They throw out the rule book and start pulling rabbits out of a hat.
Amazingly, their approach is an astounding success - the spacecraft gets enough power to transmit streams of critical data to the science community. The engineers become heroes and receive accolades from NASA. Then the team does it again. Pretty soon the group gets a reputation for this kind of last-ditch rescue.
BUSINESS AS UNUSUAL
For Ball engineers, the CloudSat and Kepler/K2 missions are just two examples of how radical ideas can turn a lost mission around, or extend an already successful one.
NASA’s CloudSat spacecraft was in deep trouble in April 2011 when Ball Aerospace and Jet Propulsion Laboratory engineers huddled to find a way to save the mission. The spacecraft was coming up to its fifth year on orbit, and had outlived its design life by three years. Batteries were showing their age. The spacecraft was operating on the power equivalent of an AA battery, crippling instruments from gathering cloud data in high demand from scientists and climatologists.
Was there any way to save the spacecraft?
LOW POWER TUMBLE
“We had a team of about 10 people working long hours on a solution,” said John Jonaitis, Ball CloudSat program manager. “It was stressful at times, but we worked closely with JPL and learned a lot as a team about the spacecraft’s batteries.”
Spacecraft Systems Engineer Brian Pieper figured out a way to operate CloudSat’s flight system on low power. The CloudSat program manager at JPL, Deb Vane, was amazed. “At times I felt like he was pulling rabbits out of a hat,” she recalled. “He always had clever ideas of what to do next, and he never gave up.”
The challenge was to keep the spacecraft tumbling so that the solar arrays always faced the sun. Brian had some help with that, provided by his Ball colleague Ian Gravseth, Attitude Design Control Systems engineer. Gravseth spent a week mulling it over and knew that he had to throw out the rule book. His solution to getting the spacecraft back into orbit was to use attitude control in a different way than ever before. He came up with something virtually never done – turn the spacecraft off, leaving only the GPS, science data recorder and computer on.
THE DO-OP SPIN
The result? A new Daylight Only-Operation (DO-Op) mode. In DO-Op mode, CloudSat autonomously wakes itself up, regains attitude control, and turns on the Cloud Profiling Radar (CPR) when the spacecraft enters the sunlit portion of its orbit. Just before entering eclipse, CloudSat spins itself up and enters a low-power hibernation state. Spinning while in eclipse allows the spacecraft to stabilize its attitude so that when it wakes up and turns itself on, the solar arrays are facing the sun.
In May 2012, the team maneuvered the spacecraft back into its position in NASA’s A-Train constellation of six Earth-observing satellites. While in DO-Op mode, the CPR instrument routinely collects 54+ minutes of science data during its roughly 98-minute orbit.
AND THE AWARD GOES TO…..
“This effort took enormous creativity, a strong stomach, and a really, really good sense of humor,” said Marda Barthuli, Ball systems staff consultant whose expertise included executing engineering processes and configuration management for the CloudSat mission.
Barthuli is one of three Ball Aerospace CloudSat team members who were recognized by NASA for their work. Engineers Pieper and Gravseth both received NASA’s Exceptional Public Achievement Medal. Barthuli won the NASA Exceptional Public Service Medal for her outstanding contributions to the CloudSat mission, becoming the first woman at Ball Aerospace to receive the honor.
MORE RABBITS – KEPLER
After four years on orbit, Kepler had completed its original mission and was extending its discoveries, continuing to revolutionize the world’s understanding of exoplanets. In May 2013, the aging spacecraft’s luck ran out when a second reaction wheel failed. Teams from Ball and NASA Ames Research Center scrambled to get the spacecraft in a safe configuration, minimize fuel use and buy time to figure out how to keep the mission going.
Reaction wheels are part of Kepler’s guidance system. They must reliably spin to counter the force of the solar wind. With two reaction wheels out of commission, the spacecraft would drift and return blurry images. Another concern was that the spacecraft could drift so far that sunlight would shine inside the telescope and deform the interior of its barrel. After the team stabilized the spacecraft, the next question was “how do we keep it pointed?"
Ball engineers built the Kepler photometer and spacecraft and used their in-depth knowledge and understanding of the system to devise a way to point Kepler with only two of four reaction wheels operating so that the spacecraft could continue delivering science data.
POINTING THE WAY
This time it was Ball staff consultant Doug Weimer who pulled a rabbit out of the hat. He came up with the idea to use the pressure of the sun to stabilize the spacecraft. The trick was to tip Kepler over on its side so the solar photon pressure would push evenly across Kepler’s solar panels, preventing the spacecraft from rolling. This would work fine; the drawback was that it would limit the telescope to pointing in the plane of its own orbit around the sun and observing fields sequentially. About every 80 days, there would be a new field of view.
NASA polled the astronomy community for ideas on how they might use data from this new K2 mission concept and discovered a few common themes: explore smaller exoplanets around smaller stars; look at black holes at the center of galaxies; and scan for supernovae.
Now the challenge was to move the concept from the blackboard to actual use on a spacecraft that was 40 million miles from Earth. Since the new concept for operation was so radically different from Kepler’s original mission, Ball engineers had to reexamine every aspect of spacecraft operations and then demonstrate the new mission would provide world class science. And they had to do it quickly to prevent being turned off when the current funding ran out.
The Ball/Ames team submitted a proposal to NASA in January, 2014 and it was accepted in May, 2014. The program was funded for $7 million over 2 years. Campaign 1, the first science observation began May 30, 2014. K2 has already continued Kepler’s legacy of discovery by spotting three exoplanets around a star in the constellation Leo. These planets are much closer than those found by the prime Kepler mission and provide an enhanced opportunity for further characterization, which was one of the main reasons for proposing K2.
The K2 mission has discovered more than 700 new worlds orbiting 305 stars, revealing multiple planet systems much like our own solar system. K2 also discovered the first Earth-size planet in the habitable zone - Kepler 186f. This confirms that planets the size of Earth exist in the habitable zone of stars other than our sun.
“The Ball team invented the K2 concept, tested it, and is now operating it,” said Kipp Larson, Ball Kepler Mission Operations Manager. “We were able to go from the initial K2 idea to a flight demonstration of planet detection in four months.”
Kepler is one of the few programs where Ball is in charge of the mission operations as opposed to being in a supporting role. A relatively small team has done some intensive operations. Kepler’s mission operations team has successfully pioneered a low cost, highly reliable model for NASA spacecraft operations in spite of a different approach.
“Typically NASA missions have a team of 25 people flying a spacecraft. On Kepler we’ve been able to do the same job with 15 people, still maintaining the same high safety standards that NASA expects,” says John Troeltzsch, Kepler program manager.
In addition to pulling another rabbit out of a hat.