What do you do with two spacecraft when their mission is complete and they’re in orbit with an ever-decreasing amount of fuel? Demonstrating a love of drama (and, arguably, a childlike glee for just smashing stuff), NASA’s answer for the Ebb and Flow spacecrafts? Crash them into the surface of the moon.
Both spacecraft were part of NASA’s Gravity Recovery and Interior Laboratory project (GRAIL), and launched in September last year with the intent of using them to orbit the moon for an extended period so scientists could gather more information about its gravitational field. Now, after more than a year in service – and 11 months or so in orbit – it’s time to say goodbye to Ebb and Flow … but that meant ensuring that both satellites would find final resting places safely and without the risk of damaging historical lunar artifacts.
It’s doubtlessly tempting to suggest that both satellites should be left in orbit permanently after their mission, as some kind of perpetually-circling tribute to the dual power of science and the thirst for greater knowledge. Still, there’s one simple problem with that romantic notion: It wouldn’t actually happen. Instead, as the satellites ran out of fuel, their orbits would decay and both would eventually crash into the moon in some entirely random and unpredictable location. The problem with that is, although it’s mostly barren and crash-site-ready, the moondoes have a handful of important landmarks that we might want to leave untouched for future generations (the site of the original Apollo landing, for example). Instead, scientists are working to ensure that both crafts crash at a pre-arranged location.
Officially, what NASA is doing with Ebb and Flow is called “de-orbiting”; as the GRAIL mission’s principal investigator (and MIT geophysics professor) Maria Zuber says, “I wouldn’t say we’re bombing the moon. They’re not bombs, they’re satellites.” Early Friday morning, NASA performed controlled burns on both satellites to alter their orbit and launch them on a collision course with a crater far away from any important site.
“It’s the rim of a partially buried crater that looks like a mountain,” Zuber told Talking Points Memo of the selected crash site a day before the burns were performed. “If we didn’t do these burns, the odds of the spacecraft disrupting one of the historical landing sites would be six in one million. But once we do the burns, the odds will be zero.”
Sadly, we won’t get to watch either crash when it happens because the mountain range is on the Dark Side of the moon (Transformers fanatics, now is the point to start your fanfic about the satellites being caught by Decepticon sleepers). NASA will use an unmanned spacecraft to confirm the satellites’ impact, with the crafts expected to make groundfall on Monday. If you’re wondering what we’ll miss, David Lehman, a project manager working on GRAIL, has a particularly visual analogy to help you picture it: “It’ll be like a washing machine landing on top of you,” he said. “It’ll be a very bad day for you.”