Arthur Bertram Cuthbert Walker, Jr.

born: Aug.24, 1936, place: Cleveland

died Apr.29, 2001 - obituary

pre-doctoral institution: B.S., 1957, Case Institute of Technology; M.S., University of Illinois, 1958

doctoral institution: Ph.D. Astrophysics (1962), University of Illinois

last employment: Stanford University - Professor of Physics and Applied Physics; Member, Hansen Experimental Physics Laboratory;

Member, Center for Space Science and Astrophysics

[email: - gone]

His paternal grandfather was James Henry Walker, a schoolmaster from Barbados. James emigrated to St. Vincent with his wife, Millicent, around the the first part of the 20th century. As an educator, he had great expectations for his four daughters and four sons. James's second son, Cuthbert, emigrated to New York to study at City College and work for the Erie Railroad.

When the Depression struck, Erie Railroad moved its headquarters in the early 1930s to Cleveland. Cuthbert followed his job. There, he attended John Marshall Law School and met his future wife.

Walker's maternal grandfather, Ormand Forte, was also from Barbados and emigrated to the United States with his wife, Ida. The ambitious Forte attended Macalester College in St. Paul and worked for Hanna Steel in Cleveland. The Fortes had a daughter, Hilda, in 1911. Steel magnate Mark Hanna noticed young Ormand and helped him set up an African American newspaper in Cleveland just four years later. The Advocate grew in influence and spawned three other papers.

Arthur Betram Cuthbert Walker was born an only child in Cleveland on Aug. 24, 1936. He had no siblings but was close to his many cousins. In 1941 the family moved to New York, where Walker's father set up his own law practice.

Young Arthur loved science. Both of his parents supported him, but his mother, Hilda, was especially key in his development. She organized parents at his elementary school to fight a problem of teachers leaving the school during the day for errands. This led to a transfer to a new school outside their district. There, Arthur discvered the library and science. His new goal became to study the universe like Albert Einstein. His mother encouraged him to take the test for the Bronx High School of Science.

His first love was chemistry, but when his teacher tried to discourage him, Hilda stepped in again and told the teacher in no uncertain terms that her son would study whatever he pleased. When Walker then decided to pursue physics, his mother encouraged him to apply to the Case Institute of Technology in Cleveland.

Arthur Walker earned a baccalaureate degree in physics with honors from there in 1957. He went on to pursue and earn a master's degree in 1958 and doctorate in 1962 from the University of Illinois. His dissertation was on the use of radiation to produce the particles that bind protons and neutrons together in the atomic nucleus.

In 1962 he joined the U.S. Air Force as a 1st lieutenant. His first assignment was to the Air Force Weapons Laboratory. There he was instrumental in developing instrumentation for an experiment that involved rocket launch of a satellite to measure Van Allen belt radiation in the Earth's magnetic field which affects satellite operation. This work ignited his interest in research carried out with space techniques.

Walker left the service in 1965, when his commitment was up. He then joined the Space Physics Laboratory of the Aerospace Corporation, where for 9 years he conducted pioneering physics experiments to study the sun and upper atmosphere of the Earth.


Arthur B. Walker started out in nuclear physics, but earned a Ph.D. in Astrophysics. From 1975 to 1985 Walker did pioneering work studying the X-ray spectrum of the solar corona and in the 1990s he lead a team of scientists who, among other things, were the first to apply normal incidence X-ray optical systems to astronomical observation. But Walker may be best known as the mentor of Sally Ride, the first female astronaut to obit the Earth, and for chairing the presidential commission that investigated the 1986 space shuttle Challenger disaster.

Walker is one of nation's bright lights in solar research. He has used his X-ray vision to see inside the sun's surface. As a solar physicist, he is a leader in the use of thin films and X-rays to study its corona. Since 1987, telescopes Walker has developed have ridden satellites into space, capturing the first pictures of that corona. In addition, Walker's penetrating long-range vision has resulted in Stanford having more minority graduate physics and applied physics students than any major research university in the country. Ever since his irate mother, Hilda, stormed into the highly academic Bronx High School of Science and set his teacher straight about discouraging her son from studying science because he is African-American, Walker has been steady on the course.

Friends, colleagues and family recently celebrated his work at a campus dinner. The 64-year-old Walker was been ill since June 2001, and was recovering from the effects of radiation and chemotherapy. Stanford mathematics Ph.D.and psychology professor Ewart Thomas has been a friend for many years. ``Art says, `You know, Ewart, all I ever wanted to be was a physicist. I've had a good life and I wanted to help students see the marvel of physics and I've done both.' '' Looking ahead Astronaut Sally Ride was his first doctoral candidate. But Walker has big plans for the future. He is working with Stanford scientist Blas Cabrera, using a technique that Cabrera and his students developed which permits them to measure energy very precisely and which allows them to measure the energy of individual X-rays from the sun. That is of value, Walker said, because it permits better analysis of the sun's composition, such as which elements are emitting radiation. And because things done in a lab must eventually be proven in space, Walker said, ``We are planning to launch a rocket probe in a couple of years to produce some high resolution spectra of the sun which we will use to demonstrate our new technique.'' Bob Beyer, Stanford's chair of applied physics, has known Walker nearly 30 years. ``I still remember the sparkle in his eye when he came with his very first X-ray image of the sun,'' Beyer said. ``He had just had a major breakthrough and he was thrilled. Art has this sort of soft-spoken, but always present-there, style.'' Modest star Those who know him understand what Beyer means. Walker is a person you can know for years and will never hear from him that when Challenger exploded, the president of the United States appointed him to the prestigious investigative committee. Friends can ask what he's up to and never hear that more than a dozen telescopes he developed were on certain space missions. Thomas says he is a ``gentleman scientist.'' In retrospect, Walker the astrophysicist is a little like the sun that he covets -- not the noonday sun, but the rising sun where people see a warm, subtle glow masking the powerful light just below the horizon. His wife, Victoria, of 17 years, recalls first meeting him and thinking, ``An astro what?!'' Walker downplayed it. ``I had to pull it out of him,'' she said. ``I've always known that he was special,'' she said. ``I'm just pleased that everyone else has found out.'' At the dinner, Beyer likened him to hokule'a which is a Polynesian name for a star that guided sailors in canoes from Tahiti to Hawaii. ``I said, `You have, by example, been the guide star by which many students have navigated early in their careers.'' And only Walker might ask him for empirical data.

After earning his Ph. D., Arthur Walker joined the Air Force Weapons Laboratory, 1962-65. From 1965 to 1973 he worked at AerospaceCorporation where, from 1971-73, he directed the Astronomy Program. He joined Stanford university as Professor, in 1974. From 1976-80, he was Associate Dean of Graduate Studies.

On September 15, 2000, Stanford had a celebration of his achievements sponsored by the departments of Physics and Applied Physics and the African and Afro-American Studies Program.

READ: Arthur Walker, Scholar, Warrior, Citizen by Hakeem Oluseyi


Specialty: Solar Physics, X-Ray Astronomy

Professor Walker's research interests are focused on the development of innovative space-borne instruments for the study of high temperature astrophysical plasmas, and the sse of X-ray far ultraviolet, and extreme ultraviolet techniques to study other astrophysical phenomena such as the elemental abundances in the interstellar medium. 

Among the techniques used are high resolution X-ray spectroscopy using Bragg crystals and diffraction gratings, and high resolution X-ray imaging using both grazing incidence and normal incidence X-ray optical systems. 

From 1965-1975, Professor Walker and his former collaborator, H.R. Rugge carried out several of the pioneering studies of the X-ray spectrum of the solar corona. 

In the early 1990's, a group lead by Professor Walker, which included T.W. Barbee and R.B. Hoover, pioneered the application of normal incidence X-ray optical systems to astronomical observations. 

Professor Walker's group's primary current interest is the study of the physical processes underlying the structure and dynamical behavior of the solar corona and chromosphere, using observations from a variety of spacecraft, including the NASA/ESA SOHO Observatory and the Walker group's Multispectral Solar Telescope Array. 

In preparation for the launch of NASA's AXAF X-ray Observatory in 1998, Professor Walker's group will be utilizing both space observations and ground-based observations (from the Hobby Eberly Telescope) to study phenomena associated with stellar chromospheres and coronae, supernova remnents, the interstellar medium, and clusters of galaxies. 

Professor Walker's group currently is establishing a Stanford AXAF Science Center, which will provide access to AXAF observations for astronomers in the western United States. 

Professor Walker's group is also involved in the application of X-ray technology to disciplines other than astronomy. Examples include X-ray imaging and X-ray microscopy of biological materials. 

These activities, as well as the group's astrophysical research, make extensive use of the Stanford Synchrotron Radiation Laboratory.   

Scholar, Warrior, Citizen

I recently said goodbye to the greatest man I have ever known. My graduate school advisor, mentor, colleague, comrade-in-arms, and friend Professor Dr. Arthur Bertram Cuthbert Walker, II had passed away on April 29, 2001.

I first met Dr. Walker, or Art as he was known by those close to him, in the spring of 1991 while I was visiting Stanford University shortly after being admitted into the Physics Department's Ph.D. program. After spending an entire day meeting with department faculty, I was introduced to Art. That initial meeting was the beginning of a ten year journey of triumphs and challenges, difficulties and laughs, and above all a shared love for discovery. I learned a lot from Art. I learned a lot of science but much, much more was gained by merely being in Art's presence daily for over six years.

Art Walker was a man of rare style and substance; not unlike Benjamin Banneker from whom Art took his inspiration as both a scientist and citizen. Banneker was America's first astronomer and also an African American. For those who knew Art, historical descriptions of Banneker were uncannily similar to Art's own refined mien, "He was very precise in conversation and exhibited deep reflection. His deportment, whenever I saw him, was perfectly upright and correct, and he seemed to be acquainted with everything of importance that was passing in the country"

It may be fitting at this time to quote from Banneker's own obituary, "He was well known in his neighbourhood for his quiet and peaceful demeanour, and, among scientific men, as an astronomer and mathematician." "In early life he was instructed in the most common rules of arithmetic, and thereafter, with the assistance of different authors, he was enabled to acquire a perfect knowledge of all the higher branches of learning." "Mr. Banneker is a prominent instance to prove that a descendant of Africa is as susceptible of a great mental improvement and deep knowledge of the mysteries of nature as that of any other nation." ­ Baltimore Daily Advertiser, October 28, 1806.

Dr. Walker has and will continue to serve as my inspiration as a scientist and as a man. It is my honor as his student and friend to compose this obituary for the National Society of Black Physicists. Please read it as informative of a great man and a celebration of a great life. If it is somewhat long, it is because we have much to celebrate.

The Scholar

Dr. Walker's innovative thought and enriched educational training led him to be a first rate researcher with many notable scientific accomplishments. His research concentrated on the development of x-ray astronomical instrumentation and on the study of high temperature low density astrophysical plasmas with space borne instrumentation. His approach was as follows. He would identify a new technology which had the potential to revolutionize astrophysical observation. He would then pioneer the application of the new technology to astrophysical observation. With the unique data obtained, Dr. Walker would develop novel techniques of analyses and fundamentally advance our understanding of the physical system under study.

Dr. Walker's advanced educational training began at Case Institute of Technology where he received his B.S. in Physics with honors in 1957; he was elected to membership in Tau Beta Pi in 1955. He received the Ph.D. Degree in Physics from the University of Illinois in 1962, where he was associated with the Betatron Laboratory and carried out research in nuclear physics and meson physics; particularly, the photoproduction of p mesons. He was elected to membership in Sigma Xi in 1960.

In 1962, Dr. Walker entered active duty with the U.S. Air Force and was assigned to the Air Force Weapons Laboratory with the rank of 1st Lieutenant. At the Weapons Laboratory, Dr. Walker instrumented a rocket probe and a satellite experiment to measure protons and electrons, radiations which affect satellite operation, trapped in the Earth's magnetosphere. It was this work that ignited Dr. Walker interest in space-based research.

In 1965, upon completing his military obligation, Dr. Walker joined the Space Physics Laboratory of The Aerospace Corporation as a member of the technical staff. He conducted experimentation in solar physics and upper atmospheric physics, specializing in studies of the solar x-ray flux. Dr. Walker and his collaborator H. R. Rugge developed the first satellite borne x-ray spectrometer and carried out a series of pioneering studies of the x-ray spectrum of the sun. Dr. Walker's innovative Bragg crystal spectrometers were flown on the Air Force OV1-10 and OV1-17 satellites and resulted in the first astronomical identification of x-ray dielectronic recombination lines and established the importance of radiative decay of metastable levels and of autoionizing levels respectively in high temperature astrophysical plasmas. These studies also helped establish the temperature, composition, and dynamic nature of the sun's corona, and provided basic insights into the interaction of matter and radiation in a diffuse million degree plasma. These early studies provided a foundation for later studies of similar astrophysical systems elsewhere, including stellar coronae, the interstellar medium, the intergalactic gas, and gas in clusters of galaxies. Note that diffuse million degree plasmas, such as those studied by Dr. Walker, constitute greater than 70% of the volume of our galaxy, and perhaps the bulk of baryonic matter in our universe.

In January of 1974, Dr. Walker was appointed Associate Professor of Applied Physics at Stanford University. He was appointed full Professor in 1982, and his appointment was made joint with Physics in 1991. Upon joining the Stanford faculty, he and his student Sally Ride (America's first female in space), performed a comprehensive analysis of the role of dust and of ionization state on the interstellar medium absorption of x-rays. The two developed the first comprehensive model of the interaction of x-rays and the interstellar gas resolving several controversies over the composition of this fundamental component of the galaxy.

Later, realizing the potential of a new technology developed by his Stanford colleague, T. W. Barbee, that permitted the fabrication of synthetic mirrors that selectively reflect x-rays of a specific wavelength, Dr. Walker and his student Joakim Lindblom with their collaborator Richard Hoover of Marshall Space Flight Center (MSFC) pioneered the application of these "multilayer mirrors" to astronomical observations. In 1987 they obtained the first high-resolution thermally differentiated images of the solar atmosphere.

Dr. Loren Acton, a solar physicist at Montana State University and a member of the American Astronomical Society, speaking about Dr. Walker's achievement said that scientists instantly recognized that a new window on the Sun and its behavior had been opened. "When that picture was shown at an A.A.S. meeting for the first time, the audience broke into applause," Dr. Acton said. That first x-ray image of the solar corona published by Art and his collaborators demonstrated the power of the new x-ray mirror technology and inspired their use in the fabrication of micro-electronics, in studies of materials' properties at synchrotron laboratories throughout the world, and in the development of the world's first x-ray microscope.

With a new generation of students: Max Allen, Ray O'Neal, Craig DeForest, Charles Kankelborg, Dennis Martinez, and myself, Dr. Walker developed a series of x-ray telescopes based on multilayer technology that provided uniquely detailed images and incisive models of the sun's corona. In a series of five scientific papers we were able to elucidate the properties of many of the individual plasma structures that comprise the hot solar atmosphere and mediate the flow of energy, fundamentally advancing our understanding of solar atmospheric physics.
Art, Max Allen, and I were the first to determine the magnetic structure and energy balance of polar plumes, one of the fundamental structures of the hot solar atmosphere. This study overturned the long-held belief that polar plumes were the sources of high-speed solar wind streams. We also established the role of thermal conduction from the corona in generating the chromosphere in coronal holes and identified the basal location of the coronal heating mechanism.

Dr. Walker and his student Charles Kankelborg, in a series of two papers, were the first to establish several properties of coronal x-ray bright points, including their detailed morphologies and thermodynamic structures. This analysis established the role of thermal conduction from the corona in generating the chromosphere at the footpoints of small coronal loops in the "quiet sun."

Dr. Walker and I, in a series of two papers, with our collaborators David Santiago of Stanford and Jason Porter of MSFC determined the detailed morphology and energy balance of the solar upper transition region, the "unknown" region of the solar atmosphere, resolving one of the long-standing and most important unsolved problems of solar atmospheric physics. This work inspired us to study the theoretical models of solar atmospheric structures resulting in the successful prediction of several new solar structures which have been subsequently confirmed to exist. These two papers, together with the papers mentioned above, comprehensively studied the structures of the solar atmosphere and established the role of thermal conduction from the corona and upper transition region in generating the chromosphere and lower transition region.

The great success of Dr. Walker's pioneering application of multilayer imaging has resulted in their being the standard in solar EUV and x-ray imaging today. They are currently in use on the United States' two premiere satellite solar observatories, The Solar Heliospheric Observatory (SoHO) and The Transition Region and Coronal Explorer (TRACE). Note that while these satellite utilize the same technology that Dr. Walker pioneered, they did not adopt Dr. Walker's complete approach. Because each multilayer telescope images plasmas at a specific temperature, Dr. Walker flew 16 ­ 19 telescopes on his rockets in order to obtain full thermal coverage of the solar atmosphere, whereas SoHO and TRACE use three and telescopes respectively. Art's complex approach led our collaborator Richard Hoover of MSFC to create the acronym "awfully-bloody complicated" out of Dr. Walker's initials, A. B. C. Nonetheless, Dr. Walker's work has inspired a central element of NASA's new "Living with a Star" initiative. NASA's next generation solar satellite will be constructed "Walker-style," with six telescopes in parallel that will take high-resolution pictures of the Sun every 10 seconds.
Dr. Walker's innovation in identifying new technologies and pioneering their application to space-based research progressed through 2001. During his last year, he and his collaborators were developing a spectroheliograph that would utilize multilayer gratings and he and his Stanford colleague Blas Cabrera were developing an x-ray microcalorimeter detector, the Transition Edge Sensor, for astronomical imaging. Dr. Walker said that he "truly believed" that this new technology would "revolutionize x-ray spectroscopy, bring x-ray spectroscopy and x-ray observations to the same level as optical observations in astronomy and revolutionize our understanding of the universe."

The Warrior

In an article written on Dr. Walker a few months before his death, the author stated that, "Arthur Bertram Cuthbert Walker, II has spent a lifetime bridging the space that separates humans from the Sun and from each other." This statement accurately characterized Art's inclusive style and unceasing commitment to bringing the physics and scientific cultures in balance with respect to the under-representation of African Americans, Native Americans, Chicanos, Puerto Ricans, and women ­ groups traditionally excluded throughout American history. Art was a front line warrior in the fight against racial and gender discrimination in the physics community at both the student and faculty levels.

Art was shrewd in his approach to choosing the position from where he would launch his effort. He once reflected on an experience he had the year before he joined Stanford's faculty; a different leading research university had offered him a professorship. "I decided not to accept that one," he said. "I remember when I went to visit that institution, the president said, 'We have one Chicano faculty member here on our campus, and if you come and join us, you'll be the first African American faculty member on our campus.' I said, 'That's kind of interesting, but I'm not sure that's exactly what I want.'"

When he was offered the professorship at Stanford, Art recalled "They said to me, 'We think we have here at Stanford the most distinguished African American faculty of any major research university, and we hope you'll come and join us.' And I said, 'Now that's the kind of attitude I want to see at the university I join.'"

Art's momentous reception into academia was contrasted by the sober observations that were apparent to all. The number of African American, Native American, Chicano, Puerto Rican, and female professional physicists and physics Ph.D. students in the United States was dismal. Many institutions were historically deplorable in their records for matriculating under-represented students and faculty. Even at Stanford the first African American graduate students in both mathematics and chemistry matriculated and graduated only in the nineteen nineties. Art was one of only two under-represented faculty member (not including women) in Stanford's seven natural and mathematical sciences departments of applied physics, biology, chemistry, mathematics, physics, statistics, and SLAC.

Art firmly believed that the availability of qualified candidates was not the principal factor limiting diversity within the natural and mathematical sciences. At Stanford he foght to ensure that every qualified minority candidate for faculty and academic admission was seriously considered. Art would identify and recruit allies within his professorial colleagues and university administration. Due to the efforts Art and a coterie of colleagues, great advances were made in training new African American physicists in the ten year period between 1978 and 1988. Stanford graduated over thirty physics and applied physics Ph.D. students during this period. However, because of the retirement or transfer of most of the conscientious professors with whom Art was allied, the situation changed drastically during the 1990's. Between 1989 and 2001 only eight Black Ph.D. physics and applied physics students would matriculate into Stanford; three of whom dropped out.

Nevertheless, Art continued to fight for under-represented students. Indeed, at least six Ph.D. students (including myself) in the nineties were able to complete their degrees in the face of faculty opposition, due to Art's direct intervention. One of these students, in his dissertation acknowledgements, speaks of his treatment and the department culture during this period, "times of political and social demoralization by the institution and academic cultures that are not only generally asocial and arrogant, but often discriminatory and intellectually hostile." The student goes on to state with respect to Art, "his politicking on my behalf during adversarial challenges posed against me by University administrators and faculty over policy, promotion or issues related to institutional discrimination, have never gone unnoticed nor unappreciated. There are no words to describe my gratitude for his relentless and unyielding support"

Art also organized African American faculty outside of his department to fight against under-representation. He organized an informal black faculty association that he called "The Banneker Group," and served as its president for many years. The Banneker Group fought for more black faculty, for the African and Afro-American Studies program to have its own billets and for a research institute to study race and ethnicity.

Art served on Stanford's African and Afro-American Studies program advisory committee longer than any other member. In speaking at Art's memorial service, John Rickford, who holds Stanford's Martin Luther King Jr. Centennial Professorship said, "All of us benefited from Art's activities on our behalf and were in turn grateful for them." "His involvement was all the more remarkable because he didn't come from African American literature or African American history or sociology or anthropology, or any of the many fields that normally intersect in a very natural way with African and Afro-American Studies. Here was a person who was doing this with no political or professional advantage of his own to be gained. It was purely his concern for the larger issues that were involved."

The Citizen

With all that Art accomplished as a scientist and mentor, he still found the time to be a generous, compassionate, principled human being. He was a consummate gentleman and was as devoted to service as he was to practicing science and to ensuring fairness within the sciences.

Public service on the part of scientists is an integral part of the American system as Congress uses committee advice to ensure that federal agencies are adhering to the recommendations of the scientific community. Throughout his illustrious career, Art has served on or chaired a number of NASA, National Science Foundation (NSF), and National Academy of Science (NAS) Committees which prepare recommendations on national research policies and priorities.

Art's committee service helped establish America's network of astronomical observatories. He played the title role in the Walker Committee, which recommended that the national observatories take over the Sacramento Peak Solar Observatory when its funding was cut. That change resulted in the establishment of our only national solar observatory.

In 1986, President Ronald Reagan called Walker to serve on one of the most important committees in U.S. history -- the commission investigating the space shuttle Challenger explosion. The 13 commission members, chosen for their professional expertise in engineering, industry, law, science and flying, included Apollo 11 commander Neil Armstrong, former Secretary of State William Rogers, Nobel Prize-winning physicist Richard Feynman and Walker's former student, astronaut Sally Ride.

Dr. Walker has served on or chaired a number of NASA, National Science Foundation (NSF), and National Academy of Science (NAS) Committees which prepare recommendations on national research policies and priorities, including the 1980's Decade Astronomy Survey Committee, the Space Studies Board of the NAS, and NASA's Astrophysics Council. Dr. Walker has chaired the Advanced Solar Observatory Science Working Group for NASA, and the Astronomy Advisory Committee of the NSF. Through his final year he was a member of the Observatories Council of the AURA Board of Directors, and the Astronomy Subcommittee of the NSF Division of Mathematical and Physical Sciences. In 1986, President Ronald Reagan appointed Dr. Walker to the Presidential Commission on the "Space Shuttle Challenger Accident". In addition, Dr. Walker has presented testimony by invitation to Congressional Committees on several occasions.

With Dr. Walker's passing we have lost a great scientist, a champion for African American scientists beginning their careers, and a wonderful citizen of our country. But those who lost the most were Art's family who lost a husband, father, and grandfather. Dr. Walker is survived by his wife, Victoria; a daughter, Heather M. M. Walker of Los Altos Hills, Calif.; two stepsons, Nigel D. Gibbs of Los Angeles and Eric D. Gibbs of Temecula, Calif.; and four grandchildren.

Dr. Arthur Walker, obituary:

Dr. Walker joined the faculty of Stanford University in 1974 as a member of the Department of Applied Physics. His scientific field of expertise was Extreme Ultraviolet (EUV) Astronomy primarily of the solar corona. He was the first astronomer to exploit the then new technology of Multilayer coated optics to construct systems which could produce images using extreme ultraviolet radiation. The role of the Multilayer coating is to produce a mirror that is an efficient reflector in the extreme ultraviolet portion of the electromagnetic spectrum. Normally this type of radiation is strongly absorbed by most materials making the fabrication of refractive optical systems impossible. However a thin film coating produced with thin (40nm or less) alternating layers of low and high atomic weight materials which is then deposited on a thick optical substrate can be use to make a mirror. Mirrors coated with these layers exhibit high reflectivity in the Extreme Ultraviolet portions of the Electromagnetic Spectrum and can be used to form high precision imaging systems capable of imaging the sun. Even the earth's atmosphere strongly absorbs EUV radiation therefore to take an EUV picture of the sun requires spaceborne cameras. A spaceborne experiment performed by Dr. Walker and his collaborators resulted in the first Extreme Ultraviolet image of the Sun and Solar Corona. This image was on the front cover of the Nov. 1988 issue of Science Magazine. The courageous decision by Dr. Walker and his team to use on a spaceborne experiment, what was in the 1980's an untried and unproven technology led to increase interest and use of EUV Multilayer coating technology. This technology which has been refined and developed is still very much in use today, and is expected to be used in the manufacture of microchips by 2006.

Dr. Walker was also a dedicated teacher and mentor. His first student, Dr. Sally Ride, was the first US female astronaut to fly aboard the space shuttle. Dr. Walkers students have gone on to take their places in academics and industry. He was also instrumental in the mentoring of many African American students of Physics and Applied Physics during his tenure at Stanford. Dr. Walker was, in no small part, responsible for Stanford being the most prolific producers of African Americans with Ph.D.'s in Physics. Among the many many wonderful things Art did for the Black community at Stanford was serve on the African and African American Studies steering committee, and act as mentor and teacher to students of color and women in Astrophysics, his specialty.

At the festschrift for Art last Fall, we celebrated his innovative research and inspiring teaching in Physics, particularly in Solar Physics, as well as his exemplary contributions to the Black community at Stanford. Happily for us at Stanford and for us as physicists, Art has transmitted his love of physics to generations of Stanford undergraduates through his introductory course on Observational and Laboratory Astronomy, and to dozens Ph.D. students in Physics and Engineering. And, further afield, Art's scientific wisdom has often been placed in the service of this country. Dr. Walker served his nation in many ways as a Lieutenant in the Air Force to being a member of the presidential commission investigating the Challenger accident. We are grateful for the many contributions of this gentleman-scholar.

Art was also a dedicated father and husband. We hope that his wife, Victoria Walker, their children, Heather and Nigel, and the rest of Art's extended family will be comforted by the knowledge that his distinguished service has created a permanent legacy at Stanford University and within the discipline of Physics.


references: Fikes: From Banneker to Best: Some Stellar Careers In Astronomy and Astrophysics; Mickens, The African American Presence in Physics,

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