Gordon Pettengill
Encyclopedia
Gordon Pettengill is a noted American
radio astronomer
and planetary physicist
.
, Rhode Island
. As a young man he was enthralled with radio and electronics, taking apart and building old radios. This was to serve as a beginning to a career using radio and its alter-ego, radar
, in many of its most practical and esoteric aspects. Most importantly he had a strong curiosity about the laws governing what he experienced as well as a keenly precise reasoning to answer it.
Pettingill's amateur radio callsign is W1OUN.
His undergraduate study at MIT was briefly interrupted by service in Europe at the end of World War II
. This was followed by work at Los Alamos
and a doctorate from Berkeley
.
.
He was the driving force behind using the then-new Millstone radar at the MIT Lincoln Laboratory
for the earliest work in radar astronomy
. When it became operational in late 1957, Pettengill used this radar to "skin track" Sputnik I, the first such observation of a satellite. His earliest research, extending well beyond the Earth's orbit was with this same radar in 1961; he used it to make the first ranging measurements to another planet, Venus, to which he would return with more distinction later in his career. These first observations yielded a value for the astronomical unit in terrestrial units which has stood the test of time and has an accuracy some 3 orders of magnitude greater than had been possible with the armamentarium of classical positional astronomy. Such knowledge was critical for the successful navigation of Mariner 2
to Venus
.
Pettengill first became famous for the successful two-dimensional radar mapping of the Moon in 1960, a key step in the U.S. preparations for the Apollo program, insuring, for example, from follow-up data, that the Apollo astronauts would not disappear under a meters-thick layer of dust.
He went to the Arecibo Observatory
(in Puerto Rico
) in the early 1960s and was largely responsible for its use as a radar astronomical tool. Most notable from this phase of Pettengill's work was the discovery that Mercury
's 'day' was about 59 Earth days, not the 88 days that had been widely believed for nearly a century. In his typical "assume nothing" fashion, he had realized that despite the 88-day period's having been "confirmed," the evidence in favor of this period was not all that secure, and he planned to make definitive measurements using the delay-Doppler technique as soon as the Arecibo radar could be instrumented for such observations of Mercury
. His "nose for an important problem" was more than amply rewarded. This discovery led to Giuseppe Colombo's realization that Mercury was in an unexpected 3:2 spin-orbit resonance and to a subsequent renaissance in the study of dynamical resonances in the solar system.
Later in the 1960s and early 1970s, Pettengill led ground-based radar studies of the surface properties of all of the inner planets, including the Earth's (via a clever "triple-bounce" experiment: Moon-Earth-Moon). Pettengill also played a leading role in the first radar studies of an asteroid (Icarus, in 1968), a comet (Encke, in 1980), and moons of other planets (the Galilean satellites, starting in 1976). In all of this work, Pettengill made use of radar systems at MIT's Haystack Observatory
and Cornell
's Arecibo Observatory
, systems whose development he had guided for astronomical applications. Also in the 1970s, he was involved in several unmanned missions to Mars
(the Viking program, for example).
For over two decades, beginning in 1977, he concentrated most heavily on Venus
, this time utilizing radars aboard spacecraft, first the Pioneer Venus orbiter and most recently, Magellan. Because of Pettengill's actions spanning the broadest political fronts to the narrowest technical details, the former was a spectacular success, only to be overshadowed by the latter. For many years, he pursued the idea for using a radar altimeter to map Venus. He also contributed key technical ideas along the way. The results, in part, were detailed reflectivity and topographic maps of virtually the entire planet of Venus, providing geologists and geophysicists, for example, with lifetimes of work to understand the development of Venus' crust and the history of its interior. Many planetary scientists feel he is one of the individuals most responsible for our present knowledge of Venus
(aside from its atmosphere).
His observations have embraced Mercury, Venus, Mars, several asteroids and comets, the Galilean satellites of Jupiter and the rings of Saturn.
He is a professor emeritus at MIT and prior to that was Director of MIT's Center for Space Research. Gordon won the Charles A. Whitten Medal
from the American Geophysical Union
in 1997.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
radio astronomer
Astronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...
and planetary physicist
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...
.
Early life and education
Pettengill was born in ProvidenceProvidence, Rhode Island
Providence is the capital and most populous city of Rhode Island and was one of the first cities established in the United States. Located in Providence County, it is the third largest city in the New England region...
, Rhode Island
Rhode Island
The state of Rhode Island and Providence Plantations, more commonly referred to as Rhode Island , is a state in the New England region of the United States. It is the smallest U.S. state by area...
. As a young man he was enthralled with radio and electronics, taking apart and building old radios. This was to serve as a beginning to a career using radio and its alter-ego, radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
, in many of its most practical and esoteric aspects. Most importantly he had a strong curiosity about the laws governing what he experienced as well as a keenly precise reasoning to answer it.
Pettingill's amateur radio callsign is W1OUN.
His undergraduate study at MIT was briefly interrupted by service in Europe at the end of World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
. This was followed by work at Los Alamos
Los Alamos National Laboratory
Los Alamos National Laboratory is a United States Department of Energy national laboratory, managed and operated by Los Alamos National Security , located in Los Alamos, New Mexico...
and a doctorate from Berkeley
University of California, Berkeley
The University of California, Berkeley , is a teaching and research university established in 1868 and located in Berkeley, California, USA...
.
Accomplishments
Pettengill was one of the first pioneers to take radar from its original military application to its use as a grand tool for astronomyAstronomy
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...
.
He was the driving force behind using the then-new Millstone radar at the MIT Lincoln Laboratory
Lincoln Laboratory
MIT Lincoln Laboratory, located in Lexington, Massachusetts, is a United States Department of Defense research and development center chartered to apply advanced technology to problems of national security. Research and development activities focus on long-term technology development as well as...
for the earliest work in radar astronomy
Radar astronomy
Radar astronomy is a technique of observing nearby astronomical objects by reflecting microwaves off target objects and analyzing the echoes. This research has been conducted for six decades. Radar astronomy differs from radio astronomy in that the latter is a passive observation and the former an...
. When it became operational in late 1957, Pettengill used this radar to "skin track" Sputnik I, the first such observation of a satellite. His earliest research, extending well beyond the Earth's orbit was with this same radar in 1961; he used it to make the first ranging measurements to another planet, Venus, to which he would return with more distinction later in his career. These first observations yielded a value for the astronomical unit in terrestrial units which has stood the test of time and has an accuracy some 3 orders of magnitude greater than had been possible with the armamentarium of classical positional astronomy. Such knowledge was critical for the successful navigation of Mariner 2
Mariner 2
Mariner 2 , an American space probe to Venus, was the first space probe to conduct a successful planetary encounter . The first successful spacecraft in the NASA Mariner program, it was a simplified version of the Block I spacecraft of the Ranger program and an exact copy of Mariner 1...
to Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...
.
Pettengill first became famous for the successful two-dimensional radar mapping of the Moon in 1960, a key step in the U.S. preparations for the Apollo program, insuring, for example, from follow-up data, that the Apollo astronauts would not disappear under a meters-thick layer of dust.
He went to the Arecibo Observatory
Arecibo Observatory
The Arecibo Observatory is a radio telescope near the city of Arecibo in Puerto Rico. It is operated by SRI International under cooperative agreement with the National Science Foundation...
(in Puerto Rico
Puerto Rico
Puerto Rico , officially the Commonwealth of Puerto Rico , is an unincorporated territory of the United States, located in the northeastern Caribbean, east of the Dominican Republic and west of both the United States Virgin Islands and the British Virgin Islands.Puerto Rico comprises an...
) in the early 1960s and was largely responsible for its use as a radar astronomical tool. Most notable from this phase of Pettengill's work was the discovery that Mercury
Mercury (planet)
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...
's 'day' was about 59 Earth days, not the 88 days that had been widely believed for nearly a century. In his typical "assume nothing" fashion, he had realized that despite the 88-day period's having been "confirmed," the evidence in favor of this period was not all that secure, and he planned to make definitive measurements using the delay-Doppler technique as soon as the Arecibo radar could be instrumented for such observations of Mercury
Mercury (planet)
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...
. His "nose for an important problem" was more than amply rewarded. This discovery led to Giuseppe Colombo's realization that Mercury was in an unexpected 3:2 spin-orbit resonance and to a subsequent renaissance in the study of dynamical resonances in the solar system.
Later in the 1960s and early 1970s, Pettengill led ground-based radar studies of the surface properties of all of the inner planets, including the Earth's (via a clever "triple-bounce" experiment: Moon-Earth-Moon). Pettengill also played a leading role in the first radar studies of an asteroid (Icarus, in 1968), a comet (Encke, in 1980), and moons of other planets (the Galilean satellites, starting in 1976). In all of this work, Pettengill made use of radar systems at MIT's Haystack Observatory
Haystack Observatory
Haystack Observatory is a group of astronomical observatories owned and operated by Massachusetts Institute of Technology. It is located in Westford, Massachusetts . It is the home of the Millstone Hill Observatory....
and Cornell
Cornell University
Cornell University is an Ivy League university located in Ithaca, New York, United States. It is a private land-grant university, receiving annual funding from the State of New York for certain educational missions...
's Arecibo Observatory
Arecibo Observatory
The Arecibo Observatory is a radio telescope near the city of Arecibo in Puerto Rico. It is operated by SRI International under cooperative agreement with the National Science Foundation...
, systems whose development he had guided for astronomical applications. Also in the 1970s, he was involved in several unmanned missions to Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
(the Viking program, for example).
For over two decades, beginning in 1977, he concentrated most heavily on Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...
, this time utilizing radars aboard spacecraft, first the Pioneer Venus orbiter and most recently, Magellan. Because of Pettengill's actions spanning the broadest political fronts to the narrowest technical details, the former was a spectacular success, only to be overshadowed by the latter. For many years, he pursued the idea for using a radar altimeter to map Venus. He also contributed key technical ideas along the way. The results, in part, were detailed reflectivity and topographic maps of virtually the entire planet of Venus, providing geologists and geophysicists, for example, with lifetimes of work to understand the development of Venus' crust and the history of its interior. Many planetary scientists feel he is one of the individuals most responsible for our present knowledge of Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...
(aside from its atmosphere).
His observations have embraced Mercury, Venus, Mars, several asteroids and comets, the Galilean satellites of Jupiter and the rings of Saturn.
He is a professor emeritus at MIT and prior to that was Director of MIT's Center for Space Research. Gordon won the Charles A. Whitten Medal
Charles A. Whitten Medal
The Charles A. Whitten Medal was established by the American Geophysical Union to honor Charles A. Whitten for his contributions to research in crustal movements. This medal, which was first awarded to Charles A. Whitten, recognizes outstanding achievement in research on the form and dynamics of...
from the American Geophysical Union
American Geophysical Union
The American Geophysical Union is a nonprofit organization of geophysicists, consisting of over 50,000 members from over 135 countries. AGU's activities are focused on the organization and dissemination of scientific information in the interdisciplinary and international field of geophysics...
in 1997.