A NASA spacecraft aims to fly closer to the sun this week than any object sent before. The Parker Solar Probe was launched in 2018 to get a close-up look at the sun. Since then, it has flown straight through the sun's corona: the outer atmosphere visible during a total solar eclipse. The next milestone: closest approach to the sun. Plans call for Parker on Tuesday to hurtle through the sizzling solar atmosphere and pass within a record-breaking 3.8 million miles of the sun's surface. At that moment, if the sun and Earth were at opposite ends of a football field, Parker "would be on the 4-yard line," said NASA's Joe Westlake.