The observatory launched early on Monday from Cape Canaveral Air Force station a Delta II rocket.

The Space Infra Red Telescope Facility (SIRTF) is the last of NASA's so-called Great Observatories and it is designed to see objects either too cold to cast their own light or obscured by interstellar dust.

"The expectation is to really revolutionise our understanding of the universe by looking in a completely new low length spectrum," said Dave Gallagher, NASA's mission project manager.

The Telescope will look into the dark, cold corners of the universe, making itself sensitive to the faintest heat signatures by cooling its own instruments to just a degree or two above absolute zero.
   
It will be able to monitor objects from failed stars that never turned on, to the galaxy's own dust-shrouded heart.

When combined with the Hubble Space Telescope, which sees in the visible light spectrum, and the Chandra X-Ray Observatory, astronomers will get their most complete view yet of matter and energy near the edge of the known universe.

Or, as NASA scientist Anne Kinney explained, when all three telescopes peer deeply into space, the Chandra will see objects that are millions of degrees in temperature, the Hubble objects that are thousands of degrees, and SIRTF those that are hundreds of degrees.

"That way, you get a full range of information about what's out there," said Kinney.

SIRTF also has a job closer to home. Scientists know little about a wide belt of icy objects that circle the sun beyond the orbit of Pluto. This area, known as the Kuiper Belt, sometimes sends one of its ice balls into the inner solar system, where it becomes a comet when heated by the sun.

With SIRTF, NASA for the first time has launched an observatory into an earth-trailing orbit around the sun so that the planet's radiation will not interfere with its observations.

Earlier infrared telescopes have given only a vague sense of what lies there, but SIRTF observations should be like turning on a light switch in a room that has never before been lit, scientists say.

And astronomers should get their best look yet at the mysterious heart of the galaxy, where the star field is much denser.

Mission project scientists explain that less than 2% of the matter in the universe is hot enough to generate light, and much of that is obscured by dust.

When viewed by SIRTF, the universe will not be a field pinpointed by individual lights but a swirling maelstrom of energy sources.

SIRTF will be given a proper name, like Hubble, Chandra and the defunct Compton Gamma Ray Observatory, about 60 days after launch, once all its systems have checked out, said NASA.

The telescope has a 35.5-inch mirror and instruments that will be kept cold by liquid helium released from an onboard tank. NASA said there should be enough of the helium to keep the satellite operating about five years.