It was action stations for the Kepler mission team last Thursday when, during a scheduled contact, it was discovered the Kepler spacecraft was in Emergency Mode (EM). NASA subsequently declared a spacecraft emergency, giving engineers priority access to its Deep Space Network ground-based communications system. The spacecraft was successfully recovered from EM on Sunday morning and is now in a stable state, however, it is still unclear what triggered the craft's brief departure from regular operations.
EM is Kepler's lowest operational mode, and is fuel intensive. With Kepler nearly 75 million miles (120.7 million km) from Earth and communications taking a 13-minutes round trip, troubleshooting was a slow process. On Sunday, engineers recovered Kepler and placed the craft in a stable low fuel burn mode, which points the craft's antenna towards Earth for data download. Once the data has been received, it will be analyzed and the health of the craft will be determined, a process that will continue through the week.
The discovery Kepler was in EM came just before Kepler was due to begin maneuvers to face the center of the Milky Way for the continuation of its K2 planet-hunting mission that began in 2013. This new leg, called Campaign 9, will involve microlensing observations – a process that detects exoplanets' gravitational influence on the light received through Kepler's sensors – which will allow scientists to locate and map free-floating exoplanets that do not orbit host stars.
This is the first time Kepler has entered Emergency Mode in its seven years of operation, over which it has identified over 1,000 exoplanets. The craft successfully completed Campaign 8 on March 23, and since then had remained in Point Rest State (PRS), a fuel-efficient data-transfer mode.
NASA is working to return Kepler to full operation, ahead of the observing window for Campaign 9 closing on July 1.