Volcanic ash is a significant hazard to aircraft engine and electronics. It has caused damage to unwary aircraft and disrupted air travel for thousands of travelers, costing millions of dollars. The small, jagged fragments of rocks, minerals, and volcanic glass that constitute volcanic ash are about the size of sand and silt. Volcanic ash is hard, does not dissolve in water, is extremely abrasive and corrosive, and conducts electricity when wet. The upper winds transport the particles away to eventual dispersal in an ash cloud. Ash clouds typically form above 20,000 feet, but the lower limit of the initial cloud depends on both the height of the volcanic vent and the vigor with which material is ejected from it.
eVADE (Volcanic Ash DEtection) is a compact device capable of providing information on the ash load in the atmosphere. It is designed to operate onboard an airborne platform. It uses a polychromator to measure optical depth and species to identify volcanic ash from other aerosols. The polychromator separates the spectral components of elastic backscatter and species associated with volcanic eruptions. It is designed to accept LIDAR return light whether in free space or through an optical fiber. The polychromator is compact and able to operate on a manned or unmanned airborne platform. The modular nature of the instrument allows operation as standalone with a LIDAR transmitter/receiver or in conjunction with other measurements, such as wind velocity and air density.
The unique features of the instrument are the compactness to operate on small aircraft, and the ability to measure multiple return signals pertaining to ash concentration.
An airborne volcanic ash detection/characterization system such as eVADE will have wide applications in the study of the threat volcanic ash poses to aircraft, and for other scientific study of volcanic plumes. Studies carried out with eVADE will allow NASA to refine their models of volcanic ash dispersion based on more data than is available at present. There is the potential to combine such a system with Michigan Aerospace Corporation’s optical air data system and icing- and turbulence- detection systems to create a unified system that would sense volcanic, turbulence, and icing hazards ahead, and report airspeed along with air temperature and density.
eVADE will have similar utility for non-NASA civil organizations (NOAA, FAA, USGS, etc.) and military services (US Air Force, etc.) in conducting scientific studies of volcanic ash characteristics and dispersal. A next generation of eVADE that is more compact would be mountable aboard UAVs to “scout” the airways during major eruptions in order to confirm that commercial and military aircraft cannot fly, or give clearance for flights if the concentrations are not judged high enough to be a threat.