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Gravity Probe B

Testing Einstein's Universe

Project Timeline

This is an extended timeline of the project that covers the earliest development of the theory all the way up to launch (1893 - 2004).


Mach's Principle - In his book The Science of Mechanics (1893), Ernst Mach put forth the idea that it did not make sense to speak of the acceleration of a mass relative to absolute space. Rather, one would do better to speak of acceleration relative to the distant stars. What this implies is that the inertia of a body here is influenced by matter far distant. This had a great influence on Einstein and in the development of his theory of general relativity.


Michelson and Morley Experiment showing the speed of light remains constant - Einstein's theories sprang from a ground of ideas prepared by decades of experiments. One of the most striking, in retrospect, was done in Cleveland, Ohio, by Albert Michelson and Edward Morley in 1887. Their apparatus was a massive stone block with mirrors and crisscrossing light beams, giving an accurate measurement of any change in the velocity of light. Michelson and Morley expected to see their light beams shifted by the swift motion of the earth in space. To their surprise, they could not detect any change. It is debatable whether Einstein paid heed to this particular experiment, but his work provided an explanation of the unexpected result through a new analysis of space and time.


Special Relativity - Special relativity is a theory proposed by Albert Einstein that describes the propagation of matter and light at high speeds. It was invented to explain the observed behavior of electric and magnetic fields, which it beautifully reconciles into a single so-called electromagnetic field, and also to resolve a number of paradoxes that arise when considering travel at great speeds. Special relativity also explains the behavior of fast-traveling particles, including the fact that fast-traveling unstable particles appear to decay more slowly than identical particles traveling more slowly. Special relativity is an indispensable tool of modern physics, and its predictions have been experimentally tested time and time again without any discrepancies arising. Special relativity reduces to Newtonian mechanics in the limit of small speeds. According to special relativity, no wave or particle may travel at a speed greater than the speed of light, c. Therefore the usual rules from Newtonian mechanics do not apply when adding large enough velocities. It is often incorrectly stated that special relativity does not correctly deal with accelerations and general relativity must be used when accelerations are involved. While general relativity does indeed describe the relationship between mass and gravitational acceleration, special relativity is perfectly adequate for dealing with relativistic kinematics.


General Theory of Relativity - A theory invented by Albert Einstein which describes gravitational forces in terms of the curvature in space caused by the presence of mass. The fundamental principle of general relativity asserts that accelerated reference frames and reference frames in gravitation fields are equivalent. General relativity states that clocks run slower in strong gravitational fields (or highly accelerated frames), predicting a gravitational redshift. It also predicts the existence of gravitational lensing, gravitational waves, gravitomagnetism, the Lense-Thirring effect, and relativistic precession of orbiting bodies.


Leonard Schiff born in Fall River, Massachusetts.


Bill Fairbank born in Minneapolis, Minnesota.


J. Lense and H. Thirring Effect - calculated that a rotating object will slowly drag space and time around with it! (A moon orbiting a rotating planet undergoes a relativistic advance of its ascending node.) (Frame Dragging)


A. S. Eddington - proposed an earth-based gyroscope or pendulum experiment of general relativity. (If the earth's rotation could be accurately measured by Foucault's pendulum or by gyrostatic experiments, the result would differ from the rotation relative to the fixed stars by this amount (credit to Schouten 1918).)


Schiff enters college (Ohio State) at age 14.


P. M. S. Blakett, inspired by Eddington, examined the prospect for building a laboratory gyroscope to measure the 19 milliarcsecond/year precession, but then concluded that it was hopeless due to existing technology. Blakett received the Nobel Prize in Physics in 1948. Francis Everitt later worked under Blackett while obtaining his Ph.D. from the University of London (Imperial College).


Schiff graduates college (Ohio State) at age 18.


Schiff gets PhD from MIT at age 22.


Bill Fairbank graduates from Whitman College (Walla Walla Washington), B. A. Chemisty.


Schiff is at UC Berkeley, working with Robert Oppenheimer who leads the creation of the atomic bomb for the U. S. Oppenheimer first starts Schiff thinking about relativity with a question about rotation and Mach's Principle.


Bill Fairbank enters graduate school in Physics & Teaching Fellow at University of Washington.


Schiff moves to position at the University of Pennsylvania as a physics instructor.


Bill Fairbank marries Jane.

Dec 7, 1941

Pearl Harbor


Bill Fairbank receives a draft notice, then a mysterious offer transmitted by one of his professors for Bill and Jane to work in the Radiation Lab at MIT. Bill was defining his thesis on a molecular physics technique. Jane was the second woman appointed to the Radiation Lab.


Schiff becomes acting head of the University of Pennsylvania Physics Department. He is 27.


During WWII - Schiff continues his work at Penn while working with a number of groups working on the military activities at Columbia, U. C. Berkeley, Navy Anti-submarine Research Group.


Bill Fairbank is staff member of Seaborne Radar Division, Radiation Lab at MIT (World War II going on). Radiation Lab was run by Larry Marshall, later by Ernest Pollard. Bill developed a new technique for calibrating Radar Systems.


Schiff moves to Los Alamo, NM under Robert Oppenheimer to work on the atomic bomb.

July 16, 1945

Schiff was one of the people present for Trinity, the first atomic bomb.


WWII ends after the bombing of Hiroshima and Nagasaki.


The war was ending, and on Pollard's recommendation Bill was accepted into grad school at Yale. Bill didn't know what field of physics to go into, and considered doing nuclear physics. Pollard advised Bill that nuclear physics would soon be ancient news. Something less developed like low temperature physics would be more rewarding and better suited for Bill's talents.


Bill Fairbank goes to grad school at Yale - Sheffield Fellow at Yale (Superconductivity and Low Temperature Physics). Yale was to become the first Physics department in the U. S. with a significant low temperature group.


Schiff returns to the University of Pennsylvania.


Schiff accepts a position at Stanford.


Bill Fairbank at Yale is one of the first investigators (with his brother Henry) to publish observations of second sound observed in Liquid Helium in the U. S.


Bill Fairbank receives Ph.D. from Yale (Superconductivity and Low Temperature Physics).


Schiff becomes the Head of the Physics Department at Stanford (he is 33).


Fairbank is assistant professor at Amherst College, Massachusetts.


Schiff publishes a book entitled "Quantum Mechanics"


Fairbank is a Professor at Duke.


Robert Cannon is an Assistant Professor at MIT (mechanical engineering), where he had previously obtained his doctorate, and went then to North American Aviation Company, contributing to highly-maneuverable man-aircraft systems (gyro accuracy 1 degree/hour) and submarine inertial guidance system that took submarines under the north pole for the first time (Nautilum and Skate, gyro accuracy 1 degree/week). At MIT he watched the fine Draper team also achieve these levels, but began wondering how to use very new approaches to achieve perhaps 1 degree per century for special missions: a more proper, university-like goal.


On October 4th, the Soviet Union launches the first satellite into orbit: Sputnik.


Von Braun's Rocket Team (eventually NASA/MSFC) launches Explorer 1, the first U. S. orbiting satellite.


Fairbank is a Professor at Stanford.


Robert Cannon starts as professor at Stanford in Aeronautics and Astronautics Department (specializing in precision gyroscopes). Robert later starts the Guidance and Control Laboratory at Stanford University. His first two Ph.D. students are Roy Smelt, who concurrently manages the Lockheed Agena Orbiting spacecraft program, and Daniel DeBra who is in charge of attitude control for Agena.


C. W. Francis Everitt obtains Ph.D. at the University of London (Imperial College) for research under P. M. S. Blackett, a Nobel prize-winning physicist. In 1930, Blackett examined the prospect for building a laboratory gyroscope to measure General Relativity [Lense-Thirring Effect (19 milliarcsecond/year precession)] but determined it was hopeless.


Physicist George Pugh, an MIT professor working with the Institude for Defense Analyses proposed testing General Relativity by observing the precession of a gyroscope in an earth-orbiting satellite with respect to a distant star, using orbiting gyroscopes in a drag-free satellite. Independently, Leonard Schiff of Stanford University was also thinking of using gyroscopes to test the effects of general relativity, but in a ground-based system. After consulting with his colleages Bill Fairbank and Bob Cannon, it became clear that orbiting gyroscopes would provide both the pristine laboratory and the precision required to make the tests. According to Schiff's calculations a gyroscope in polar orbit at 400 miles should turn with the Earth through an angle amounting after one year to 42 milliarc-seconds.

Pugh's paper, "Proposal for a Satellite test of the Coriolis Prediction of General Relativity", 1959, Pentagon Weapons System Evaluation Group (WSEG) memo #11, was never published in any public source until the year 2003. Its first public appearance is in the text "Nonlinear Gravitodynamics: The Lense - Thirring Effect" by Remo Ruffini (Editor), Costantino Sigismondi (Editor), World Scientific Publishing Company, May 2003, pp 414-426.

Schiff's calculations were published in 1960 in his paper "Motion of a Gyroscope according to Einstein's theory of Gravitation", L.I. Schiff, from the Proc. Nat. Acad Sci. 46, pp. 871-882 (1960); also Phys. rev. Lett. 4, pp. 215-219(1960)


Bill Fairbank introduces his boss, Leonard Schiff, to Robert Cannon at the Stanford swimming pool. In his first exposure to the laboratory equipment that Schiff and Fairbank are discussing (a gyro measuring 0.5 arc sec per year) Cannon notes that (a) the support force required in the earth's 1 g gravity field would produce drift errors much too large to do the experiment on earth; However, (b) it might well be do-able in orbit at one millionth g or less, and (c) orbital flight, tailor made, was sure to be available for this experiment. United States' capability surprises the others, for Sputnik had been launched only two years earlier. But Cannon knows of Agena, and has earlier been at NASA headquarters and learned from Dr. Nancy Roman of NASA's plans for an orbiting astronomical observatory. A potentially perfect match. Schiff responds that the geodetic effect would of course be 15 times as large in orbit (15 orbits per day begets 7 arc sec per year). Schiff later notes to Cannon that being in orbit would also enable seeing for the first time the gravity frame-dragging predicted by Einstein. (Cannon: "And how large would that be?" Schiff: "0.040 arc sec per year. And we need that to within 1 per cent." Cannon's personal goal of 1 degree per century has been replaced by the goal of 1 degree per million years. A fine reward for simply coming to Stanford University.) Fairbank and his team then rapidly lay out a remarkable in-depth first design for an orbiting experimental system.


Francis Everitt spends two years at the University of Pennsylvania working on liquid helium and was responsible for the experimental discovery of the "third sound", a surface wave on superfluid helium films.


First formal contact w/NASA - Fairbank writes Dr Abe Siberstein describing an instrument that would measure the geodetic precession to a few percent.


Francis Everitt joins William Fairbank and Leonard Shiff at Stanford on the Gravity Probe B experiment.


NASA funding commences (retroactive to 1963) with supplement from U. S. Air Force (Cannon & Fairbank co-principal investigators).


With help from Honeywell, start developing gyroscopes.


1st fused quartz telescope built.


Cannon brings Daniel DeBra back to Stanford on the GP-B program as Research Associate Professor in Aeronautics and Astronautics.


Bob Cannon becomes U. S. Assistant Secretary of Transportation for Systems Development and Technology.


NASA begins examining feasibility of a flight experiment. Ball Aerospace completed a Mission Definition Study which was the first look at the spacecraft layout, including a dewar spaceflight test, a gyro spaceflight test, and then the science mission. The dewar spaceflight test was accomplished in the 1982 flight of the IRAS (Infra-red Astronomy Satellite) dewar.


Dan Debra's extrememly successful flight of a drag-free satellite (the Transit navigation satellite: 5 x 10-12g for two years. The first time anyone connected to the GP-B team has operated in space a sub-system that will become an integral part of GP-B. Robert Fischell of Johns Hopkins Space Laboratories is the GP-B partner who makes this possible.


Bob Cannon moved from U. S. Government to Professor & Chairman, Division of Engineering & Applied Science, Caltech.


Gravity Probe A - GP-A was launched from NASA-Wallops Flight Center in Virginia. The 1 hour 55 minute flight of a MASER atomic clock demonstrated that time changed as it rose to weaker levels of gravity, then fell back to the Earth. The primary objective of the mission was to test a portion of Einstein's gravitation and relativity theories called the "Principle of Equivalence," or "redshift" to an accuracy of 200 parts per million. It attained an altitude of 6,200 miles above the Earth before crashing into the Atlantic Ocean.


End of grant, which represented the end of the longest running single continuous research grant ever awarded by NASA (11/63-7/77). This ended the exploratory phase of the program.


Fairbank was engrossed in finding a free quark. He was the first to provide experimental evidence of the existence of quarks (1977).


Cannon returns to Stanford as Professor & Chairman, Department of Aeronautics and Astronautics. At the request of the Provost, he establishes a GP-B engineering advisory team, which includes Emery Reeves of TRW, Roy Smelt of Lockheed (see above), Robert Parks chief engineer at JPL --each a top engineering manager of a major spacecraft enterprise-- and Steven Chu of Stanford (later a Nobel prize winner).


NASA conducts major review of technological readiness. The review team remarked "the remarkable technical accomplishments of the dedicated Stanford experiment team give us confidence that, when they are combined with a strong engineering team in a flight development program, this difficult experiment can be done. " Phase A study at MSFC for planning flight program.


NASA launches first Shuttle.


NASA/MSFC had already completed a Phase A study in-house and a more in-depth Phase B study that determined that GP-B would need to be a somewhat large spacecraft (5300 lbs needing 576 Watts of power) that would be too expensive.


IRAS flight of proves out feasibility of spaceflight dewar.


Stanford restructured the program, which cut the weight to 2800 lbs and 143 W and lowered the cost to $130M. It was decided to build the dewar and science instrument first and launch it on a seven-day test flight on the shuttle in 1989. Once back on earth, the dewar could go through minor refurbishment while the rest of the spacecraft was being finished. The dewar with the science instrument within would then be integrated with the rest of the spacecraft and launched in 1991 (both on the shuttle).


The first phase called STORE (Shuttle Test of the Relativity Experiment), and was fully endorsed by NASA. Lockheed Martin was selected as the prime subcontractor to assist Stanford in building the equipment.


Gyro production throws out Beryllium, Hollowed Beryllium, Hollow Quartz spheres and focuses on Quartz rotors. Stanford pulls gyro rotor manufacturing, lapping, polishing, and coating process in house from NASA/MSFC. Ongaley, one of the scientists that came with Wernher Von Braun from Germany after WWII, is one of the developers of the system.


Challenger explodes. It takes NASA 2.5 years to get Shuttle back in space. NASA eliminates plans for a Shuttle Western launch facility at VAFB, which is needed for polar orbits of the shuttle (and Gravity Probe B). Science Mission switched to Delta 2 launch vehicle.


Stanford's first prolonged levitation of a quartz sphere.


First Flight Hardware within the Science Mission starts to be built.


Dewar starts fabrication.


NASA cancels Shuttle Test and directs Stanford to go directly to flight.


Science Dewar delivered to Stanford.


Dewar goes cold & Stanford establishes magnetic shield in Dewar.


Probe Delivered to Stanford.


Gyroscopes, Quartz Block, & Telescope complete.


Integration of Gyroscopes, Quartz Block, & Telescope.


Integration of Science Instrument with Probe.


Integration of Probe with Dewar & Ground Testing.


Probe Repair & Gyro #4 replaced.


Probe & Dewar Re-Integrated.


Payload Acoustic Test.


Integrated Payload Testing.


Integrate Payload with Spacecraft.


Payload Electronic Boxes Delivered.


Modal Test


Space Vehicle Acoustic Test

November 2002

Thermal Vacuum Test


Spin Balance

May 2003

Thermal Vacuum Re-Test

June 2003

Final Space Vehicle Testing

July 2003 -

Shipment to Launch Site

September 2003

Integration with Delta II Rocket

January 2004

ECU is removed for rework, launch delayed.

February 10, 2004

ECU is scheduled to return to VAFB

April 20th 2004

Gravity Probe B successfully launches out of Vandenburg Air Force Base at 9:55am.