The Sentinel Mission was announced in 2012 for the purposes of mapping the trajectories of asteroids that may pose a future danger to humanity — giving us the time we need to deflect them. The Sentinel design is for an infrared space telescope that will orbit the Sun interior to the orbit of Earth. From this vantage point, Sentinel can provide an ideal counterpart to Earth based observatories such as the Large Synoptic Survey Telescope which will also track asteroids.
Together, Sentinel and LSST form an ideal combination for tracking asteroids that will eventually hit Earth. After just a decade of operation, they can find nearly 90% of impacting asteroids larger than the one that struck Tunguska, and provide decades of advance warning before impact.