Watch a firsthand account of Hubble's first service mission to repair its faulty mirror

Hubble overcame early optical failure and became a critical scientific instrument

The flaw in Hubble's mirror was smaller than the width of a human hair, but fixing it required a space mission as complex as a Hollywood rescue story—with astronauts installing corrective optics like contact lenses for a giant eye in the sky.

An imperfection 1/50th the width of a human hair blurred Hubble's initial images

Not all parts of the space telescope's primary mirror focused incoming light to the same location, an effect known as spherical aberration. Because Hubble was designed to reside in low Earth orbit and be serviced by astronauts, service missions were deployed in the years after its launch to conduct repairs.

Between 1993 and 2009, Hubble was serviced for repairs and upgrades 5 times

Across 21 space walks totaling 144 hours, replacement instruments, gyroscopes, solar arrays, batteries, and computer systems have helped extend the Hubble Space Telescope's operational lifetime beyond its planned 15 years.

The Challenger disaster delayed the launch of the Hubble Space Telescope

The 1986 explosion of the space shuttle shortly after liftoff killed seven crew members and grounded NASA's space fleet. Scientists used the downtime to refine ground control software and upgrade telescope instrument sensitivity, but maintaining the telescope's clean room storage cost NASA approximately $6M per month.

Hubble's first light test produced an underwhelming photograph

This test represents the first time light travels entirely through an observatory's optical system and reaches its detectors, producing an image. Although the telescope's warped mirror was not discovered and announced until a month after first light, the issue was not responsible for the simplicity of the first light image.

The twenty-year effort to design the Webb's optics

Since its located 1 million miles from Earth, the Webb space observatory has to be able to repair itself—no Space Shuttles can be dispatched with astronaut engineers to repair it. That's why over two decades teams reiterated, cross-checked, and hyper-optimized the Webb's observing surface. Their efforts produced the world's largest space-based optical surface that is peering billions of years back in time. Learn the wild engineering of the telescope here.

Space telescope development was driven by a desire to bypass Earth's atmosphere

The most important figure in the effort to create what would become the Hubble Space Telescope was Lyman Spitzer, who first proposed a telescope in orbit in 1946. The nearly 50-year endeavor led to space-based observatories, which are not limited by Earth's atmosphere absorbing or distorting most wavelengths of light.

Designs for the Hubble Space Telescope were based on Cold War spy satellites

By incorporating elements of the KH-11 KENNEN reconnaissance satellites, NASA could incorporate existing classified manufacturing expertise and infrastructure from the intelligence community to expedite the research project.

Take a 360-degree tour of Discovery with Kathryn Sullivan and Charles Bolden, who flew together on the space shuttle during its deployment of the Hubble Space Telescope. (VR device-compatible)

The Hubble Space Telescope uses curved mirrors to collect and focus light

Classified as a Cassegrain reflector, the observatory bounces incoming visible light and some infrared and ultraviolet light off a primary mirror with a diameter of 2.4 meters. The reflected light is directed to a secondary mirror, which reflects it through a tiny hole in the primary mirror and onto detectors.

View galleries of images taken by the Hubble Space Telescope

With more than 1.7 million observations made since 1990, the Hubble Space Telescope has captured images of space missions, planets, stellar nurseries, interstellar comets, star clusters, galaxies, and more. This search tool allows users to sort and filter across these celestial objects to explore over 35 years of Hubble's astrophotography.

Play an interactive game to explore and learn about Hubble images

Aboard the fictional USS Hubble, users can choose their own adventure to investigate the solar system, our galaxy, and the universe beyond. Each option directs users to a real image accompanied by relevant information and additional media elements, such as a time-lapse of the moon Phobos orbiting Mars.

Atmospheric drag is causing the Hubble Space Telescope to drift toward Earth slowly

Without interventions to boost the observatory to a higher orbit, Hubble is expected to fall to Earth's surface in the mid-2030s. In the meantime, the telescope is expected to continue to be productive by shifting its mode of operation to rely on a single gyroscope, down from three.

Major milestones of the Space Shuttle program's 135 missions included the launches of the Hubble Space Telescope and the Chandra X-ray Observatory, and the first American woman and African-American astronauts in space.

Nancy Roman, NASA's first chief of astronomy and the architect of the Hubble Space Telescope, was discouraged from pursuing science throughout her academic career.

Over a decade before the launch of the Hubble Space Telescope, Nancy Roman oversaw the Orbiting Solar Observatory program, which launched eight spinning spacecraft into low Earth orbit to study the sun.

Mixed reality technology helped make repairs to a quantum physics facility in space

In 2021, astronaut Megan McArthur used a HoloLens to work alongside Earth-based engineers and make hardware replacements to the International Space Station's Cold Atom Lab, the first quantum science facility in Earth orbit. The facility cools atoms to near absolute zero to perform quantum chemistry experiments in a microgravity environment.

The Challenger disaster grounded the space shuttle fleet for nearly three years, exposed deep flaws in NASA's leadership, and prompted significant changes to the agency's safety oversight and decision-making culture.

Watch the Challenger disaster, which killed all seven astronauts aboard, unfold live.

Explore what Challenger was supposed to do on its mission

STS-51L's planned seven-day mission included deploying satellites, studying Comet Halley, conducting fluid dynamics experiments, and broadcasting live lessons from orbit—routine scientific and educational tasks that were never carried out after the shuttle was lost shortly after launch.

The Hubble Space Telescope is named after astronomer Edwin Powell Hubble

Using the Hooker Telescope at the Mount Wilson Observatory in California in the 1920s, Hubble identified Cepheid variable stars in what was believed to be the Andromeda nebula. These stars can be used to determine distance in space, allowing Hubble to realize that Andromeda was a galaxy of its own.

Nicknamed the 'mother of Hubble,' Nancy Roman gave lectures on the potential of space science, coordinated between astronomers and engineers, and secured government funding for the space telescope.

The Columbia disaster exposed fatal flaws in NASA's shuttle program

On Feb. 1, 2003, Space Shuttle Columbia broke apart during reentry, killing all seven astronauts aboard. The tragedy revealed long-ignored safety warnings, leading NASA to ground the shuttle fleet and overhaul its safety culture.

The Polaris Dawn program led to the first commercial spacewalk

As part of the Polaris program, this first mission included a crew comprising astronauts and SpaceX engineers, who conducted scientific experiments and cultural outreach, such as raising funds for St. Jude Children's Research Hospital.

Hubble's average used power is less than half the power generated by its solar arrays

The space telescope's components use about 2,100 watts, or about as much power as five refrigerators. When exposed to sunlight, the solar arrays can generate over 5,200 watts for the observatory, which was engineered by a team that included Judith Love Cohen, mother of actor Jack Black.

The breakthrough that changed our perception of the universe

In the 1920s, the Hooker Telescope helped Edwin Hubble make a discovery that forever changed how we see the universe. Building on the work of astronomers like Henrietta Leavitt and Harlow Shapley, Hubble used the telescope to prove that galaxies exist beyond the Milky Way—revealing a vast and expanding universe.

The next generation of space-based observatories

How exactly does a space telescope come to be funded by NASA? NASA's most famous telescopes, like Hubble and James Webb, were once featured in the decadal survey–a once per decade survey run by the National Academy of Science that recommends which projects to support. This article and podcast covers which telescope designs are in contention to be part of NASA's next generation of space-based observatories.

Hear how the first moon landing was saved

This podcast series explores Apollo 11 through firsthand stories from the engineers, mission controllers, and astronauts who made the moon landing possible, culminating in 13 minutes of NASA archive audio leading up to the landing.

Watch the Challenger disaster unfold in real time

On January 28, 1986, Space Shuttle Challenger broke apart just 73 seconds after liftoff. This live CNN broadcast captures the tragedy as it happened—second by second—showing the shock and confusion of one of NASA's darkest moments.

Listen to the five-part podcast series that reconstructs how Challenger failed

The "American Scandal" podcast devotes a five-part series to Challenger, tracing the engineering warnings, internal pressure to launch, the moment of the explosion, and the long aftermath that reshaped NASA's safety culture.

Fly through the deepest image of space ever taken by the Hubble Space Telescope

Taken over 11 days between 2003 and 2004, when the space telescope was aimed at a seemingly empty patch of the sky, the Hubble Ultra-Deep Field revealed about 10,000 sources of light, most of which are entire galaxies. This visualization expands the 2D image into a 3D view spanning 12 billion years.

View a simulated demonstration of how the Nancy Grace Roman Space Telescope will survey large portions of the sky to capture in 90 minutes what took three years for the Hubble Space Telescope.

The Columbia disaster contributed to the end of the Space Shuttle program and NASA's reliance on commercial partners such as SpaceX and Boeing to transport astronauts and cargo.

Relive the Apollo 11 moon landing minute by minute

This interactive project lets you experience Apollo 11 in real time—listening to exchanges between the astronauts and NASA's Mission Control as they guided humanity's first journey to the lunar surface and safely home.

In 2013, an astronaut's helmet began filling with water during a spacewalk

A leak in the cooling system of Luca Parmitano's spacesuit caused water to obscure his vision and silence his radio as the International Space Station entered Earth's shadow, forcing him to feel his way back to the airlock in darkness.

Space tourism opportunities have been explored since the end of the Apollo era

In the 1970s, Rockwell International, a NASA contractor, and others investigated manufacturing passenger modules that could fit into the Space Shuttle's payload bay. NASA also opened spaceflights to nongovernment professionals, but many such programs were ended after the Challenger disaster, which killed the first Teacher in Space participant.

The Hubble Space Telescope made discoveries within our solar system and across the universe

The observatory helped confirm the presence of water on Jupiter's moon Europa, and uncovered seasonal variations on planets like Uranus. It also observed exoplanets and gravitational lensing, proved the existence of supermassive black holes at the centers of galaxies, and detected the accelerated expansion of the universe.

A 'holoported' medical team has been beamed into the International Space Station

In 2021, using the Microsoft HoloLens Kinect camera and custom Aexa Aerospace software, NASA's flight surgeon led a team of hologram doctors on a pioneering visit to the space station, marking a significant advancement in communication and telemedicine technologies that will be crucial for future deep-space missions.

View a timeline of NASA's Space Shuttle program, which saw five reusable orbiters take a total of 355 astronauts across a combined distance of almost six trips to the sun.

Infrared vision gives Webb telescope access to the oldest light in the universe

To peer into the universe’s earliest moments, the Webb had to solve several immense engineering challenges: deploying a massive sun shield, surviving extreme cold, and stabilizing ultra-sensitive instruments. The telescope’s mirrors can adjust themselves in steps 10,000 times smaller than a human hair.

The James Webb Space Telescope is rewriting what we know about the early universe

Thanks to its advanced infrared sensors and massive mirror, the James Webb Space Telescope can see farther back in cosmic history than Hubble, revealing galaxies formed just 500 million years after the Big Bang.

Watch a documentary on what the first 10,000 days of colonizing the moon look like

Alongside the construction of the first lunar base with help from SpaceX's Starship Human Landing System, transported astronauts would establish a sustainable human presence through the construction of lunar dust shields, light-bending towers, and 3D-printed habitats.

The Challenger disaster ended NASA's plan to fly ordinary Americans in space

The explosion of the Challenger halted NASA's civilian spaceflight ambitions for decades, including plans to send teachers, journalists, artists, and other nonastronauts into orbit—an effort aimed at building public support that quietly disappeared after the 1986 disaster.

During Nancy Roman's tenure as the agency's chief of astronomy, NASA launched Stargazer—the first successful space telescope—as part of the Orbiting Astronomical Observatory program.

Richard Feynman exposed NASA's safety failures on the Rogers Commission

The Nobel Laureate served on the Rogers Commission investigating Challenger, famously demonstrating O-ring failure with ice water and eventually criticizing NASA's culture of risk normalization and management pressure in the final report.

The Teacher in Space program was launched in 1984 to highlight spaceflight in US classrooms

Announced by President Ronald Reagan, the program drew more than 11,000 teacher applicants nationwide. Christa McAuliffe was selected to fly on STS-51L, with plans to teach live lessons from orbit before the Challenger disaster ended the mission.

About 2.5 million American students watched the Challenger disaster live

Because of the publicity of the Teacher in Space program, millions of students viewed Challenger's liftoff in school classrooms—turning the explosion into a shared national traumatic experience marked by shock, silence, and grief.

Watch the lessons Christa McAuliffe was supposed to teach aboard Challenger

After the Challenger disaster prevented McAuliffe from teaching in orbit, educators-turned-astronauts Joe Acaba and Ricky Arnold filmed her planned science demonstrations aboard the International Space Station during the 2017-18 school year.

Overcoming industry skeptics, SpaceX provides low-cost, high-publicity spaceflights

From recovering and reusing rocket components to launching a mannequin and Tesla into orbit to the tune of David Bowie's "Starman," Elon Musk drove public interest and government contracts to his company as he transformed space launches into spectacles.

View a 3D visualization of how space shuttles were built and launched into orbit from NASA's Kennedy Space Center.