Spacecraft of the Week is a feature showing the engineering and design that went into creating the vehicles that explore our universe. Illustration by Larry Corby.
The Juno mission is on its way to Jupiter, where it will send back data that will teach people more about the planet’s composition and the history of its stormy atmosphere.
This ambitious craft didn’t actually require much ambitious new instrumentation at all – NASA says that all of its individual instruments are “straightforward” designs, and the mission didn’t require the development of any new devices. However, instruments such as a color camera will give NASA the first detailed looks at Jupiter’s poles. Juno’s instruments will explore how Jupiter formed, how much water or oxygen may be present, what the planet’s interior structure looks like and whether it is moving and/or has a solid core, how its powerful magnetic field was generated, and more.
Juno is a 66 foot by 15 foot cube surrounded by three solar panel ‘arms’ made up of 11 individual solar panels It was built at Lockheed Martin Space Systems in Denver, and is managed by JPL for the Southwest Research Institute. Its payload consists of nine instrument suites made up of 26 different sensors. It was launched on Aug. 5, 2011 from Cape Canaveral, Fla. on board an Atlas V551 rocket.
One important element of the creation of the spacecraft was its spin. Like the Pioneer spacecraft, which explored the solar system from the late 1950s to the 1970s, Juno was spun in order to make its orientation more stable and easy to control. This spin rate remains consistent dependent on the part of the mission – at cruise it rotates at 1 RPM, at 2 RPM during science operations, and at 5 RPM during maneuvers.
The field of view of the instruments will cross Jupiter once per rotation once the craft arrives at the planet. This is all intended to keep operations as simple as possible, without having to point any particular instruments in different directions.
Weight is always a factor when it comes to building spacecraft, so in order to cut down on weight Juno uses a dual-mode propulsion subsystem, incorporating a bi-propellant main engine and mono-propellant reaction control system thrusters. The doubled equipment also provides redundancy. The instruments were also fixed to the body of the spacecraft in order to decrease weight and simplify the design.
Juno does have one technology that is completely new: it’s the first to use a radiation shielded electronics vault in order to protect its command and data handling box, power and data distribution, and about 20 other electric assemblies from the highly irradiated environment around Jupiter. This vault contributes about 500 pounds of weight to the total launch weight, 7,992 pounds. (Even with this protection, Juno’s mission is designed such that it avoids Jupiter’s most powerful radiation belts.)
Another new technology on Juno was necessitated because of the distance at which Jupiter orbits from the sun. Juno will be the first solar-paneled spacecraft designed to use such a low amount of light, and that’s why its solar panels are so long. Its solar cells are more efficient than the ones used for spacecraft before, and its science instruments were also designed to be energy-efficient. The mission was designed to keep the craft out of Jupiter’s shadow so that it can run consistently on solar energy.
From the three solar arrays, power goes to two 55 amp-hour lithium-ion batteries and a power bus.
Juno will arrive at Jupiter in July of 2016, and will take scientific readings there until October of 2017.
Along with its scientific payload, Juno carries three Lego figures, representing its namesake and other mythological figures, and a plaque dedicated to Galileo Galilei.
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