The Ardbeg Distillery on Islay blasted compounds of unmatured malt to the International Space Station (ISS) in an unmanned cargo spacecraft in October 2011, along with particles of charred oak.
Scientists hope to understand how they interact at close-to-zero gravity.
Specially designed for the mission, the vial of Ardbeg has been orbiting the Earth's atmosphere at 17,227mph, 15 times a day for 1,045 days.
At the same time, an identical bottle was housed at the distillery on Islay to act as a control sample.
The single malt is expected to land back on solid ground in Kazakhstan aboard a rocket on September 12.
The two samples will then be reunited at a laboratory in Houston, Texas, where scientists will compare them to examine the interaction of the Ardbeg-crafted molecules with charred oak to see what differences occur between Earth whisky and space whisky.
Dr Bill Lumsden, Ardbeg's director of distilling and whisky creation, said: "Ardbeg is known for taking risks in its development of some of the most coveted whiskies in the world, so it is fitting that it is the first distillery ever in space. We are now close to the end, close to finding answers to something previously unknown which is truly exciting.
"This is one small step for man but one giant leap for whisky, and the team hope to uncover how flavours develop in different gravitational conditions - findings which could revolutionise the whisky-making process.
"We hope to shine new light on the effect of gravity on the maturation process but who knows where it will lead us? It could be to infinity and beyond."