Gordon Pettengill

Lore & Background

Pettengill grew up in Dedham, Massachusetts, where he developed a fascination with radio and electronics, often taking apart and rebuilding old radios. He was an amateur radio operator with callsign W1OUN. He began studying physics at MIT in 1942 at age 16, but his studies were interrupted by service in Europe at the end of World War II; he was drafted into the U.S. Army, served in the infantry and then with a Signal Corps company in Austria, and returned to MIT after the war.

At MIT Lincoln Laboratory from 1954, Pettengill used the Millstone Hill radar for early radar astronomy. In late 1957, he used it to 'skin track' Sputnik I, the first such observation of a satellite. In 1961, he made the first ranging measurements to another planet, Venus, yielding a value for the astronomical unit three orders of magnitude more accurate than classical methods. He completed a two-dimensional radar mapping of the Moon in 1960, aiding Apollo program preparations.

At Arecibo Observatory, Pettengill and Rolf Dyce used radar pulses to measure Mercury's spin rate, finding it to be 59 Earth days, not 88. He led ground-based radar studies of all inner planets, including a triple-bounce experiment (Moon-Earth-Moon), and played a leading role in the first radar studies of asteroid Icarus (1968), comet Encke (1980), and the Galilean satellites (starting 1976). From 1977, he concentrated on Venus, using radars aboard Pioneer Venus and Magellan spacecraft, contributing key ideas for a radar altimeter to map Venus, producing detailed reflectivity and topographic maps of virtually the entire planet.

Reader's Guide

Pettengill's significance lies in his transformation of radar from a military tool into a fundamental instrument for planetary science. His early ranging of Venus provided the precise astronomical unit needed for navigation of Mariner 2, and his lunar radar mapping ensured Apollo astronauts would not encounter deep dust. At Arecibo, his measurement of Mercury's rotation corrected a long-held error. His ground-based radar studies of inner planets, asteroids, comets, and Galilean satellites expanded knowledge of surface properties across the solar system. Over two decades, his work on Venus using spacecraft radars produced comprehensive maps that gave geologists and geophysicists extensive data to study Venusian crust and interior history. Many planetary scientists consider him one of the individuals most responsible for present knowledge of Venus (aside from its atmosphere). His legacy includes guiding development of radar systems at MIT's Haystack Observatory and Cornell's Arecibo Observatory for astronomical applications.

Did You Know?

• Pettengill's amateur radio callsign was W1OUN.
• He used radar to 'skin track' Sputnik I in late 1957, the first such observation of a satellite.
• He and Rolf Dyce found Mercury's day to be 59 Earth days, not 88 as previously thought.
• Asteroid 3831 Pettengill is named after him.