Nasa has launched a super-pressure balloon from New Zealand's South Island Wanaka Airport to conduct near-space scientific investigations.
The launch marks the fifth attempt to get the massive balloon airborne, with previous bids thwarted by bad weather, Nasa said.
Long-duration balloon flights at constant altitudes play an important role in providing inexpensive access to the near-space environment for science and technology.
The 532,000 cubic metre balloon is expected to circumnavigate the globe about the southern hemisphere's mid-latitudes once every one to three weeks, depending on wind speeds in the stratosphere. The aim is for it remain airborne for more than 100 days.
The 2,366kg super-pressure balloon was inflated with as much as 3,600kg of helium before it launched.
It cost $1.94m (£1.34m) to produce and will carry a $1.5m science payload, the Compton Spectrometer and Imager.
The gamma-ray imager will allow scientists from the USA and Taiwan to make new discoveries about the evolution of the universe.
According to Nasa, the balloon's operational float altitude is 33.5km and it will be visible from the ground, particularly at sunrise and sunset, in the southern hemisphere's mid-latitudes, such as Argentina and South Africa.
Nasa's balloon experts at its Columbia Scientific Balloon Facility will control balloon flight operations throughout the mission.
The current record for a Nasa super-pressure balloon flight is 54 days. Tuesday's launch was the second super-pressure balloon mission from Wanaka. The first launch took place on 27 March 2015, flying 32 days, 5 hours, and 51 minutes.
Interest in researching balloon technology has been increasing in recent times.
Last year Google launched internet-beaming balloons into the sky over Indonesia in order to boost online access in the country.
Helium balloons are also attracting interest in the airborne transport sector with the recent launch of the 92m-long Airlander 10, a hybrid aircraft using elements of both planes and airships.