Five years after a NASA satellite to track carbon dioxide plunged into the ocean after lift-off, the US space agency is launching a carbon copy - this time on a different rocket.
The $US468 million ($A506.36 million) mission is designed to study the main driver of climate change emitted from smokestacks and tailpipes.
Some of the carbon dioxide is sucked up by trees and oceans, and the rest is lofted into the atmosphere, trapping the sun's heat and warming the planet.
NASA suffered a major scientific - and financial - disaster in 2009 when a rocket carrying the original satellite plummeted into the waters off Antarctica minutes after soaring from Vandenberg Air Force Base along the central California coast.
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After the loss, engineers went back to the drawing board and built a near-identical twin that was set to launch before dawn on Tuesday.
Instead of using the same rocket, the replacement will be flown on a Delta 2, a workhorse booster that once faced a murky future.
Scientists who have no role in the mission welcomed the latest flight attempt.
They said it would have taken even longer to get to the launch pad with a completely new design.
"We don't have time to waste. We need solutions now," said Elisabeth Holland, a professor of climate change at the University of South Pacific in Fiji who helped write the 2007 Intergovernmental Panel on Climate Change report.
There has not been an Earth-observing satellite dedicated to tracking carbon dioxide since the Japanese launched one in 2009.
"It's really the fate of carbon dioxide once it's in the atmosphere that we're trying to really put our finger on," project scientist Michael Gunson of the NASA Jet Propulsion Laboratory said during a recent pre-launch news conference.
Since the industrial age, the concentration of carbon dioxide in the air has increased dramatically. Some 40 billion tons of the greenhouse gas are pumped out yearly from the burning of fossil fuels.
About half ends up trapped in Earth's atmosphere while a quarter is absorbed into the ocean. Another quarter is sucked up by trees and plants.
The mission, designed to last at least two years, will identify places on Earth responsible for inhaling carbon dioxide.
Scientists hope for better luck at the upcoming launch of Orbiting Carbon Observatory-2, or OCO-2 for short.
The new mission costs almost twice as much as the original, mainly because it will ride on a more expensive rocket. Engineers also had to swap out obsolete parts, adding to the mission price tag.
Once in polar orbit 705 kilometres high, the satellite will circle Earth every 100 minutes, measuring carbon dioxide levels. It will join a constellation of 17 other NASA spacecraft that stare down at the planet.
