NASA has scrubbed today's launch of its planet-hunting spacecraft to allow additional time for Guidance and Control Analysis.

The washing-machine-sized spacecraft, dubbed TESS, will travel to nearby stars in our galaxy to find hidden planets that have yet to be discovered.

Prowling our nearest celestial neighbors, Tess will look for exoplanets - planets that are outside our solar system.

It is hoped that by understanding the stars and their planets better, we might one day be able to tease out signs of alien life.

TESS is flying on a SpaceX Falcon 9 rocket, and was initially scheduled to blast off at 6:32 pm ET (11:32 pm BST) from Cape Canaveral in Florida.

But, NASA is now targeting Wednesday, April 18.

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This image made available by NASA shows an illustration of the Transiting Exoplanet Survey Satellite (TESS). The spacecraft will prowl for planets around the closest, brightest stars. These newfound worlds eventually will become prime targets for alien life

‘Launch teams are standing down today to conduct additional Guidance Navigation and Control analysis,’ NASA tweeted Monday afternoon.

‘The NASA TESS spacecraft is in excellent health and remains ready for launch on the new targeted date of Wednesday, April 18.’

Tess - The Transiting Exoplanet Survey Satellite - is set to embark on a two-year quest to find and identify mystery worlds thought to be lurking in our cosmic backyard.

The spacecraft aims to add thousands of exoplanets, or planets beyond our solar system, to the galactic map for future study.

Life might be out there, whether microbial or more advanced, and scientists say Tess and later missions will help answer the age-old question of whether we're alone.

'It is very exciting. ... By human nature, we look for exploration and adventure, and this is an opportunity to see what's next,' NASA's Sandra Connelly, a science program director, said yesterday.

The $337 million (£236 million) spacecraft's primary goal is to study more than 200,000 of the brightest stars for signs of planets circling them.

It will do this by looking for a dip in brightness, known as a transit.

Nasa predicts that Tess will discover 20,000 exoplanets, including more than 50 Earth-sized planets and up to 500 planets less than twice the size of Earth.

WHAT IS THE TESS SPACECRAFT? NASA's new 'planet hunter,' set to be Kepler's successor, is equipped with four cameras that will allow it to view 85 per cent of the entire sky, as it searches exoplanets orbiting stars less than 300 light-years away. By studying objects much brighter than the Kepler targets, it's hoped TESS could uncover new clues on the possibility of life elsewhere in the universe. Its four wide-field cameras will view the sky in 26 segments, each of which it will observe one by one. In its first year of operation, it will map the 13 sectors that make up the southern sky. Then, the following year, it will scour the northern sectors. 'We learned from Kepler that there are more planets than stars in our sky, and now TESS will open our eyes to the variety of planets around some of the closest stars,' said Paul Hertz, Astrophysics Division director at NASA's Headquarters. 'TESS will cast a wider net than ever before for enigmatic worlds whose properties can be probed by NASA's upcoming James Webb Space Telescope and other missions.' Tess is 5 feet (1.5 meters) wide and is shorter than most adults. The observatory is 4 feet across (1.2 meters), not counting the solar wings, which are folded for launch, and weighs just 800 pounds (362 kilograms). NASA says it's somewhere between the size of a refrigerator and a stacked washer and dryer. Tess will aim for a unique elongated orbit that passes within 45,000 miles of Earth on one end and as far away as the orbit of the moon on the other end. It will take Tess two weeks to circle Earth. Advertisement

'They are going to be orbiting the nearest, brightest stars,' Elisa Quintana, TESS scientist at NASA's Goddard Spaceflight Center, told reporters yesterday.

'We might even find planets that orbit stars that we can even see with the naked eye,' she added.

'So in the next few years we might even be able to walk outside and point at a star and know that it has a planet. This is the future.'

Just a couple of decades ago, the notion of finding habitable planets was a mere fantasy, said Paul Hertz, astrophysics division director at NASA.

'Humans have wondered forever whether we were alone in the universe, and until 25 years ago the only planets we knew about were the eight in our own solar system,' he told reporters on the eve of the Tess launch.

'But since then, we have found thousands of planets orbiting others stars and we think all the stars in our galaxy must have their own family of planets.'

Tess (pictured) is designed as a follow-on to the US space agency's Kepler spacecraft, which was the first of its kind and launched in 2009

Tess is designed as a follow-on to the US space agency's Kepler spacecraft, which was the first of its kind and launched in 2009.

The aging spacecraft is currently low on fuel and near the end of its life.

Kepler found a massive trove of exoplanets by focusing on one patch of sky, which contained about 150,000 stars like the Sun.

The Kepler mission found 2,300 confirmed exoplanets, and thousands more candidate planets. But many were too distant and dim to study further.

Tess, with its four advanced cameras, will scan an area that is 350 times larger, comprising 85 per cent of the sky in the first two years alone.

Tess, with its four advanced cameras, will scan an area that is 350 times larger than what Kepler studied, comprising 85 per cent of the sky in the first two years alone

'By looking at such a large section of the sky, this kind of stellar real estate, we open up the ability to cherry-pick the best stars to do follow-up science,' said Jenn Burt, a postdoctoral fellow at the Massachusetts Institute of Technology (MIT).

'On average the stars that TESS observes are 30-100 times brighter and 10 times closer than the stars that Kepler focused on.'

Tess uses the same method as Kepler for finding potential planets, by tracking the dimming of light when a celestial body passes in front of a star.

The next step is for ground-based and space telescopes to peer even closer.

The Hubble Space Telescope and the James Webb Space Telescope, scheduled to launch in 2020, should be able to reveal more about planets' mass, density and the makeup of their atmosphere - all clues to habitability.

WHAT IS AN EXOPLANET? Every star in the night sky likely plays host to at least one planet. Worlds orbiting other stars are called 'exoplanets,' and they come in a wide variety of sizes. Some are gas giants larger than Jupiter and some are small, rocky planets about as big around as Earth or Mars. They can be hot enough to boil metal or locked in deep freeze. They can orbit their stars so tightly that a 'year' lasts only a few days; they can orbit two suns at once. Some exoplanets are sunless rogues, wandering through the galaxy in permanent darkness. There are potentially trillions of planets in the Milky Way. Our nearest neighboring star, Proxima Centauri, was recently found to possess at least one planet – probably a rocky one. It’s 4.5 light-years away – more than 25 trillion miles (40 trillion kilometers). The vast majority of exoplanets have been found by searching for shadows: the incredibly tiny dip in the light from a star when a planet crosses its face. Astronomers call this crossing a “transit.” Advertisement

Tess uses the same method as Kepler for finding potential planets, by tracking the dimming of light when a celestial body passes in front of a star. By focusing on planets dozens to hundreds of light-years way, Tess may enable future breakthroughs

'Tess forms a bridge from what we have learned about exoplanets to date and where we are headed in the future,' said Jeff Volosin, Tes project manager at Nasa's Goddard Spaceflight Center.

By focusing on planets dozens to hundreds of light-years way, TESS may enable future breakthroughs, he said.

'With the hope that someday, in the next decades, we will be able to identify the potential for life to exist outside the solar system.'