estimated $175 to $300 million price tag, nor be viable in time to save the telescope.

A preliminary design review of the robot is scheduled for March, with a critical review to follow in the autumn.

Hubble needs an urgent upgrade

Plan B would be not to service Hubble and bring it down at the end of its observing life.

In this case, a robot could also be developed to de-orbit the instrument.

While Dr Borkowski stressed that the NRC recommendation of a shuttle flight would be "key input" into the ultimate decision about repair, he also reiterated that Nasa had no plan to conduct shuttle servicing.

Rodger Thompson, a University of Arizona astronomer and principal investigator of the Near-Infrared Camera and Multi-Object Spectrometer, which astronauts placed on Hubble in 1997, reiterated the appeal of the NRC finding.

He told the BBC News website that Hubble was specifically designed for shuttle servicing, and that four prior astronaut missions to the telescope were "very successful."

The timing for pursuing a course of action for Hubble comes at a time of great uncertainty and restructuring for Nasa.

Nasa is shuffling priorities and funding to accommodate President Bush's back-to-the-moon initiative and is in leadership limbo as Mr O'Keefe prepares to step down.

"A new administrator will have final decision in where we go," said Nasa spokeswoman Susan Hendrix, of Goddard Space Flight Center.

Robot tests

The telescope's science instruments are still working well, said Rodger Doxsey, head of Hubble Mission Office at the Space Telescope Science Institute (STScI) which operates Hubble for Nasa.

Although one, the Space Telescope Imaging Spectrograph (STIS), did go out of action last year.

While Hubble awaits its tune-up, Nasa scientists weigh options for battery and gyroscope conservation.

One flight to the Hubble Space Telescope will produce far more science than 25 flights to the ISS Rodger Thompson, University of Arizona

"Our goal is to get the longest lifetime that we can," said Dr Doxsey, "We don't want to lose science waiting for the servicing to take place."

The ultimate lifetime limiters for Hubble are its batteries. Without servicing, the batteries will die in 2007 to 2008.

Hubble has six gyroscopes which keep the telescope stable. So far two have failed, although it only needs three to control it.

The proposed fixer robot that could do the job is a slightly modified version the dexterous robot built to service the ISS.

It is designed for complex manoeuvres in space and has been tested at Goddard on a mock-up of Hubble.

Dr Thompson said that, although he is impressed with the robot's performance, an unprecedented robotic repair of Hubble is too risky to be pursued single-mindedly.

He said that a return to shuttle flight was inevitable and that many flights were necessary to complete construction of the ISS anyway.

"One flight to the Hubble Space Telescope will produce far more science than 25 flights to the ISS," he said.

Great Hubble discoveries are still to come, agreed Dr Doxsey, and efforts should be made to encourage them.

"We want to think twice about turning off a telescope that is at its prime," he said.