5 million miles away. To me and you, it seems an unfathomable distance. To NASA’s Juno spacecraft? It’s just turning the final corner and getting ready for its first of dozens of close approaches with Jupiter.
Yesterday at 3:41 p.m. EDT, Juno reached apojove. That’s the scientific term for the farthest point from an object a spacecraft is orbiting. In Juno’s case, Jupiter. From here on out, Jupiter’s tight gravitational grip will pull the spacecraft closer and closer until it’s just 2,600 miles above the gas giant’s cloud tops.
The spacecraft is in the process of completing the first of two lengthy orbits around Jupiter. Each one taking 53.5 days. The NASA image below illustrates where Juno was at yesterday, and how its current orbit differs from the orbits Juno will be in later this year.
It will take almost 27 days for Juno to complete its orbit. The spacecraft will complete its first lap around Jupiter at its closest point to the gas giant. When August 27 gets here, all nine instruments aboard the spacecraft will be on and observing Jupiter during its closest approach.
The mission team is using the first close approach as a sort of trial run to make sure everything is working smoothly.
“We’re in an excellent state of health, with the spacecraft and all the instruments fully checked out and ready for our first up-close look at Jupiter,” said Rick Nybakken, Juno project manager at NASA’s JPL.
Did You Know: Juno is the farthest solar powered spacecraft from Earth. At a distance five times farther from the sun than Earth, Juno will receive 25 times less sunlight. This method of power is only possible thanks to the advances made in solar cells. The cells used on this spacecraft are 50% more efficient than the ones NASA used in the mid-1990s. Even with improvements in solar cells, each of Juno’s solar arrays measures 29.5 feet by 8.7 feet. The three solar arrays are home to 18,698 solar cells.
Juno’s final burn
In October, Juno’s engine will fire one last time. The 22-minute burn will shorten the spacecraft’s orbit from 53.4 days to just 14 days. And that’s when the real fun begins.
Over the course of more than 30 orbits, Juno’s instruments will poke and prod through Jupiter’s dense cloud layer.
What’s the composition of Jupiter like beneath its clouds? How do the clouds move? How much water is in the atmosphere? What can Jupiter’s aurorae tell us about its magnetic field? These are just some of the questions Juno’s mission team wants the answers to.
In a broader sense, scientists want to understand where Jupiter came from and how exactly it formed. The more we can learn about Jupiter, the better we can understand the planets we discover every year orbiting distant stars.
The clock is running for Juno. In about 20 months, the spacecraft will be intentionally crashed into Jupiter. Why don’t we just leave it hanging around Jupiter in the off-chance we can keep gathering science? NASA’s Planetary Protection Office doesn’t want it to accidentally impact a world with possible water like Callisto, Europa or Ganymede.