50 Year Anniversary of Explorer 7 Launch



On 13 October 1959, Verner Suomi and Robert Parent crouched in a bunker at Cape Canaveral, sweating through the countdown for the Juno II rocket perched on its launching pad 150 yards away. Would the rocket burst into a cloud of flaming debris, as had so many previous attempts, or would it survive and shoot skyward on a pillar of smoke and fire?


explorer 7 countdown


Explorer 7 and Juno II rocket being prepared for launch. 

Photo credit: NASA

Sitting atop the missile was the Explorer 7 satellite, bristling with several experimental devices from some of the top researchers in the country. Suomi and Parent, professors from the University of Wisconsin-Madison, had conceived, designed, and built the innovative radiometer nestled into the body of the satellite. If their instrument made it into orbit, and operated properly once it got there, it would open the world to satellite meteorology.


It would be the first successful satellite measure of the Earth’s climate – if it survived the launch.


There was absolutely no guarantee that it would. Suomi and Parent, only three months before, had watched Explorer 7x, containing another of their radiometers, explode just after launch, intentionally detonated as its guidance systems failed and it veered dangerously off-course. And before that their instruments on the Vanguard TV3 were vaporized when a fuel leak immolated the rocket just after launch.


vanguard explodes


Vanguard TV3 explodes on the launch pad.

Photo credit: NASA

In the first years of the “Space Race,” nothing was certain.


In 1959, the competition between the United States and the Soviet Union to orbit satellites was on the front page worldwide. Only two years before, the Russians had rocked the world with its launch of Sputnik, the first artificial satellite to orbit the planet. Within months the United States responded with Vanguard 1. Both countries had successes and failures. Some satellites made it into orbit; many disintegrated into fire and explosion.


Though these first steps off the planet were difficult, no one doubted the possible worth of satellite observations.


UW Professor Verner Suomi realized earlier than most the importance of understanding the intricacies of the Earth’s climate. His 1953 dissertation measuring the difference between the amount of energy absorbed from the sun in a cornfield and

Verner Suomi and colleagues in a corn field


Verner Suomi  (second from right) and colleagues conducting his heat budget experiment
in a cornfield.

Photo credit: Iowa State College (University) Experiment Station, courtesy of

Space Science and Engineering Center,
University of Wisconsin-Madison

the amount of energy radiated back into the atmosphere served as a springboard for ongoing studies of Earth-atmosphere energy balances. He became one of the first professors at the UW’s new Department of Meteorology, but it was when he partnered with a professor of electrical engineering, Robert Parent, that the pieces of satellite meteorology began to fall into place.


With Suomi’s conceptions and designs, and Parent’s technical wizardry, a new chapter in the study of the Earth’s climate was born. They knew that if they could get their radiometer into orbit it would lead to the first successful measurements of the vital balance between the heat received from the sun and the heat exiting the

atmosphere as a result of reflection and emission processes. They could measure the primary driving force of atmospheric circulation on a planetary scale.


Modest in size by today’s standards, Explorer 7 weighed 41.5 kg (91.5 pounds) and was 75 cm (29.5 inches) high and 75 cm wide. Solar cells and 15 nickel-cadmium batteries powered instruments measuring solar proton radiation and cosmic rays. However, Explorer 7’s most important potential was its capability of making the first satellite observations of the Earth's heat balance.

Professors Suomi and Parent work on a satellite instrument


Verner Suomi (right) and Robert Parent work on an early satellite instrument


If it could be launched successfully, that is.


At 10:36, Eastern Standard Time, the countdown reached zero and the Juno II rocket was ignited. The rocket seemed to pause briefly as the thundering engine came to full power and then, shaking the earth beneath it, it rose into the sky. Verner Suomi and Robert Parent watched unblinking as it flew higher and higher.


The launch was successful and Explorer 7 entered its orbit moments later.


Augmenting the satellite’s observations with ground based measurements, Verner Suomi and his team discovered that the Earth absorbed more of the Sun's energy than originally thought and demonstrated that it was possible to measure and quantify seasonal changes in the global heat budget.


Juno II rocket on the launchpad


Explorer 7 launch, 13 October 1959.

Photo credit: NASA

Explorer 7 was the first step in a fifty-year journey toward understanding the forces that govern the environment in which we live. Suomi and Parent went on to design and build increasingly more sophisticated instruments over the next two decades: the flat-plate radiometer that rode in the TIROS satellite and the spin-scan camera that made Earth observations from a geostationary orbit possible. Verner Suomi also conceived of and led the team that created the McIDAS (Man-Computer Interactive Data Access System) software, a suite of sophisticated software packages that perform a wide variety of functions with satellite imagery, observational reports, numerical forecasts, and other geophysical data.


Climate studies have proven their vital importance to humanity again and again, and will continue to do so far into the future. And it all started with a pair of nervous scientists hunkered down in a bunker, hoping for a successful launch.


Explorer 7 faithfully transmitted continuous data through February of 1961 and finally went silent in August of 1961. Verner Suomi and Robert Parent, with their radiometer on Explorer 7, began the era of satellite-based climate studies that have continually grown in importance and will continue to supply us with vital data far into the future.


Model of Explorer 7


This full-scale recreation of the Explorer 7 satellite will be on display at the 50th Anniversary celebration.

Photo credit: Space Science and Engineering Center,

University of Wisconsin-Madison


Last Updated:
October 12, 2009
SSEC, 1225 W. Dayton Street, Madison, WI 53706, USA
For questions or problems about this page, please contact
SSEC Webmaster