Or at least, attempt to answer. Juno’s nearly five-year long trip to Jupiter is nearly over. The success or failure of the mission hinges on a 35-minute burn of its rocket motor. Everything is riding on this short burn. If the instrument isn’t designed to place Juno in Jupiter’s orbit, it’s getting switched off.
That means no pictures of Jupiter during final approach. We’ll know on July 4th if the orbital insertion was successful.
Juno’s tricky orbit
Studying Jupiter is tricky. Especially, if you want to do it up close. The spacecraft will be in an environment (temporarily) unlike any in the solar system. Deep beneath the cloud tops we see from Earth lies a layer of hydrogen under immense pressure. This pressure is so high the layer acts as an electrical conductor. Scientists believe this layer of hydrogen along with Jupiter’s fast spin creates a powerful magnetic field.
Any spacecraft entering this field will be subject to some of the highest radiation in the solar system. And that’s not good news for a delicate spacecraft.
To skirt this radiation, Juno’s mission team selected a highly elliptical orbit. Imagine an oval. Juno will dip within 3,000 miles above Jupiter’s cloud tops and then slingshot around and fly away from Jupiter before doing the close pass again. Every 11 days, Juno will complete an orbit.
The spacecraft will enter Jupiter’s orbit as a polar orbit. It will travel above the planet in a north-south direction. These first few orbits keep it away from Jupiter’s radiation concentrated in belts around the planet’s equator. But as each 11-day orbit goes by, Juno’s orbit will tilt closer and closer towards the equator.
Did You Know: Juno’s mission calls for 33 orbits. But Jupiter’s intense radiation is expected to destroy several instruments by orbit 11. The Jovian Infrared Auroral Mapper (JIRAM) and JunoCam (the spacecraft’s camera) aren’t expected to last past orbit 8. The microwave radiometer will be lucky to reach orbit 12.
Six hours of study
The three hours before and after closest approach will be when most of the science happens. After that, Juno’s mission team will be busy checking the spacecraft’s orbit and sending data back to Earth.
Every minute counts for several of Juno’s instruments.
The Jovian Infrared Auroral Mapper (JIRAM) is designed to probe the origins of the powerful magnetic field Juno hopes to mostly avoid. This environment is home to the most stunning auroras in our solar system. JIRAM will peer through into the thick atmosphere down to 45 miles below the cloud tops.
How this intense magnetic environment affects Jupiter’s atmosphere is just one of the mysteries Juno will shed light on.
The JunoCam is all about us. The astronomy fans. The public. It’s hitching a ride as a public outreach instrument. It’ll give us the visual flare to ooh and ahh at while scientists crunch the data. Data is cool, but it just doesn’t have the punch a stunning close-up image of Jupiter’s thick cloud tops will have.
Don’t expect fancy images for the entire duration of Juno’s mission, though. The mission team doesn’t expect it to last past orbit 8. But who knows. Maybe JunoCam will surprise us.
How much water is in Jupiter’s atmosphere? That’s a question for the Microwave Radiometer (MWR). It will study the microwave radiation coming from inside the planet and determine the atmosphere’s structure and chemical composition.
Which current theory of planet formation is correct? Or, do we need new ones? The data gathered by MWR should help scientists out on this front.
Other instruments aboard Juno include:
Magnetometer (MAG – mapping the magnetic field)
Gravity Science (GS – measuring gravity to map Jupiter’s mass distribution)
Jovian Auroral Distribution Experiment (JADE – an energetic particle detector measuring ions and electrons at low energy)
Jovian Energetic Particle Detector Instrument (JEDI – same as JADE but measuring them at high energy)
Radio and Plasma Wave Sensor (Waves – will measure radio and plasma spectra in the auroral region)
Ultraviolet Imaging Spectrograph (UVS – snap ultraviolet images of Jupiter’s atmosphere and auroras)
Juno’s mission ends in fire
If everything goes smoothly, Juno’s downfall won’t be Jupiter’s powerful radiation. A 400-pound titanium vault housing the spacecraft’s electronics and many of its science instruments will make sure of that. Nope. Juno’s more than one-year long mission will end as the spacecraft dives deep into Jupiter’s atmosphere and burns up.
Juno’s mission will live on, though. The answers we get over the next few years will only give rise to new questions.