User:Sharath780/sandbox

This is my sandbox page. I am going to draft an article on Sense and Avoid (SAA) technology.

Unmanned Aircraft Systems (UAS) face limitations on their utilization in civil airspace because they do not have the ability to Sense and Avoid (SAA) other air traffic. Detect, Sense and Avoid (DSA) refers to the technology that can address this issue and enable the safe operation of a UAV in the National Air Space (NAS). It involves the use of sensors on board the aircraft or off board (air or ground) to help a UAV detect and avoid other aircraft. Currently, the UAS operator performs the avoidance manoeuvres in accordance with the regulations found in 14 Code of Federal Regulation (CFR) Part 91 of FAA.

Significance of the technology
The use of Unmanned Air Systems (UAS) in both civilian and military domains is increasing rapidly. The applications include border protection, pipeline surveys, weather forecasting, chemical, biological, and radiological detection, national emergency management, wildfire detection, search and rescue, aerial photography and mapping, and in the future, cargo transport and so on. The UAS requires unrestricted access to National Air Space to carry out the missions effectively and efficiently. Currently, Unmanned Aircraft Systems (UAS) face limitations on their utilization in civil airspace because they do not have the ability to 'See and Avoid' other air traffic. This is one of the main differences between UAS and manned aviation is the ability to see-and-avoid other air traffic. The regulation established by Title 14 Code of Federal Regulations (CFR) Part 91: General Operating and Flight Rules section 113 is one of the biggest factors that currently prevent UAS from entering the NAS. The rule specifically states, “regardless of whether an operation is conducted under instrument flight rules or visual flight rules, vigilance shall be maintained by each person operating an aircraft so as to see and avoid other aircraft.

Since UAS are by design unmanned, they cannot currently fulfil the 'See and Avoid' requirement and therefore must attempt to comply by some other means. To reduce the risk that UAS may pose to other air traffic and also to property and persons on the ground, the Federal Aviation Administration (FAA) has rules for UAS to operate in the National Airspace System (NAS). As outlined in FAA Special Order 7610.42 on Special Military Operations, military UAS need to obtain a Certificate of Waiver or Authorization (COA) in order to fly in the NAS. Civil UAS need to go through a complicated airworthiness certification process in order to conduct flight operations in the NAS.

The COA process can take up to 60 days for approval and does not grant unfettered access to the NAS. In some cases, the DoD can forecast requests to allow for the 60-day approval process, but it may not be practical or feasible in all circumstances. Until an effective SAA system is demonstrated, UAS operations within the NAS will be governed by the above rules. So, the FAA endorsed the composition of a special committee, called Special Committee 203 (SC-203), put together by the Radio Technical Commission for Aeronautics (RTCA) comprised of members from the FAA, DoD, MITRE, and other Academia. Their goal is to establish “a clearly defined set of Sense and Avoid functions, Levels of Safety, and methods for assessing safety" to ensure that the UAS can meet a equivalent level of safety (ELOS) as that of a manned aircraft.

In the United States, government agencies such as the Air Force, the Federal Aviation Administration (FAA) and the Department of Homeland Security (DHS), research organizations such as the MIT Lincoln Laboratory and the MITRE Center for Advanced Aviation Systems Development (CAASD), and industrial corporations such as Northrop Grumman, Lockheed-Martin, General Atomic have been actively working towards a DSA solution.

Cooperative and Non-Cooperative Technologies
One of the requirements for a DSA system is the ability to detect and avoid both cooperative and non-cooperative air traffic. Broadly speaking, a DSA system has the following three components : The overall performance of a DSA system depends on the performance of each of the three individual DSA components. Cooperative technologies involve the usage of technologies like the Traffic Collision Avoidance System (TCAS) and the relatively recent Automatic Dependent Surveillance – Broadcast (ADS-B) to exchange information regarding position, velocity etc. Non-Coopertaive technologies on the other hand utilize sensors such as radar and laser radar, electro-optical and infra-red imaging sensors, and acoustic sensors to detect and avoid other air traffic. The disadvantage of cooperative technologies is that the installation of TCAS and ADS-B is not mandatory in all airspace classes and it is expected that even in the foreseeable future, air traffic in the National Airspace will consist of a mix of both cooperative and non-cooperative aircraft. A Non-Cooperative DSA system includes:
 * A component to detect the presence of any kind of traffic
 * Algorithms to analyze whether a detected intruder is on a collision course (threat) and
 * A collision avoidance system to issue an avoidance command in case of a threat.
 * 1) Active sensors: These sensors transmit a signal to detect a obstacles: Examples include RADAR, LASER
 * 2) Passive sensors: These systems rely on the detection of signal emanating from the obstacles. Examples include Electro-Optical (EO) and Infra-Red(IR) imaging systems, acoustic sensors

Challenges

 * False alarm rate
 * Passive sensors and ranging
 * Weather conditions and ground clutter