It flew for long 20 years and nine days, and when it made its homecoming, nobody knows its whereabouts. Almost six years after ceasing operation, the decommissioned NASA satellite finally landed somewhere on Earth, but even NASA doesn't know the exact landing location and may never know.

In a latest statement, NASA said that the Upper Atmosphere Research Satellite (UARS) fell back to Earth between 11:23 p.m. EDT Friday, Sept. 23, and 1:09 a.m. EDT Sept. 24. However, the space agency did state that the accurate re-entry time and location of debris crashes have not been determined yet.

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The seven-ton Upper Atmosphere Research Satellite (UARS) is deployed by the Space Shuttle Discovery (STS-48) in this NASA handout photo dated September 1991. NASA is expecting the satellite to re-enter Earth's atmosphere in late September or early October. REUTERS/NASA

NASA believes that during its fiery dive, UARS broke apart and most probably plunged into the Pacific Ocean far off the U.S. coast. It also stresses the possibility of 26 pieces of the satellite, weighing about 1,200 pounds, which could have survived the fall.

During its entire 20 years on orbit as well as its re-entry this past week, the research satellite was monitored by the Operations Center for JFCC-Space, the Joint Functional Component Command at Vandenberg Air Force Base, California.

Based on the data provided by the Joint Space Operations Center, NASA said that while re-entering, the UARS passed from the east coast of Africa over the Indian Ocean, then the Pacific Ocean, then across northern Canada and the northern Atlantic Ocean, to a point over West Africa. The uncontrolled satellite made majority of its orbital transit over water.

According to NASA, because of its orbit, the satellite should have showered any surviving components within a zone between 57 degrees north latitude and 57 degrees south latitude, with a possible debris track that could be 500 miles long.

The UARS was 10 meters long and 4.5 meters in diameter. It was a 5897-kilogram satellite and was one of the 20,000 pieces of space debris in orbit around Earth, Reuters reported.

NASA conducted a re-entry risk assessment for UARS in 2002 and determined that the debris from the satellite would not harm human beings. It estimated that human casualty risk (updated to 2011) was only about 1 in 3200. As of now, no space junk-related injuries or damage have been reported.

The UARS, launched from the space shuttle Discovery on Sept. 15, 1991, is the biggest piece of space debris to fall from the sky since the 68,000-kilogram Sky Lab in 1979.

Russia's Mir, weighing 122,000-kilogram, plummeted into the Pacific Ocean in 2001. However, it was a controlled fall.