NASA has postponed the third launch attempt of its super-pressure balloon (SPB) from Wanaka this morning because of poor weather.
The SPB was due to be launched at 4.30am but wind speeds were slightly above those required for launch, NASA said in an update.
The US space agency will announce by 2pm if tomorrow's weather will support a launch attempt.
The balloon has the potential for a 100-day journey.
Gabe Garde, mission manager for the 2017 Wanaka Balloon Campaign, earlier said the stratosphere, at 33.5km, had ideal winds forecast to take the balloon due east after launch.
This morning's attempt was to be the third scheduled launch attempt for NASA's campaign.
The first attempt was cancelled because of unacceptable stratospheric wind conditions; the second attempt was canceled due to a mechanical issue with a crane used for launch operations, which has since been resolved.
This is the third consecutive year NASA will launch the long-duration, heavy-lift super-pressure balloon (SPB) into one of the most dynamic and severe flight regimes inside the Earth's atmosphere.
The SPB is about the size of the Forsyth-Barr Stadium in Dunedin when fully inflated. The balloon is made from polyethylene film, which is similar in appearance and thickness to the type used for sandwich bags, but stronger and more durable.