Juno Simply Burned Its Thrusters For an Intense 10 Hours to Outrun Jupiter’s Shadow

In a death-defying maneuver for the spacecraft, NASA’s Juno has accomplished an unprecedented and unplanned engine burn. The aim? To save lots of the spacecraft’s ‘life’, or a minimum of the remainder of its mission to Jupiter.

Jupiter casts a deep, darkish shadow. Darkish sufficient, in actual fact, to successfully kill Juno if it flies by way of it.

Slightly than let the spacecraft spend 12 battery-draining hours in Jupiter’s shadow, after which try a dangerous resuscitation on the opposite aspect, NASA took one other plan of action: a 10.5 hour burn of Juno’s response thrusters that may steer it away from Jupiter’s life-draining shadow.

10.5 hours is a really lengthy burn, and it used up about 73 kg (160 lbs) of gas. However with out doing so, Juno would have been plunged into Jupiter’s deep darkish shadow on November three, its subsequent shut method to the gasoline large. It could’ve spent 12 hours within the shadow, lengthy sufficient to utterly drain its batteries.

The spacecraft’s temperature would’ve plummeted, and with no energy in its batteries, it seemingly would’ve succumbed to the chilly, by no means to awaken once more.

Fortunately, the burn was profitable, and in accordance with Juno’s Principal Investigator, Scott Bolton, it was an “amazingly inventive answer” to the issue of Jupiter’s shadow.

“With the success of this burn, we’re on observe to leap the shadow on November three,” stated Scott Bolton, Juno principal investigator on the Southwest Analysis Institute in San Antonio.

“Leaping over the shadow was an amazingly inventive answer to what appeared like a deadly geometry. Eclipses are typically not associates of solar-powered spacecraft. Now as an alternative of worrying about freezing to dying, I’m wanting ahead to the subsequent science discovery that Jupiter has in retailer for Juno.” 

This shadow-evading burn highlights how tough Juno’s orbit is general.

Juno has been at Jupiter since July 2016. Since that point, it is carried out a sequence of lengthy, elliptical orbits.

Darkness is not the one factor Juno has to keep away from. Jupiter’s intense radiation means the spacecraft treads very rigorously by way of the planet’s neighborhood. Every pole-to-pole orbit takes it shut the extreme radiation belts that encircle Jupiter, the place the spacecraft dives down under the belts, to do its finest science.

(NASA/JPL)

However it could actually solely spend a quick period of time near Jupiter throughout every orbit. The radiation is so intense that every shut cross damages the spacecrafts electronics and devices a bit of bit, shortening their life-span. Ultimately, although they’re housed in a protecting titanium vault, the devices will fail, and the mission will finish.

However a 12-hour interval spent in Jupiter’s shadow would have ended the mission prematurely, with all of its devices intact and working. That untimely finish would’ve disadvantaged us of a number of information, and superior JunoCam photos.

So Juno, adept at avoiding hazards, was instructed to keep away from the darkness. It took sources to do this, although, within the type of the response management system’s hydrazine propellant.

Juno was by no means designed to journey by way of the darkish. The truth is, throughout its total mission, it spent solely 10 minutes at midnight, when it travelled by way of Earth’s shadow throughout a fly-by early within the mission.

That is as a result of quite than an RTG (radioisotope thermoelectric generator) energy supply widespread in different missions so removed from the Solar, Juno depends on solar energy for its operations. Juno is the primary mission to journey this removed from the Solar with solar energy.

The spacecraft has three photo voltaic arrays that produced as much as 490 watts at first of the mission. However over time, the effectivity of photo voltaic arrays is lowered, in order that by the top of the mission they’re going to produce solely about 420 watts.

However even at peak effectivity, Juno’s solar energy system merely will not assist the spacecraft survive 12 midnights. It lacks the battery capability. And batteries are heavy; you do not launch a spacecraft with further batteries, “simply in case”.

This is not the primary wrinkle in managing Juno’s orbit. The truth is, this shadow-evading maneuver is important due to one other change in Juno’s orbit.

When it first entered orbit round Jupiter, it took 53 days to finish one orbit. The plan was to carry out a thruster burn, and alter the orbit to solely 14 days. However when engineers suspected a fuel-delivery drawback, they maintained the 53-day orbit.

The shorter 14 day orbit would have meant much less time between science flybys. Juno will nonetheless full all of its orbits, however as a result of Juno could not enter its 14 day orbit, the science is taking longer. So whereas the preliminary mission plan by no means needed to deal with the upcoming 12 hours of shadow, the revised plan did. That is what necessitated the 10.5 hour burn.

Ed Hirst is Juno venture supervisor at NASA’s Jet Propulsion Laboratory in Pasadena, California. In a press launch, He praised each the ability of the staff working it, and the flexibility of the spacecraft itself.

“Pre-launch mission planning didn’t anticipate a prolonged eclipse that may plunge our solar-powered spacecraft into darkness,” stated Hirst.

“That we might plan and execute the mandatory maneuver whereas working in Jupiter’s orbit is a testomony to the ingenuity and ability of our staff, together with the extraordinary functionality and flexibility of our spacecraft.”

The Juno mission to Jupiter is managed by NASA’s Jet Propulsion Laboratory. It was launched on 5 August 2011, and entered Jupiter orbit on 5 July 2016. The mission is because of finish in July 2021, when the spacecraft will plunge to its destruction in Jupiter’s ambiance.

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