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The Case Against Hubble

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by Bruce Moomaw
Sacramento CA (SPX) Aug 18, 2004
As is widely known, NASA Administrator Sean O'Keefe has ruled out any final Shuttle mission to repair the Hubble Space Telescope and install its two final planned instruments: the Wide Field Camera-3 and the Cosmic Origins Spectrograph.

He has done this because Hubble is in a radically different orbital inclination from the ISS. This means that any Shuttle sent up to repair it, which became stranded in orbit (after the crew, for example, discovered reentry shield damage of the type that destroyed Columbia), would be unable to match orbits with and dock with the Station to provide its crew with an emergency shelter (on which to wait for later rescue by another Shuttle or Russian Soyuz spacecraft).

Instead, O'Keefe has now become an eager fan of a proposed robotic Hubble repair mission.

It will, in any case, be necessary to launch a "Deorbit Stage" that will automatically rendezvous and dock with Hubble. After Hubble finally becomes scientifically useless, the Deorbiter can eventually be used to bring Hubble down over a selected safe spot, rather than the telescope eventually burning up at some uncontrollable location, where any of its large surviving pieces might hit some unlucky Earthling.

O'Keefe proposes to augment this Deorbit Stage ("DS") with a two-armed robot repairman that could perform all the important repair work that had been planned for the final Shuttle Hubble repair mission ("SM-4").

It would be built by MD Robotics, the same Canadian company that has built the robotic arms for the Shuttle and Station.

The Deorbit Stage, by itself, could easily do one part of that job. Hubble's batteries are gradually deteriorating; and the DS could carry its own solar panels and batteries and start feeding replacement power to the Hubble through an umbilical plug fastened to Hubble's bottom. The other parts of the repair work, though, would be much harder.

The highest priority of all is to replace Hubble's super-precise attitude-sensing gyroscopes, which are also slowly wearing out. It needs three of them to operate perfectly, and it also carries three spares.

Two of its six gyros have already failed - which means that when two more gyros wear out, Hubble must switch to a "two-gyro" operating mode that will place some serious restrictions on its scientific observations (although it could still do a lot of useful work).

And if one more gyro were to fail (and certainly after they all failed), Hubble would be utterly useless for science (although its remaining attitude control sensors could keep its solar panels pointed at the Sun to ensure that the satellite kept functioning).

NASA's latest estimates suggest the odds are better than 50-50 that this crisis point - when Hubble has only two working gyros left - will be reached by December 2005, and that 15 months after that there's a 50-50 chance that it will lose one of the remaining two gyros and become scientifically useless.

(If NASA deliberately turns off one of the working gyros next January to turn it into a spare, they might be able to get an additional 10 months out of the Telescope.)

Aviation Week magazine reports that Hubble's engineers have concluded that the problem can't be solved simply by docking a Deorbit Stage to it- equipped with its own set of super-precise gyros- to precisely stabilize Hubble itself, or to radio precise attitude information from the Stage's gyros to Hubble's own attitude-control system.

This is because the docking fixture- where the Stage must attach itself to Hubble- is fastened to a thin, mildly flexible aluminum bulkhead on Hubble's rear.

No matter how precisely the Stage tries to control its own and the attached Hubble's attitude, the Telescope will wiggle back and forth - only slightly, but more than enough to ruin the super-precise pointing which Hubble must carry out to make any usable astronomical observations.

The only way to carry out the single, highest-priority repair to Hubble is to actually open the door on the equipment compartment containing the gyros, slide them out, and slide in some new replacement gyro packages. The Canadian two-armed robot may be up to this chore, judging from ground tests.

But can it perform the other important part of the cancelled Shuttle repair mission: installing the two new science instruments? One of these - the Wide Field Camera-3 ("WFC-3") - would replace the considerably less capable "WFPC-2" camera currently on Hubble.

The other - the Cosmic Origins Spectrograph ("COS") - would replace the "COSTAR" package of corrective mirrors that was installed in Hubble by the first repair mission back in December 1993 to correct for its faultily shaped main mirror.

Astronauts had to remove the least important of Hubble's five original science instruments, the High Speed Photometer, to install COSTAR.

Every new instrument that Shuttle crews have installed since then has carried its own built-in corrective mirror. Only after this last cancelled Shuttle repair mission would Hubble finally be working the way it was originally supposed to: with five science instruments and a properly focussed mirror view.

However, the WFC-3 wouldn't just replace WFPC-2; it would also take over most of the duties of one of the other current instruments: NICMOS - "Near-IR Camera and Multi-Object Spectrometer". In practical terms, then, Hubble would still be using only four instruments.

Can the Canadian robot do this? It may be able to successfully replace WFPC-2 with WFC-3, which (as with the gyro replacements) is a relatively simple task of opening the camera compartment door, unfastening two bolts, pulling out the old camera, sliding in the new camera package to replace it, and rebolting it.

But this will still be a trickier job than replacing the much smaller and lighter gyro packages - and if the robot can't completely close the compartment door afterwards, the small amount of sunlight that will leak into it through a tiny gap in the doorjamb will ruin the camera's pictures.

Replacing the COSTAR package with the COS spectrograph is much harder as it requires unplugging small, individual electrical connections designed to be handled by human hands, and plugging in new ones - the sort of detailed work that the astronauts on Shuttle crews have done very well.

Is a robot - even a sophisticated robot - up to it? This question is genuinely open at this time; it may not be practical for a long time for any robot to do it reliably.

Finally, there's the serious matter of cost. The cost of simply flying a Deorbit Stage without the repair robot has been thought to be about $300 million - but on August 11 NASA presented an estimate to Congress that adding the repair robot to such a mission would raise its cost to fully $1.6 billion.

This makes the robotic repair mission even more expensive than the manned Shuttle servicing flight would have been - although with no risk to astronauts' lives. (Any manned Hubble repair mission, incidentally, cannot cram the Deorbit Stage into the Shuttle's cargo bay along with all the other needed equipment -it would have to be separately built and launched.)

Moreover, "Space News" reported on August 13 that NASA's official $1.6 billion is actually its private minimum cost estimate for the repair robot: "An internal NASA study completed in recent weeks, according to government and industry sources, estimated the cost of such an undertaking to be $1.6 billion to $2.3 billion."

And any such servicing mission - manned or robotic - has a 50-50 chance of prolonging Hubble's working lifetime by only another 3 1/2 years.

NASA Administrator O'Keefe remains enthusiastic about the idea despite the cost, on the grounds that such robotic repair technology must be developed at some point anyway for application to America's later space exploration and exploitation program.

But finding the money for it will be difficult, at a time when Congress (as the House Appropriations Committee has just shown) is extremely reluctant to oblige President Bush's appeal for an increase in total NASA funding.

And this is also a time when the costs of qualifying the Shuttle for any acceptably safe return to flight are growing at an bloodcurdling rate. (Just in the last few months, another $450 to $750 million has been added to NASA's FY 2004 and 2005 costs for this alone.)

The mushrooming Shuttle cost seems likely to devastate the rest of NASA's budget over the next few years. Piling another billion dollars on top of that may be unbearable (unless the government finally cuts the Gordian knot at some point by canceling both the Shuttle and the Space Station).

Moreover, there is a genuine - and serious - risk that the robot could fail.

Last month, the National Academy of Sciences committee- assigned by NASA to judge the advisability of such a mission- said that the mission would be "highly complex, due to the inherent difficulty with supervised autonomy in the presence of time delays; the integration of vision and force feedback in six-degree-of-freedom assembly and disassembly tasks with high-degree-of-freedom, dexterous manipulators; and the coordinated control of the high-inertia Robotic Vehicle with a long-reach robotic arm grappling with a high-inertia payload.

"Robotic... replacement of instruments and subsystems on Hubble will require... a human in a telerobotic loop that has a substantial (on the order of 2-second) time delay...

"Based on information provided to the committee and the knowledge of members who have deep experience with Shuttle flights and spacecraft servicing, the committee believes that the proposed robotic mission to Hubble will essentially be an experimental test program that is expected to accomplish specific programmatic objectives at the same time."

Are there any workable alternatives to a robotic or manned Hubble repair mission? Yes indeed. As Jeffrey Bell noted in an April 28 "SpaceDaily" article, there has been quite a lot of discussion about the alternative of building and launching an entirely new large orbiting telescope carrying the two new instruments intended for installation on Hubble.

It's now widely realized that NASA's earlier insistence that Shuttle repair flights to the Hubble were cost-savers was not only mistaken, but downright fraudulent - part of NASA's mammoth, deliberate 30-year hoax on Congress and the public to start the Shuttle program in the early 1970s and to preserve it during the following years of cost increases.

At about $1.3 billion per flight, each Shuttle repair flight has cost at least as much as it would cost to build a new duplicate Hubble Space Telescope and launch it on an expendable booster - and maybe a good deal more.

The possibility of building a new space telescope to carry WFC-3 and COS has been under discussion among NASA's science advisors for over a year.

Last November the scientific subcommittee in charge of the "Origins" branch of NASA's space science program - one of the two somewhat fuzzily separated space science branches connected with the astronomy observations of targets beyond our Solar System - recommended that NASA initiate a new program of "Origins Probes".

These medium-cost missions would be intended "to observe the birth of the earliest galaxies, the formation of stars, to find all the planetary systems in our solar neighborhood, to find planets that are capable of harboring life, and to learn whether life does indeed exist beyond our solar system."

This February NASA put out an official request to independent science teams to propose possible ideas for such missions, to be flown about every four years starting around 2010, if the money proves available.

The Origins branch holds sway over a large part of the Hubble Telescope program, despite the fact that just as many of its observations can be said to better fit the goals of the Structure and Evolution of the Universe ("SEUS") branch, which deals with cosmology - the origin of the Universe itself and the most fundamental nature and structure of space, time, matter and energy within it.

When NASA, on July 29, finally announced a list of the nine mission concepts to be funded for further study, most of them also had strong relevance to cosmology as well as to the development of stars within this galaxy and the search for their possible planets.

And one of those concepts was the Hubble Origins Probe ("HOP") proposed by Colin Norman of the Space Telescope Science Institute, which operates Hubble.

HOP would fly the WFC-3 and COS instruments- intended for installation on Hubble- on a new orbiting space telescope, in a similar low Earth orbit, with a 2.4 meter mirror just as big as Hubble's.

But (like the other Origins Probe ideas) it would cost less than $670 million, thanks to the major cost-saving advances in technology that have occurred since Hubble itself was built in the 1980s.

(For instance, the European Space Agency's "Herschel" infrared space telescope, set for launch in 2007, costs only about a billion dollars and weighs less than one-third as much as Hubble - but it carries three instruments, and its mirror is almost half again as wide as Hubble's and has over twice as much light-collecting area.)

And the cost of each generation of new replacement instruments on Hubble itself has dropped at the same time that their data return has literally skyrocketed.

If HOP - or a spacecraft like it - is viable, then obviously a second HOP could be flown carrying copies of Hubble's other two current instruments (not including the mostly-redundant NICMOS).

So, at a total cost of a little over $1.3 billion - the same or less than the proposed robotic or manned Hubble repair missions that would renovate the telescope for one final lifespan of 3 1/2 years - the same four primary Hubble instruments could be flown and operated for a comparable period on two new orbiting telescopes.

Besides having a higher chance of success, such a split mission has other major advantages. Its total cost - two separate spacecraft, with the first not launched until 2009 and the second a few years later - would be spread out over the coming years in a way making it vastly easier to fund than the robotic or manned Hubble repair mission, either of which requires quick and massive funding to save the original Hubble by 2007.

Also, this setup- splitting the copies of Hubble's four main instruments among two separate telescopes- would have enormous scientific advantages in itself.

On Hubble now, only one instrument can be used to observe any specific scientific target at a time. All the other instruments, which use different parts of the telescope's focal plane, must stare off at random parts of the sky.

But if Hubble's four main instruments were split among two separate telescopes, obviously two of those instruments could stare at specific targets at any one time - thus doubling the mission's scientific productivity for the same cost.

Finally, there's an important new development: on August 3, one of Hubble's four instruments failed. This is the Space Telescope Imaging Spectrograph ("STIS"), which can take detailed ultraviolet spectra of hundreds of individual spots on a celestial object to provide a detailed map of its composition and temperature.

Its primary power distribution system had failed earlier; now the backup has. It's not impossible that some way may be devised to revive it with the right radio commands, but the odds aren't good.

STIS had already worked for two years beyond its five-year design lifetime, but it was definitely still one of the stars of the Hubble mission. 30% of Hubble's observational time was devoted to using it, as against 45% for Hubble's Advanced Camera for Surveys, or "ACS". (Hubble's other two instruments - WFPC-2 and NICMOS - are definite also-rans. The telescope devotes only a quarter of its time to both of them combined; and in any case the WFC-3 camera would completely replace both of them and be able to do more to boot.)

STIS' observations must currently be replaced with lower-priority ones, using the remaining three instruments. And the Cosmic Origins Spectrograph - although important - could fill in for only a small fraction of STIS' observations; COS is a more sensitive UV spectrometer, but takes spectra from only one spot at a time.

No matter how complex the installation of a replacement STIS in Hubble might be, it's seriously doubtful that the repair robot could successfully carry and install three new instruments on Hubble during one mission - and there is also almost certainly no way that a replacement STIS could be added to the Shuttle's load for a single manned repair mission. Moreover, it would also be troublesome to dig up the money to hastily build a replacement STIS in time for a 2007 repair mission.

By contrast, flying the second Hubble Origins Probe around 2012, with replacements of the STIS and ACS, would be far easier (even given the cost of building a second ACS camera).

In short, the case is extremely strong for not flying a 2007 Hubble repair mission of any sort, but instead letting the first Hubble die a natural death and replacing it over the next four or five years with two new vastly cheaper telescopic satellites- even if these end up costing somewhat more than the total $1.3 billion that Dr. Norman suggests.

Administrator O'Keefe's chief rationale for flying the repair robot is that this would allow the development of new space technology - for the automated repair of orbiting satellites - which the US will need at some point in the future anyway.

But O'Keefe's ignorance of basic details of aerospace technology is now infamous. And this is not the first time he has been tricked into backing a seriously questionable major new program by his more experienced NASA underlings. They hold a strong and predictable desire to keep the agency's total funding level pumped as high as possible, whether it's justified or not.

There's also the equal eagerness with which he cancelled the proposed billion-dollar Europa Orbiter, and shocked everyone instead by proposing to replace it with the Jupiter Icy Moons Orbiter - a 26-metric-ton behemoth, propelled by a revolutionary new nuclear-electric propulsion system powered by a miniaturized nuclear reactor, which would cost at least $9 billion to create.

The JIMO mission would also carry out orbital studies of Ganymede and Callisto -- which NASA's own planetary scientists say have far lower priority scientifically than Europa does, and could be done far more cheaply later by simply flying a couple of separate near-duplicates of Europa Orbiter.

And JIMO is so big that the US currently doesn't even have a booster strong enough to launch it! Unless we develop a new Heavy Lift booster, JIMO will have to be launched into Earth orbit in two separate pieces, which will then automatically rendezvous and dock in earth orbit, before the craft is propelled to escape velocity.

Once again, O'Keefe has tried to justify JIMO on the grounds that nuclear-electric propulsion will be important for US space exploration at some point, and so we might as well start developing it immediately.

But NASA's own scientific advisory group on Solar System exploration says flatly that the earliest planetary mission that actually needs NEP is a proposed Neptune orbiter that does not need to fly until the early 2020s.

So NEP could be developed on a far more gradual and acceptable funding schedule. Indeed, its development cost for such a mission would be far lower, since a Jupiter-orbiting mission is unique among all possible Solar System NEP missions, in requiring very expensive technology to make NEP's electronics resistant to Jupiter's own extremely intense radiation belts.

Congress seems to agree - the House Appropriations Committee has just voted to remove all the planned fiscal year 2005 funding for the JIMO mission, and almost half of the money for the overall "Prometheus Project" to develop nuclear-electric propulsion in general.

Similarly, while orbiting robot repairmen for satellites will indeed be useful for some US space missions in the moderately near future, one is definitely not required - and in fact is seriously counterproductive, both scientifically and economically - for Hubble.

Once again O'Keefe has been tricked by his technological ignorance and his dishonest underlings into backing a seriously over-hasty project which would further bloat NASA's funding, and which would actually be destructive to the nation's scientific and space interests, instead of following a far more rational development schedule for it. It's to be strongly hoped, in the cases of both JIMO and the Hubble Repair Robot, that his serious error will be corrected either by himself or by Congress.

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Hubble Peers Inside A Celestial Geode
Paris (ESA) Aug 13, 2004
Real geodes are handball-sized, hollow rocks that start out as bubbles in volcanic or sedimentary rock. Only when these inconspicuous round rocks are split in half by a geologist, do we get a chance to appreciate the inside of the rock cavity that is lined with crystals.



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