R4AsH: a triple frequency laboratory radar for characterizing falling volcanic ash

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Citation (Scopus)
6 Downloads (Pure)


Airborne ash generated by explosive volcanic eruptions presents a significant danger to aviation. Accurate modelling and predictions of the dispersal of hazardous ash into the atmosphere are currently hampered by uncertainties in the ‘source term’ parameters associated with the initial eruption plume, specifically the amount and size of ash particles released into the atmosphere. Ground based radar offers the means to remotely measure ash reflectivity, however estimation of source term parameters from reflectivity measured by single frequency radar is limited by ambiguity between the contribution of particle size distribution (PSD) and ash concentration in the plume. This means that one of these parameters must be assumed rather than measured directly, leading to uncertainties in forecasting eruption hazards. We report on R4AsH, a close range FMCW radar designed to resolve this ambiguity by simultaneous characterization of falling volcanic ash in a laboratory-controlled environment at three different frequencies: 10, 35 and 94 GHz. The R4AsH design uses a single DDS based chirp generator as a common source, multiplied and upconverted to feed three sets of transmit-receive horn antennas directed at a common target volume such that measurements will give spatially and temporally coincident measurements of falling ash. In addition, there will be independent measurement of the PSD using optical imaging and logging of the landing particle mass to calibrate results and inform analysis. The aim of R4AsH is to develop a triplefrequency inversion algorithm to enable simultaneous retrieval of PSD and ash concentration from radar data suitable for future volcano monitoring systems.
Original languageEnglish
Title of host publicationRadar Sensor Technology XXV
EditorsKenneth Ranney, Ann Raynal
Number of pages8
Publication statusPublished - 12 Apr 2021
EventSPIE Defense + Commercial Sensing - online
Duration: 12 Apr 202116 Apr 2021
Conference number: 11742

Publication series

NameProceedings of SPIE
PublisherInternational Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceSPIE Defense + Commercial Sensing
Internet address


  • Volcanic ash
  • FMCW radar
  • Radar cross section
  • Reflectivity
  • Horn antenna
  • Multi-frequency


Dive into the research topics of 'R4AsH: a triple frequency laboratory radar for characterizing falling volcanic ash'. Together they form a unique fingerprint.

Cite this