Second time lucky? Watch LIVE as Nasa attempts satellite launch after rocket encountered problem yesterday
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Nasa's Orbiting Carbon Observatory-2 (OCO-2) satellite should launch today at 10:56 BST (05:56 EST) after an attempt to lift-off yesterday was cancelled.
The launch was cancelled 24 hours ago when mission controllers noticed a water flow problem, and they are hoping the issue has been resolved for today.
If the rocket does take off today, as expected, the event can be watched live in the stream below.
The satellite has to be launched at exactly the right time to ensure it enters the right orbit.
HOW THE LAUNCH WILL UNFOLD
Lift-off (zero seconds): Three solid rocket motors are ignited.
100 seconds after launch: The solid rocket motors are jettisoned as the rocket climbs to space.
Four minutes: Main engine is cut off.
Four minutes and eight seconds: Rocket splits in two as the stages separate.
Five minutes: Nose cone opens up.
10 minutes: Second engine cuts out (Seco-1).
11 minutes: The satellite coasts in space for 40 minutes.
51 minutes: A second engine fires to place the satellite into the right orbit.
56 minutes: Final rocket engine separates from the satellite.
45 days: First science observations of carbon dioxide levels on Earth begin.
This will bring it in line with a series of other Earth-observing satellites known as the 'A-train'.
In fact, the orbit is so precise that there is only a 30 second launch window within which it can take off; any delays and Nasa will have to try again another day.
'We are in great shape for today's attempt!' said Nasa Launch Manager Tim Dunn of the agency's Launch Services Program.
If the attempt is successful, OCO-2 will be carried into space by the United Launch Alliance Delta II rocket.
It is the second of five Nasa Earth science missions to be launched this year.
Nasa monitors Earth's vital signs from land, air and space with a fleet of satellites and airborne and ground-based observation campaigns.
OCO-2 is Nasa's first mission dedicated to studying atmospheric carbon dioxide, the leading human-produced greenhouse gas driving changes in Earth's climate according to Nasa.
It will collect 24 measurements every second, totaling about a million every day.
Of these, about 100,000 are expected to be sufficiently cloud free to provide highly usable carbon dioxide data.
The best carbon dioxide-observing satellite currently in orbit takes 4 seconds to make one such observation and collects fewer than 20,000 pieces of data per day, with about 500 of those being highly useful.That is the reason why today's launch was cancelled, as the problem delayed the rocket lifting off by more than 30 seconds.
This long exposure photo shows the United Launch Alliance Delta II rocket with the Orbiting Carbon Observatory-2 (OCO-2) satellite onboard, at the Space Launch Complex Two, of the Vandenberg Air Force Base, California. The launch is set to take place at 10:56am BST today
OCO-2 (illustration shown) is Nasa's first mission dedicated to studying atmospheric carbon dioxide, the leading human-produced greenhouse gas driving changes in Earth's climate according to Nasa. It will collect 24 measurements every second, totaling about a million every day
Launch cancellations like yesterday's are not uncommon
WHY WAS YESTERDAY'S LAUNCH CANCELLED?
The issue was with the pulse suppression water system.
This protects the launch mount holding the rocket from the high temperatures of a launch.
And it helps protect from the shockwave of ignition from the engine.
The water flow would have begun at T-minus 45 seconds.
But when it was found not to be working properly, the launch had to be cancelled for safety reasons.
The soonest next launch could be tomorrow in what is known as a '24 hour recycle'.
Rockets are a very dangerous business, so great care must be taken before attempting a launch and a host of safety checks must be met.
Even the most minor of faults can lead to a cancellation; after all, Nasa and other agencies would rather delay a launch by a day or two than lose hundreds of millions of dollars worth of equipment.
Just a week ago, for example, private company SpaceX delayed the launch of its own Falcon 9 rocket when an issue was discovered that threatened the success of the flight.
When OCO-2 makes it into orbit it will study carbon dioxide by looking at the colors (or wavelengths) of sunlight that carbon dioxide absorbs.
To identify very small changes in this absorption from one wavelength to the next, the OCO-2 instrument separates light into many narrow bands of wavelengths.
But OCO-2's field of view is only about one square mile (three square kilometers) - smaller than New York City's Central Park.
This allows it to dodge clouds, which regularly cover about two-thirds of Earth; even a tiny wisp of cloud in OCO-2's view compromises the measurement.
Six to seven weeks after launch, OCO-2 will be maneuvered into its final operational orbit in the A-Train constellation, 438 miles (705 kilometers) above Earth.
And the first science observations of carbon dioxide levels on our planet are slated to begin about 45 days after launch.
Technicians are seen making last minute preparations before the launch of the rocket. Nasa had said there was zero chance of the launch being cancelled today. OCO-2 will be able to pinpoint where the planet's forests and ocean are reabsorbing atmospheric carbon, a cycle that is key to Earth's temperature
Pictured here is Vandenberg Air Force Base in California. The upper levels of the launch gantry can be seen, surrounding the United Launch Alliance Delta II rocket with the Orbiting Carbon Observatory-2 (OCO-2) satellite onboard, at the Space Launch Complex 2 on 29 June 2014
'Carbon dioxide in the atmosphere plays a critical role in our planet's energy balance and is a key factor in understanding how our climate is changing,' said Michael Freilich, director of Nasa's Earth Science Division in Washington.
'With the OCO-2 mission, Nasa will be contributing an important new source of global observations to the scientific challenge of better understanding our Earth and its future.'
Michael Gunson, OCO-2 project scientist at Nasa's Jet Propulsion Laboratory (JPL), Pasadena, California, added: 'Knowing what parts of Earth are helping remove carbon from our atmosphere will help us understand whether they will keep doing so in the future.
'Understanding the processes controlling carbon dioxide in our atmosphere will help us predict how fast it will build up in the future.
'Data from this mission will help scientists reduce uncertainties in forecasts of how much carbon dioxide will be in the atmosphere and improve the accuracy of global climate change predictions.'
The United Launch Alliance Delta II rocket with the Orbiting Carbon Observatory-2 (OCO-2) satellite onboard sits at the launch pad at the Vandenberg Air Force Base. About five minutes after launch the nose cone, pictured, will open up, unleashing the satellite into space and allowing it to enter its final orbit
Dave Crisp, OCO-2 science team leader at JPL (Jet Propulsion Laboratory), left, and Annmarie Eldering, OCO-2 deputy project scientist, also at JPL, are seen during a science briefing on 29 June 2014 ahead of the launch of the Orbiting Carbon Observatory-2 satellite
The spacecraft will sample the global geographic distribution of the sources and sinks of carbon dioxide and allow scientists to study their changes over time more completely than can be done with any existing data.
Since 2009, Earth scientists have been preparing for OCO-2 by taking advantage of observations from the Japanese Gosat satellite.
OCO-2 replaces a nearly identical Nasa spacecraft lost because of a rocket launch mishap in February 2009.
That was when the original Orbiting Carbon Observatory failed to separate during ascent, and subsequently re-entered the atmosphere, crashing into the Indian Ocean near Antarctica.
At approximately 400 parts per million, atmospheric carbon dioxide is now at its highest level in at least the past 800,000 years, according to Nasa.
The burning of fossil fuels and other human activities are currently adding nearly 40 billion tons of carbon dioxide to the atmosphere each year, producing an unprecedented buildup in this greenhouse gas.
OCO-2 measurements will be combined with data from ground stations, aircraft and other satellites to help answer questions about the processes that regulate atmospheric carbon dioxide and its role in Earth's climate and carbon cycle.
Mission data will also help assess the usefulness of space-based measurements of carbon dioxide for monitoring emissions.
Nasa Administrator Charles Bolden answers social media attendees questions on Monday 30 June from just outside the launch pad where the United Launch Alliance Delta II rocket with the Orbiting Carbon Observatory-2 (OCO-2) satellite onboard will launch from
The United Launch Alliance Delta II rocket with the OCO-2 satellite onboard, moments after the launch gantry was moved at the Space Launch Complex Two, of the Vandenberg Air Force Base. OCO-2 replaces a nearly identical Nasa spacecraft lost because of a rocket launch mishap in February 2009
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