Trailing Earth’s orbit at 94 million miles away, the Kepler space telescope has survived many potential knock-outs during its nine years in flight, from mechanical failures to being blasted by cosmic rays.
At this rate, the hardy spacecraft may reach its finish line in a manner we will consider a wonderful success. With nary a gas station to be found in deep space, the spacecraft is going to run out of fuel. We expect to reach that moment within several months.
How Kepler had to stop
In 2013, Kepler’s primary mission ended when a second reaction wheel broke, rendering it unable to hold its gaze steady at the original field of view.
The spacecraft was given a new lease on life by using the pressure of sunlight to maintain its pointing, like a kayak steering into the current. Reborn as “K2,” this extended mission requires the spacecraft to shift its field of view to new portions of the sky roughly every three months in what we refer to as a “campaign.”
Initially, the Kepler team estimated that the K2 mission could conduct 10 campaigns with the remaining fuel. It turns out we were overly conservative. The mission has already completed 16 campaigns, and this month entered its 17th.
Our current estimates are that Kepler’s tank will run dry within several months — but we’ve been surprised by its performance before! So, while we anticipate flight operations ending soon, we are prepared to continue as long as the fuel allows.
The Kepler team is planning to collect as much science data as possible in its remaining time and beam it back to Earth before the loss of the fuel-powered thrusters means that we can’t aim the spacecraft for data transfer.
We even have plans to take some final calibration data with the last bit of fuel, if the opportunity presents itself. Without a gas gauge, we have been monitoring the spacecraft for warning signs of low fuel— such as a drop in the fuel tank’s pressure and changes in the performance of the thrusters.
But in the end, we only have an estimate — not precise knowledge. Taking these measurements helps us decide how long we can comfortably keep collecting scientific data.
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? 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.
Kepler updates to come
We will continue to provide updates on the science and the spacecraft, which has yet to show warning signs. Many NASA missions must set a course for a clear-cut ending and reserve enough fuel for one last maneuver.
For example, Earth-orbiting spacecraft must avoid collisions with other satellites or an uncontrolled fall to the ground, while planetary missions like Cassini have to reserve fuel to avoid contamination of a potentially life-bearing environment.
In Cassini’s case, NASA sent the spacecraft into Saturn rather than risk it falling into one of the planet’s moons.
Deep space missions like Kepler are nowhere near Earth or sensitive environments, which means we can afford to squeeze every last drop of data from the spacecraft — and ultimately that means bringing home even more data for science.
Who knows what surprises about our universe will be in that final downlink to Earth?
While Kepler continues to bring us exciting data as it draws close the finish line, the Transiting Exoplanet Survey Satellite (TESS) will be launching on April 16 from Cape Canaveral, Florida.
TESS will search nearly the entire sky for planets outside our solar system, focusing on the brightest stars less than 300 light-years away, and adding to Kepler’s treasure trove of planet discoveries.
Provided by: NASA[Note: Materials may be edited for content and length.]
Notanee Bourassa knew that the purple lights he was seeing in the night sky were not normal. Bourassa, an I.T. technician in Regina, Canada, trekked outside of his home on July 25, 2016, around midnight with his two younger children to show them a beautiful moving light display in the sky — an aurora borealis.
He often sky gazes until the early hours of the morning to photograph the aurora with his Nikon camera, but this was his first expedition with his children.
When a thin purple ribbon of light appeared and started glowing, Bourassa immediately snapped pictures until the light particles disappeared 20 minutes later. Having watched the northern lights for almost 30 years since he was a teenager, he knew this wasn’t an aurora. It was something else.
From 2015 to 2016, citizen scientists — people like Bourassa who are excited about a science field, but don’t necessarily have a formal educational background — shared 30 reports of these mysterious lights in online forums and with a team of scientists that run a project called Aurorasaurus.
The citizen science project, funded by NASA and the National Science Foundation, tracks the aurora borealis through user-submitted reports and tweets.
The Aurorasaurus team, led by Liz MacDonald, a space scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, conferred to determine the identity of this mysterious phenomenon.
Purple lights phenomenon named STEVE
MacDonald and her colleague Eric Donovan at the University of Calgary in Canada talked with the main contributors of these images, amateur photographers in a Facebook group called Alberta Aurora Chasers, which included Bourassa and lead administrator Chris Ratzlaff. Ratzlaff gave the phenomenon a fun, new name, STEVE, and it stuck.
But people still didn’t know what it was.
Scientists’ understanding of STEVE changed that night Bourassa snapped his pictures. Bourassa wasn’t the only one observing STEVE. Ground-based cameras called all-sky cameras, run by the University of Calgary and the University of California, Berkeley, took pictures of large areas of the sky and captured STEVE and the auroral display far to the north.
From space, ESA’s (the European Space Agency) Swarm satellite just happened to be passing over the exact area at the same time and documented STEVE. For the first time, scientists had ground and satellite views of STEVE.
Scientists have now learned, despite its ordinary name, that STEVE may be an extraordinary puzzle piece in painting a better picture of how Earth’s magnetic fields function and interact with charged particles in space. The findings are published in a study released today in Science Advances.
THIS IS A LIGHT DISPLAY THAT WE CAN OBSERVE OVER THOUSANDS OF KILOMETERS FROM THE GROUND,” SAID MACDONALD. “IT CORRESPONDS TO SOMETHING HAPPENING WAY OUT IN SPACE. GATHERING MORE DATA POINTS ON STEVE WILL HELP US UNDERSTAND MORE ABOUT ITS BEHAVIOR AND ITS INFLUENCE ON SPACE WEATHER.
The study highlights one key quality of STEVE: STEVE is not a normal aurora. Auroras occur globally in an oval shape, last hours, and appear primarily in greens, blues, and reds.
Citizen science reports showed STEVE is purple with a green picket fence structure that waves. It is a line with a beginning and end. People have observed Steve for 20 minutes to 1 hour before it disappears.
If anything, auroras and STEVE are like different flavors of ice cream, said MacDonald. They are both created in generally the same way: Charged particles from the Sun interact with Earth’s magnetic field lines.
Specifically, the aurora and STEVE creation process starts with the Sun sending a surge of its charged particles toward Earth. This surge applies pressure on Earth’s magnetic field, which sends the Sun’s charged particles to the far side of Earth, where it is nighttime.
On this far night side of Earth, Earth’s magnet field forms a distinctive tail. When the tail stretches and elongates, it forces oppositely directed magnetic fields close together that join in an explosive process called magnetic reconnection.
Like a stretched rubber band suddenly breaking, these magnetic field lines then snap back toward Earth, carrying charged particles along for the ride. These charged particles slam into the upper atmosphere, causing it to glow and generating the light we see as the aurora — and now possibly STEVE.
The uniqueness of STEVE is in the details. While STEVE goes through the same large-scale creation process as an aurora, it travels along different magnetic field lines than the aurora. All-sky cameras showed that STEVE appears at much lower latitudes.
That means the charged particles that create STEVE connect to magnetic field lines that are closer to Earth’s equator, hence why STEVE is often seen in southern Canada.
Perhaps the biggest surprise about STEVE appeared in the satellite data. The data showed that STEVE comprises a fast-moving stream of extremely hot particles called a sub auroral ion drift, or SAID. Scientists have studied SAIDs since the 1970s, but never knew there was an accompanying visual effect.
The Swarm satellite recorded information on the charged particles’ speeds and temperatures, but does not have an imager aboard. Donovan, a co-author of the study, said:
People have studied a lot of SAIDs, but we never knew it had a visible light. Now our cameras are sensitive enough to pick it up and people’s eyes and intellect were critical in noticing its importance.
Donovan led the all-sky camera network and his Calgary colleagues lead the electric field instruments on the Swarm satellite. STEVEis an important discovery because of its location in the sub auroral zone, an area of lower latitude than where most auroras appear that is not well researched.
For one, with this discovery, scientists now know there are unknown chemical processes taking place in the sub auroral zone that can lead to this light emission.
Second, STEVE consistently appears in the presence of auroras, which usually occur at a higher latitude area called the auroral zone. That means there is something happening in near-Earth space that leads to both an aurora and STEVE.
STEVE might be the only visual clue that exists to show a chemical or physical connection between the higher latitude auroral zone and lower latitude sub auroral zone, said MacDonald:
“STEVE can help us understand how the chemical and physical processes in Earth’s upper atmosphere can sometimes have local noticeable effects in lower parts of Earth’s atmosphere. This provides good insight on how Earth’s system works as a whole.”
The team can learn a lot about STEVE with additional ground and satellite reports, but recording STEVE from the ground and space simultaneously is a rare occurrence.
Each Swarm satellite orbits Earth every 90 minutes and STEVE only lasts up to an hour in a specific area. If the satellite misses STEVE as it circles Earth, STEVE will probably be gone by the time that same satellite crosses the spot again.
In the end, capturing STEVE becomes a game of perseverance and probability.
“It is my hope that with our timely reporting of sightings, researchers can study the data so we can together unravel the mystery of STEVE’s origin, creation, physics, and sporadic nature,” said Bourassa. “This is exciting because the more I learn about it, the more questions I have.”
As for the name “STEVE” given by the citizen scientists? The team is keeping it as an homage to its initial name and discoverers. But now it is STEVE (Strong Thermal Emission Velocity Enhancement).
If you live in an area where you may see STEVE or an aurora, submit your pictures and reports to Aurorasaurus through aurorasaurus.org or the free iOS and Android mobile apps. To learn how to spot STEVE, click here.