Indian American astronaut Sunita Williams is all set to return home on June 21 after a record breaking 194-day space odyssey by a woman as space shuttle Atlantis successfully undocked on Tuesday at 10.42 am (8.12 pm IST) from the space station and head back to Earth.
"STS-117's constructive stay at the International Space Station came to a close on Tuesday when space shuttle Atlantis undocked. The two spacecraft parted ways at 10:42 am EDT as they flew over the Coral Sea northeast of Australia," US space agency NASA said.
The space shuttle is scheduled to touchdown at the Kennedy Space Centre, Florida at 1.54 pm (11.24 pm IST) Thursday, it said.
Sunita had set off from here Dec 9 on space shuttle Discovery on what was to become the longest space journey by a woman.
Earlier, Sunita and six other astronauts, who came June 10 to fetch her, bid farewell to her replacement Clayton Anderson and two Russian cosmonauts on the International Space Station (ISS) before the hatches between their spaceship and the station closed at 6.51 pm on Monday (4.21 am IST Tuesday).
"I'm sad to say goodbye, but that means progress is being made and it's time for the International Space Station to grow a little more," Williams told ground control before the astronauts floated into space shuttle Atlantis that would take them home.
Sunita, who with four excursions also holds the record for most space walks by a woman, crossed the new milestone Saturday surpassing the 188-day, 4-hour mark set by US astronaut Shannon Lucid in 1996 on a mission to the Russian Mir space station.
The Atlantis received the go-ahead on Monday after the Space Station's revived Russian computers passed a final test. The station's three main computers had crashed shortly after astronauts installed a new set of solar power panels to give it additional power in readiness for the arrival of new laboratories owned by the European and Japanese space agencies.
Space station commander Fyodor Yurchikhin and flight engineer Oleg Kotov were able to restore the system by bypassing suspect protection circuits. The computers control the firing of rocket thrusters needed to keep the station properly positioned in space for tracking the sun for power, pointing communications antennas and warming or cooling parts of the complex.
The departure of Atlantis was delayed by two days to let the astronauts repair a thermal blanket that had come loose near the tail during its June 8 launch.
Although it is only her first space flight, Sunita became the world's most experienced woman walker in space Feb 4 with four excursions over 29 hours and 17 minutes to top Kathy Thornton's 21-hour space walking record.
"It was very exciting to watch her spacewalks and to watch her accumulate more spacewalk time than any other female in the universe," said Lucid.
"These (long-term) flights are providing the needed confidence so that some day in the near future we can depart low-Earth orbit and head on out to Mars."
During her stay at the space station, Williams has worked with experiments across a wide variety of fields, including human life sciences, physical sciences and Earth observation as well as education and technology demonstrations.
Some of these experiments give scientists critical insight into the effects of weightlessness on human bodies while others show ways to prevent effects already known about like muscle and bone loss.
In addition to rigorous exercise, Williams also collected and stored her blood while in space to add to an ongoing study on nutrition, another key element of living in space for long stretches of time. The results of this study may impact nutritional requirements and food systems developed for future ventures in space.
"Her mission has been critically important to our overall space program," said astronaut Eileen Collins, another female pioneer in space flight. Collins became the first woman to command a space flight mission on Space Shuttle Columbia in July 1999.
"She truly is a space marathoner who shows young women everywhere that there's a place in the space programme for them."