DOD defines an unmanned aircraft as a powered aerial vehicle that does not carry a human operator, uses aerodynamic forces to provide vehicle lift, can fly autonomously or be piloted remotely, can be expendable or recoverable, and can carry a lethal or nonlethal payload. Generally, unmanned aircraft systems consist of the aerial vehicle; a flight control station; information and retrieval or processing stations; and, sometimes, wheeled land vehicles that carry launch and recovery platforms. According to DOD, many elements are needed for the use of UAS, including a systems architecture that allows data to be moved, adequate spectrum and bandwidth for communication, airspace management and deconfliction, common data standards and formats to allow sharing and data fusion, common operating systems, and system interoperability. Potential missions considered appropriate for unmanned aircraft systems have expanded from the original focus on the intelligence, surveillance, and reconnaissance mission areas to the area of limited tactical strike capabilities, with projected plans for persistent ground attack, electronic warfare, and suppression of enemy air defenses. As shown in table 1, DOD had more than 3,000 unmanned aircraft as of February 2006, compared to fewer than 50 unmanned aircraft in 2000. As of January 2006, more than 2000 of these aircraft were supporting ongoing operations in Iraq. Over 88 percent of the unmanned aircraft currently in inventory are small UAS, those launched by hand or by bungee. As a point of comparison, no small unmanned aircraft were in inventory in 2000. Similarly, UAS flight hours have also increased. For example, as shown in figure 1 below, flight hours have increased from about 5,000 hours in 1996 to 109,000 hours in 2005. As the numbers of unmanned aircraft and flight hours have increased, so has UAS funding. Total UAS funding shows an increase from about $363 million in fiscal year 2001 to about $2.06 billion in fiscal year 2006. In addition, the fiscal year 2007 President’s Budget projects funding will grow to about $3.02 billion in fiscal year 2011. These figures do not include supplemental funding. DOD has requested approximately $208 million for UAS in its fiscal year 2006 supplemental request. In December 2002, DOD created the 2002-2027 Unmanned Aerial Vehicles Roadmap, which was designed to guide U.S. military planning for UAS development and describe current programs, identify potential missions for UAS, and provide guidance on developing emerging technologies. In August 2005, DOD issued an updated version of the roadmap covering the period 2005-2030. Like its predecessor, the 2005 roadmap contains broad goals for unmanned systems that support the department’s larger goals of fielding transformational capabilities, establishing joint standards, and controlling costs. Furthermore, DOD’s 2006 QDR published in February 2006 validates the importance of unmanned systems. Overall, the QDR provides direction for accelerating the department’s transformation to focus more on combatant commanders’ needs and to develop portfolios of joint capabilities. In particular, the QDR report highlighted the department’s plans to expand investment in unmanned systems and their use in military operations. For example, it states DOD’s intent to nearly double unmanned aircraft coverage by accelerating the acquisition of the Predator and Global Hawk systems. It also plans to restructure the Joint Unmanned Combat Air Systems program and develop an unmanned longer-range carrier-based aircraft to increase naval reach and persistence. Further, the QDR plans to develop a new land-based, penetrating long-range strike capability by 2018 and sets a goal that about 45 percent of the future long-range strike force be unmanned. Lastly, the 2006 QDR directs the Air Force to establish an unmanned aerial vehicle squadron under the U.S. Special Operations Command. DOD has experienced a high level of mission success using UAS in combat operations, but faces some operational challenges that could hamper joint operations. We previously identified interoperability and limited bandwidth as challenges and, according to our preliminary work, as the number of unmanned systems increases, airspace integration is becoming a growing challenge. While DOD has taken initial steps to address these challenges, limited progress has been made and the effectiveness of these actions cannot be adequately assessed until they are fully implemented. DOD has achieved significant operational successes in combat operations from its use of a variety of unmanned aircraft and their sensor, communications, and armaments payloads, thereby increasing the demand for and use of UAS. In operations in Iraq and Afghanistan, U.S. forces have used a variety of UAS, such as the Predator, Raven, and Shadow, in integral roles on intelligence, surveillance, reconnaissance, and offensive strike joint or service-specific missions. For example, a Predator UAS provided video to a U.S. military element which provided situational awareness that contributed to the success of a mission that resulted in the capture of an al Qaida operational commander. Similarly, the Army used its Shadow UAS to identify an improvised explosive device and guide U.S. forces to the location of the enemy forces, enabling the capture of the enemy forces and safe detonation of the improvised explosive device. Additionally, small UAS such as the Raven have been instrumental in enabling troops to find, locate, and destroy numerous targets. For example, a Raven was used to identify a suspicious vehicle in the courtyard of a residence, which facilitated the discovery of a large weapons and ammunition cache when soldiers conducting the ground combat operations confirmed the vehicle contained explosives. As a result of successes such as these, the demand for and use of UAS are continuing to grow. Notwithstanding these operational successes, DOD continues to face challenges in effectively integrating unmanned systems into joint combat operations, and progress in addressing these challenges has been limited. Key challenges identified in ongoing operations in Iraq and Afghanistan relate to interoperability, the availability of communications bandwidth, and managing UAS and manned systems in the same airspace. First, while numerous UAS are being called on to conduct important missions in recent operations, interoperability remains a challenge. For example, as we reported in December 2005, some unmanned aircraft sensor and communications payloads and ground stations cannot easily exchange data because they were not designed to interoperable communications standards, even within a single service in certain circumstances. When communication systems are incompatible, operating forces may be required to operate their own UAS to accomplish a mission, rather than using UAS that are already operating in the same area, thus increasing the numbers of systems being operated. To permit the sharing of tactical intelligence obtained by unmanned aircraft sensors, the services or combatant commands have developed certain technical patches that permit compatibility but slow data transmission. DOD guidance requires interoperability and DOD’s 2005 roadmap identifies it as a key goal. In the absence of specific standards, the services have tended to initiate separate development programs, specifically tailored to service specific requirements. Officials from U.S. Central Command have also emphasized the need for improved interoperability and standards. For example, the commander of U.S. Central Command recently testified that while UAS have transformed the battlespace and demand for their capabilities is significant, there is a need to develop an integrated architecture of many sensors to support operational units. He further stated that experiences to date highlight the importance of an established interoperability standard for all intelligence systems that can function in a joint and combined environment. Second, communications bandwidth continues to represent a major challenge for UAS. Unmanned aircraft and their sensor, armaments, and communications payloads depend on reliable access to communications bandwidth. Bandwidth is needed to support systems that control the flight of certain unmanned aircraft, to transmit data collected by payload sensors, and to interface with air traffic control centers. Because UAS and other weapons or communications systems, including manned aircraft, often operate on the same frequency, certain frequencies can become congested and interference can occur. Such capacity constraints may limit the number of UAS and other systems that can be effectively operated simultaneously and the amount of available data that can be transmitted. Despite having the capability to operate multiple UAS simultaneously, DOD’s roadmap states that the limited number of frequencies available often restricts the number of unmanned aircraft airborne at any point in time to one. As we reported in December 2005, the problem with constrained bandwidth cannot be easily overcome without potentially costly modifications to existing systems because DOD has not established standards requiring unmanned aircraft or sensor payloads to be reprogrammable from one band to another. To address these challenges, we recommended that DOD develop standards, including overall UAS interoperability standards and standards that will allow for future UAS to be reprogrammable to different frequencies. We are also aware that, in the Fiscal Year 2006 National Defense Authorization Act, Congress required that the Secretary of Defense take such steps to ensure that all service tactical unmanned aerial vehicles are equipped and configured so that the data link used is the Tactical Common Data Link and those vehicles use data formats consistent with the architectural standard for tactical UAS. We understand that some of the military services have provided a report to Congress to identify which systems are currently in compliance with the Tactical Data Link requirement. According to DOD, use of this link is expected to reduce the amount of bandwidth used and allow the UAS to utilize a broader band of frequencies; however, it will not totally alleviate the problem because it is too heavy to use on small UAS and may result in shifting the frequency congestion to other bands. Third, our preliminary work indicates that effectively integrating UAS into the airspace is becoming a growing challenge in ongoing operations. With the growing numbers and increasing use of UAS of various types and sizes to support combat missions, particularly in Iraq, coordination, integration, and deconfliction of airspace among UAS and manned systems are becoming more complex.