Events will take place in the United States today to celebrate the 60th anniversary of the launch of the first spacecraft sent into space by the US.
Explorer 1, a two-metre long satellite carrying a scientific instrument, was launched from Cape Canaveral in Florida on 31 January 1958.
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The craft was not the first object launched into space, as almost a year earlier the USSR successfully put a small metal satellite, Sputnik 1, into orbit.
A month later, they also successfully launched a second, Sputnik 2.
However, the Explorer 1 launch is still seen a seminal moment in scientific, US and global history, marking the start of an era of space exploration led by NASA, which was set up later that year.
The Explorer 1 launch happened in the depths of the Cold War at a time when the US and the Soviet Union were competing for a military and technological edge over one another.
In 1954, an international council of scientists called for artificial satellites to be orbited as part of a worldwide science programme called the International Geophysical Year.
This sparked a space race between the two countries. Within the US, the army, air force and navy each began developing separate satellite and launch vehicles.
In the wake of the Sputnik launches, President Dwight Eisenhower came under pressure to restore confidence in the US's abilities both home and abroad.
In an attempt to address growing doubts about the US capacity to send a satellite to space his administration, invited media to attend the test launch of the navy designed Vanguard booster on 6 December 1957.
It had previously successfully launched into below Earth orbit and the US thought it was the best bet for a successful satellite launch.
However, the booster only lifted three feet off the launchpad before bursting into flames.
That embarrassing failure prompted the US government to order the army to deliver a satellite into orbit within 90 days.
The Army Ballistic Missile Agency had been working on a launch system known as the Jupiter-C developed by Wernher von Braun and his team.
They in turn had been working with the Jet Propulsion Lab (JPL) at the California Institute of Technology in Pasadena where a team led by William Pickering were building a satellite capable of carrying an experiment to measure the "cosmic rays" around Earth developed by University of Iowa physicist James Van Allen.
In early 1958, the rocket and satellite were deemed ready and at 10.48pm on 31 January Explorer 1 was launched.
The success of the craft and others that were launched in its wake led to President Eisenhower signing an order setting up NASA.
It also established JPL as the pre-eminent US centre for the development of space craft and propulsion systems.
It has since led hundreds of Nasa missions to put craft and humans into space.
What was Explorer 1?
Explorer 1 was around two metres in length. Within that the science instrument took up about 95cm.
The main instruments were a cosmic-ray detection package; internal, external and nose-cone temperature sensors; a micrometeorite impact microphone; a ring of micrometeorite erosion gauges; and two transmitters.
There were two antennas in the body of the satellite and its four flexible whips that formed a turnstile antenna.
Electrical power was provided by batteries that made up 40% of the total weight.
Explorer 1 and missions that came after it were responsible for the first space-based discovery - radiation belts around the Earth called the Van Allen Belts.
