How to watch NASA Jupiter probe's flyby of Earth

Space watchers hoping to get a glimpse of a near-Earth object of the NASA kind will want to look to the skies this weekend as Jupiter-bound probe Lucy makes a close pass of our planet for a gravity assist, just in time for its first anniversary.

Launched last year on October 12, Lucy will pass just 490 miles (790 km) above the Earth on Sunday, October 16.

That means skygazers in north western Australia should be able to see Lucy with the naked eye for a few minutes beginning at 1055 until 1102 UTC (from 1855 AWST or 2025 ACST.)

For those with a suitable telescope and in western north America, you should be able to glimpse the bird from 1126 UTC (0426am PDT, 0526am MDT, 0126am HST) after it emerges from the Earth's shadow.

"The last time we saw the spacecraft, it was being enclosed in the payload fairing in Florida. It is exciting that we will be able to stand here in Colorado and see the spacecraft again," said Lucy principal investigator Hal Levison. 

Lucy will be coming in close to Earth, flying within the orbit of the International Space Station where satellite traffic is heavy. To avoid collisions, Lucy can be told by its controllers to perform maneuvers that can adjust its orbit by either two or four seconds: "a small correction, but it is enough to avoid a potentially catastrophic collision," said Lucy deputy navigation team chief Coralie Adam. 

Rich Burns, Lucy's project manager at the Goddard Space Flight Center in Maryland, said the satellite was supposed to pass 30 miles closer to Earth, though those plans were changed when one of Lucy's solar panels failed to properly latch into place.

Lucy's near-Earth flight plan brings it close enough that NASA had to account for atmospheric drag, which an unlatched solar panel would make even worse.

"We chose to use a bit of our fuel reserves so that the spacecraft passes the Earth at a slightly higher altitude, reducing the disturbance from the atmospheric drag on the spacecraft's solar arrays," Burns said.

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This first gravity assist will take Lucy on a two-year orbit of the Sun, which still won't be enough to send the probe to its ultimate destination: Jupiter's Trojan asteroids. For that, Lucy will return for a second gravity assist in 2024 before it becomes the first mission to take a look at space rocks beyond our system's asteroid belt.

Lucy's 12-year mission, of which we're already one year in, will see it meet up with one asteroid in the belt before heading off to the Trojans, which share an orbit around the Sun with Jupiter. 

Lucy will fly past six Trojans to gather data before returning to Earth yet again in 2030 for a third gravity assist. The final fling will see Lucy meeting up with a binary asteroid pair in the trailing Trojan swarm, while the first six Trojans it will inspect lead Jupiter around the Sun. ®