Larry and Mary Egan, who run Egan’s Opticians in Cork, were at the Kennedy Space Center in Florida to support their daughter, Jane, whose astronaut husband Dan Tani, is a mission specialist and flight engineer on board Nasa’s 23rdshuttle mission.
The family had ringside seats as the shuttle lifted off from launch pad 39A at 4.38pm Irish time bound for the International Space Station.
The shuttle is carrying a multi-million dollar Italian-built multi-port module, called Harmony, for the station.
The shuttle is due to dock with the ISS tomorrow.
Mr Tani will replace flight engineer Clayton Anderson on board the space station.
Anderson will return to Earth aboard Discovery in the coming days.
Mr Tani will remain in orbit for several months and will be responsible for installing the module, which provides additional ports for more laboratories.
He will perform three spacewalks and numerous robotic operations in support of the installation.
He is due to return to Earth aboard Atlantis on mission STS-122.
A tentative launch date in early December has been set but Mr Tani is prepared to remain in orbit over Christmas.
Speaking minutes after the launch, his mother-in-law, Mary Egan, said: “Tears flowed. It was just amazing, very emotional. It was nerve wracking, but thankfully, everything went smoothly.
“It is terrifying to watch the shuttle and think of him inside. But he rang us yesterday morning before the launch to say that everything was OK.”
The family will be able to email him over the coming months.
They have also arranged for a very special Christmas present, in case he has to remain in orbit.
The family and several friends were recorded on video performing a rendition of Jingle Bells in several pubs around Kinsale.
The package was edited onto a DVD which was placed on board the shuttle with strict instructions that it not be opened until Christmas Day.
Mr Tani is a highly qualified engineer who has worked on previous shuttle missions.
He has also been responsible for defining, training, and leading the team of engineers who worked in the launch and control room.
He was selected as an astronaut candidate in April 1996, and flew on shuttle mission STS-108 in 2001.
He has logged 11 days in space, including more than four hours of space walks.
In 2002, he was a crewmember on Nasa’s Aquarius undersea research habitat mission.
He then qualified as the backup flight engineer for Expedition 11, which launched aboard the Soyuz rocket in April 2005.
He has accomplished 185 Earth orbits, travelling 4.8 million miles in 283 hours and 36 minutes.
Mr Tani met Jane while playing golf at the Old Head of Kinsale, where she worked several years ago. The couple married seven years ago and now live in Heuston, Texas.