The JUNO mission (which forms one of the spacecraft in NASA’s New Frontiers Programme) is to go into orbit around Jupiter on the 4th July 2016. It will be doing so under the power of a Moog Westcott produced main engine, otherwise known as the LEROS 1b.

NASA's Juno spacecraft will plunge into uncharted territory, entering orbit around the gas giant and passing closer than any spacecraft before. Juno will see Jupiter for what it really is, but first it must pass the trial of orbit insertion.

On August 5th 2011, an Atlas V launch vehicle carried aloft the NASA/JPL Juno spacecraft, destined for a rendezvous with Jupiter. Once in orbit the probe’s trajectory was being controlled solely through its own internal propulsion system. Performing the trajectory velocity change is the Moog UK Westcott designed and built LEROS 1b main engine – known for its high thrust, robust performance and reliability. This engine burns a combination of Hydrazine and MON-3, providing a perfect fit for a range of dual mode propulsion systems often used on interplanetary missions.

This engine design has been to Mars on board Mars Global Surveyor and Mars Odyssey and to Mercury on board the Messenger spacecraft. The engine’s popularity for interplanetary missions is due to its compact size, relatively high thrust at 635N and high specific impulse at 318s. These factors and a proven track record make it the engine for high risk, high profile missions.

Since the launch of Juno, the LEROS 1b main engine has been fired a number of times including two long duration burns in 2012. During these manoeuvers, the spacecraft was at the furthest point from the Sun at 298 million miles from Earth where radio signals take nearly an hour for a round trip. Each burn was 30 minutes long and set Juno up for a swing by the Earth thirteen months later, skimming past the Earth at 348 miles’ altitude. As it passed the Earth, Juno was travelling at 16,330mph and became the fastest man made object in history (at this speed, Juno would travel from London to New York in 12 minutes!). This extreme velocity put Juno on an arcing trajectory out to Jupiter to arrive 2 years and 9 months later.

With Jupiter approaching on July 4th 2016 Juno’s main computer will command the LEROS 1b’s fuel valves to open which will allow the ignition to establish the combustion process. The engine will burn for approximately 35 minutes, firing against the direction of travel. The braking effect allows the massive gravity of Jupiter to capture the probe and enter into Jovian orbit. This is a critical manoeuver and represents the most significant burn of the LEROS 1b which has to operate as advertised in order to ensure the correct orbit is achieved or the mission will be lost.

An additional 22 minute LEROS 1b burn is planned to trim the orbit. At this point the main science can begin to uncover the internal deep structure including water content and the magnetic field of Jupiter. This will help planetary scientists unlock the origins of Jupiter.

Moog also provided the solenoid control valves for the LEROS 1b thruster, the solenoids control valves for the 12 1 lbf monopropellant thrusters and the propellant feed system valves, and the electronics for on-board motion control devices.

Moog UK Westcott is a rocket propulsion research, development, test and manufacturing company based at the Westcott Venture Park located between Bicester and Aylesbury in Buckinghamshire. The 650-acre Westcott Venture Park site became a Government Research Establishment known as a Guided Projectile Establishment on 1st April 1946 and has just celebrated 70 years as home of rocket propulsion research in the UK.

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