In the early 1950s the International Geophysical Year (IGY) was launched by the physics community. Like the polar years, the AGI aimed to study the last unknown places on Earth, in this case the upper atmosphere and the near suburbs. In this context, the bids are going well between Americans and Soviets who announced in 1955 the launch of the first artificial satellites.

At the origins of Vanguard

In the aftermath of World War II, Americans and Soviets embarked on a " rocket race " to develop, among other things, the first ballistic missiles for their nuclear strike force. It appears that this type of rocket will quickly be able to carry important loads, even satellites with the help of one or more additional stages. In the United States, the question of the satellite is very early advanced, a report is presented on this subject on December 29, 1948 to the American Congress by James V. Forrestal, Secretary of Defense.

As AGI loomed, satellite programs were underway within the military. For example, the Army's Redstone Arsenal (where von Braun's team works) is proposing its Redstone, a ballistic missile under development for the nuclear strike force, to satellite (Project Orbiter) with Navy support. However, the latter, through its Naval Research Laboratory (NRL), is defining another project (Vanguard) by developing a launcher from its Viking sounding rocket.

A satellite for peaceful purposes

On July 29, 1955, the political authorities decided that the first satelliteization, taking place within the framework of the AGI, would be done " with strictly scientific purposes ". This is the reason why the operation is entrusted to the Navy with its Vanguard project (" Avant-garde "). This one consists in using Viking as first stage on which come to add two higher stages to satellite. The project is conducted within the NRL, under the direction of Professor John P. Hagen, astronomer seconded to the NRL since 1935. The Vanguard program proposes to realize both the launcher and the satellite which, for a time nicknamed "the bird", will finally bear the same name as the launcher. The first suborbital flights were made on December 8, 1956 (Vanguard Test-Vehicle 0) and May 1, 1957 (Vanguard TV1) with respectively one and two stages.

Double bad surprise

However, on October 4, 1957, the Soviets created the surprise by placing Sputnik 1, the first artificial satellite in history, into orbit. A few days later, in order to play down the situation, the American Secretary of State John F. Dulles tried to calm people down by minimizing the event. The Soviets repeat the following November 3 with a second Sputnik which, in addition, embarks the dog Laïka. Meanwhile, on October 23, Vanguard TV2 with three stages is experimented, but it is still only a suborbital flight...

The Americans do not disarm, however, and present to the media the launch of Vanguard TV3, which, this time, must satellite. However, the satellite, compared to Sputnik 2, appears quite modest : a sphere of 16.3 cm with a total mass of... 1.46 kg against 508 kg for Sputnik 2, to the point that the amused media nicknamed it " grapefruit ". For example, in France, La Liberté of December 5, 1957 headlines : " At Cape Canaveral PAMPLEMOUSSE 1st satellite U.S. " [prepares for launch]. On December 6, in front of the cameras, Vanguard TV3 with its satellite falls back down after having risen about 1.20 m... It is the consternation in the American media which qualify the event of " flopnik ", " Kaputnik ", etc. In France, La Nouvelle République titles December 7, 1957 by " The VANGUARD that was to launch the U.S. satellite explodes on the spot "  Paris Match headlines December 14 : " Satellite Pamplemousse : l'humiliation ". To save the honor, it is called upon the team of von Braun, which, using an improved Redstone manages to satellite Explorer 1 on February 1, 1958 ... without calling into question the continuation of the Vanguard program.

From one humiliation to another

On February 5, a new attempt is made and... cfifty-seven seconds after launch, Vanguard TV3Bu (Test Vehicle 3 Back up) noses down and then breaks in two. The cause of the failure is attributed to a false guidance signal which led the first stage to carry out involuntary pitching manoeuvres. The French press reports the setbacks. La Montagne of February 6 headlines : " New failure of the Vanguard rocket. It had to be destroyed after deviating from its course " ; Ouest-France : " For the second time PAMPLEMOUSSE misses the start " ; Le Parisien libéré : " New failure of Pamplemousse. Installed on the roof, I HAVE SEEN VANGUARD EXPLOSION IN A GERB OF FIRE " testifies Jean Lagrange.

Finally Successful

On March 17, the third attempt, Vanguard TV4, was finally successful and was hailed by the media. Thus, Le Républicain Lorrain announces " VANGUARD I, US Navy satellite finally orbits in space ", stating that it " has joined Explorer I and Sputnik II ". Similarly, Le Parisien libéré of March 18 reports to its readers that " PAMPLEMOUSSE HAS FINALLY TAKEN THE START " Placed in an elliptical orbit of 654 km perigee and 3 969 km apogee, with an inclination of 34.25°, the satellite, named Vanguard 1, becomes the fourth satellite in history, the second American. Vanguard has a mercury battery pack, a telemetry transmitter, a Minitrack beacon transmitter powered by solar cells mounted on the satellite's body, with six 30-cm-long spring-loaded aluminum alloy antennas protruding from the sphere. Vanguard also has a system that measures the interior temperature of the satellite to track the effectiveness of the thermal protection.

As for the scientific results, the on-board transmitters show that the Earth is slightly pear-shaped. The collected signals also allow determination of the total electron content between the satellite and some ground receiving stations. The solar cell-powered transmitter operated for more than 6 years, the signals gradually weakened and were last received at the Minitrack station in Quito, Ecuador, in May 1964.

Some references

- A book: "American Artificial Satellites", John Shirley Hurst, Ed. Two Shores, 1957

- A Nasa publication, Vanguard. A History, Constance McLaughlin Green and Milton Lomask, The NASA Historical Series, Washington, 1970

- A news report, Vanguard 1, Hearst Metrotone News, 1958.

Philippe Varnoteaux is a doctor of history, a specialist in early space exploration in France, and the author of several reference works