Whipple’s Moonwatch: Amateur Astronomers in the Space Age

October 4, 2017 marked the 60th anniversary of the launch of Earth’s first artificial satellite “Sputnik,” in 1957. The world was astonished by the news that the Soviet Union had successfully put a satellite into Earth’s orbit for the first time in history. Sputnik had a profound impact on international relations, military affairs, science, and technology. Through “Operation Moonwatch,” distinguished astronomer Dr. Fred L. Whipple brought together scientists and ordinary citizens from all over the globe, establishing satellite-tracking stations to look toward the skies. Moonwatch signified more than observing the skies for glimpses of Sputnik: it created an international network of amateur astronomers, celebrating and participating in an enormous scientific endeavor that was the beginning of the Space Age. 

Fig. 1: Sputnik Spotted. The first official photograph of the Soviet Satellite Rocket carrying Sputnik into orbit, taken using the giant IGY satellite tracking camera (Baker-Nunn) at South Pasadena, CA at 5:06am, Oct 17, 1957 by Smithsonian Astrophysical Observatory.

Few generally think much about the cultural and historical impact that these satellites have had on our society today. Our lives are substantially connected to these objects casually floating far above us. We obtain data and information from them that help us determine global positioning and weather patterns, circulate music and entertainment, and connect to each other in a massive web of communication.

The idea of artificial satellites and orbiting telescopes took off in the years following World War II. In the 1950s, the United States and Europe began paying closer attention to the development of military rockets to explore the upper atmosphere and outer space. In the early phases of developing a scientific space program in the United States, Fred Whipple of the Harvard College Observatory (HCO) thought about the potential difficulties and problems with artificial satellites. His 1946 paper “Possible Hazards to a Satellite Vehicle from Meteorites” proposed the development of a metal meteor-bumper to help shield orbital satellites from external damage. Gradually, scientists started exchanging ideas for various satellite studies, which eventually snowballed into the possibility of an orbiting satellite station from which we could observe and ‘track’ the Earth. Whipple foresaw the need for immense computing power and precision to be able to follow and calculate an orbit for a space station.

Fig. 2: Fred L. Whipple, From Wolbach Library Special Collections.

Dr. Fred Lawrence Whipple (1906-2004) was a Professor of Astronomy at Harvard University (1945-1977) and a Senior Physicist at Smithsonian Astrophysical Observatory (1955-2004). After graduating from UCLA with a degree in mathematics in 1927, he found a passion for astronomy and went on to obtain his Ph.D. at University of California at Berkeley in 1931. Shortly after, he moved to the Harvard College Observatory and became the program director there. Early in his career, he used his mathematical skill to analyze the historical positions of comets and determine their paths. Whipple was best known for his advancement of the study of comets and meteors, for which he became the world’s leading expert as he discovered six new comets. His great passion for the study of space permeated throughout his career. (Read about Whipple’s personal interest in space exploration here: “Why Conquer Space?”) 

With the goal of a space station in mind, U.S. scientists started their energy on launching the first artificial satellite into orbit. In 1954, Whipple had joined Project Orbiter, the unofficial military effort to launch a satellite. Whipple proposed and took charge of an optical tracking system for the satellite project. He also began thinking about a broad satellite tracking network. Soon, however, the Eisenhower administration chose the Naval Research Laboratory’s competing proposal for Project Vanguard.

In 1955, Whipple became the director of the Smithsonian Astrophysical Observatory (SAO), which at that time was relocating to Cambridge, MA. This position put him at the center of scientific policy during a time when international relations amplified scientific endeavors. Whipple’s initial studies for Project Orbiter and his work at Harvard set him up to be a leading voice in satellite tracking.

Whipple dreamed of creating the first artificial satellite, and he envisioned an international program that included amateur astronomers and citizen scientists to support it. While many professionals refused to believe that amateurs could make major contributions to such significant scientific projects, Whipple was determined to prove them wrong. 

Fig. 3: Operation Moonwatch Event, Biloxi, Mississippi; Smithsonian Institution Archives, Image # 91-6389.

Whipple knew how important it would be to welcome the cooperation of amateur astronomers in order to establish a successful program: “Astronomy recognizes no boundaries in time, nor in space, nor among the peoples and cultures of the world. It is scientifically international and interdisciplinary” (Whipple, The Call of Space). With Whipple’s curiosity and expertise, he was able to establish the first worldwide network of amateur astronomers for the purpose of tracking and determining the orbits of these objects: Operation Moonwatch.

The Moonwatch optical tracking program came to fruition as a project of the International Geophysical Year (IGY), a worldwide effort to advance modern science and technology. The IGY was known as the greatest scientific project of the 20th century and it encompassed endeavors in varying fields of study, from geophysics to oceanography, during the period of July 1957 to December 1958. On July 29, 1955, President Eisenhower announced that the United States would contribute to the IGY by launching an artificial satellite into Earth’s atmosphere. Many consider this event the beginning of the Space Race between the U.S.S.R. and the U.S.A. The Soviets responded four days later with their intent to launch their own artificial satellites. IGY committees soon set up a worldwide organization that would track the satellite, both visually and by radio. Optical tracking was assigned to the Smithsonian Astrophysical Observatory in Cambridge (while radio tracking was given to the Naval Research Laboratory in Washington).

Fig. 4: Baker-Nunn Camera. Smithsonian Institution Archives, Image # 2002-32252.
The Baker-Nunn Camera, one of the world’s most sensitive devices for observing artificial satellites.

Whipple conceived of the IGY optical tracking program to consist of three major factors: a community of amateur astronomers to scan the skies, a program of twelve specialized telescopic cameras (Baker-Nunn cameras) set up at various locations around the globe to track the satellites, and a control center at the SAO in Cambridge, MA, to compute the data. Teams of amateurs and citizen scientists would relay their observations and data to Cambridge, where professional scientists generated orbit calculations.

Sputnik’s launch on Friday evening of October 4, 1957, came as a complete surprise as this news arrived while IGY representatives were meeting at the Soviet Embassy. When Sputnik was successfully launched, Whipple’s team assembled back in Cambridge in a rush to start optical observations. (Read their reactions here: CFA1982When the call came through, it was up to the Observatory to notify 2,000 Moonwatch observers all over the globe, and Cambridge quickly became the central information hub of the early Space Age. Luckily, Whipple had given some thought to the possibility of an early satellite launch. He decided that the announcement-card system of the HCO would be a useful tool to rapidly publish data, and spread information. (See Bulletin1_Jul1956). The team published irregular updates in the “Bulletin for Visual Observers”, which appeared in Sky & Telescope, the top amateur astronomy magazine (which had formerly been distributed out of HCO during the 1940s).

Fig. 5: HCO Announcement Card #1374

(Click through to see the following five cards: HCO Announcement Cards #1374 (Fig. 5), 1384, 1387, 1391, 1392)

The Cold War’s impact on the international culture of science and technology also proved to be a significant ground for the Moonwatch program. Everyone had their eyes on the skies looking for the Soviet satellites, which created a common worldwide interest in satellite tracking and the Moonwatch program. “Satellite tracking was crucial for reasons far beyond monitoring the craft’s well-being. By studying changes in its orbit due to gravitational forces and atmospheric drag, scientists could understand more about the structure of Earth and its upper atmosphere. In addition, being able to keep tabs on Soviet satellites was essential for a country still on edge from the Cold War” (Pulliam, 31).

As America’s anxiety over the looming threat of nuclear war grew, Sputnik’s launch could not have been more frightening: “If the Soviets could send a satellite spinning around the globe every ninety-six minutes, it took no great feat of imagination to believe that they could loft some more menacing projectile toward the United States” (Dickson, 116). For several days we didn’t even know what it looked like — paranoia ensued; the object’s incessant beeping sounds didn’t help. The office of President Eisenhower told the public not to worry and not to panic, however difficult that may be, and that the United States would continue plans with scientific satellites, missiles, military hardware, and spy satellites. However, apprehension continued throughout October as Sputnik visibly flew over the United States four to six times per day. It was the collaboration between the Moonwatchers and the Smithsonian Astrophysical Observatory in Cambridge the provided answers for the media, keeping accurate information regarding the tracking of the Soviet satellites.

In Whipple’s thinking, amateurs and enthusiasts in astronomy would be brought together by Moonwatch, and in reality, the program did attract an assortment of people, coming together in the common spirit of science. Whipple recognized the importance of their contributions:

In short, following the satellites and reading the information they have to give is fully as important as launching them successfully. To track these objects, and find their exact orbits is a far more difficult task than it may seem. Their positions and motions against the background of stars have to be measured with great precision. Never before have astronomers been asked to track objects moving so rapidly as these artificial moons. Only a worldwide cooperative effort of many observers makes it possible at all.   (Whipple and Hynek, 1957)

Fig. 7: Fred Whipple’s Moonwatch satellite-tracking telescope; Loaned from the Harvard Collection of Historical Scientific Instruments.


Fig. 6: Photograph from “Table-top observing with telescopes” Sky & Telescope, Feb. 1957, p182.



Fig. 8: Trackers of the Skies by N.E. Hayes; Whipple’s personal copy signed by SAO team members.

Whipple intended the program to be collaborative, campaigning that, “Men and women of all hues, creeds, and ideas will work together in a science so new it does not even have a name” (McCray, Keep Watching the Skies 90). Whipple cleverly termed the activity of satellite spotting as “PLORB-ing” – “placing of artificial moons in orbits in space.” (See “Wanted: Spotters for the Satellites”) The SAO’s optical tracking program for the IGY was directed by J. Allen Hynek in 1956, and Moonwatch was guided by coordinator Dr. Armand Spitz. Leon Campbell Jr., another veteran of HCO, become the first of several Moonwatch directors and helped manage communications between the Moonwatch citizen teams and the SAO professionals. 


Fig. 9: Moonwatch Volunteers, 1965. Smithsonian Institution Archives (Image # 96-960). Volunteer satellite trackers in Pretoria, South Africa using the fence method.

Together they promoted the optical program, enlisting about 230 teams worldwide at its height. Promotions for Moonwatch were included in the Sky & Telescope bulletins, along with instructions on the technical aspects and team functions. Members would use special “satellite spotters” that an amateur could easily assemble on their own or purchase. (See Fig. 7 and read Design of a Moonwatch Telescope) Equipped with telescopes, Moonwatchers organized themselves in a “fence method” position in order to spread out observations into sections of the sky. Once a satellite was spotted, the leader sent the information via telegram or collect-call to the SAO in Cambridge. The SAO would then send a predicted orbit to the Baker-Nunns, where scientists would track and photograph the satellites.

Fig. 10: Sputnik IV cast fragment

The first Sputnik observation was made by teams in Australia on October 8, and again in New Haven, Connecticut on October 10. Moonwatchers would continue on in their observations and be the first to spot the U.S. satellite Explorer I, see Sputnik II as it reentered the atmosphere, and find satellites of which the professionals had lost track. In September 1962, volunteers were on the lookout for the Soviet Union’s Sputnik IV, which finally fell back to earth after an orbit of over 800 days. Milwaukee Moonwatchers witnessed the fiery blaze of the dying satellite and discovered a large fragment of it off a Manitowoc street. The object was then sent to the SAO where Whipple then displayed it at a press conference.

Fig. 11: Whipple receives the President’s Award for Distinguished Public Service. Wolbach Library Special Collections.


In 1963, President John F. Kennedy presented to Dr. Fred L. Whipple the President’s Award for Distinguished Public Service, the highest civilian honor given to a government employee.  Kennedy praised the successes of the Moonwatch program and recognized Whipple’s “imaginative foresight and boundless faith in the possibilities of science” (McCray, Keep Watching the Skies, 210). Fred Whipple achieved his vision of a massive network of scientific collaboration which lasted for years after the program ended, changing the perception of amateur science everywhere.

Fig. 12: Thank you from Whipple

The Moonwatch program lasted for 18 years, with its dedicated volunteers supporting over 400,000 valuable, time-consuming observations of satellites. Long after the buzz around Sputnik ended, Moonwatch remained relevant in providing a low-cost method of collecting satellite orbital data as well as data on the physics of the upper atmosphere. Finally, in 1975, it was announced that the program would officially end June 30th. In a letter thanking his Moonwatchers, Whipple celebrated the success of the program, even though others believed it would fail. (See Fig. 12 and its transcription: WhippleThankYou)


To me it is the call of space that has insistently motivated all astronomers throughout all ages to observe and to attempt to explain the great unknowns of the universe about and beyond us. The call of space is part of the motivating force that has led man beyond a purely animal existence to great intellectual and artistic expression. It is also a call in time as well as in space, for the finite speed of light carries us back to antiquity billions of years ago in our study of distant objects in the sky. Even with the naked eye we can see back 2 million years in time, to the great spiral galaxy in Andromeda.  (Whipple, The call of space)



Dickson, P., 2003. Sputnik: the shock of the century, New York: Berkley Books.

Hayes, E.N., 1968. Trackers of the skies, Cambridge, Mass.: H. A. Doyle Pub. Co.

McCray, W.P., 2008. Keep watching the skies! : the story of Operation Moonwatch & the dawn of the spage age, Princeton: Princeton University Press.

McCray, W., 2006. “Amateur Scientists, the International Geophysical Year, and the Ambitions of Fred Whipple”. Isis, 97(4), pp.634–658.

Pulliam, Christine, October 2007, “Project Moonwatch: Satellite Tracking at the Dawn of the Space Age”, Sky & Telescope, vol. 114, no. 4, pp. 30-35.

Smithsonian Institution Archives, Record Unit 108, Box 2, Folder: 5

Smithsonian Institution Archives, Record Unit 371, Box 4, Folder: December 1983

Smithsonian Institution Archives, Record Unit 9520, Box 1, Fred L. Whipple Oral History Interviews

Whipple, F.L. & Smithsonian Astrophysical Observatory, 1972. The collected contributions of Fred L. Whipple., Cambridge, Mass.: Smithsonian Astrophysical Observatory.

Whipple, “Why Conquer Space?” Astronautics vol 1, no. 1, p7, 1974.

Whipple, F.L., 1967. The call of space. (Lecture presented at the Dedication of the Lindheimer Astronomical Research Center, Northwestern University, Evanston, Ill., May 4, 1967.)

Whipple, F.L., and Hynek, J.A. “Observations of Satellite I.” Scientific American, vol. 197, no. 6, 1957, pp. 37–43., www.jstor.org/stable/24941993.

Whipple, F.L., 1929. Papers of Fred Lawrence Whipple, 1929-1997. Harvard University Archives.

Jenny Koch

About Jenny Koch

Jenny is a Digital Projects Assistant at the Wolbach Library.

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