A Doppler velocity sensor (DVS) is a specialized Doppler radar that uses the Doppler effect to measure the three orthogonal velocity components referenced to the aircraft. When aircraft true heading, pitch and roll are provided by other aircraft systems, it can function as a navigation sensor to perform stand-alone dead reckoning navigation calculations as a Doppler Navigation Set (DNS).
Doppler navigation systems are independent of surrounding conditions, perform with high accuracy over land and sea anywhere in the world, and are independent of ground-based aids and space-based satellite navigation systems.
To measure an aircraft three-dimensional velocity, a Doppler radar antenna is caused to radiate a minimum of three non-coplanar microwave electromagnetic beams toward the earth's surface.[1] Some of the energy is backscattered to the radar by the earth surface. With knowledge of the beam angles, three or more beam-Doppler frequencies are combined to generate the components of aircraft velocity.[2]
DVS transmission is performed at a center frequency of 13.325 GHz in the internationally authorized Ku band of 13.25 to 13.4 GHz.[3]
Usesedit
DVS are used on helicopters for navigation, hovering, sonar dropping, target handover for weapon delivery and search and rescue. Because the Doppler radar measures velocity relative to surface, sea current and tidal effects create biases.[citation needed] However, for sonobuoys dropping and over water search and rescue, velocity of the aircraft relative to water movement is expected.[4][5]
These radars were formally approved under the FAA TSO-65a[6] until 2013, and are designed in accordance with the Radio Technical Commission for Aeronautics (RTCA) DO-158 standard titled Minimum Performance Standards − Airborne Doppler Radar Navigation Equipment.
Limitationsedit
The functional operation and accuracy of Doppler velocity sensors is affected by many factors, including aircraft velocity, attitude and altitude above terrain. It is also affected by environmental factors, including the type of terrain the radar is illuminating, and precipitation in the atmosphere.[5]
As the aircraft moves, the backscattering coefficient changes within the beam width, and this causes a shift and some skewing of the Doppler spectrum, and hence an error in the measurement of velocity.[2] A major limitation of using DVSs for navigation is that they typically suffer from accumulated error. Because the guidance system is continually integrating velocity with respect to time to calculate position ''(see dead reckoning)'', any measurement errors, however small, are accumulated over time. This leads to 'drift': an ever-increasing difference between where the system thinks it is located and the actual location. Due to integration a constant error in velocity results in a linear error in position.
^"Doppler Velocity Sensor APN-200 Error Model And Flight Test Results" (PDF). Defense Technical Information Center. 8 March 1974. (PDF) from the original on March 25, 2020.
^ abFried, Walter R. (Summer 1993). "History of Doppler Radar Navigation". Journal of the Institute of Navigation. 40 (2): 121–136. doi:10.1002/j.2161-4296.1993.tb02299.x.
^International Communication Union. "Feasibility of MSS operations in certain frequency bands" (PDF). Itu.int.
^Kayton, Myron., Fried, Walter R. (1997). (PDF) (2nd ed.). New York: Wiley. ISBN0471547956. OCLC 34798180. Archived from the original (PDF) on 2018-12-22. Retrieved 2019-01-02.{{cite book}}: CS1 maint: multiple names: authors list (link)
doppler, velocity, sensor, this, article, includes, list, general, references, lacks, sufficient, corresponding, inline, citations, please, help, improve, this, article, introducing, more, precise, citations, february, 2019, learn, when, remove, this, template. This article includes a list of general references but it lacks sufficient corresponding inline citations Please help to improve this article by introducing more precise citations February 2019 Learn how and when to remove this template message A Doppler velocity sensor DVS is a specialized Doppler radar that uses the Doppler effect to measure the three orthogonal velocity components referenced to the aircraft When aircraft true heading pitch and roll are provided by other aircraft systems it can function as a navigation sensor to perform stand alone dead reckoning navigation calculations as a Doppler Navigation Set DNS Doppler navigation systems are independent of surrounding conditions perform with high accuracy over land and sea anywhere in the world and are independent of ground based aids and space based satellite navigation systems Contents 1 Operational principles 2 Uses 3 Limitations 4 See also 5 References 6 External linksOperational principles editTo measure an aircraft three dimensional velocity a Doppler radar antenna is caused to radiate a minimum of three non coplanar microwave electromagnetic beams toward the earth s surface 1 Some of the energy is backscattered to the radar by the earth surface With knowledge of the beam angles three or more beam Doppler frequencies are combined to generate the components of aircraft velocity 2 DVS transmission is performed at a center frequency of 13 325 GHz in the internationally authorized Ku band of 13 25 to 13 4 GHz 3 Uses editDVS are used on helicopters for navigation hovering sonar dropping target handover for weapon delivery and search and rescue Because the Doppler radar measures velocity relative to surface sea current and tidal effects create biases citation needed However for sonobuoys dropping and over water search and rescue velocity of the aircraft relative to water movement is expected 4 5 These radars were formally approved under the FAA TSO 65a 6 until 2013 and are designed in accordance with the Radio Technical Commission for Aeronautics RTCA DO 158 standard titled Minimum Performance Standards Airborne Doppler Radar Navigation Equipment Limitations editThe functional operation and accuracy of Doppler velocity sensors is affected by many factors including aircraft velocity attitude and altitude above terrain It is also affected by environmental factors including the type of terrain the radar is illuminating and precipitation in the atmosphere 5 As the aircraft moves the backscattering coefficient changes within the beam width and this causes a shift and some skewing of the Doppler spectrum and hence an error in the measurement of velocity 2 A major limitation of using DVSs for navigation is that they typically suffer from accumulated error Because the guidance system is continually integrating velocity with respect to time to calculate position see dead reckoning any measurement errors however small are accumulated over time This leads to drift an ever increasing difference between where the system thinks it is located and the actual location Due to integration a constant error in velocity results in a linear error in position See also editContinuous wave radar Dead reckoning Frequency modulation Guidance systems Radio navigationReferences edit Doppler Velocity Sensor APN 200 Error Model And Flight Test Results PDF Defense Technical Information Center 8 March 1974 Archived PDF from the original on March 25 2020 a b Fried Walter R Summer 1993 History of Doppler Radar Navigation Journal of the Institute of Navigation 40 2 121 136 doi 10 1002 j 2161 4296 1993 tb02299 x International Communication Union Feasibility of MSS operations in certain frequency bands PDF Itu int Kayton Myron Fried Walter R 1997 Avionics navigation systems PDF 2nd ed New York Wiley ISBN 0471547956 OCLC 34798180 Archived from the original PDF on 2018 12 22 Retrieved 2019 01 02 a href Template Cite book html title Template Cite book cite book a CS1 maint multiple names authors list link a b Mike Tooley 2017 Aircraft Communications and Navigation Systems 2nd ed Wyatt David 2nd ed London CRC Press ISBN 9781317938347 OCLC 1006392205 Technical Standard Order TSO C65a Airborne Doppler Radar Ground Speed and or Drift Angle Measuring Equipment For Air Carrier Aircraft Federal Register 2012 09 04 Retrieved 2019 02 18 External links editDoppler Navigation Radar on Friends of CRC CMA 2012 Doppler Velocity Sensor and Navigation System Archived 2020 05 04 at the Wayback Machine on CMC Electronics AN ASN 157 Doppler Navigation Set on BAE Systems ANV 353 on Leonardo S p A Retrieved from https en wikipedia org w index php title Doppler velocity sensor amp oldid 1185785000, wikipedia, wiki, book, books, library,
