of Defense desired to create missile defense systems along the west coast of the United States, namely in both California and Alaska.There are still technological hurdles to an effective defense against ballistic missile attack. The United States National Ballistic Missile Defense System has come under scrutiny about its technological feasibility. Intercepting midcourse (rather than launch or reentry stage) ballistic missiles traveling at several miles per second with a "kinetic kill vehicle" has been characterized as trying to hit a bullet with a bullet. Despite this difficulty, there have been several successful test intercepts and the system was made operational in 2006, while tests and system upgrades continue. Moreover, the warheads or payloads of ballistic missiles can be concealed by a number of different types of decoys. Sensors that track and target warheads aboard the kinetic kill vehicle may have trouble distinguishing the "real" warhead from the decoys, but several tests that have included decoys were successful. Nira Schwartz's and Theodore Postol's criticisms about the technical feasibility of these sensors have led to a continuing investigation of research misconduct and fraud at the Massachusetts Institute of Technology. In February 2007, the U.S. missile defense system consisted of 13 ground-based interceptors (GBIs) at Fort Greely, Alaska, plus two interceptors at Vandenberg Air Force Base, California. The U.S. planned to have 21 interceptor missiles by the end of 2007. The system was initially called National Missile Defense (NMD), but in 2003 the ground-based component was renamed Ground-Based Midcourse Defense (GMD). As of 2014, the Missile Defense Agency had 30 operational GBIs, with a total 44 GBIs in the missile fields in 2018. In 2021 an additional 20 GBIs of 64 total were planned, but not yet fielded. They are tasked with meeting more complex threats than those met by the EKV. Defending against cruise missiles is similar to defending against hostile, low-flying manned aircraft. As with aircraft defense, countermeasures such as chaff, flares, and low altitude can complicate targeting and missile interception. High-flying radar aircraft such as AWACS can often identify low flying threats by using doppler radar. Another possible method is using specialized satellites to track these targets. By coupling a target's kinetic inputs with infrared and radar signatures it may be possible to overcome the countermeasures. In March 2008, the U.S. Congress convened hearings to re-examine the status of missile defense in U.S. military strategy. Upon taking office, President Obama directed