OCT. 2006 (Updated MAY 2009)
Preparing for Hubble's Servicing Mission 4
Third mission, SM3A:
Astronauts replace parts
Long before NASA was formed and the first satellite was launched into space, a young American scientist named Lyman Spitzer, Jr. proposed that a visible light telescope should be placed in space. A space telescope, he wrote, would reveal much clearer images of far-off objects than any ground-based telescope. Ground-based telescopes are hampered by our Earth’s atmosphere, which blurs light from stars and makes them appear to twinkle.
A dream come true
Spitzer worked for more than 50 years to make his dream come true. On April 24, 1990, he watched NASA launch the Hubble Space Telescope (HST) into orbit around
Hubble was not only the first space telescope to snap
images in visible light, it also was the first space observatory designed
to be serviced in space. Periodic servicing missions, scientists
believed, would extend the telescope’s operating life
and would keep the observatory up-to-date. Astronauts visiting
the telescope would replace aging parts and would install science
instruments with advanced technology.
Servicing Mission 3B:
New solar panels installed
Astronauts, in fact, have visited Hubble four times during
the telescope’s 19-year lifetime. Now, NASA is planning
another service call to Hubble. The visit, called Servicing
Mission 4 ("SM4"), is planned for May 2009. This servicing mission will help keep Hubble operational
until at least 2013.
About the telescope
Hubble is about 380 miles (611 kilometers) above Earth, just above our planet’s atmosphere. It is the size of a school bus (43.5 feet, or 13.3 meters long) and weighs more than 12 tons (11,000 kilograms). The telescope’s primary mirror is 94.5 inches wide (2.4 meters). Hubble is named after U.S. astronomer Edwin P. Hubble who, early last century, discovered that galaxies are composed of stars and reside outside our Milky Way galaxy. In further observations, Hubble determined that space is expanding.
Hubble gets a tune-up
Astronauts aboard the space shuttle will make several spacewalks to install six batteries, six gyroscopes, and a Fine Guidance Sensor. Normally, Hubble’s instruments run on sunlight collected by its twin solar panels, which make the observatory look like it has wings. The batteries power Hubble’s science instruments when the telescope is in Earth’s shadow. The gyroscopes help keep Hubble steady as it orbits Earth and allow scientists to point the telescope at celestial targets. Hubble has three Fine Guidance Sensors, which also help in pointing the telescope at objects.
Making Hubble even better
Another part of SM4 is to boost Hubble’s scientific
power by installing two state-of-the-art science instruments:
the Cosmic Origins Spectrograph (COS) and the Wide Field Camera
COS will examine the ultraviolet light streaming from distant objects. The new instrument will allow Hubble to study galaxy formation and the births of stars and planetary systems. COS will complete observations much faster than Hubble’s previous spectrograph.
A WFPC2 sampler:
Gems from Hubble's "workhorse"
WFC3 will replace Hubble’s “workhorse” camera,
the Wide Field Planetary Camera 2 (WFPC2), which has been observing
celestial objects for 15 years. The new camera will
greatly improve Hubble’s ability to image large and distant
objects, such as galaxies and clusters of galaxies, as well
as planets in our solar system.
Astronomers will use WFC3 to
make wide-field surveys of the distant universe to study how
galaxies formed and evolved from about 2 billion years after
the Big Bang to the present. WFC3 will allow Hubble
to see objects that are about five times fainter than Hubble’s
landmark deep view of the cosmos, called the Hubble Deep Field,
taken in 1996 with WFPC2.
An American icon
Helping astronomers solve many of the universe’s mysteries
is nothing new for Hubble. With its sharp vision, Hubble has
brought the wonders of the universe to millions of homes worldwide.
its jaw-dropping images are elegant-looking galaxies, the shattered
pieces of a comet plunging into Jupiter’s atmosphere,
and the gaseous remains of exploding stars. Hubble’s
greatest science contributions include providing clues to how
stars are born and die, how galaxies evolve over time, and
helping astronomers determine a more exact age for the universe.
Servicing Mission 4, Hubble will continue to scan
the sky, capturing images of space that have made it one of
the most celebrated observatories in the history of astronomy.