Success: Jupiter's first date with Juno

Updated July 4 9:03 p.m. PDT: NASA says its Juno spacecraft has successfully entered orbit around Jupiter.

Jupiter was named after the king of the Roman gods. The god of light and sky, and protector of the state and its laws, he is brother of Juno, who is also his wife.

The largest planet in the Solar System, Jupiter alone contains two-thirds of the mass of the other nine planets (counting Pluto).

How big is it?

Look at the moon in the sky. Now imagine it 40x bigger. That’s Jupiter, if it sat at the same distance. With the supreme God taking up that much of our view we would probably pay much better attention to celestial civic commands.

Now here comes Juno. At the closest encounter in November she will fly 80 times closer to Jupiter's clouds (3000 miles/5000 km) than we are relative to the moon.

How close is that?

Imagine the moon again, still 40 times bigger but 80 times closer. Sky no more, just you (and Juno) dipping your nose somewhere you probably shouldn't. Why not?

Imagine smelly and toxic ammonia thunderclaps rushing in layers of orange and white. Towards the middle what looks like a big red tornado head, bigger than the Earth, swirling at you with some of the highest wind speeds ever detected on any planet; double the speed of a Category Five.

A sun-like planet that somehow never evolved into a star, Jupiter is almost a solar system on its own: trailed by 67 known moons, some with salty oceans floating under their surface, other spewing volcanic plumes and lava flows.

The first embrace

For Juno, Jupiter's first hug would prove a cold one: The temperature in the clouds is about -145 Celsius (-234 F). If she got closer Jupiter would warm up: The core temperature may be about 24,000 C (43,000 F) famously five times hotter than the surface of the sun.

Hot or cold, it would be a tight squeeze. Despite its size, 11 times the diameter of Earth, Jupiter rotates twice as fast - roughly every 10 hours - and has a surface gravity 2.5 times that of ours. Multiply your body weight with that last number, that's what walking around Jupiter would feel like.

The planet's magnetic field - the biggest in our solar system - sucks in and concentrates the high energy particles whirled around by our Sun and the other stars. If you were to visit in a spaceship, the particles would enter your cabin at immense speeds and then ricochet between the walls breaking up in photons, quarks and other nano bullets; think sitting bulls eye in Cern’s Large Hadron Collider.

The good news is it doesn’t get worse for the rest of your journey through our solar system. In terms of radiation, electromagnetic forces and violent atmosphere - when it comes to planets Jupiter is as bad as it gets.

How do we survive?

So how do we survive the sampling coming up?

Because we haven't been able to use radioisotope power systems in space for a while, mostly for political reasons, Juno flies on solar panels.

The probe is encased in a 180 kilogram (400 lbs) titanium-enforced box roughly the size of a big fridge that will reduce ambient radiation exposure about 800 times.  Three solar arrays span 20 meters (66 ft), charging two 55Ah batteries.

Juno's orbits were designed to have as much face time as possible with the distant sun, 25 times dimmer than on Earth, and the instruments run on minimal power.

What's below the clouds?

Juno carries eight scientific instruments and a camera for panoramic pictures. It’ll be skimming the gas giant’s polar cloud tops, hoping to find oxygen and more. As for the crest, we don’t know what we’ll find. The immense gravity may force us to reconsider what we call a solid surface. Instead of a crust we may find an ocean filled with helium or metallic hydrogen.

Liquid metallic hydrogen has just recently been observed on Earth in experiments, it could revolutionize rocketry as propellant cutting down the time it takes to get to Mars from nine months to about two, and be used to make room temperature super-conductors.

Pointing to some physical perimeters some folks even think Jupiter is not that bad at all, that braving the nasty layers veiling the planet we could be rewarded by a gentle ocean with floating islands on top.

At this point, nobody really knows.

The gas samples will hopefully give us new data to simulate the conditions and find out.

The Big Burn

Juno launched aboard an Atlas V rocket from Cape Canaveral Air Force Station on August 5th, 2011. When it enters Jupiter’s orbit at 8:18 p.m. PDT (11:18 p.m. EDT) this evening, Juno's 35-minute main-engine burn will begin. This will slow it enough to be captured by the giant planet’s gravity. We need at least 20 minutes burn to make it.

48 minutes later, the time the signal from Juno takes to reach Earth, we will know if we hit target.

Fingers crossed.

Update July 9:03 p.m. PDT: NASA says its Juno spacecraft has successfully entered orbit around Jupiter. Congrats!

Cool Jupiter video

Mission Events

Jupiter arrival - July 2016, 
Spacecraft will orbit Jupiter for 20 months (37 orbits), 
End of mission (deorbit into Jupiter) - February 2018.

Scientific Instruments videos

- Gravity Science
- Magnetometer (MAG)
- Microwave Radiometer (MWR)
- Jupiter Energetic Particle Detector Instrument (JEDI)
- Jovian Auroral Distributions Experiment (JADE)
- Waves
- Ultraviolet Imaging Spectrograph (UVS)
- Jovian Infrared Auroral Mapper (JIRAM)
- JunoCam

Progress to be monitored by the mission teams at NASA's Jet Propulsion Laboratory in Pasadena, California, and Lockheed Martin Space Systems in Denver, via signal reception by Deep Space Network antennas in Goldstone, California, and Canberra, Australia.