In lieu of an abstract, here is a brief excerpt of the content:

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Venus—December 14, 1962. The tiny Mariner 2 spacecraft neared the end of a 109-day voyage to the brightest jewel then visibleinthedawnsky.Centuriesofhumanbeingshadgreeted Venus as the morning star. Now JPL scientists sent a greeting toMarinerwithradiosignalsthatswitchedontheinstruments forearth’sfirstclose-upexplorationofanotherplanet.Against great odds, Mariner 2 hurled across 180 million miles of space with a small haven full of instruments prepared to unravel the secrets of Earth’s cloud-shrouded neighbor. Newspaper articles speculated about finding clues “to the possibility of the existence of life on Venus.” The instruments flashed into action at about 10:55 A.M. Pacific Standard Time. Passing nearly 21,500 miles above the planet, they transmitted observations about the atmosphere and blistering temperatures at Venus. Twenty-second spurts of scientific data alternated with eighteen-second spurts of operating updates from JPL until the craft approached the dark side of the planet and temporarily lost touch with Earth at 11:37 A.M. In those previous, precious forty-two minutes, instruments measured the microwaves and infrared light streaming from the planet to determine the scorching heat at Venus and the composition of the gaseous clouds shrouding it. Van Allen’s particle detectors looked for a magnetic field and radiation belts. Other investigators mapped the planet’s rotation. Despite the historic moment and Pickering’s personal invitationtocometoJPLforthefly -by,VanAllenhadstayedhome, crossed his fingers, and listened for word of Injun 3. The satellite still hadn’t shed the final stage of the launch rockets and Van Allen’s group agonized over the weak signals intercepted at the Iowa City tracking station. “Fuddled,” Van Allen remarked in his journal, describing communications thus far. The Mariners 15 To make matters worse, McIlwain called from the cape with disappointing reports about the Relay satellite, launched the night before with Iowa instrumentstostudytheinnerradiationbelts .Batteryproblemsonthesatellitewere already jeopardizing the detectors. VanAllenstuckbythephone.ThenLouFrankstoppedbyfornewsofMariner 2,eagerforreadingsfromtheexperimenthehadhelpedbuild.VanAllenlooked up. It was already dark outside, streetlights glistening in the cold, as Mariner sped beyond Venus and approached an orbit around the sun. Frank and Van Allen phoned Hugh Anderson at JPL for a rundown on the mission. “The SUI 213Geigercountershowed—onquickinspection—noincreaseofcountingrate,” VanAllenwroteinhisjournal.TherewasnoincreaseonJPL’sGeigertubeeither and no trace of a magnetic field on the University of California’s magnetometer. The readings at Venus matched the background veil of outer space and meant that Venus simply didn’t have a magnetic field to find. “We sailed by with our detectors as though the planet wasn’t there.” Van Allen said. • • • Van Allen began to speculate on the possibility of looking for radiation belts aroundVenusandMars,ourclosestneighbors,almostassoonasthefirstsatellites orbited the earth. “One of my driving aspirations right away was to push onwithmagnetosphericstudiesoftheotherplanetsandthesolarsystem,”Van Allen said. With the first satellite missions, Van Allen helped define a new geography of space. It encompassed the radiation belts, the aurora and the region influenced by the earth’s magnetic field, a region flattened as the solar wind slammed into it on the side facing the sun and flaring out on the side open to interstellar space. Physicist Thomas Gold coined the term magnetosphere to cover the new area Van Allen helped define to study the region of a planet’s magnetic field. The term defined one clear mandate for the probes to the other planets. Did they have magnetic fields and radiation belts? And what about the solar system? The idea of a heliosphere suggested a bubble encasing it and a boundary , or heliopause, where the solar wind lost momentum and slammed back like tidal waves from the onslaught of currents of cosmic rays. The concept made it unreasonable to consider Pluto, considered a planet until 2006, as the back door to the solar system. The only way to define the new boundaries would be to send out probes to explore—and to remap the solar system. The Mariner missions to Venus and Mars, to the other planets and beyond the solar system offered a gold mine for scientific discoveries. Van Allen and 214 The Mariners other members of the Space Science Board, an advisory board to NASA, decided to congregate the space community for a comprehensive forum that promoted such missions in a wide-ranging agenda for space research. Van Allen agreed to chair the “Space Science Summer Study” as the board planned it early in 1962. “I was very keen on this and offered to be the host for the meeting and participate very heavily in it, and so, I made all the practical arrangements for the meeting in Iowa City,” Van Allen said. He opened the...

Share