Ground controllers issued the final commands for NASA's Kepler telescope, turning off the transmitters of the spacecraft and shutting down the ship's automatic retrieval software after the planet-hunting observatory ran out of fuel last month.
The latest signals for Kepler were transmitted from a control center at the University of Colorado at Boulder's Atmospheric and Space Physics Laboratory via NASA's Deep Space Network late Thursday.
The engineers ordered Kepler to turn off his radio transmitters, a standard procedure during deactivation of a space mission to ensure that erroneous signals did not interfere with communications using the same or similar frequencies. The controls also prevented Kepler's on-board computer from attempting to reconnect the transmitters and contact Earth.
"As the spacecraft is spinning slowly, Kepler's team had to carefully calculate the commands for the instructions to arrive at the spacecraft during periods of viable communication," NASA said in an update on Friday. "The team will monitor the spacecraft to ensure the commands are successful."
NASA announced on Oct. 30 that Kepler had run out of fuel and no longer had the stability to aim to search for planets around other stars.
Launched in 2009, Kepler is circling the sun about 151 million kilometers from Earth. On its current path, Kepler is flying a little further from the sun than the Earth, and traveling around the sun a little slower than Earth.
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The spacecraft will move away from Earth in the next few decades, before Earth begins to recover. In 2060, Kepler will return to the vicinity of Earth – but well out of the moon's orbit – and the gravity of the planet will take the telescope to an orbit a little closer to the Sun, and one that moves faster than Earth.
The reverse will happen in 2117, when Kepler and Earth converge again and gravity pulls the spacecraft into the farthest and slowest orbit. The standard is expected to continue into the foreseeable future, according to NASA.
Meanwhile, scientists continue to analyze data collected during Kepler's $ 692 million nine-year mission.
Kepler collected his latest scientific observations in September, ending a race that saw more than 530,000 stars and returned 678 gigabytes of data. Kepler's findings also helped astronomers write nearly 3,000 scientific papers, a number that will continue to rise.
Astronomers using data collected by Kepler confirmed the existence of 2,681 planets orbiting other stars, with another 2,899 planets candidates that could be confirmed with later observations.
"We find small, potentially rocky planets around some of these bright stars, and these are the main targets of current and future telescopes, so we can move on and see how these planets are made, how they are formed, and how their atmospheres are," Said Jessie Dotson, a scientist at the Kepler project in Ames.
"As we cease operations on spacecraft, the scientific results of the Kepler data will continue for many years to come," she said.
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