Hubble should be in a museum at the end of its life. Why won't you bring it back to Earth once it stops working?

NASA has considered the possibility of bringing Hubble back to be exhibited at the Smithsonian, but there are two main reasons why this is not considered feasible.

First, Hubble was specifically designed to function with the space shuttle. Since the shuttle program is expected to be retired in the near future, and Hubble is expected to function at least until 2014, no shuttles will be available to bring it back. Second, shuttle missions have risks, and while everyone would like a museum exhibit, it's not a worthwhile risk to send astronauts out for that sole purpose. The last visit to Hubble is expected to take place via an robotic spacecraft, which will attach a propulsion module to the telescope to guide it through its de-orbit.

Instead of letting Hubble burn up in the atmosphere, why not just push it out of its orbit so it can continue to take pictures as it drifts away?

Hubble will be used up until the point at which its instruments no longer function, which means the telescope will not be de-orbited until it has finished its useful lifetime as an astronomical observatory. When Hubble is no longer able to provide forefront science, it will be shut down. Sending Hubble into a higher orbit at that time will not provide any added benefit.

Can the upcoming Webb Telescope be serviced like Hubble?

At its distant orbit, Webb is much too far from Earth to be reached by the space shuttle. Webb's science mission length is 5 years with a 10 year goal. To insure the 5 year mission, NASA has engineered the observatory so that all critical subsystems have a backup or will degrade gracefully with age. For instance, the Near Infrared Camera has two identical camera systems so that the optical quality can be maintained even if one fails.

Webb will also contain enough fuel for 10 years of maneuvers. As with Hubble, Chandra, and Spitzer, the Webb science and operations center has the ability to change the operations of the observatory to maximize its scientific potential as it ages.

When was Servicing Mission 4 and what was done to the telescope?

Servicing Mission 4 (SM4), the fifth astronaut visit to the Hubble Space Telescope (Servicing Mission 3 was split into two parts) was scheduled for 2006. But on February 1, 2003, the Space Shuttle Columbia, returning from a research mission, broke apart while re-entering Earth's atmosphere.

Shuttles were grounded. Then-NASA Administrator Sean O'Keefe called the Hubble mission off, citing the safety guidelines that had been developed following the Columbia tragedy. The next NASA Administrator, Mike Griffin, revisited the cancellation upon his appointment in 2005, and on October 31, 2006, announced that Hubble would be serviced again.

Another delay occurred in September 2008, only two weeks before the mission was to launch. A malfunction occurred in one of the Hubble systems — the Science Instrument Command and Data Handling Unit (SIC&DH) — that commands the science instruments and directs the flow of data within the telescope before it is transmitted to Earth. A backup system took over, but NASA was unwilling to leave the telescope without another backup in case of future problems. Engineers tested and readied for installation a spare unit that had been constructed when Hubble was first built.

On May 11, 2009, the Space Shuttle Atlantis launched for the Hubble Space Telescope. Over the course of five spacewalks, astronauts installed two new instruments, the Wide Field Camera 3 and Cosmic Origins Spectrograph. They repaired two others, the Advanced Camera for Surveys and Space Telescope Imaging Spectrograph. They replaced Hubble's batteries with new versions, and a Fine Guidance Sensor with a refurbished one; installed six new gyroscopes; and added new insulating panels to areas where Hubble's blankets had broken down. They replaced the SIC&DH and attached a ring-like structure that will allow a robotic module to connect itself to Hubble in the future, in order to guide the telescope through its de-orbit at the end of its life.

What is the Hubble Space Telescope?

The Hubble Space Telescope (HST) is a space-based telescope that was launched in 1990 by the space shuttle. From its position 343 miles (552 km) above Earth’s surface, the HST has expanded our understanding of star birth, star death, and galaxy evolution, and has helped move black holes from theory to fact. In its first 15 years, the telescope recorded over 700,000 images.

Hubble's view is so spectacular because of its location above Earth's atmosphere. Shifting pockets of air distort light from space — that's why stars seem to twinkle when viewed from the ground. Furthermore, the atmosphere blocks some wavelengths of light partially or entirely, making space the only place where it is possible to get a truly clear and comprehensive view of the universe.

Hubble's large mirror collects light from celestial objects and directs it to the telescope's instruments, the astronomer’s eyes to the universe. Hubble's current instruments are the Wide Field Camera 3 (WFC3), Cosmic Origins Spectrograph (COS), Near Infrared Camera and Multi-Object Spectrometer (NICMOS), Advanced Camera for Surveys (ACS), Space Telescope Imaging Spectrograph (STIS), and Fine Guidance Sensors (FGS).

These are not the only instruments that have flown aboard Hubble. The telescope was designed to be visited periodically by astronauts, who bring new instruments and technology, and make repairs. Perhaps the most famous of these servicing missions is the first, in 1993. After its 1990 launch, Hubble's primary mirror was discovered to be out of shape on the edges by 1/50 of a human hair. This very small defect made it difficult to focus faint objects being viewed by Hubble. Astronauts installed corrective optics on the telescope, fixing the flawed vision. Four more astronaut visits would follow, each boosting Hubble's observatory capabilities.

Can Hubble see the Apollo landing sites on the Moon?

No, Hubble cannot take photos of the Apollo landing sites.

An object on the Moon 4 meters (4.37 yards) across, viewed from HST, would be about 0.002 arcsec in size. The highest resolution instrument currently on HST is the Advanced Camera for Surveys at 0.03 arcsec. So anything we left on the Moon cannot be resolved in any HST image. It would just appear as a dot.

Here is a picture that Hubble took of the Moon:

Can Hubble take pictures of Earth?

The surface of the Earth is whizzing by as Hubble orbits, and the pointing system, designed to track the distant stars, cannot track an object on the Earth. The shortest exposure time on any of the Hubble instruments is 0.1 seconds, and in this time Hubble moves about 700 meters, or almost half a mile. So a picture Hubble took of Earth would be all streaks.

To find images of Earth from other sources in space go to The Gateway to Astronaut Photography of the Earth:


Can we see live photos from Hubble?

There is no "real time" camera or Web cam on board the telescope for live relay links. The images that the Hubble takes are digital pictures and spectra released to the public after one year (to allow the investigators time to do their research).

The data, which are transmitted from the telescope in digital form, needs to be converted from this digitized information by computers into black-and-white photos. These are then enhanced to discern details in the images.

For more detailed information on how the telescope and its instruments operate, visit HubbleSite's Nuts & Bolts.

Does Hubble withhold information from the public?

No. Information and images taken by Hubble Space Telescope are not withheld, but they do take time to get to the public.

Many of the images taken by Hubble are never formally released to the public because they are typically only of interest to the scientific community. Full access to these data, which can be processed into viewable images, is available online via the Hubble Data Archive. The archive's mission is to serve the scientific community. It may not be useful to or easily operated by the general user.

Hubble images produced by the Space Telescope Science Institute are covered by copyright law, as stated on our Web site at This copyright covers most images displayed on all of our Web sites.

Here is the scoop on why it takes time to get the photos out to the public.

The areas of the sky and the objects that Hubble's various optical and spectrographic cameras take pictures of are very carefully planned and scheduled. Scientists from universities and scientific institutions prepare proposals to use the telescope. If their proposal is accepted, time on the telescope is scheduled. Once the scientists have their raw data from the telescope, they then have one year in which to conduct their research and prepare papers. After this one year, the information becomes available to the public.

Sometimes “Early Release Observations” are released to the public, as is the case when a new instrument is installed. Photos are then released as soon as possible after the installation to let the world know that the camera is performing up to its expectations.

If you would like to see a "scrapbook" of photos, as they look when they are "translated" from the original digitalized pixels sent from the instruments aboard the Hubble, you can see them at the MAST Scrapbook:

Again, these are photos that have become available after the one-year grace period for the astronomers.

Why service the Hubble Space Telescope?

NASA decided early in the telescope’s development to design the observatory so it could be serviced while in orbit. Instruments were designed as modular units, comparable to dresser drawers that could be easily removed and replaced. In addition, designers equipped the telescope with handholds and other special features to make servicing tasks less difficult for astronauts wearing bulky spacesuits.

By periodically upgrading the science instruments, NASA also reasoned that it could provide the science community worldwide with state-of-the-art technology that took advantage of Hubble’s unique position high above Earth’s obscuring atmosphere.

Why does Hubble need servicing missions?

Your car needs a tune-up; so you take it to your mechanic for servicing. Engineers and scientists designed the Hubble Space Telescope with the same principle in mind. When a component breaks or a more technologically advanced instrument becomes available, astronauts install the new equipment using wrenches, screwdrivers and power tools during periodic servicing missions. Servicing missions have occurred in 1993, 1997, 1999, 2002 and 2009.

When was the first servicing mission and what instruments were replaced?

The first servicing mission took place in December, 1993. Below is a list of the most important events that took place during the mission:

  • Astronauts removed the original Wide Field Planetary Camera and installed an updated model equipped with built-in corrective optics that compensate for the flaw in the telescope’s primary mirror. The replacement instrument, built at the Jet Propulsion Laboratory, is called the Wide Field Planetary Camera 2 (WFPC2).
  • Astronauts removed the High Speed Photometer and replaced it with the Corrective Optics Space Telescope Axial Replacement (COSTAR), which includes an assembly of coin-sized mirrors that are polished to a special prescription to compensate for the telescope’s flawed primary mirror.

Other replaced components:

  • Solar Array Panels — Wing-like structures that produce electricity to power the observatory.
  • Solar Array Drive Electronics — Modular hardware that controls the position of the solar arrays.
  • Magnetometer -- Device that measures the telescope’s orientation within Earth’s magnetic field to help in attitude control.
  • DF-224 Flight Computer Coprocessor — Computer memory that improves backup and computational power.
  • Two Rate Sensor Units — Part of the telescope’s pointing system.
  • Two gyroscope Electronics Control Units (ECUs) — Dedicated electronics that process measurements taken by the rate sensor units.
  • Fuses — Fuse plugs for the gyroscopes.
  • GHRS Redundancy Kit — A wiring kit that provides power to one of the detectors on the Goddard High Resolution Spectrometer.

Find out more from HubbleSite:

When was the second servicing mission and what was done to the telescope?

The second servicing mission was in February, 1997.

After the space shuttle crew captured the observatory in orbit and berthed it in the Shuttle cargo bay, four astronauts worked in pairs on alternating days, doing four days of spacewalks to replace instruments and installing other critical components.

The primary objective was to replace the Goddard High Resolution Spectrograph and the Faint Object Spectrograph with two dramatically improved instruments: the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) and the Space Telescope Imaging Spectrograph (STIS).

Astronauts also replaced a Fine Guidance Sensor needed to point the telescope at celestial objects; a tape recorder used to record data; an electronics package that drives the telescope’s solar arrays; and a communications unit that translates ground-based commands and relays the information to onboard instruments and systems. In addition, astronauts installed a new solid-state data recorder, which is important because the two new science instruments gather enormous quantities of data.

Find out more from HubbleSite:

When was the third servicing mission and what was done to the telescope?

The third servicing mission was split into two parts. The split was required to address the urgent need to replace Hubble's failing gyroscopes, which point the telescope at celestial targets.

Servicing Mission 3A took place in December, 1999. The crew replaced a transmitter, all six gyroscopes, and one of three fine guidance sensors, which allow fine pointing and keep Hubble stable during operations.

The astronauts also installed an advanced central computer, a digital data recorder, an electronics enhancement kit, battery improvement kits, and new outer layers of thermal protection.

Servicing Mission 3B took place in February 2002. Astronauts added the Advanced Camera for Surveys, the first new instrument to be installed in Hubble since 1997. ACS doubled Hubble's field of view and collects data 10 times faster than the Wide Field and Planetary Camera 2, which was installed in 1993.

The crew also replaced Hubble's solar array panels with smaller, more effective ones, replaced the Power Control Unit and one of the four reaction wheel assemblies that make up Hubble's pointing control system, and installed a new cooling system for the Near Infrared Camera and Multi-Object Spectrometer. In order to replace the Power Control Unit, the telescope had to be powered down for the first time since its launch in 1990.

Find out more from HubbleSite:

What is NICMOS?

NICMOS stands for: Near Infrared Camera and Multi-Object Spectrometer.

NICMOS can see the universe at near-infrared wavelengths more sensitively and in sharper detail than any other existing or planned telescope. What does that mean to astronomers? Infrared light, which falls between visible and radio waves on the electromagnetic spectrum, isn’t absorbed or scattered like visual light by the clouds of gas and dust found abundantly in the universe. Therefore, astronomers are able to see newly forming stars and measure the properties of the disks of dust particles believed to give birth to planetary systems. They are able to peer into the centers of galaxies, including our Milky Way, to study quasars and other exotic objects.

University of Arizona Professor Rodger Thompson and a 16-member science team developed the instrument.

Find out more from HubbleSite:

What is STIS?

STIS stands for Space Telescope Imaging Spectrograph.

STIS separates ultraviolet and optical light into their component colors, giving scientists much-needed information about an object's composition, temperature, motion and other chemical and physical properties.

The instrument was developed by Goddard Space Flight Center's Laboratory for Astronomy and Solar Physics. The principal investigator was Dr. Bruce E. Woodgate.


Find out more from HubbleSite:

What is ACS?

ACS stands for the Advanced Camera for Surveys.

The ACS is three cameras in one: a wide-field camera, a high-resolution camera, and a solar-blind camera, which is sensitive to ultraviolet light. The camera also has a coronagraph, which blocks out the glare of quasars and stars so astronomers can study fainter objects in the same vicinity. The camera's vision ranges from ultraviolet to visible light.

Find out more from HubbleSite:

Who is Edwin P. Hubble and what has he to do with galaxies?

Edwin P. Hubble revolutionized cosmology by proving that the clouds of light astronomers saw in the night sky were actually other galaxies beyond our Milky Way.

His greatest discovery was in 1929, when he identified the relationship between a galaxy's distance and the speed with which it is moving. The farther a galaxy is from Earth, the faster it is moving away from us. This is known as Hubble's Law. He also constructed a method of classifying the different shapes of galaxies.

Edwin Powell Hubble was born in Marshfield, Missouri. In 1910, he received his undergraduate degree from the University of Chicago and studied law under a Rhodes Scholarship at Oxford University. His true love, however, was astronomy, and he returned to the University of Chicago to earn a Ph.D. in that subject and work at the Yerkes Observatory. He served in the infantry during World War I.

He once said that he "chucked the law for astronomy," knowing that even if he was second-rate or third-rate, it was astronomy that mattered.

What are you hiding by not showing us the upper right corner of the images?

The strange, stair-shaped images come from the Wide Field and Planetary Camera 2, or WFPC2. WFPC2 consists of four cameras, each of which takes a picture of a section of the target. It's like taking four pictures of a single scene, then putting them together to create the whole picture.

But one of WFPC2's cameras takes a magnified view of the section it's observing, to allow us to study that section in finer detail. When the images are processed, that magnified section is shrunk down to the same size as the other sections, so that it fits into the image.

For a more thorough explanation for the stair-stepped shape of the Hubble photos, visit our Web site.

Read Hubble's Wacky Window on HubbleSite.

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