In March and April 2013, several weeks after the Chelyabinsk meteor explosion injured some 1,500 people, the U.S. Congress held hearings for "...the Risks, Impacts and Solutions for Space Threats". They received testimony from B612 head Ed Lu (see video at right), as well as Dr. Donald K. Yeomans, head of NASA's NEO Program Office, Dr. Michael A'Hearn of the University of Maryland and co-chair of a 2009 U.S. National Research Council study on asteroid threats, plus others. The difficulty of quickly intercepting an imminent asteroid threat to Earth was made apparent during the testimony: