Juno spacecraft makes Earth flyby

A Jupiter-bound spacecraft swungpast Earth Wednesday afternoon in order to get a boost from Earths gravity.

NASAs Juno spacecraft, which launched from Earth toward Jupiter on Aug. 5, 2011, waslateryanked back toward the inner solar system by the suns gravity. It made its closest approach toEarth at 3:21 p.m. ET,pass about 560 kilometres above South Africa.

Scott Bolton, principal investigator of the Juno mission, said in a statement that the force of Earths gravity during the flyby wouldboost the spacecrafts speed relative to the Earth from 126,000 kilometres per hour to 140,000 kilometres per hour.

The gravity assist essentially provides as much propulsion as a second rocket launch.

Bolton is the director of the space science department at the Southwest Research Institute in San Antonio, Texas. He said Juno, which had a mass of 3.6 tonnes, including fuel and propellant, when it blasted off from Earth, is so big and heavy that even a larger rocket couldnt provide enough propulsion to get us all the way to Jupiter.

Juno, named for the mythological wife and sister of the Roman god Jupiter, is expected to arrive at our solar systems largest planet on July 4, 2016. After the spacecrafts arrival, it will circle the planet 33 times from pole to pole. Unlike spacecraft that have visited Jupiter, Juno will be able to see through the gas giants dense cloud cover, observing the planets magnetic fields, atmosphere and chemical composition.

Its goal is to uncover how Jupiter formed and evolved over its history.

Message to space

During Wednesdays close approach, the Juno mission invitedamateur radio operators to say hi to the spacecraft using Morse code.

Juno's radio and plasma wave experiment, called Waves, should be able to detect the message if enough people participate, saida page for the event on the website of NASAs Jet Propulsion Laboratory at the California Institute of Technology.

During the flyby, Juno was toapproach Earths sunlit side from deep space, allowing it to take never-before-seen images of the Earth-moon from a perspective similar to that of someone on Mars or Jupiter, said Bolton. A movie of the images wasexpected to be released shortly after the flyby.

The Juno mission teamalso tookthe opportunity to check and calibrate the spacecrafts nine scientific instruments during the flyby.

The mystery of the extra boost

Meanwhile, the European Space Agency plannedto measure the spacecrafts radio signals during the flyby from tracking stations in Argentina and Australia. Its scientists are trying to figure out why some spacecraft pick up or lose an unexpected amount of speed as they swing past the Earth to get a gravity boost.

The variations are very small so small that in some cases, such as when the NASAs Cassini and Messenger flew by in 1999 and 2005 respectively, they couldnt be confirmed. But they have been as large as 13 millimetres per second in the case of NASAs NEAR spacecraft in 1998.

Daniel Firre, who is responsible for tracking support at the ESAs European Space Operations Centre, said in a statement that gathering more data is critical if we are ever to solve this perplexing mystery.