A field mill is a specialized instrument used for measuring the strength of electrical fields in the atmosphere near thunderstorm clouds. They are used in the launch criteria for the Space Shuttle to avoid lightning strikes. They are also used in outdoor laboratories for lightning protection equipment to determine favorable experiment conditions.

The "mill" is a typical rotating shutter design in the instrument. It is usually deployed airborne and flown through anvil head clouds

Cumulonimbus incus

A cumulonimbus incus is a cumulonimbus cloud which has reached the level of stratospheric stability and has formed the characteristic flat, anvil-top shape...

 to make measurements.

KSC electric field mill network

At Kennedy Space Center

Kennedy Space Center

The John F. Kennedy Space Center is the NASA installation that has been the launch site for every United States human space flight since 1968. Although such flights are currently on hiatus, KSC continues to manage and operate unmanned rocket launch facilities for America's civilian space program...

 (KSC) in Florida, 31 field mills are deployed around KSC and the nearby Cape Canaveral Air Force Station

Cape Canaveral Air Force Station

Cape Canaveral Air Force Station is an installation of the United States Air Force Space Command's 45th Space Wing, headquartered at nearby Patrick Air Force Base. Located on Cape Canaveral in the state of Florida, CCAFS is the primary launch head of America's Eastern Range with four launch pads...

. Data from the field mills help forecasters determine when electric charge aloft might trigger lightning during a launch.

External links

• About Electric Field Mill Operation
• CAMEX-4 MIPS Field Mill
• Application of Airborne Field Mill Data for Use in Launch Support
• Florida Airborne Field Mill Research May Improve Launch Weather Criteria
• http://www.precisionstrobe.com/jc/fieldmill/fieldmill.html Build a homemade field mill
• INEO SUEZ
• Lightning Research Laboratory—University of Florida