WASHINGTON -- The venerable Hubble Space Telescope has returned images that have changed our perception of the universe, but the 10-year-old mission's fate has hung lately in the balance.

Now, scientists say the Earth-circling observatory may get a new lease on life. Better to do that, they argue, than slap an "abandon in place" sticker on the side of this old workhorse of a science machine.

Dropped off in orbit via Shuttle astronauts in April 1990, the $1.5 billion Hubble Space Telescope (HST) continues to crank out stunning cosmological findings. And thanks to stopover visits by shuttle crews, the facility is far more fit and capable today than it was during its early years of operation.

But talk is cheap … taking action is expensive.

Hubble was last visited in December 1999. New, improved, and upgraded equipment was installed: Six fresh gyroscopes, six battery voltage/temperature improvement kits, a faster and more powerful main computer, a high-tech solid state data recorder, a new transmitter, an enhanced fine guidance sensor, and new insulation.

Now on the books is the fourth shuttle hop to fix, service, replace, adjust, and generally tune-up the Hubble.

A team of astronauts is busy prepping for the flight, Servicing Mission 3B, set for January 2002. During five days of spacewalks, the HST gets a replacement of solar array panels, a new power control unit, and an experimental cooling system for one of its science instruments.

In addition, astronauts are going to plug into Hubble a new and powerful device -- the Advanced Camera for Surveys. This wide field-of-view camera can yield 10 times more discovery power than the camera it replaces. The instrument is composed of three different cameras that work in wavelengths ranging from visible to ultraviolet.

Scientists are eager to see what Hubble's advanced camera sees. It is expected to churn out detailed photos of the inner regions of galaxies and search neighboring stars for planets and planets-to-be.

Once again, the astronaut-supplied technological makeover of Hubble increases the overall worth of the scientific asset.

Nevertheless, at a cost of hundreds of millions of dollars a trek, Hubble stopovers are far from cheap.

A final service mission to Hubble is targeted for 2004.

Preliminary plans are for shuttle spacewalkers to replace a by-then decade-old imaging camera with an instrument loaded with the latest in charge coupled device (CCD) electronics. Also, a new Cosmic Origins Spectrograph is to be plugged into the observatory.

NASA thinking at the moment has Hubble being retired in 2010.

At that time, one of a trio of possibilities may happen. A shuttle U-haul flight could pluck Hubble from orbit. By safely returning the telescope down to Earth it would make a nice addition to the Smithsonian's National Air and Space Museum collection.

Or, Hubble could be shoved to a higher, out-of-the-way orbit, possibly with the aid of an attached booster.

Another possibility is placing the tractor-trailer size telescope into some sort of controlled nose-dive to Earth -- following in the fiery tradition of Russia's Mir space station and NASA's Compton Gamma Ray Observatory -- with chunks of surviving Hubble leftovers plunking into remote ocean waters.