This image made available by the Johns Hopkins University Applied Physics Laboratory on Wednesday, May 31, 2017 depicts NASA's Solar Probe Plus spacecraft approaching the sun.
The probe's main goal will be to learn the secrets of the corona, the unusual atmosphere surrounding the sun.
The heat shield is built to withstand radiation equivalent up to about 500 times the Sun's radiation here on Earth.
NASA postponed until Sunday the launch of the first ever spacecraft to fly directly toward the Sun on a mission to plunge into our star's sizzling atmosphere and unlock its mysteries.
The probe was expected to launch early Saturday morning but was delayed twice, once at 3:53 a.m. and again at 4:28 a.m., during the 65-minute launch window that began at 3:33 a.m. ET.
NASA's $1.5 billion Parker Solar Probe spacecraft, the size of a auto, aims to plunge into the Sun's sizzling atmosphere and become humanity's first mission to explore a star.
The probe is protected by an ultra-powerful heat shield that is just 11.43 centimetres thick.
With one minute and 55 seconds left on the countdown timer, a launch controller ordered "Hold, hold, hold" when a pressure alarm sounded, showing that there was a fault with the Delta IV Heavy rocket's helium system.
According to NASA, the forecast shows a 60 percent chance of favourable weather conditions for launch.
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The corona is not only 300 times hotter than the sun's surface but it also discharges powerful plasma and energetic particles that can unleash geomagnetic space storms that can wreak havoc on Earth by disrupting power grids.
At Parker Solar Probe's closest approach to the Sun, temperatures on the heat shield will reach almost 1,371 degrees Celsius, but the spacecraft and its instruments will be kept at a relatively comfortable temperature of about 29.4 degrees Celsius.
The corona gives rise to the solar wind, a continuous flow of charged particles that permeates the solar system. He's now 91 and eager to see the solar probe soar.
Tools on board will measure high-energy particles associated with flares and coronal mass ejections, as well as the changing magnetic field around the Sun.