(CNN)Here's a look at what you need to know about the National Exercise Program, the US system for emergency preparation drills. These exercises are mandated by Congress to test and strengthen federal, state, and local government ability to respond to potential catastrophic events.
TOPOFF - is short for TOP OFFICIALS. Governors, mayors, city managers, top federal and state officials, and others play active roles.
May 20, 2000 - The first TOPOFF drill is mandated by Congress in 1998. It lasts ten days and cost $3.5 million.
2009 - It is announced that TOPOFF exercises will continue under a new name, Tier 1 National Level Exercise (NLE). These are conducted annually in accordance with the National Exercise Program (NEP). The exercises are still designed to provide all levels of government an opportunity to prepare for crises ranging from terrorism to natural disasters.
July 27-31, 2009 - Takes place at federal headquarters facilities in the Washington DC area, and in federal, regional, state, tribal, local and private sector facilities in Arkansas, Louisiana, New Mexico, Oklahoma, Texas and California. Additionally, Australia, Canada, Mexico and the United Kingdom participate.
May 17-18, 2010 - NLE 2010 engages federal, state and local partners in a series of events to demonstrate and assess federal emergency preparedness capabilities pertaining to a simulated terrorist attack involving an improvised nuclear device. As part of NLE 2010, all federal agencies within the NCR participate in Eagle Horizon 2010, an exercise that requires federal departments and agencies to demonstrate their capability to perform mission essential functions in the event of a major emergency.
May 2011 - Takes place at command posts, emergency operation centers and other locations, including federal facilities in the Washington, DC, area and federal, regional, state, tribal, local and private sector facilities in the eight member states of the Central United States Earthquake Consortium (CUSEC). The eight member states are: Alabama, Kentucky, Mississippi, Tennessee, Illinois, Indiana, Arkansas and Missouri.
NLE 2012 is the first NLE that tests the existing plans and procedures to address the challenges in anticipating and responding to cyber incidents that have "virtual and real-world implications."