From: LARRY KLAES (ljk4_at_msn.com)
Date: Mon Mar 08 2004 - 09:32:31 PST
Hubble's Improving View Worth Servicing Mission Risk, Argue Astronomers
Aviation Week & Space Technology
03/08/2004, page 56
Frank Morring, Jr.
Washington
Astronomers press Hubble servicing mission, arguing telescope's view outweighs risk
Lost Vision
Astronomers angry and confused at NASA's decision not to mount another servicing mission to the Hubble Space Telescope say Administrator Sean O'Keefe has cut down the orbiting observatory in its prime, using specious reasoning about the risk of a mission at a time when the telescope may offer answers to some very basic questions about the Universe.
New Hubble-bound instruments grounded by O'Keefe's decision would give scientists their best chance yet to answer the riddle of so-called "dark energy" that is believed to make up some 70-75% of the Universe. Yet many of the safety concerns cited for not returning to Hubble to install the new instruments appear to hold as well for the International Space Station. That is the planned destination for 25-35 missions--including some of the most complex ever attempted--before the space shuttle is retired after 2010.
"They're planning to have the same failure they had before," said George N. (Pinky) Nelson, a former astronaut who flew on the first shuttle mission after the 1986 Challenger accident. "If they haven't fixed that one, they probably shouldn't be launching anyway."
NASA has pushed its earliest return-to-flight date back to Mar. 6, 2005, to give engineers more time to fix the big shuttle external tank so it won't shed the insulating foam blamed in the Columbia disaster, and to harden the orbiter against any foam or other debris that does strike it (AW&ST Feb. 23, p. 98). Also in the works are upgrades that would enable a shuttle crew to inspect for damage while in orbit and repair the damage if necessary, requirements set by the Columbia Accident Investigation Board (CAIB) for return to flight.
With the shuttle now set for retirement "by the end of the decade," the Hubble servicing mission is unique on the flight manifest in that the International Space Station would not be available as a repair station or as a "safe haven" for the crew of an irreparable orbiter. CAIB set on-orbit inspection and repair as a return-to-flight requirement, and NASA has developed ways to inspect most of the orbiter using a camera and laser sensor mounted on a 50-ft. boom attached to the end of the robot arm.
Late last month engineers at Johnson Space Center validated two different ways to repair the reinforced carbon-carbon (RCC) panels that protect the orbiter from the highest heat of reentry (and that cracked on Columbia when hit by loose foam), subjecting them to 900 sec. of arc-jet heating that mimicked the reentry environment. The techniques --a patch and anchor-bolt combination for small cracks and holes, and a carbon silicon carbide composite overwrap for larger damage--still must be engineered for flight operations and manufactured, according to Steve Poulos, manager of the Orbiter Project Office at JSC.
Poulos said the boom is not sturdy enough to support an astronaut working at its end, since it would take only an estimated 2 lb. of force from there to overpower a fully extended arm's brakes. Nor is the arm/boom combination able to cover the entire orbiter. Because of the lack of visual cues when the arm is reaching across the open payload bay door to extend the boom along the starboard side of the orbiter, 20-30% of that side would be out of reach of the boom sensors. Present plans call for using the ISS arm to complete the inspection, and to support an astronaut if repairs are needed.
Still to be developed is a way to inspect and repair the orbiter if it achieves orbit but fails to reach the station, a condition critics like Nelson point out would leave it in the same circumstance as a Hubble servicing mission. Poulos said one idea would be to attach an adhesive mat near the end of the boom to anchor it during repairs, but much work remains.
"I've got a much better feel today for how we're going to repair and those types of things while we're attached to station, but the autonomous repair part is not as clear to me yet," Poulos said.
Without a way to conduct repairs away from the ISS, the crew of a damaged shuttle would find itself just as stranded as Columbia's crew would have been had it known of the fatal hole in the RCC protecting their orbiter's left wing. NASA is making preparations to send a second orbiter aloft within 90 days to rescue a stranded crew that has reached the ISS, but no provisions have been made for one that fails to reach the station haven (AW&ST Feb. 23, p. 27).
Skeptics like Nelson don't believe NASA would actually take the risk of a rescue mission in the wake of a mishap "that would typically ground the fleet for a couple of years."
"Safety's got to be your most important function, but to me, if you determine the shuttle is safe to fly, then it's just as safe to fly to the space station as to the telescope," said Nelson.
Adm. (ret.) Harold Gehman, who was the CAIB chairman, is expected to offer his view on the risk of another Hubble servicing mission as early as this week. O'Keefe sought Gehman's opinion after Sen. Barbara Mikulski (D-Md.) questioned the mission cancellation, but the NASA administrator left little hope he would change his mind (AW&ST Feb. 2, p. 21).
That approach doesn't sit well with astronomers accustomed to the peer-review process that determines who gets to use major observatories like the Hubble and whether the resulting scientific papers are published. "You don't shut it down by doing an in-house discussion and announcing your results," said Garth D. Illingworth, an astronomer at the University of California, Santa Cruz, who sits on the NASA Advisory Council's space science panel. "I think you have to set up an open process which involves talented, knowledgeable people from outside as well as inside."
ILLINGWORTH WORKS with the Hubble's advanced-cameras team. As part of a $158-million instrument upgrade during the cancelled servicing mission, the Wide Field Camera 3 was to have been installed on the telescope in mid-2006 along with a new "Cosmic Origins Spectrograph" with optimized capability in the far ultraviolet wavelength. That new camera would be particularly useful in researching dark energy because of its wide field of view and high angular resolution, which would allow astronomers to seek and pinpoint the supernovae "standard candles" they use to measure the expansion rate of the Universe.
Dark energy is the term astrophysicists use to explain why the Universe is expanding at accelerating rates that don't make sense given the effect of gravity. A recent Hubble survey discovered 42 new supernovae, providing researchers with data that suggest Albert Einstein's idea of a "cosmological constant" counteracting gravity might have been correct, even though Einstein himself later rejected the idea as his "greatest blunder."
"Nobody knows what this stuff is," said Bruce Margon, associate director for science at the Space Telescope Science Institute, which operates the Hubble science program for NASA. "The Hubble has just returned the first quantitative constraints on what it might be and what it might not be. It's still a huge mystery, but Hubble is actively homing in on it. Nothing else can tackle this problem the way Hubble can."
Margon argues that the Hubble "gets better with age" as servicing missions upgrade its instruments and scientists use them to follow up on questions raised earlier in its service lifetime. His institute has counted almost 3,600 scientific papers published in refereed journals over the first 12 years of Hubble observations, the number steadily growing from year to year (see chart above).
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Message: 6
Date: Mon, 8 Mar 2004 08:33:01 -0500 (GMT-05:00)
From: DwayneDay <zirconic1_at_earthlink.net<mailto:zirconic1_at_earthlink.net>>
Reply-To: DwayneDay <zirconic1_at_earthlink.net<mailto:zirconic1_at_earthlink.net>>
To: fpspace_at_friends-partners.org<mailto:fpspace_at_friends-partners.org>
Subject: [FPSPACE] Hubble safety explained
Because I perceived a lack of a comprehensive explanation of NASA's decision to cancel the Hubble Servicing Mission due to safety concerns, I wrote the following summary:
http://www.thespacereview.com/article/111/1 This is simply a factual recounting of the safety decision, not a commentary piece.
Also at The Space Review you can find a discussion of NASA's new Code T exploration office.
DDAY
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