Reaction wheel

After Kepler completed its primary mission, the second of four reaction wheels on Kepler ceased to work properly, preventing Kepler from continuing to point with precision.

Kepler's preliminary mission was to look at a batch of 150,000 stars, but the mission ended in 2013 due to a problem in the spacecraft's orientation-assisting reaction wheels. When the agency found a way to stabilize its condition, the second phase of the mission, called K2, began.

Remedia, "Experimental and numerical investigation of coupled microvibration dynamics for satellite reaction wheels," Journal of Sound and Vibration, vol.

The failure of one or more reaction wheels can cause a satellite to lose its ability to maintain position and thus potentially cause a mission failure.

However, they have ruled out both the maneuvers and the craft's orientation-adjusting reaction wheels as the cause.

On January 10, engineers sent a command to spin Philae's reaction wheels, which helped stabilize the lander during its descent.

Cage Instability of XMM-Newton's Reaction Wheels Discovered During the Development of an Early Degradation Warning System.

Astronomers and engineers worked day and night to devise an ingenious way to repurpose the spacecraft, that was written off after the failure of its reaction wheels cut its mission short last year.

Kepler was launched in March 2009, and last year lost the use of two of its reaction wheels that helped keep it precisely oriented.

This also gave engineers the time to find workarounds for two glitches that threatened the mission: a problem with two of the four reaction wheels used to turn the spacecraft, and a small helium leak that could affect the thrusters vital for its final maneuvers.

The observatory lost the second of its four reaction wheels in May, meaning it can no longer hold completely steady as it looks towards the stars.