Prepare to say goodbye to the most prolific planet hunter in history, the Kepler telescope, which is running dangerously low on fuel.

In an attempt to save its energy, NASA has put the spacecraft in hibernation mode for now.

Kepler Goes To Sleep

According to a statement from NASA, the Kepler team recently noted that the fuel of the spacecraft is running out.

The spacecraft is currently on its 18th observation campaign, which began in May 2018 and focused on the Cancer constellation. It's the second time scientists are closely observing this particular region, in hopes of confirming exoplanet candidates and perhaps even discovering new ones.

NASA says that it's their top priority for the data collected over the observation period to be sent back to Earth. To do this, there needs to be enough fuel left on Kepler's tank to transmit the copious amounts of data during its scheduled Deep Space Network time in early August.

Until the scheduled data transmission, the Kepler team is keeping the spacecraft in sleep mode, so it doesn't burn its precious remaining fuel.

Of course, the engineers are seeking to maximize the fuel in both collecting as much data as possible and making sure it gets to send the observations to Earth.

"It's like trying to decide when to gas up your car. Do you stop now? Or try to make it to the next station?" Charlie Sobeck, Kepler system engineer, wrote in the agency's mission update last March. "In our case, there is no next station, so we want to stop collecting data while we're still comfortable that we can aim the spacecraft to bring it back to Earth."

An Iconic Planet Hunter Nears Its End

Although scientists are trying to stretch the Kepler's lifespan, NASA acknowledges that the spacecraft's fuel tank will soon dry up. In the March update, Sobeck estimated several months left. Now, the agency knows for sure that there's not much left.

If there's fuel left after the data transmission in August, the Kepler team will launch the 19th observational campaign in Aug. 6.

The Kepler telescope has played a huge part in adding to astronomers' knowledge of space, discovering 70 percent of the 3,750 known exoplanets, according to Space.com. It's an impressive feat that can be appreciated, especially as the Kepler nears the finish line.

NASA's new Transiting Exoplanet Survey Satellite will take up the planet-hunting duties moving forward.