Exploring the Hubble Space Telescope

The Hubble Space Telescope, named after American astronomer Edwin Powell Hubble, was launched into Earth’s orbit in April 1990.

What is the Hubble Space Telescope?

The Hubble Space Telescope (HST) is a NASA telescope that weighs 12 tons and is approximately the size of a bus. It operates in Earth’s orbit at an altitude of about 610 km, which is about 220 km higher than the International Space Station (ISS). Traveling at a speed of approximately 7500 m/s, Hubble can complete one orbit around Earth in 97 minutes, making 15 orbits each day. Hubble is named after astronomer Edwin Powell Hubble (1889-1953), who is credited with the theory of an expanding universe and providing substantial evidence for the formation and evolution of the universe during the Big Bang.

This is a reflecting telescope equipped with a computer system and a primary mirror with a diameter of 240 cm.

Although it was not the first space telescope launched into the cosmos, Hubble is considered the largest and most powerful “eye in the sky” until the launch of its successor, the James Webb Space Telescope. Hubble operates in Earth’s orbit at an altitude of over 610 km, which is 220 km higher than the orbit of the ISS.

Hubble is fully equipped with solar-powered instruments designed to capture images of the universe in visible light, ultraviolet (UV), and near-infrared wavelengths. Naturally, all instruments aboard Hubble are designed to function outside of Earth’s atmosphere; if Hubble were placed on the ground, many of its instruments would cease to be effective.

Hubble Telescope as seen from the Space Shuttle Atlantis.

History of Development

As early as the 1940s, the idea of a space telescope began to take shape, but it was not until the late 1970s that it remained just an idea, with proposals and sketches on paper. Over those 30 years, NASA incurred a massive budget of nearly $1 billion, prompting them to seek additional funding from European partners to continue the project. In response, the European Space Agency (ESA) provided NASA with some of the initial equipment for Hubble, along with solar panels, in exchange for guaranteed access to Hubble for at least 15% of its operational time.

However, the construction of Hubble did not proceed smoothly according to NASA’s plans. The infrastructure development had to be postponed several times due to issues that arose in contracts. After numerous efforts, Hubble was finally completed and officially launched into orbit from Cape Canaveral Air Force Station in the United States in April 1990. However, upon reaching orbit and capturing its first images, scientists quickly realized that, for some reason, all the photos were extremely blurry, not matching their initial expectations.

After an investigation, they concluded that the culprit was an optical defect known as “spherical aberration.” This phenomenon occurs when parallel monochromatic light rays passing through a lens fail to converge at a single point, resulting in a loss of sharpness and resolution. Dr. Robert Arentz from Ball Aerospace explained, “The issue was caused by the outer edges of the mirror being too flat; its curvature was only 4 microns, less than the thickness of a human hair.”

Ball Aerospace was the primary supplier of equipment for Hubble and subsequently developed the Corrective Optics Space Telescope Axial Replacement (COSTAR)—a movable mirror system designed to correct Hubble’s spherical aberration. Fortunately, Hubble was designed with the foresight that astronauts could repair and upgrade it while in orbit, making it the only space telescope capable of such feats. In December 1993, astronauts successfully approached and installed COSTAR onto Hubble.

The process of deploying COSTAR into orbit was also not straightforward; senior director at Ball Aerospace, John Troeltzsch, recalled, “You had to pack it securely in a box the size of a phone and withstand the pressure of being launched by the shuttle. Then, astronauts had to perform a spacewalk, using a robotic arm to position COSTAR with an accuracy of 1/10 mm.”

The deployment of Hubble into space is regarded as one of the greatest achievements in space science to date. This event is compared with other significant milestones, including sending humans into space and landing on the Moon.