Hubble Space Telescope

The Hubble Space Telescope (HST) is a premier space-based observatory located in low Earth orbit.

It serves as a vital research tool for astronomers worldwide. The telescope is one of NASA's Great Observatories. This program includes other specialized telescopes like the Chandra X-ray Observatory and the Spitzer Space Telescope. While Spitzer focuses on infrared bands, Hubble observes the ultraviolet, visible, and near-infrared regions of the electromagnetic spectrum.

This wide range of observation allows scientists to study many different cosmic phenomena.

Hubble operates by capturing light that would otherwise be distorted by Earth's atmosphere. On the ground, atmospheric turbulence causes stars to twinkle, a phenomenon known as seeing. This turbulence limits the angular resolution of ground-based telescopes. In space, Hubble is limited only by diffraction. This allows for extremely high-resolution images with very low background light.

The telescope uses a Cassegrain reflector of Ritchey–Chrétien design. This system employs two hyperbolic mirrors to focus light. These mirrors must be incredibly precise to work correctly. The telescope's primary mirror was designed to be polished to an accuracy of 10 nanometers. This is only about 1/65 of the wavelength of red light.

To maintain its mission, Hubble was designed to be serviced by astronauts. This was a unique feature of its construction. Five Space Shuttle missions were sent to repair and upgrade the telescope. These missions replaced all five of the main instruments.

One mission in 1993, STS-61, was especially critical. It corrected a major flaw in the telescope's optics. This flaw was called spherical aberration. It happened because the main mirror had been ground incorrectly. Without this servicing mission, the telescope's scientific capabilities would have been compromised.

The history of the project began decades before its 1990 launch.

In 1946, astronomer Lyman Spitzer published a paper about the advantages of an extraterrestrial observatory. He argued that space would allow for better resolution and the ability to see ultraviolet light. Later, Nancy Grace Roman, known as the "Mother of Hubble," advocated for the project. She served as the program scientist and worked to secure funding from Congress. The telescope was eventually named after Edwin Hubble. He was an astronomer who helped confirm that the universe is expanding.

Building the telescope was a complex and expensive process. NASA and the European Space Agency (ESA) collaborated on the project. ESA provided funding, solar cells, and one of the first instruments.

Funding was often difficult to secure. In 1974, Congress actually deleted all funding for the project. Astronomers had to organize massive lobbying and letter-writing campaigns to win it back. These budget struggles even changed the design of the telescope. The mirror diameter was reduced from 3 meters to 2.4 meters to save money. This change allowed for a more compact configuration of the hardware.

Hubble's scientific impact has been massive and measurable. It has helped determine the rate of expansion of the universe.

The telescope has been in operation for over 30 years, reaching that milestone in April 2020. Scientists predict it may continue to function until 2030 or even 2040. It has provided some of the most detailed visible light images ever recorded. These images allow for a deep view into the history of space. Its data is processed by the Space Telescope Science Institute (STScI). Meanwhile, the Goddard Space Flight Center (GSFC) maintains control of the spacecraft.

Today, Hubble is part of a new era of space observation. It is being succeeded by the James Webb Space Telescope (JWST).

The JWST was launched on December 25, 2021, to cover mid-infrared to visible bands. Another successor, the Nancy Grace Roman Space Telescope, is expected to follow in 2027. Hubble remains a cornerstone of astrophysics. It connects our understanding of light, physics, and the history of the cosmos. Even as new telescopes launch, Hubble's legacy of discovery continues to shape how we see the universe.