The end is finally near for NASA’s Kepler spacecraft, with the fuel tanks expected to
run dry in August of 2018.
But before the undisputed champ of exoplanet hide-and-seek retires and drifts off quietly
into space, we thought we’d look back on the highlights of the nine year mission.
Kepler was launched in March of 2009 with one mission: to search for planets outside
our solar system.
Rather than orbiting the Earth like the Hubble Space telescope, Kepler was placed in what’s
called an earth-trailing orbit around the sun, a little wider and a little slower than
ours, So, over time it would slowly drift away from Earth until it was millions of miles
out.
That means we can’t send astronauts to repair Kepler like we’ve done with Hubble, but
so long as nothing goes wrong this orbit has a lot of advantages.
It keeps the Earth from photobombing the shot, and since it’s out of Earth’s atmosphere,
the stars won’t twinkle.
The orbit also eliminates external torques caused by atmospheric friction or Earth’s
magnetic field, meaning the craft can stably point at one spot in the sky for a long time.
The largest external torque on Kepler comes from solar pressure, but four small wheels
that act as gyroscopes stabilize the craft and counteract that.
Aside from a disposable cover, these are the only moving parts on the spacecraft, reducing
the chances that something will break.
Once in orbit, Kepler continuously stared at the same patch of sky in the Cygnus-Lyra
region, watching 150,000 main sequence stars for the tiniest drop in light levels that
indicate a transiting planet.
The only time it broke its gaze was once a month when it turned to transmit data back
to Earth.
It was basically the most formidable staring contest opponent humanity could create, and
it caught stars blinking.
Kepler identified over 2,300 confirmed extrasolar planets, 30 of which are less than twice earth’s
size and in the habitable zone, making them candidates to support extraterrestrial life.
Kepler chugged along just fine for a while, even though one of it’s reaction wheels
broke in July of 2012.Then in 2013, four years after launch, disaster struck.
Remember all that foreshadowing I did, about the wheels being the only moving parts and
the craft being too far away to repair?
Well a second wheel broke, and two functional wheels was not enough to keep the camera steady.
Without the ability to stabilize itself Kepler couldn’t continue the original mission,
and it looked like the end.
Until, someone had a brainwave: why not use the solar pressure to act like a third stabilizing
wheel?
Kepler wouldn’t be able to look where it had before, but it could point at one spot
for about 80 days at a time, until sunlight would start leaking in.
At which point it could rotate and stare at a different spot for another 80-ish day “campaign”.
The crazy plan worked, and the new mission, dubbed K2, was underway.
The K2 mission has discovered another 323 confirmed exoplanets, and there’s still
lots of data to dig through so more could be confirmed years from now.
K2 has even had some unexpected benefits.
By looking at a variety of stars, many of them in early stages of their lives, Kepler’s
observations have lead to discoveries and insights into how stars and young planets
form.
After 5 years of the K2 mission, Kepler is running out of fuel, meaning soon it will
not be able to point itself back towards Earth to transmit scientific data.
While NASA originally estimated it would only have enough fuel for 10 campaigns, the little
spacecraft that could completed 18!
It makes me want to light a menorah or something.
Its successor, the Transiting Exoplanet Survey Satellite, or TESS, was launched in April
of 2018, and will search almost the entire night sky for exoplanets.
But if exciting news ever comes out about a planet with Kepler in its name, you’ll
know the story of the amazing spacecraft that discovered it.
If you like this video don’t forget to subscribe!
Kepler isn’t the only space telescope whose time is running out, soon the legendary Hubble
space telescope will be put out of commission too.
For a fond farewell to this stargazer, check out Athena’s video here.
One cool thing thing about the Kepler mission is it was operated by undergrad students as
young as 20.
It’s the next best thing to being a self-made billionaire.
Thanks for watching and I’ll see you next time on Seeker.