Members of the Adler Planetarium Operation Moonwatch team using satellite tracking telescopes on the roof of the Adler Planetarium in the 1950s.  Photo courtesy of the Adler Planetarium.

One thing astronomer Mike Seeds remembers about the winter of 1957-58 in Danville, Ill. It was cold. He and some fellow astronomy club members spent much of that winter outside, watching for satellites that were scheduled to launch during the International Geophysical Year (IGY).  And this could be done only at night, when everyone else was sleeping soundly in their warm beds.

“We had to spot satellites right after sunset or right before sunrise,” said Dr. Seeds, now a retired Professor of Astronomy at Franklin & Marshall College in Lancaster, Pa. “During the daytime we couldn’t see them at all, and in the middle of the night the satellite would be in darkness. That got to be really cold work when winter came.”

As they peered through their telescopes and shivered in the dark, the Danville Astronomy Club joined thousands of people across the globe in one of the largest citizen science programs of its time: Operation Moonwatch, whose mission was to spot satellites as they orbited earth.  

The United States and the Soviet Union had announced plans to launch satellites during the IGY – the 18-month world-wide scientific study of Earth’s crust, surface and atmosphere. The U.S. planned to have both scientists and volunteer amateur astronomers around the world ready to track the new spacecraft. It was those volunteers – on Moonwatch teams like the one in Danville – who made some of the most reliable satellite sightings during those first exciting months of the Space Age.

The Moonwatch Plan
Fred Whipple, a Harvard astronomy professor and director of the Smithsonian Astrophysical Observatory (SAO), organized an optical satellite tracking program that would link scientists operating large Baker-Nunn telescope cameras with Operation Moonwatch volunteers. (At the time, satellites were often called “artificial moons.”) The Naval Research Laboratory was also setting up more than a dozen “Minitrack” stations to track satellites by radio.  

The plan called for Moonwatchers to look for satellites through small, specially designed telescopes. If they spotted one, they would call, telegraph or radio the time and location to the SAO, which would use such reports to calculate the satellite’s orbit. Then the SAO would notify the 12 Baker-Nunn stations located around the globe so they could position their 10-foot-tall cameras to photograph the passing satellite.  

Moonwatch Mania   
When Dr. Whipple announced Operation Moonwatch in a 1956 issue of Sky and Telescope magazine, the response was fervent, according to Patrick McCray, author of the 2008 book “Keep Watching the Skies! The Story of Operation Moonwatch and the Dawn of the Space Age.” Amateur skywatchers flooded the SAO with letters asking how to get started, and some groups began organizing themselves even before formal guidelines were issued. Moonwatch quickly grew in popularity, as articles about the program appeared in magazines and newspapers.  

People of all ages and occupations formed Moonwatch teams throughout the United States, on practically every continent including South America, Africa, Australia, and even a floating island in the Arctic Ocean. They ranged from beginners eager to explore the new frontier to seasoned hobbyist astronomers who had built their own telescopes.

Teams created “spotting stations” in yards, parks, planetariums, and on the rooftops of grade schools, libraries, universities – almost anyplace with wide open views of the sky.  The Danville Moonwatch team built their spotting station in a field under the antenna for their local radio station, WDAN, and borrowed electricity from them through a very long extension cord.  

Practicing for the Real Thing
Since no one had seen a satellite before, Moonwatch teams practiced spotting airplanes, insects or objects thrown into their telescopes’ view. Moonwatchers commonly used an 8-inch-long refracting telescope with a large eye piece. It was aimed down to a mirror that faced the sky, for comfortable downward viewing.  

Teams positioned their telescopes so the fields of view overlapped slightly, providing the largest swath of sky possible in which to spot a satellite.  

The SAO arranged practice drills with the Air Force and Civil Air Patrol, which flew planes throughout the country trailing a lighted toilet plunger to simulate a satellite.  

The Danville team arranged similar practice flybys with local pilots. Dr. Seeds admitted that the team became bored pretending to watch for satellites, but it was still summer, he said, and the weather was pleasant.  

After satellites starting going up, Dr. Seeds said his Moonwatch team saw quite a few, and they used a special system to document the sightings.  

When a satellite entered their field of view, the spotter yelled out their telescope number, then yelled “Two!” when the satellite reached the center, and “Three!” when it disappeared out the other side.

The team tape recorded each viewing session, including a radio broadcast of WWV – the U.S. time signal that announces the exact time every minute – so they knew precisely when the satellite was seen. Then they would troop up to the radio station in the dark to report their sighting to the SAO.

“We’d call the SAO, and we all wanted to hear, so we would distribute ourselves around the office and listen on the other phones,” Dr. Seeds said.  

The team was also excited about the SAO’s using a computer to analyze Moonwatch data.  

“We thought that was amazing because a computer was the size of a small building, and there weren’t many around in 1957,” he said. Once in a while the WDAN disc jockey would hear them in the building and call them into his little studio (“the size of a phone booth,” Dr. Seeds said) wanting to know if they had seen a satellite.

Satellites Gave a New View of Earth
Astronaut William Anders famously photographed “Earthrise” while orbiting the moon in 1968. But a decade prior, Earthlings could only imagine how the entire planet looked from afar. IGY satellites provided the opportunity to observe earth from space, and scientists knew reliable tracking of their orbits was the key.  

“The orbit alone, and changes in it, tell us a great deal about the earth,” wrote Fred Whipple in a December 1957 Scientific American article, “Observations of Satellite I,” which detailed what scientists had learned based on observations of Sputniks 1 and 2.  

“In the first few weeks of their flight, [satellites] told us more about the shape of the earth than 2,000 years of observation of our natural satellite, the moon.”  

Dr. Whipple co-wrote the article with astrophysicist J. Allen Hynek, who taught astronomy at Northwestern University from 1960 to 1978.

Drs. Whipple and Hynek explained how changes in the shape, speed and plane of Sputnik’s orbit confirmed the extent of thickening at Earth’s equator, called the “equatorial bulge,” as well as the upper atmosphere’s density and temperature. They speculated that future satellites might help chart Earth’s internal structure through the distribution of its mass.

Moonwatchers to the Rescue
The Baker-Nunn cameras and Minitrack stations were not operational when Sputnik went up in October 1957, so only Moonwatchers could track the little satellite’s flight. Sputnik itself was quite small and tricky to spot, but amateurs made more than three dozen confirmed observations before the satellite burned up in early January 1958, Patrick McCray wrote in “Keep Watching the Skies!”

“Initial data Moonwatchers collected, some 400 reports in all, enabled the mathematicians at the Smithsonian observatory to calculate a preliminary estimate of the satellite’s orbit,” wrote Mr. McCray.  

The SAO wrote that Moonwatchers’ reports provided “with very few exceptions, the only scientifically valuable visual observations.”  Moonwatch teams also looked out for a satellite’s “deathwatch” phase. Moonwatchers, Mr. McCray wrote, were making meaningful contributions to one of the largest science enterprises in history.

Operation Moonwatch Flares and Fades
The number of Moonwatchers peaked in mid-1958, according to Mr. McCray’s book, by which time the SAO had registered 230 active teams with 8,000 participants all over the world.  

Participation waned after the Baker-Nunn and Minitrack systems went online, but some Moonwatchers continued documenting satellite sightings until the program officially ended on June 30, 1975.  

The SAO recognized Moonwatchers like Mike Seeds and the Danville team for their dedication, awarding unique IGY pins to teams reporting successful sightings.  

Dr. Seeds still has his original pin attached to the lapel of one of his suits, and he received another pin during a recent Moonwatch anniversary event.

For all his nostalgic remembrances of spotting satellites and the thrill of talking with the SAO, the frosty dusks and dawns of that IGY winter really stand out.  

“We all had our special boots and extra socks and hand-warmers and gloves and earmuffs,” recalled Dr. Seeds who, as an astronomer, is no stranger to long cold work nights (his e-mail signature quips “Sleep is for wimps”).

“It was just bitter cold. We started in the summer time, then Sputnik went up in October. But I remember the cold nights, waiting for sunrise.”