Sunita and six other astronauts are expected to be launched into orbit aboard the Discovery spacecraft at 8:05 IST on Friday (Thursday, 9:35 pm US time) from the Kennedy Space Centre in Florida, the first night launch since the 2003 Columbia disaster.
The Ohio-born Sunita, 41, will stay back at the ISS for a six-month-period and German astronaut Thomas Reiter of the European Space Agency, will return to Earth in her place.
Besides Sunita, the crew includes mission commander Mark Polansky, pilot William Oefelein, mission specialists Joan Higginbotham; Nicholas Patrick; lead spacewalker Bob Curbeam; and the European Space Agency's Christer Fuglesang, who will become the first Swede in space.
"I just can't wait to get to my new home," she said in a pre-flight interview released by NASA. "I have always wanted to fly a long-duration mission."
Sunita, the daughter Deepak and Bonnie Pandya, is aware of the interest her spaceflight has aroused in India.
"I am half-Indian and I have got a... I am sure, a group of Indian people who are looking forward to seeing this second person of Indian origin, flying up in space," she said.
NASA says the Discovery shuttle will be on the most complex mission yet -- to give the International Space Station a new electricity system.
Sunita is expected to take a spacewalk with her Discovery colleague Robert Curbeam to help rewire the ISS space lab and also operate the space station's robotic arm, among other tasks.
"It is my first time doing a space walk, first time opening the hatch and seeing the earth with just my visor. It would be amazing," she said.
In two spacewalks the astronauts will rewire the orbiting station, replacing its eight-year-old temporary power cable system with a permanent one, made possible after the previous mission in September installed two huge electricity-generating solar array panels on the ISS.
"A long-duration spaceflight will supply answers... to what happens to the human body, how materials work in space," she said.
Unlike Chawla, who was born in Karnal in Haryana, Sunita was born and brought up in the US. Born in Ohio to Deepak N Pandya, a physician who migrated to the US and Ursaline B Pandya, she grew up and went to school in Massachusetts. She has a BS, Physical Science degree from the US Naval Academy, and a MS in Engineering Management from Florida Institute of Technology.
Trained to remain aboard the space station until July, Williams will also join space station commander Mike Lopez-Alegria for three spacewalks early in 2007.
"I'm just really happy to be here. It's been a long time coming," Sunita said, adding that she's spoken with her Expedition 14 crewmate-to-be Mikhail "Misha" Tyurin.
"Misha Tyurin called the other day and said 'Suni, we're waiting for you!' so I just can't wait to get to my new home."