Launch of NASA's Space Infrared Telescope Facility aboard Boeing's Delta 2-Heavy rocket is being delayed at least two days -- to early Monday morning -- because a tracking ship needed to support the mission in the Indian Ocean is being held up by bad weather.

A Delta 2-Heavy rocket will deploy SIRTF from Florida's East Coast. Photo: NASA

There is just an instant in time to launch the rocket each day from pad 17B at Cape Canaveral Air Force Station, Florida. Monday's opportunity is 1:35:39 a.m. EDT (0535:39 GMT).

"Winter conditions in the southern hemisphere are bringing high wind and high seas delaying the arrival of a tracking and instrumentation ship in the Indian Ocean that is mandatory to support launch," NASA announced in a statement.

"The progress of the ship toward its support location is being monitored. Weather conditions are gradually forecast to improve over the next few days but the arrival time of the ship on station is tentative."

A further delay in the launch is possible, depending on when the ship arrives on station.

The U.S. military ship, which is sailing from South Africa, is used to receive data from the Delta's second stage for relay back to engineers at Cape Canaveral, NASA spokesman George Diller said.

"We've got to have that ship because it sends us the second stage telemetry," said Diller.

The portion of launch in question is when the second stage engine is ignited about 40 minutes into flight. It is the second of two planned firings by the stage during ascent to propel SIRTF into an orbit that trails behind Earth while circling the Sun.

This map shows the Delta flight path. The ship's coverage zone is depicted with a circle and MT. Credit: Boeing

Meanwhile, workers at pad 17B today completed fueling the rocket's second stage with its storable propellants. Diller said no technical issues are being addressed with the Delta or SIRTF observatory.

Built by Lockheed Martin and Ball Aerospace, the 1,907-pound SIRTF will use its infrared vision to study -- among other things -- dusty discs around nearby stars in the search for Earth-like planets that could harbor life.

SIRTF is the fourth and final member of NASA's Great Obseratories, following the 1990 launch of the Hubble Space Telescope, the 1991 launch of the Compton Gamma Ray Observatory and the 1999 deployment of the Chandra X-ray Observatory.

"The Space Infrared Telescope Facility will complete NASA's suite of Great Observatories, a program that includes three previous missions that studied the Universe with visible light, X-rays and gamma rays," said Dr. Ed Weiler, associate administrator for space science. "Many cosmic objects produce radiation over a wide range of wavelengths, so it's important to get the whole picture."

"With this mission, we will see the Universe as it was billions of years ago, helping us pinpoint how and when the first objects formed, as well as their composition," added Dr. Anne Kinney, director of the astronomy and physics division and the Origins program in the Office of Space Science at NASA Headquarters.