Facts about the Hubble space telescope

The world's first space-based optical telescope marks its 25th anniversary this week. Here are some facts about the Hubble Space Telescope.

The telescope launched aboard the Space Shuttle Discovery in 1990 and is named after US astronomer Edwin Hubble (1889-1953).

About two months after launch, a problem with its primary mirror was discovered. It was repaired in 1993 by astronauts who traveled to the telescope aboard the space shuttle.

Its main accomplishments include confirming the "expanding" universe, which provided the foundation for the Big Bang theory.

The size of a bus, it is 43.5 feet (13.3 meters) long and its maximum diameter is 14 feet (4.3 meters).

The telescope is so steady and accurate that it can take an image of a target without deviating more than 7/1000th of an arcsecond, or about the width of a human hair seen at a distance of one mile (1.6 kilometers), according to NASA.

This is also like being able to shine a laser beam on a dime 200 miles away.

Hubble orbits the Earth at an altitude of 340 miles, not much higher than the International Space Station.

It completes one orbit every 95 minutes, and travels at a speed of 17,000 miles per hour.

The telescope is unable to observe the sun or Mercury.

However, it has peered into the very distant past, to locations more than 13.4 billion light years from Earth.

Hubble sends back about 140 gigabits of raw science data every week, and has helped scientists publish more than 12,800 scientific papers, making it one of the most productive scientific instruments ever built, according to NASA.

The telescope has five instruments that have been updated or added in space, as well as some others that have been removed over the course of five maintenance missions by astronauts on the space shuttles in 1993, 1997, 1999, 2002 and 2009.

It is powered by the sun, and its electricity is stored in six nickel-hydrogen batteries, the equivalent of 20 car batteries.

Hubble's cost at launch time was $1.5 billion. It was built by NASA with contributions from the European Space Agency.