Chaff (countermeasure)

Modern US Navy RR-144 (top) and RR-129 (bottom) chaff countermeasures and containers. Note how the strips of the RR-129 chaff (bottom) are of different widths, while those of the RR-144 (top) are all the same width. The RR-144 is designed to prevent interference with civil ATC radar systems.

Chaff, originally called Window[1] or Düppel, is a radar countermeasure involving the dispersal of thin strips of aluminium, metallized glass fiber, or plastic.[2] Dispersed chaff produces a large radar cross section intended to blind or disrupt radar systems.[3]

Modern military forces use chaff to distract active radar homing missiles from their targets. Military aircraft and warships can be equipped with chaff dispensing systems for self-defense. During its midcourse phase, an intercontinental ballistic missile may release chaff along with its other penetration aids.

Contemporary radar systems can distinguish chaff from legitimate targets by measuring the Doppler effect;[4] chaff quickly loses speed after leaving an aircraft, and the resulting shift in wavelength of the radar return can be measured. To counter this, a chaff cloud can be illuminated by the defending vehicle with a doppler-corrected frequency. This is known as JAFF (jammer plus chaff) or CHILL (chaff-illuminated).[5]

  1. ^ Churchill, Winston Spencer (1951). The Second World War: Closing the Ring. Houghton Mifflin Company, Boston. p. 643.
  2. ^ Whigham, Nick. "It looks like rain but it's actually secret military exercises". news.com.au.
  3. ^ Garbacz, R. J. (1978-05-01). Chaff Radar Cross Section Studies and Calculations (Report). Ohio State University Columbus Electroscience Lab.
  4. ^ Wang, Husheng; Chen, Baixiao; Zhu, Dongchen; Huang, Fengsheng; Yu, Xiangzhen; Ye, Qingzhi; Cheng, Xiancheng; Peng, Shuai; Jing, Jiaqiu (2022-08-07). "Chaff identification method based on Range-Doppler imaging feature". IET Radar, Sonar & Navigation. 16 (11): 1861–1871. doi:10.1049/rsn2.12302. ISSN 1751-8784.
  5. ^ "Chaffs". EMSOPEDIA. Retrieved 2024-02-02.