NASA and SpaceX are all set to launch the Transiting Exoplanet Survey Satellite (TESS) on a Falcon 9 rocket from Space Launch Complex 40 at Cape Canaveral Air Force Station in Florida at 6:32 pm CDT (5.02 am IST, Tuesday) on Monday, April 16. TESS aims to detect exoplanets, which are planets planet orbiting stars outside the solar system.

Meteorologists with the US Air Force 45th Space Wing have predicted an “80 per cent chance” of favourable weather for the launch.

The primary weather concern at the moment is strong winds, NASA has said in a statement.

The TESS spacecraft arrived at NASA’s Kennedy Space Center in Florida on February 12 for payload processing.

The survey is NASA’s next step in the search for exoplanets, including those that could support life.

According to a statement issued by NASA earlier, the spacecraft, with the help of a gravitational assist from the Moon, will settle into a 13.7-day orbit around Earth.

Once there, TESS will spend about two years surveying 200,000 of the brightest stars near the Sun to search for planets outside the solar system.

NASA has uploaded a video on YouTube in which the spacecraft can be seen seen beginning its final round of critical pre-launch testing. See the video here.

According to NASA, TESS is its Astrophysics Explorer mission led and operated by MIT in Cambridge, Massachusetts, and managed by NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Dr George Ricker of MIT’s Kavli Institute for Astrophysics and Space Research serves as principal investigator for the mission.

Additional partners include Orbital ATK, NASA’s Ames Research Center, the Harvard-Smithsonian Center for Astrophysics and the Space Telescope Science Institute. More than a dozen universities, research institutes and observatories worldwide are participants in the mission. NASA’s Launch Services Program is responsible for launch management.

Launching Monday, our planet-hunting @NASA_TESS spacecraft will fly in a unique orbit that’ll allow it to study nearly the entire sky over 2 years. This special orbit is key in potentially finding thousands of new planets outside our solar system. Watch: pic.twitter.com/2ONGXewAji

— NASA (@NASA) April 16, 2018

What is an exoplanet?

Apparently, it is likely that every star plays host to at least one planet. And, in simple words, the worlds orbiting other stars in the sky are called “exoplanets”.

Pat Brennan, who is part of NASA’s Exoplanet Exploration Program, has written a detailed post on the existence of exoplanets, how they were found and how much more can be known about them.

Brennan says exoplanets come in a wide variety of sizes — from gas giants larger than Jupiter to small and rocky planets around the size of 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,” says his post on the NASA website.

According to Brennan, the first exoplanet to burst upon the world stage was 51 Pegasi b, which was a “hot Jupiter” 50 light-years away and locked in a four-day orbit around its star.

“Now we live in a universe of exoplanets. The count of confirmed planets is 3,700, and rising,” he says. And that, Brennan underlines, is from only a small sampling of the galaxy as a whole.

The count will rise with an increase in the number of robotic telescopes lofted into the space, he claims.

The launch of TESS is evidently a step in that direction. Previously, Kepler surveyed the stars looking for transiting planets.

TESS will reveal the best candidates for a closer look with the James Webb Space Telescope, currently scheduled to be launch into the space in 2020, according to Brennan.

What is Transiting Exoplanet Survey Satellite, or TESS, and how it works?

NASA says the Transiting Exoplanet Survey Satellite (TESS) is the next step in the search for planets outside of the solar system. These planets may include those that could support life. The mission aims to find ‘transiting’ exoplanets, which periodically block part of the light they get from their host stars. TESS plans to survey 200,000 of the brightest stars near the sun to search for these exoplanets.

Scientists expect the mission will catalog thousands of planets, which will increase the current number of known exoplanets by a great number. Approximately 300 of these planets are expected to be Earth-sized and super-Earth-sized exoplanets. TESS aims to find the “most promising exoplanets” orbiting the brightest stars that are nearest to Earth. This will give future researchers a rich set of new targets for comprehensive follow-up studies.

The space agency says TESS will survey the entire sky over the course of two years by “breaking it up into 26 different sectors, each 24 degrees by 96 degrees across”. Its powerful cameras will stare at each sector for at least 27 days.

The stars TESS plans to study are 30 to 100 times brighter than those the Kepler mission and K2 follow-up surveyed. TESS will cover a sky area 400 times larger than what Kepler monitored.

TESS will create a catalog of thousands of exoplanet candidates after which the mission will conduct ground-based follow-up observations to confirm they are not false positives but true exoplanet. Using the known planet size, their orbit and mass, the mission will be able to determine the compositions of these planets to know if they are rocky like Earth or gas giants like Jupiter — or something completely different and unusual. Additional follow-up, also involving NASA’s James Webb Space Telescope, may allow study of the atmospheres of many of these planets by astronomers.