​​What Is The Oldest Spacecraft Still In Orbit?

Today, following over sixty years of space exploration, over 6,000 satellites are orbiting the Earth. Around half of these are in operation, while the other half are now inactive, providing no useful commercial or scientific function.

The number of spacecraft in orbit is expected to rise exponentially, with companies such as SpaceX and Amazon planning to launch many new satellite constellations into space over the next few decades. 

Source: Britannica

Although the presence of many satellites in space improves technology and enhances connectivity across the world, it also causes crowding in the skies due to the thousands of defunct satellites, or “space junk” already littering the low-Earth orbit. This increases the risk of space debris collision and is also bad for the environment.

These days, the majority of satellites are launched into space for commercial reasons, but it wasn’t always this way.

The first-ever spacecraft to orbit the Earth, Sputnik 1, was launched in 1957 by the Soviet Union and initiated the beginning of humankind’s exploration into space. The Sputnik 1 was an extraordinary technological advancement, which prompted the United States and other countries to join in the “space race”. 

However, the first spacecraft is no longer in orbit, as it burned up while re-entering the Earth’s atmosphere after just three months. This leaves the US-made satellite; Vanguard 1, as the oldest spacecraft still in orbit to this day.

Is Vanguard 1 Still Working?

Vanguard 1 was launched into space by the United States in March 1958, in response to the Soviet Union’s Sputnik launch, and as part of the American contribution to the 1957-58 International Geophysical Year.

It followed the first spacecraft launched by the US, Explorer 1, which was also the first satellite to carry scientific instruments; a radio transmitter, cosmic ray detector, and temperature and micrometeoroid sensors. It was the US’s stake in the space race, a competition between the Soviet Union and the US during the Cold War.

Explorer 1 was a revolutionary spacecraft, but it didn’t last too long. It transmitted its final signal in May 1958, then re-entered the Earth’s atmosphere and burned up in March 1970.

Vanguard 1 may not have been the first satellite, but it still proved groundbreaking in our knowledge of space missions. Not only did it demonstrate the capability of a new three-stage launcher system, but it also helped us to understand more about the effects of a space environment on satellites.

The spacecraft was created under Project Vanguard, originally commissioned by the Naval Research Laboratory, and was the first solar-powered satellite in existence. Solar power was new technology at this point, with the invention of the silicon solar cell being announced only months before.

The spacecraft’s solar cells allowed it to transmit signals for years, rather than the days that battery-powered satellites lasted.

Researchers used Vanguard to measure atmospheric densities as a function of solar activity, altitude, latitude, and season, providing the first measurements of the Earth’s outer atmospheric properties.

To achieve this, they conducted orbit analysis to monitor the spacecraft’s flight path. Tracking its trajectory and how it deviated from predictions allowed researchers to discover new knowledge about the effects of the Earth’s atmosphere.

Vanguard also showed us that Earth bulges out around the equator, revealed its pear-like shape, and gave us insight into the capabilities of satellites which are a significant part of our lives today. It aided future space technology and provided the basis for systems such as the Delta launch vehicle, which is one of the most effective launchers in space history. 

After Vanguard’s groundbreaking success, the project was transferred across to NASA, along with many of its personnel.

The spacecraft is a small aluminum sphere, equipped with two radio transmitters. The radio transmitters consist of a 10 mW mercury-battery-powered transmitter on the 108 MHz band, used for International Geophysical Year scientific satellites, and a 5 mW, 108.03 MHz Minitrack transmitter with six solar cells.

Signals were transmitted through the six spring-loaded aluminum aerials. 

Tracking of the satellites occurred using the transmitters and Minitrack ground stations located around the Earth. Successful usage helped to prove the effectiveness of ground station technology for future space endeavors.

Communications were lost with the satellite in 1964, after six years of transmitting signals. The signals had weakened slowly over time up until the point they were completely lost, with the last signal received by the Minitrack ground station in Quito, Ecuador, in May 1964. But it remains the oldest man-made object still circling the Earth.

Vanguard’s size contributes greatly to its longevity in space, weighing only 1.5 kg (3lb), with a diameter of 6.5 inches (16.5 cm) across its body. Vanguard’s tiny size earned it the nickname “the grapefruit satellite”, coined by the former First Secretary of the Soviet Union, Nikita Khruschev.

The spacecraft managed to reach the highest altitude of any man-made object in space at the time of its launch. Scientists originally predicted that due to its high orbit, Vanguard could remain in the void of space for around 2,000 years.

However, new findings revealed that space drag and solar radiation pressure are significant in reducing the longevity of satellites. This is because these factors affect a satellite’s perigee, which is the point in an orbit where an object is closest to the Earth.

When the perigee is affected to a certain extent, the satellite will re-enter the planet’s atmosphere and burn up. Therefore, researchers dropped their predictions of Vanguard’s life expectancy in orbit to around 240 years.

In terms of Vanguard’s usefulness now it is classed as a derelict object, researchers still observe the spacecraft using telescopes. However, without the ability to transmit signals, it has become another piece of space junk orbiting our planet with no further contributions to our knowledge of space.

Many argue that Vanguard is an important artifact that showcases the living history of space exploration and that it deserves to be remembered, long after it crashes back to Earth in a couple of centuries. 

Gordon Watts