NASA’s Juno spacecraft is making a quick pass by Earth to get a gravity boost to slingshot itself towards Jupiter
The time of closest approach is 3:21 p.m. EDT (12:21 p.m. PDT / 19:21 UTC) when Juno will pass about 350 miles over South Africa
Dr. Scott Bolton of Southwest Research Institute is the Juno principal investigator, said that Juno is a large, massive spacecraft, which has three large solar panels, measuring 9 by 29 feet, and a titanium vault to protect sensitive electronics from the harsh environment around Jupiter.
Bolton said that even a large rocket couldn’t provide enough propulsion to get the probe all the way to Jupiter, so the probe is flying by the Earth for a gravity-assist that will provide about 70 percent of the initial boost provided by the Atlas V 551 rocket.
He asserted that the gravity assist essentially provides as much propulsion as second rocket launch
The Juno spacecraft was launched toward Jupiter from Kennedy Space Center on August 5, 2011. The rocket provided Juno enough speed to reach the asteroid belt, at which point the Sun’s gravity pulled it back toward the inner solar system.
The Earth flyby gravity assist increases the spacecraft’s speed relative to the Sun from 78,000 miles (126,000 kilometers) per hour to 87,000 miles (140,000 kilometers) per hour
Juno will arrive at Jupiter on July 4, 2016.