Gordon Hemenway Pettengill (February 10, 1926 – May 8, 2021) was an American radio astronomer and planetary physicist. He was one of the first to take radar from its original military application to its use as a tool for

astronomy Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest includ ...

. He was professor emeritus at the

Massachusetts Institute of Technology The Massachusetts Institute of Technology (MIT) is a Private university, private research university in Cambridge, Massachusetts, United States. Established in 1861, MIT has played a significant role in the development of many areas of moder ...

Early life and education

Gordon Pettengill was born in Providence,

Rhode Island Rhode Island ( ) is a state in the New England region of the Northeastern United States. It borders Connecticut to its west; Massachusetts to its north and east; and the Atlantic Ocean to its south via Rhode Island Sound and Block Is ...

, and grew up in

Dedham, Massachusetts Dedham ( ) is a New England town, town in, and the county seat of, Norfolk County, Massachusetts, United States. Located on Boston's southwestern border, the population was 25,364 at the 2020 United States census, 2020 census. First settled by E ...

where he developed a fascination with radio and electronics. He often took apart and rebuilt old radios. Pettengill was interested in

amateur radio Amateur radio, also known as ham radio, is the use of the radio frequency radio spectrum, spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emer ...

and his callsign was W1OUN. Pettengill began studying physics at the

(MIT) in 1942 at the age of 16. His studies were briefly interrupted by service in Europe at the end of

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

. When he turned 18, he was drafted into the

United States Army The United States Army (USA) is the primary Land warfare, land service branch of the United States Department of Defense. It is designated as the Army of the United States in the United States Constitution.Article II, section 2, clause 1 of th ...

where he served in the infantry and then with a

Signal Corps A signal corps is a military branch, responsible for military communications (''signals''). Many countries maintain a signal corps, which is typically subordinate to a country's army. Military communication usually consists of radio, telephone, ...

company stationed in Austria. After World War II ended, he returned to MIT where he received a Bachelor of Science in 1948. This was followed by work at Los Alamos and a doctorate in physics from the

University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California), is a Public university, public Land-grant university, land-grant research university in Berkeley, California, United States. Founded in 1868 and named after t ...

in 1955.

Career and research

Pettengill began his career at the

MIT Lincoln Laboratory The MIT Lincoln Laboratory, located in Lexington, Massachusetts, is a United States Department of Defense federally funded research and development center chartered to apply advanced technology to problems of national security. Research and dev ...

in 1954. By the late 1950s, he was part of a group using the then-new Millstone Hill radar for the earliest work in

radar astronomy Radar astronomy is a technique of observing nearby astronomical objects by reflecting radio waves or microwaves off target objects and analyzing their reflections. Radar astronomy differs from ''radio astronomy'' in that the latter is a passive ob ...

. When it became operational in late 1957, Pettengill used this radar to "skin track"

Sputnik Sputnik 1 (, , ''Satellite 1''), sometimes referred to as simply Sputnik, was the first artificial Earth satellite. It was launched into an elliptical low Earth orbit by the Soviet Union on 4 October 1957 as part of the Soviet space progra ...

I, the first such observation of a satellite. His earliest research extending 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. These first observations yielded a value for the astronomical unit in terrestrial units which has an accuracy 3 orders of magnitude greater than had been possible with the armamentarium of classical positional astronomy. Such knowledge was critical for the navigation of

Mariner 2 Mariner 2 (Mariner-Venus 1962), an American space probe to Venus, was the first robotic space probe to report successfully from a planetary encounter. The first successful spacecraft in the NASA Mariner program, it was a simplified version of t ...

Venus Venus is the second planet from the Sun. It is often called Earth's "twin" or "sister" planet for having almost the same size and mass, and the closest orbit to Earth's. While both are rocky planets, Venus has an atmosphere much thicker ...

. Pettengill successfully completed a two-dimensional radar mapping of the Moon in 1960, a key step in the U.S. preparations for the

Apollo program The Apollo program, also known as Project Apollo, was the United States human spaceflight program led by NASA, which Moon landing, landed the first humans on the Moon in 1969. Apollo followed Project Mercury that put the first Americans in sp ...

, ensuring that the Apollo astronauts would not disappear under a meters-thick layer of dust. From 1963 to 1965, Pettengill served as associate director and from 1968 to 1970 as Director of the

Arecibo Observatory The Arecibo Observatory, also known as the National Astronomy and Ionosphere Center (NAIC) and formerly known as the Arecibo Ionosphere Observatory, is an observatory in Barrio Esperanza, Arecibo, Puerto Rico owned by the US National Science F ...

Puerto Rico ; abbreviated PR), officially the Commonwealth of Puerto Rico, is a Government of Puerto Rico, self-governing Caribbean Geography of Puerto Rico, archipelago and island organized as an Territories of the United States, unincorporated territo ...

. At Arecibo, Pettengill and Rolf Dyce used radar pulses to measure the spin rate of Mercury and found that Mercury's day was 59 Earth days, not 88 as had been previously thought. He was appointed Professor of Planetary Physics in the Department of Earth and Planetary Sciences at MIT in 1970. In the late 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 "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 The Massachusetts Institute of Technology (MIT) is a private research university in Cambridge, Massachusetts, United States. Established in 1861, MIT has played a significant role in the development of many areas of modern technology and sc ...

's Haystack Observatory and Cornell's

, systems whose development he had guided for astronomical applications. Also in the 1970s, he was involved in several unmanned missions to

Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...

(including the Viking program). For over two decades, beginning in 1977, he concentrated most heavily on

, this time utilizing radars aboard spacecraft, first the Pioneer Venus orbiter and later, Magellan. For many years, he pursued the idea for using a radar altimeter to map Venus and contributed key technical ideas. The results, in part, were detailed reflectivity and topographic maps of virtually the entire planet of Venus, providing geologists and geophysicists with lifetimes of work to understand the development of Venus' crust and the history of its interior. Many planetary scientists feel he was one of the individuals most responsible for our present knowledge of

(aside from its atmosphere). His observations embraced Mercury, Venus, Mars, several asteroids and comets, the Galilean satellites of Jupiter and the rings of Saturn.

Awards and honours

He won the Charles A. Whitten Medal from the

American Geophysical Union The American Geophysical Union (AGU) is a 501(c)(3) nonprofit organization of Earth, Atmospheric science, atmospheric, Oceanography, ocean, Hydrology, hydrologic, Astronomy, space, and Planetary science, planetary scientists and enthusiasts that ...

in 1997. The asteroid 3831 Pettengill is named after him.

Publications

*G.H. Pettengill and D.E. Dustin, "A Comparison of Selected ICBM Early-Warning Radar Configurations," MIT Lincoln Laboratory Technical Report 127, 1956.

References

External links

Annual Review of Astronomy and Astrophysics 3:377-411 (September 1965)

NASA Technical Reports

Venus: Global Surface Radar Reflectivity

Venus Surface Radiothermal Emission as Observed by Magellan
* Gordon H. Pettengill personal archives, MC 609, Massachusetts Institute of Technology, Institute Archives and Special Collections, Cambridge, Massachusetts. {{DEFAULTSORT:Pettengill, Gordon 1926 births 2021 deaths Scientists from Providence, Rhode Island Members of the United States National Academy of Sciences American astronomers Massachusetts Institute of Technology School of Science alumni University of California, Berkeley alumni Amateur radio people MIT Lincoln Laboratory people Scientists from Massachusetts United States Army soldiers People from Dedham, Massachusetts Military personnel from Massachusetts United States Army personnel of World War II