Here are six spacecrafts rescued after their missions could have terminated.
1. Wake up, Philae!
Credit: ESA
This past week, the Philae spacecraft “spoke up” on the surface of Comet 67P/Churyumov–Gerasimenko after about seven months in hibernation.
While scientists aren't sure how healthy the plucky, solar-powered probe is after its sleep and wild landing into a shadowy area - it drifted off course for two hours after touching down in November - the fact that it is communicating is huge news for the Rosetta mission.
Philae isn't the only spacecraft that was “rescued” over the years. Here are a few spectacular examples of probes that could have lost their mission but for the ingenuity of engineers on Earth.
2. Kepler: Still in the Exoplanet-Hunting Business
Credit: NASA/Ames/JPL-Caltech
Kepler is a planet-hunting satellite NASA launched in 2009. It has found more than 1,000 new worlds in the constellation Cygnus - and many more candidate possibilities. But in 2012, one of its four reaction wheels stopped working. Because Kepler needed a minimum of three to point properly, its primary mission ended in 2013 when a second reaction wheel failed.
Since the rest of the spacecraft was in good shape, NASA decided to attempt a new mission called K2. To keep Kepler in place, the spacecraft uses its remaining reaction wheels and also takes advantage of the solar wind - the constant stream of particles flowing from the sun. While the pointing isn't as accurate and Kepler has to change positions a few times a year, the spacecraft is still seeking planets to this day.
3. Bringing ISEE-3 Back From Retirement
Credit: NASA
NASA launched the International Sun-Earth Explorer 3 (ISEE-3) spacecraft in 1978 and put the machine through several missions before its retirement in 1997. After ISEE-3 studied the sun and did comet science, NASA put the spacecraft into hibernation and ceased communications.
In 2014, a team co-led by space entrepreneur Dennis Wingo and NASA Watch's Keith Cowing tried rescuing and moving the probe for new science. They crowd-funded tens of thousands of dollars from space fans, enlisted technical support from engineers and some of the ISEE-3 team, and got NASA's approval.
The team took control with the formerly sleeping spacecraft that May. While ISEE-3 had too little fuel pressurant to do the manoeuvres for Wingo's and Cowing's long-term vision, some of the instruments still worked and sent back data for a few months.
4. Galileo's Glitched High-Gain Antenna
Credit: NASA/JPL-Caltech
Galileo's mission to Jupiter appeared to be greatly limited just one year after its launch in 1989. After a flyby of Earth, engineers tried to deploy its high-gain antenna and discovered it would not unfurl fully - even after thousands of attempts. A lack of lubricant was blamed for the situation.
Forced onto a backup antenna with less communication capacity, there were fears Galileo would not collect as many images as planned. NASA, however, upgraded Galileo and the Deep Space Network of satellite dishes on Earth to send and receive more information, which worked. Galileo sent thousands of images and data about the solar system's largest planet back to Earth before the mission's demise in 2003.
5. Solar Storm Problems for Anik E2
Artist's conception of a successor satellite to Anik E2, called Anik F2, in orbit around the Earth.
The Canadian telecommunications satellite got hit by a solar storm in January 1994 that affected its momentum wheels - making it unable to consistently point at Earth as it was designed to do. Its company, Telesat, quickly shifted TV stations, wires and other services to twin satellite Anik E1. But Telesat was out of satellite capacity unless it could rescue Anik E2.
Telesat put together an emergency team and spent months creating an innovative ground fix to keep Anik E2 pointed in the right direction. They took readouts of the satellite's position. Then, a computer on the ground would inform the satellite if it needed to expend fuel to correct itself. Fix in place, Anik E2 returned to normal service late that June.
6. FUSE Reaction Wheels
Credit: NASA
Launched in 1999 to do ultraviolet observations of the universe, NASA's Far Ultraviolet Spectroscopic Explorer (FUSE) hit a major crisis just two years later. Two of its four reaction wheels failed - the spacecraft needed a minimum of three to point correctly - and the mission was close to dead.
Engineers, however, didn't give up. They created a new pointing system that took advantage of electromagnets on board the satellite, which were used to “push and pull on the Earth's magnetic field,” NASA wrote at the time. The system worked so well that FUSE was able to continue its science work for years - even after another reaction wheel failed in 2004. It was decommissioned in 2007 after the last wheel died.
Top image: Artist’s concept of the Philae lander at work on Comet 67P/Churyumov-Gerasimenko. Credit: European Space Agency.
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