THE FORTNIGHTLY CLUB
OF REDLANDS, CALIFORNIA  - Founded 24 January 1895

4:00 P.M.

October 21, 2004

The Hubble Space Telescope

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by William K. Fawcett

Assembly Room, A. K. Smiley Public Library


Abbreviated Curriculum Vitae
of William K. Fawcett

                                    Born New Albany, Indiana,  1923

                                    Graduated from New Albany High School

                                    MBA from Indiana

                                    World War II service in Europe

                                    Korean War service in the Pentagon

                                    Acquired wife Marty and three daughters along the way

                                    Retired from Lockheed Corporation


Summary

An orbiting telescope became a realistic possibility in the 1960s when rackets became capable of boosting large payloads into apace. Only then could the distortions on grand-based astronomy caused by the Earth's atmosphere be overcome.

NASA approved the telescope program in the early 1970s, and funded competitive contractor studies until the two major contractors–- Perkin-Elmer for the Optical Telescope Assembly and Lockheed NOW and Space Company for the Support Systems Module -- were awarded contracts for dean and development in 1977. Launch was scheduled for 1993. In the meantime NASA to    bad selected Marshall Space Flight Canter over the Goddard Spaceflight Center to manage the program add serve as the systems engineer.

The Congress finally approved a budget of $475 million The program turned out to be more complex and difficult than envisioned, so funding was a continuing problem. As a result the participants were kept under constant pressure to reduce costs

The Telescope was not ready for the scheduled 1983 launch. The Challenger disaster in 1986 provided a reprieve. Finally on April 24th, 1990, the Hubble was launched aboard the Space Shuttle Discovery. The first images revealed that the primary mirror had been incorrectly ground by Perkin-Elmer as a result of an imperfection in its test set-up. Three years later a fix was installed by a Space Shuttle crow. The Hubble has performed flawlessly since. Cost at launch was $1.5 billion

NASA has been studying the next-generation Jane Web Space Telescope several years. It will be in orbit one million miles from Earth so it must be launched by rocket rather than by the Space Shuttle. It will operate in the infrared spectrum, so its temperature will be maintained near absolute zero by the ambient temperature of its position. It will have a folding 72 by 33 foot sunshade to protect it from heat and light. Its 20-foot mirror will be made of 18 segments of beryllium shoot that will unfold on orbit. Launch is scheduled for 2011. Cost is estimated at $824.8 million.

The Hubble Space Telescope

 The Hubble Space Telescope is one of NASA’s crowning achievements. It has enabled us to see where we have never seen before by removing the distortions imposed by the earth’s atmosphere. Hubble is not the largest or most powerful telescope built during the last three generations, but it is not a toy.  Optically, it is almost as big as the Mt. Wilson telescope, which pioneered many early astronomical studies.

The Hubble is about the size of a large school bus.  It is 43 1/2 feet long, 14 feet in diameter, and weighs about 24,500 pounds.  It was placed in a 350-mile near-earth orbit on April 25th, 1990, by the Space Shuttle Discovery, and circles the earth at a speed of 17,500 miles per hour every 97 minutes.  It is inclined at an angle of 28.5 degrees with respect to the earth’s equator.

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There are three principal parts of the Space Telescope: 1-the Optical Telescope Assembly, which receives light from sources being observed and, via its mirrors, delivers a focused beam to the second component, an array of scientific instruments, which measure and evaluate the beam; and 3-the Support Systems Module, which points the telescope and provides housekeeping services and structural support.

The heart of the telescope is the primary mirror of the Optical Telescope Assembly.  It is a concave mirror that reflects and focuses incoming light onto a much smaller convex secondary mirror a precise distance away.  The secondary mirror sends the beam back through a hole in the center of the primary mirror to the focal plane behind the mirror, where it is picked up by the scientific instruments that surround the focal plane.  This is shown by the figure.  This type of telescope is called a modified Cassegrain telescope.  It is essentially the same as those used as far back as Isaac Newton.

Astronomers have long recognized the limitations the earth’s atmosphere places on observations.made from the ground. German rocket scientist Hermann Oberth advanced the first serious concept of a space-based telescope in 1923.  His book The Rocket Into Planetary Space imagined a telescope in geo-synchronous (23,000 mile) orbit.  He recognized the advantages such a telescope would have, but his idea was way ahead of its time.  There was no such rocket at that time.  He helped develop a rocket much later by mentoring Wehrner Von Braun in World War II rocket development at Peenemunde, Germany

The Hubble Space Telescope is named for an astronomer who had no direct connection, but whose pioneering observations and theory of galaxy classification were important contributions to understanding of the universe. Edwin P. Hubble was born in Marshfield, Missouri, in 1889, received a B.S. in math and astronomy at the University of Chicago, and studied law at Oxford as a Rhodes Scholar. His research with the 100-inch Hooker Telescope of the Mt. Wilson Observatory in the 1920s and 30s helped change the concept of the universe. Our theory now is that our Milky Way galaxy of stars is not alone, but is merely one of billions of galaxies; and we can observe that the farther a galaxy is from Earth, the faster it appears to be moving away.  This formed the basis for the Big Bang theory.  Hubble died in 1953; the Space Telescope was named in his honor in 1977.

The person who can be considered the father of the Space Telescope is Princeton astrophysicist Lyman Spitzer, Jr. (1914-1997). In 1946 Spitzer proposed the development of a space-based observatory free from the distortions of the earth’s atmosphere.  Starting in the 1960s he lobbied Congress and a sometimes-reluctant scientific community on behalf of the telescope.  After the launch of the Hubble he continued to promote its use and to make important astronomical observations with it.

Interest in an orbiting telescope began to increase during the 1960s and early 1970s when the lifting capability of rockets made such a heavy satellite feasible. Meetings and conferences of numerous scientific societies and committees began to discuss the possibilities.  This was the beginning of the long process to get NASA to adopt the telescope as a project, and ultimately the Congress to fund it.

There were a number of basic questions that had to be addressed:

        Should it be part of a Space Station or tethered to it? Or orbiting freely?

        Should it be permanently configured at launch or capable of module replacement?   Should replacement be performed on-orbit or on Earth?

        Should it be rocket-launched or sent up on the Space Shuttle? How will it be compatible with the Space Shuttle, which was then being developed?  What limitations would be imposed by the Space Shuttle or by its crew?

Technical societies and committees, particularly in the field of astronomy, began to debate the various aspects of the orbiting telescope. Because so many of its projects are one-of-a-kind, NASA relies heavily on outside committees and boards to supplement its in-house experience and to review and advise as a project progresses.  Without the endorsement of the committees and boards a project has little chance of being approved by NASA.

The Space Telescope was emerging at a time when NASA was funding other major programs:  the Apollo launches and the moon landing of 1969; the advancing Space Shuttle program; and the cherished Space Station.  Each of these programs had its advocates within NASA, within the administration, and within the Congress as programs competed against each other for funding.  This was also the era of the Great Society of the Lyndon Johnson administration and the Vietnam War.  In this environment NASA’s budget was squeezed to the point that made planning very difficult.  So progress on the telescope was very slow.

As the technical questions were being addressed, informally at first and then by funded studies, the item of paramount interest became the telescope mirror, because its diameter established the outer diameter of theTelescope, which in turn had to fit in the cargo bay of the Space Shuttle if that were the launch vehicle.  The baseline mirror at that stage was 3 meters in diameter, which is slightly less than 10 feet, the equivalent in English units which will be used hereafter for ease of understanding. Ten feet was probably the largest diameter compatible with the Space Shuttle.

PHASE A

In early 1971 NASA decided to formalize the Space Telescope program.  Goddard Space Flight Center of Beltsville, Maryland, and the Marshall Space Flight Center of Huntsville were authorized to conduct Phase A studies for one year.  They were to make analyses to determine whether or not a spacecraft could be built to provide the desired performance.  Cost was not to be a factor at this early stage.  In effect, the two centers were also competing to determine which would become the lead center if the program continued into Phase B.  Phase B is when the design is finalized and costs refined.  Phase C/D, which follows, is when hardware would be developed, tested and launched.

Goddard had always been the lead center for astronomy; it had overseen the development of many instruments and spacecraft used for planetary and space explorations; it had conducted the missions involving those probes.  Marshall, on the other hand, had been involved with much larger and heavier items; it had developed the largest rockets, including the stages of the Apollo Saturn rockets, and was the lead center for the upcoming Space Shuttle.

Both Goddard and Marshall prepared preliminary designs of the telescope as each envisioned it.  They both found that a telescope would probably perform as expected and answer many of the astronomical questions contemplated.

In May of 1972 NASA Headquarters selected Marshall Space Flight Center to manage the Space Telescope program.  This decision sent shock waves throughout the world of astronomy.  Goddard was the home of astronomy.  Marshall did not have a single PhD astronomer on its staff.  One writer referred to Marshall as a backwater of astronomy.  And yet Marshall was going to manage the Space Telescope.   NASA Headquarters was accustomed to turf battles among its centers, and it had just created a beauty. The Goddard-Marshall relationship had always been among the rockiest.  It would turn out to be even more strained because while Goddard was responsible for the scientific instruments aboard the Telescope and for flight operations, it would be taking orders from Marshall.

As part of their Phase A studies, both Goddard and Marshall had recommended that to save costs the program should be managed by the lead NASA center, rather than by a prime contractor. This meant the selection of the Associate Contractors for the Support System Module and the Optical Telescope Assembly would be made by Marshall rather than by a prime contractor.  It meant that Marshall was responsible for integrating all parts of the program, which is the crucial systems engineering role often played by a prime contractor.  We’ll see the consequences of this decision later.  But it did place the most worrisome subcontract, the mirror, directly under control of Marshall instead of a prime contractor.

During Phase A and early Phase B many areas of investigation were studied, both by NASA and by interested contractors, some of whose efforts were funded.  A few will be cited to illustrate how basic many of the questions were.

        During the 15-year projected life of the telescope, should it be retrieved from orbit and serviced on the ground, or serviced by astronauts from the Space Shuttle?

        Should a prototype telescope be built for testing on the ground to make any necessary design modifications prior to construction of the flight vehicle?

        Should an instrument module be rotated to the focal plane, and thereby block the view of the other instruments, or should each instrument be allocated a segment around the periphery of the focal plane?  This lead to fixed-position instrument modules, all the same size, each with an unobstructed view.

        How were telescope sightings to be recorded and transmitted to Earth?  Film had been used for years by reconnaissance satellites, but it had many problems such as storage life and  insensitivity to certain portions of the viewing spectrum.  But its biggest need was for a device to read the film on-orbit for electronic transmittal of the data to the ground instead of by parachute..  On the horizon were electronic devices, called detectors, one of which called the Charge Coupled Device (CCD) had been developed by the Bell Laboratories just two or three years earlier.  This device is a silicon chip that produces an electrical photograph when light falls upon it.   It has since become widely used in video cameras, but at that time it was relatively unproven, and therefore risky, even though it had obvious advantages.

        After the mirror the second biggest concern highlighted by Phase A studies was how to attain the pointing accuracy the Space Telescope needed to achieve the desired targeting; and how to stabilize the spacecraft in that position. The required accuracy was defined as 0.005 arc seconds, an almost unheard of number.  This is an angle 1/360,000 of the angle subtended by the diameter of the moon (2160 miles) when viewed from the Earth.  The Telescope’s 97-minute orbital period meant that for most orbits, every hour-and-a-half the viewing activity would be interrupted for about 36 minutes, which would require the spacecraft to be repositioned accurately and the target reacquired.  On what benchmarks would the initial positioning and re-positioning depend?

These questions are typical of those raised on all new programs where the state-of-the-art is being advanced, whether for space vehicles or military systems.  Correct answers are even more critical for NASA, however, because usually only one item will be built and system performance is difficult to test on the ground.

PROGRAM COST

During Phase A cost estimates for the program began to emerge.  They ranged from $300 million to $750 million. The $750 million figure sent shivers through NASA Headquarters, because it had the responsibility for selling the program to the White House and to the Congress at a time when the cost of the Vietnam War was affecting the national economy. At the same time NASA was also trying to sell the Space Shuttle program and the Space Station.

Program cost would turn out to be the driving force behind the entire Space Telescope program. NASA Headquarters took the position that the program could not be sold if the projected cost exceeded $300 million.  This drove studies throughout its life to re-design the telescope to reduce its cost, sometimes by as much as half. The re-designs were aimed at reducing the size and the capability of the spacecraft, which aroused suspicion among astronomers that the benefits might not be worth the cost.

Negotiations with the Congress and the Office of Management and Budget over many years became very heated.  Committee chairmen who had been burned by past NASA cost overruns were determined not to let it happen again, so they forced NASA to the mat to defend its cost estimates.

Having established that program cost would always be a major issue for the Space Telescope, let’s table the topic until we see how the program fared.

PHASE B

In August of 1973 Perkin-Elmer and Itek each received $800,000 Phase B contracts for preliminary design and program definition studies of the Optical Telescope Assembly.  They were both experienced optical houses and they were the only companies submitting proposals.  The contracts were for 17 months. Major areas for study were the primary and secondary mirrors, the metering truss to maintain the precise alignment of the two mirrors; and the Fine Guidance Sensors for positioning the telescope on the reference stars.  At that time the cost of a man-year of labor was about $50,000. The $800,000 contracts, then, equated to about 16 man-years of effort, which when spread over almost a year-and-a-half, provided funding for about12 people.  We will come back to this later.

Six months later Marshall issued its Phase B Request for Proposals for the Support Systems Module.   This module provides structural support for the spacecraft, pointing control, thermal control, electrical power, communications, and data handling.  Martin Marietta, Boeing, McDonnell Douglas, Lockheed, and Grumman responded. On the 15th of November 1974 contracts for $700,000 were awarded to Martin Marietta, Boeing and Lockheed.  Each was directed to study the effect of mirror diameter on performance and cost.  Boeing was assigned the 6-foot mirror, Lockheed the 8-foot, and Martin Marietta the 10-foot.  These options would lead to selection of a diameter by NASA, and then all the contractors would concentrate on that diameter.

Three weeks before the proposals for Phase B were due, Congress voted to delete funding for the Space Telescope.  The pure science nature of the program and its projected cost were a bad combination in an atmosphere of Congressional fiscal restraint.  Even many members of the astronomy community, especially those who were ground-based, were not convinced of the worth of the program because of its potential impact on the NASA budget.  Unless the astronomers could be convinced to be more supportive, there was no chance that the program would be funded. 

Already NASA had been holding discussions with the European space community to determine what relationship, if any, could be worked out to share in the funding.  Full partnership was ruled out because the Europeans could not afford it. Responsibility for one or more of the instrument packages was the natural candidate for European participation, but they were not willing to expend funds without a guarantee of being selected.  They therefore insisted on being assigned one or more instrument slots in advance without competing.  To NASA and its advisory groups not only didn’t that seem the best way to ensure the best complement of instruments, but also it didn’t seem fair to US interests that were being encouraged to fund and develop instruments to compete for the slots.  After Congress cut off funds for the telescope in mid-1974, it dictated cost reductions and directed NASA to seek international participation.  The directive forced NASA to abandon the preferred 10-foot mirror in favor of an 8-foot mirror to reduce cost. ESA agreed to pay 15% of the development costs by supplying an instrument (the Faint Object Camera) and the solar arrays, and to furnish staff members to the Telescope operating team after launch.  In return ESA was guaranteed 15% of the available viewing time.

PHASE C/D

In January 1977, Marshall issued Requests for Proposal to Itek and Perkin-Elmer for the Phase C/D Optical Telescope Assembly contract.  The RFPs were based on the findings of the Phase B work performed by the companies and Marshall. The RFPs generally described the performance as best NASA could define it at that time, but they did not define the design. The only specific requirement was that the mirrors were to be made of Corning ultra-low expansion, titanium-silicate glass Code 7971, one of the Pyrex family of glass compounds. One surprise occurred in the bids:  having been encouraged by the NASA Administrator,  Eastman Kodak prepared a joint bid with Itek.

At the same time Requests for Proposal for the Support Systems Module were issued to Boeing, Martin Marietta, and Lockheed, the Phase B contractors.  Again the performance requirements were described in a general manner, with the specifics to be worked out as the designs progressed.

In July 1977 the Administrator announced the selection of Perkin-Elmer to build the Optical Telescope Assembly and Lockheed Missiles and Space Company to build the Support Systems Module.   Very likely one of the reasons the two were selected was that for many years they had worked very closely together on military photo-reconnaissance satellites, experience that was expected to pay off for the Space Telescope.  Perkin-Elmer also presented a winning design for the Fine Guidance System, which had become a particularly big challenge in Phase B.

Perkin-Elmer’s contract was for $69.4 million and Lockheed’s for $82.7 million.  These were 15% below NASA’s estimate, so NASA was pleased that they fit well with the $475 million Congress had finally approved.  This was also the occasion for the name change from Space Telescope and Large Space Telescope to the Hubble Space Telescope.

To make certain that the program stayed within the approved budget, NASA Headquarters placed a “cap” on the number of personnel Marshall could employ on the Space Telescope.   That number was 72 for the first year, a woefully inadequate number; it was gradually increased over the next four years to a maximum of 116.  We’ll come back to this later.

Launch of the Telescope was scheduled for December 1983, six years downstream.  Because at least two of those years were required to procure and polish a mirror, NASA ordered two 8-foot Pyrex blanks from Corning well ahead of the time they normally would be ordered.  One was to be delivered to Perkin-Elmer, the Associate Contractor, to be polished by a new, computer-controlled method, and the other to Eastman Kodak to polish and test the backup mirror by the Foucault technique.  The Foucault method was devised by the French physicist about 1850, and it had become the standard test..

The mirror blanks had a honeycomb core that resulted in a weight of only one ton instead of a four-ton solid disc one foot thick.  It looks like the illustration of the 17-foot Palomar honeycomb mirror.

It soon became apparent to everyone involved—NASA Headquarters, Marshall, the contractors and the astronomers—that the Hubble Space Telescope was much more difficult and complex than had been visualized, and was grossly underfunded.  As a result the program was in constant financial and political difficulties because of contractor performance and NASA management deficiencies.

Marshall was saddled with an overwhelming management task. Its function was to be the prime contractor responsible for the entire project, yet the number of people assigned was limited to 72.  It was the systems engineer, responsible for pulling all the pieces together so the overall system worked as it was supposed to.  But Marshall was not allowed enough people to do that, so it gave Lockheed the responsibility for providing systems engineering support on everything except the Optical Telescope Assembly. As a result of this split of engineering oversight, Lockheed could perform only a coordination function as advisor to Marshall because it had no authority over, and only limited visibility into, some of the program elements.

Perkin-Elmer in particular was a problem.  It operated more like a hobby shop than a major aerospace contractor. For example, NASA was using the military PERT/critical path cost and schedule system to plan and control the Hubble, but Perkin-Elmer was still a back-of-the envelope operation. As a result, its management of costs and schedules resulted in persistent cost overruns and behind-schedule performance.   Its Fine Guidance Sensors, which had played such a prominent role in its selection as the Associate Contractor, did not meet requirements and had to be redesigned, a totally unexpected cost.  Lockheed’s performance was partially obscured by the attention Perkin-Elmer required, but it too was having problems, especially cost. Scientific instrument costs also were running well above budget.

Fast forward to 1980, three years after the start of design and development.  Costs had risen dramatically in spite of NASA’s efforts to hold them down.  The launch date of 1983 was in jeopardy.  Perkin-Elmer finished the rough grinding of its mirror in August 1980, about a year late, partly due to defects in the blank received from Corning.  Fine polishing was completed in April 1981.  In the meantime Marshall canceled Eastman Kodak’s contract to save money even though it was almost finished polishing the back-up mirror.

THE INSTITUTE

Goddard Space Flight Center had retained the responsibility for managing the flight operations of the Hubble after launch. It had been engaged in a turf battle for many years with university-based astronomers who wanted an independent agency to select and control the scientific studies. The astronomy community did not trust NASA to be fair in distributing viewing time among all the scientists, both inside and outside NASA. NASA of course did not want to relinquish control over any part of the program to outsiders. The final compromise was the establishment in 1981 of the Space Telescope Science Institute, the science center manned by a staff of 200 on the campus of the Johns Hopkins University in Baltimore.    Although the Institute reports administratively to Goddard, it operates independently and is managed by a consortium of American universities. It receives requests for observation times; selects users and allocates viewing times to them; coordinates the schedules so Goddard can issue commands to the spacecraft stores and makes available data from scientific observations; and serves as the interface between Hubble and the public.  One of its first tasks was virtually unplanned: creating a catalog of stars to serve as guide stars for the Hubble Fine Guidance Sensors to position the Hubble.  This  proved to be very challenging.  By 1986 the Institute had been authorized a staff of 300 and by 1988 the staff totaled 470, including 143 PhD astronomers and scientists.

ASSEMBLY & VERIFICATION

It became clear that the telescope was not going to be ready for the 1983 launch date.  The Telescope was given a reprieve in January 1986 when the Space Shuttle fleet was grounded by the Challenger disaster.  This meant a new launch date could not be set until the Shuttle program was reactivated.

The original plan for testing and verification had been for the two Associate Contractors each to independently verify their own system and then mate the two in final preparation for launch.  This was an unacceptably risky and nave approach, and had long since been abandoned in favor of a thermal-vacuum test of the totally assembled spacecraft.  Preparation for the test was underway at the time of the Challenger accident, and the thirty-day test was completed six months later in July of 1986.  During the test, while all systems were operating in a vacuum, the temperature was alternated quickly between 350 F and -350 F to simulate the conditions to be faced in each orbit.  All systems performed well, except that more electrical power was consumed than expected, resulting in replacement of the solar arrays with new, more efficient arrays.

Because NASA could not estimate the duration of the grounding of the Space Shuttle, it was faced with the need to retain the staffs of the various Telescope teams until launch.  Key personnel especially would be in demand by other projects within their respective organizations. The best that could be done was to keep these people meaningfully employed in activities designed to reduce risk. In the meantime the Telescope remained in the ultra-clean Vertical Assembly and Test Area at Lockheed.

Finally,   it was ready and the Space Shuttle fleet was operational again.  In late 1989 the Hubble was transported by barge from Sunnyvale to Cape Canaveral.  On April 24, 1990, it was launched aboard the Shuttle Discovery.  Eighteen years had passed since the project was formalized, and thirteen years since the start of the design and development phase. Costs, of course, had continued to increase.  They stood at $1.175 billion when Hubble was launched..

With the launch came a sense of euphoria for the teams that had been under great pressure for so long.   Now it was time to sit back and enjoy the result.

After one month in orbit the Hubble was programmed to show its first observation, the so-called “first light”.  Usually this event occurs quietly without fanfare on a remote mountaintop at night with only an astronomer and some assistants present.  Not so with the Hubble.  This was well choreographed, with scientists and press congregated at Goddard, Marshall, and the Institute awaiting the first images.  This was the most excitement for NASA since the Moon landings.

The first images were less than spectacular, but that was usually expected.  The starlight had a small core surrounded by a huge halo of scattered tendrils.  (The scatter is shown on the left of the figure.) Everyone knew that some adjustments and refinements were always needed.  Everything would be okay.  But when the adjustments in the days after first light didn’t bring the scatter into focus, the sense of uneasiness grew.  Several analyses confirmed the worst fear: the main mirror had been incorrectly ground.  The.curve at the center did not match the curve at the edge; a condition called spherical aberration. Instead of focusing 80 to 85% of the light, only 10 to 15% was focused onto the core.  The severity of the problem was withheld from the press for about a month while the scientists tried to figure out what could be done..

On June 27th two months after launch, NASA held the press conference everyone had been expecting.  It was embarrassed to have to acknowledge publicly that the mirror was incorrectly ground.  After all those years, how had that happened?  The press, which had generally been supportive to that point, now had a field day in criticizing the Hubble and NASA.  Public interest, which had peaked with the launch, was now badly eroded by the negative publicity.

Let’s examine how the spherical aberration occurred and how it escaped detection.  To make sure the primary mirror was ground and polished accurately, Perkin-Elmer built a special device called a ‘reflective null corrector’ for testing the accuracy.  For about a hundred and fifty years the Foucault method for testing had been the standard.  Perkin-Elmer’s was a variation of that technique which introduced the new laser technology.  A tiny lens was suspended at a fixed distance above the main mirror, the distance critical to the accuracy of the test.  A light beam was flashed through the lens onto the surface of the mirror to create an interferogram, the same “fingerprint” used by the Foucault method to inspect the mirror surface.  But Perkin-Elmer’s test was thrown off by a mechanical problem that misread the distance between the lens and the mirror.  As a result three tiny shims were inserted to correct the position of the lens. This gave a false reading indicating that more grinding was needed.  For whatever reason, further grinding was not done, so the mirror was not ruined.

As a Monday-morning quarterback 25 years after-the-fact, I have three questions about the management of the mirror contract.  Why did Marshall permit Perkin-Elmer to re-invent the wheel by developing an untested method to verify the accuracy of grinding?  The Foucault technique had been proven, including its use on the twice-larger Palomar mirror in the 1940’s. And secondly why wasn’t the mirror double-checked by Foucault, especially since grinding was completed three and a half years before it was delivered to Lockheed in November of 1984?  The Foucault is the simplest of tests because it requires only an experienced technician, a light, a knife-edge, and a plate with a very small hole.  And the last question, if Eastman Kodak had been permitted to finish polishing and testing its mirror, on what basis would Marshall have chosen the mirror for flight?

RECOVERY

After NASA acknowledged that the spherical aberration of the primary mirror had resulted from faulty inspection, it assigned some of its brightest people to figure out ways to compensate for the telescope’s flaws.  Panels of experts were convened to study and evaluate the problem.  Tod Lauer of the Kitt Peak Observatory near Tuscon suggested the solution that was adopted.  His solution called COSTAR consisted of coin-sized mirrors placed in front of the science instruments.  The tiny mirrors refocused the light for the instruments to correct for the spherical aberration of the primary mirror.  One instrument package, the High Speed Photometer, was removed to accommodate COSTAR, which was built by Ball Aerospace.  Not only was improved vision at stake, NASA’s public image was hurting, and anyone who tried and failed to repair the problem would share in the disgrace.

Some consideration was given to returning Hubble to Earth for installing COSTAR, but the idea was abandoned because of fear that it might not be re-launched due to NASA’s tarnished reputation.  Instead, Space Shuttle Endeavour with a crew of 11 well-prepared astronauts was launched on December 2, 1993, to perform the first servicing mission of the Hubble.  They were assigned 11 EVA tasks, which they performed flawlessly. We all remember watching them on television. Chief among the tasks was removal of the High Speed Photometer so that COSTAR could be installed to correct for the spherical aberration of the primary mirror. Normal maintenance and instrument checks were conducted; for example, one scientific instrument was replaced by an updated one.  Because Hubble was in a near-earth orbit and therefore affected by low-level aerodynamic drag, the Endeavour’s final task boosted it back to its original orbit.

The great news was that COSTAR was successful. Observations before and after COSTAR are shown on the figure.  After three and a half years of frustration, the Hubble was finally capable of doing all the science it was intended to do.  For 11 years now it has performed flawlessly.  It has opened up the universe as never before.  Observations are being routinely shown in full color.  The most spectacular occurred March 9th this year when it observed light originating an estimated 12.5 billion years ago.  That is very close to the theoretical time of the “big bang.”

There have been three more servicing missions performed by astronauts, in 1997,1999 and 2002.

Each servicing mission has involved housekeeping functions and replacement of instrument modules, as improvements become available and the emphasis on science subjects shifts. Computers and gyroscopes have been exchanged.  The two 25 -foot solar arrays, which generate 2800 watts of power for communications, housekeeping and temperature control, have been replaced twice.  The Nickel-Hydrogen storage batteries have been replaced; there are six of them.  Together they provide power equal to 20 automobile batteries and are used during that portion of an orbit when the sun is obscured.  They also generate enough emergency power for five orbits.

A fifth mission, scheduled for this year, was canceled by the NASA Administrator after the Columbia accident to avoid further risk to the safety of the astronauts.  That brings us face-to-face with the question of what is going to happen to Hubble.  It was anticipated that the fifth servicing mission in 2004 would probably extend the useful life to 2010.  Without further maintenance it is likely that performance will begin to degrade as early as next year as components wear out or their efficiencies drop. NASA currently is studying the feasibility of using robots to service the telescope.  And it is possible that NASA Administrator Sean O’Keefe will change his decision, perhaps from pressure not to let the Hubble expire when it is giving such great results.

We have purposely not disclosed Hubble’s final cost to this bunch of skeptical taxpayers until it was fulfilling its promise to provide historic glimpses of the universe. The cost at launch was $1.5 billion. 

THE FUTURE

NASA has been studying Hubble’s successor for several years.  It was called the Next Generation Space Telescope until two years ago when it was re-named the James Webb Space Telescope to honor NASA’s second administrator.   The Webb is going to be a quantum leap from Hubble. Here is an artist’s rendering of the concept.  The color makes it look like it’s straight from the Arabian Nights..  

It will observe primarily in the infrared spectrum, versus the visible spectrum for Hubble, for better visibility by virtue of its greater wavelength into the dense, dusty clouds created as stars and planets are formed.  Selection of infrared drives many of the Webb’s other features.  For the system to work, it must be kept extremely cold: –378 degees F. The spacecraft will have a folding 72 x 33 foot sunshade (the size of a tennis court) to screen it from heat and light from the Sun, Moon and Earth.

The orbit in which it will be placed is one million miles from Earth termed the L2 Lagrange point, where the gravitational pull of the Sun and the Earth are about equal, and where the ambient temperature is within about 50 degrees of absolute zero.  Therefore the Webb does not need an enclosing structure like the Hubble to control the temperature.  The orbit will obviously be outside the capability of the Space Shuttle to place it on orbit or to service it with replacement modules, so it must work well as launched.  There can be no second chance.  One of three candidate heavy-lifting rocket systems will launch it, after which it is programmed to take three months to reach its final orbit

Goddard Space Flight Center is the NASA center responsible for the program, with funding coming from the European and Canadian Space Agencies. The Space Telescope Science Institute at Johns Hopkins will continue to provide its services. Launch is scheduled for August 2011.

 Goddard has selected Northrop Grumman as the prime contractor.   Webb’s size has not been determined yet, but the diameter of the primary mirror has been set at 20 feet to take full advantage of the location in space.  But that diameter exceeds the capability of any rocket shroud, so the mirror must fold in order to fit.

Following a six-month detailed evaluation of candidate materials for the mirror, Northrop has selected Ball Aerospace to design and build the primary mirror, which will be made of very thin sheets of beryllium because of its ultra-low temperature sensitivity..  Pyrex glass was the other candidate material. 

The 20-foot mirror will consist of 18 hexagonal beryllium segments that will unfold on orbit. (hold up photo)  For the mirror to focus incoming light properly, the segments must be aligned relative to each other within a few nanometers. The weight is expected to be only one-third that of the Hubble mirror even though it is 2.5 times larger. The mirror is one of the major acknowledged technological developments of the Webb telescope.

And now for the price tag. The Webb is “projected to cost one-fourth to one-third the cost of Hubble,…. the savings to be achieved primarily through advanced technology”.   The cost is estimated at $824.8 million.   Amen.

BIBLIOGRAPHY

Robin Kerrod   Hubble: The Mirror on the Universe  Firefly Books  2002

Robert W. Smith  The Space Telescope; A Study of NASA, Science, Technology and Politics

Cambridge University Press  1989

Carolyn Collins Petersen and John C. Brandt  Hubble Vision:  Further Adventures with the Hubble Space Telescope  First and Second Editions  Cambridge University Press   1995,1998


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