How NASA recovered the planet-hunting Kepler probe from emergency mode?

The planet-hunting Kepler spacecraft, which had gone into emergency mode about 75 million miles from Earth, has successfully been recovered by the NASA scientists. The spacecraft, that hunts for Earth-like planets orbiting other stars, reached a stable state with the communication antenna pointed toward Earth, enabling telemetry and historical event data to be downloaded to the ground. During a scheduled contact on April 7, mission operations engineers discovered that the Kepler spacecraft was in Emergency Mode (EM) - the lowest operational mode which is fuel intensive.

The spacecraft is now operating in its lowest fuel-burn mode, NASA officials said. The mission has cancelled the spacecraft emergency, returning the Deep Space Network ground communications to normal scheduling, they said. Once data is on the ground, the team will thoroughly assess all on board systems to ensure the spacecraft is healthy enough to return to science mode and begin the K2 mission’s microlensing observing campaign, called Campaign 9.

Earth-based observatories participating in Campaign 9 will continue to make observations as Kepler’s health check continues. The K2 observing opportunity for Campaign 9 will end on July 1, when the galactic centre is no longer in view from the vantage point of the spacecraft. After data was downlinked to the ground, the spacecraft was placed in what is termed Point Rest State (PRS).

While in PRS, the spacecraft antenna is pointed towards Earth and it operates in a fuel-efficient mode, with the reaction wheels at rest. The Emergency Mode began about 14 hours before the planned manoeuvre to orient the spacecraft towards the centre of the Milky Way for Campaign 9.

The team has therefore ruled out the manoeuvre and the reaction wheels as possible causes of the EM event. An investigation into what caused the event will be pursued in parallel, with a priority on returning the spacecraft to science operations, NASA said.

The anomalous EM event is the first that the Kepler spacecraft has encountered during its seven years in space. “It was the quick response and determination of the engineers throughout the weekend that led to the recovery,” said Charlie Sobeck, Kepler and K2 mission manager at NASA’s Ames Research Centre.

Kepler completed its prime mission in 2012, detecting nearly 5,000 exoplanets, of which, more than 1,000 have been confirmed. In 2014, Kepler began a new mission called K2. In this extended mission, K2 continues the search for exoplanets while introducing new research opportunities to study young stars, supernovae and many other astronomical objects.