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
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.
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.
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
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
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 NASAs
crowning achievements. It has enabled us to see where we have never seen before by
removing the distortions imposed by the earths 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 earths equator.
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
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 earths 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 earths 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?
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
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 NASAs 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
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. Well 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 Telescopes 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.
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
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, lets table the topic until we see
how the program fared.
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
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 didnt that seem the best way to ensure the
best complement of instruments, but also it didnt 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.
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-Elmers contract was for $69.4
million and Lockheeds for $82.7 million. These
were 15% below NASAs 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. Well 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
involvedNASA Headquarters, Marshall, the contractors and the astronomersthat
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
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. Lockheeds
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
Fast forward to 1980, three years after the
start of design and development. Costs had
risen dramatically in spite of NASAs 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 Kodaks contract to save money even though it was almost finished polishing
the back-up mirror.
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 naïve 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.
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
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 didnt 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
Lets 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-Elmers
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-Elmers 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 1940s. And secondly why
wasnt 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?
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 telescopes 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, NASAs 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 NASAs 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 Endeavours 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
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
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 OKeefe 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
Hubbles 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.
NASA has been studying Hubbles
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 NASAs second administrator.
The Webb is going to be a quantum leap from Hubble. Here is an artists
rendering of the concept. The color makes it
look like its 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
Webbs 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.
has selected Northrop Grumman as the prime contractor.
Webbs 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
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.
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