NASA’s Juno to Gain Gravity Speed Boost from Earth to Slingshot Towards Jupiter

NASA's Juno to slingshot towards Jupiter using Earth Flyby

NASA’s Juno spacecraft is due to gain a gravity assist speed boost, during a flyby of Earth today; the process will increase the spacecraft’s speed, and slingshot it towards Jupiter. Juno is to be tasked with uncovering some of the many mysteries of Jupiter, exploring its atmospheric constituents whilst attempting to see whether it has a rocky core.

Juno’s Earth Flyby

Juno was launched from Cape Canaveral on Aug. 5, 2011, with the primary ambition centering around studying Jupiter’s composition, polar magnetosphere, as well as its magnetic and gravitational fields.

The 8,000-pound spacecraft is currently undergoing part of a five-year journey to the heavy gas giant, with its arrival anticipated on July 4, 2016, after traversing a total distance of close to three billion kilometers. However, Juno is destined to be within approximately 350 miles of Earth, as it whizzes by mankind on Wednesday Oct. 9, at 3:21 p.m. Eastern Daylight Time.

It is believed that Juno’s pass around the Earth will provide it with the gravity speed boost necessary to successfully reach Jupiter. According to, the event will accelerate Juno from 78,000 miles per hour to 87,000 miles per hour.

Principal Investigator Scott Bolton, working with the Southwest Research Institute in San Antonio, Texas, explained the need to exploit Earth’s gravitational fields to deliver the sizable spacecraft to Jupiter:

“Even a large rocket couldn’t provide enough propulsion to get us all the way to Jupiter, so we are 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. The gravity assist essentially provides as much propulsion as a second rocket launch.”

The eccentric musings of Bill Nye explains the process in further detail, throughout the following clip:

Luckily, the government shutdown, which resulted in 97 percent of all NASA employees being furloughed, has not affected operations associated with Juno’s Earth flyby, and the event is even due to be streamed live by (see below for link).

Juno’s Objectives

Once it has reached its final destination, Juno will be configured into a polar orbit, and will revolve around Jupiter 33 times each year. Juno boasts a series of infrared and

Jupiter Cloud Pattern in 2010
Image highlighting Jupiter’s cloud patterns, during 2010

microwave instruments, and will commence its new life measuring the thermal radiation released deep from within Jupiter’s atmosphere.

Jupiter’s atmosphere is considered the biggest planetary atmosphere in the Solar System, predominately comprising of helium and hydrogen, and trace amounts of water, ammonia and methane. For almost half a century, observations suggest that Jupiter radiates far more heat than it is subjected to from the Sun. This discrepancy in the amount of generated heat is likely derived from the early stages of Jupiter’s formation, but could also be caused by precipitation of helium into the planet’s core.

Juno will conduct observations that will clue astronomers into the composition of the atmosphere, and provide data that can be used to establish the relative abundance of water and oxygen.

The Craft’s Scientific Instruments

To achieve its scientific objectives, Juno is fitted with a microwave radiometer (MWR) and the Jovian Infrared Auroral Mapper (JIRAM). MWR can probe the planet’s deep atmosphere by using microwaves in the one to 50 centimeter range, whilst JIRAM can investigate the upper layers using infrared wavelengths of between two and five micrometers.

Meanwhile, the planet’s magnetic and gravitational fields will be monitored using the Magnetometer (MAG) and Gravity Science instruments, respectively. MAG has a Flux Gate Magnetometer that can determine the direction and power of the magnetic fields. Ultimately, NASA is hoping to understand more about Jupiter’s magnetosphere, as well as the planet’s interior structure and dynamics.

NASA's Juno Payload System

Juno will also use its Radio and Plasma Wave Sensor to study auroral currents, whilst JADE and JEDI instruments are responsible for investigating Jupiter’s polar magnetosphere.

Amongst the dizzying array of technologies is JunoCam, a visible light telescope that is designed to showcase Juno’s mission to the public. JunoCam’s operation will be limited to approximately seven orbits of Jupiter, as the device will be subjected to the planet’s punishing radiation and magnetic fields.

In commemoration of Galileo Galilei, who discovered the four biggest satellites around Jupiter, the Italian Space Agency created an aluminum plaque with a portrait of the famous astronomer etched into the metal. As a symbolic gesture, this plaque, along with LEGO models of Galileo, have been added to Juno.

During Juno’s Earth flyby, NASA will also take the opportunity to ensure the craft’s instruments remain fully functional and are properly calibrated. Jeff Lewis, the operations lead at Lockheed Martin Space Systems, indicates that the Earth’s magnetosphere will provide ground control teams with the opportunity to test these intricate technologies, before it begins the final leg of its journey.

For those interested in watching Juno gain its gravity speed boost from Earth, and slingshot towards Jupiter, will be streaming the event live on their website here.

By: James Fenner

Juno Website Link

Juno Payload Suite of Instruments Link

Spaceflight Now Link

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