lightning from space
March 5, 2014

When Lightning Strikes, Instruments On The Space Station Will See It

April Flowers for - Your Universe Online

Just as you might keep a spare tire in your car, or a spare filter for your air conditions, NASA keeps spares as well. These "spare" flight hardware units allow NASA to continue work without interruption in the event that something goes down for repair. These spare parts are kept even after the project ends, sometimes finding second lives in new areas.

A sophisticated piece of flight hardware, called a Lightning Imaging Sensor (LIS), was developed by researchers at NASA's Marshall Space Flight Center and launched into space in 1997 as part of NASA's Tropical Rainfall Measuring Mission (TRMM). The sensor, used to detect and locate lightning over the tropical region of the globe, undertook a three year primary mission to return data that could be used to improve weather forecasts. LIS continues to operate aboard the TRMM satellite today.

Of course, the researchers responsible for building LIS in the 1990s built a spare unit as a precaution. That other unit is now being brought into play as well. The second LIS sensor is scheduled to launch aboard a Space Exploration Technologies (SpaceX) rocket to the International Space Station (ISS) in February 2016. LIS will be mounted to the station for a two year baseline mission as part of a U.S. Department of Defense (DoD) Space Test Program (STP)-H5 science and technology development payload.

The LIS hardware was selected by NASA to take advantage of the ISS's high inclination, which will give the sensor the ability to "look" farther towards Earth's poles than the original LIS aboard the TRMM satellite. The sensor will have many duties once installed, including monitoring global lightning for Earth science studies, providing cross-sensor calibration and validation with other space-borne instruments, and ground-based lightning networks. LIS will also supply real-time lightning data over data-sparse regions, such as oceans, to support operational weather forecasting and warning.

"Only LIS globally detects all in-cloud and cloud-to-ground lightning -- what we call total lightning -- during both day and night," said Richard Blakeslee, LIS project scientist at Marshall. "As previously demonstrated by the TRMM mission, better understanding lightning and its connections to weather and related phenomena can provide unique and affordable gap-filling information to a variety of science disciplines including weather, climate, atmospheric chemistry and lightning physics.”

Without land-ocean bias, LIS measures the amount, rate and radiant energy of global lightning, providing storm-scale resolution, millisecond timing, and high, uniform-detection efficiency.

The LIS hardware consists of an optical imager enhanced to locate and detect lighting from thunderstorms within its 400-by-400-mile field-of-view. As it orbits Earth, the ISS travels more than 17,000 mph. This will allow LIS to observe a point on Earth, or a cloud, for almost 90 seconds each time it passes overhead. This viewing duration, despite its short length, is long enough to estimate the lightning-flashing rate of most storms.

More than 70 percent of all lightning occurs during daylight hours, making daytime detection the driving force for the technical design of LIS. Lightning, when seen from space, looks like a pool of light on top of a thundercloud. During the day, however, sunlight reflected off the cloud tops can completely mask the lightning signal. This makes it challenging to detect the lightning. LIS applies special techniques that take advantage of the differences in the behavior and physical characteristics between lightning and sunlight, however, allowing LIS to extract the lightning strikes from background illumination.

A real-time event processor inside the LIS electronics unit performs a final step in processing by removing the remaining background signal. This enables to system to detect the lightning signatures and achieve 90-percent detection efficiency.

The LIS team will operate the unit remotely once it is installed on the ISS. The team will assess the data returned by the unit, then disseminate it to forecasters and researchers from the Global Hydrology Resource Center, one of NASA’s Earth science data centers.

The LIS team expects that data from the unit will be applicable in many ways here on Earth. They have received strong endorsements from national and international organizations, including National Oceanic and Atmospheric Administration (NOAA), European Space Agency (ESA), Japan Aerospace Exploration Agency (JAXA) and the Geostationary Operational Environmental Satellite R- Series Program (GOES-R). For their operational weather warning, forecasting and even validation applications, such operational users as NOAA’s National Weather Service (NWS), Aviation Weather Center (AWC), Ocean Prediction Center (OPC) and Pacific Region will be interested in the data from LIS. Other science and application investigations will be improved from the new lightning observations provided by LIS, as well.

LIS might also serve a purpose for the Federal Aviation Administration (FAA) from a research standpoint. The information obtained could help with validation activities of several oceanic convection ensemble model products the FAA is developing, either in real-time or archive mode, according to Randy Bass, a member of the FAA's Aviation Weather Research Team.

"It could also be used for validation of detection of convection from other ground- and space-based sensors we will be using at the time," said Bass. "Any data we can use for 'ground truth' over oceanic areas will be extremely helpful in development of better observing and forecasting products used for offshore aviation, especially as we expand our coverage throughout the Atlantic and Pacific oceans."

This could mean better short-term forecasts of thunderstorms over offshore areas, giving pilots and air traffic controllers the ability to reroute plans around hazards—like lightning and turbulence—with more accuracy. Planes already have weather radar on board, but the range is limited. The LIS data would allow the FAA to improve their capabilities and give controllers the opportunity to see the weather activity as well.

"Measuring lightning is important for knowledge about the weather and also operationally important for aviation safety. By adding an instrument on space station, we can add observations from higher latitudes covering the 48 contiguous states,” said International Space Station Chief Scientist Julie Robinson, Ph.D. “This is a prime example of science on the International Space Station benefiting our nation.”

Image 2 (below): Discussing the Lightning Imaging Sensor engineering test unit are, from left, Bill Lopez and Jim McLeroy from the Department of Defense (DoD) Space Test Program (STP); John Davis from Marshall; Nathan Harnagel from DoD STP; and Mike Stewart from the University of Alabama in Huntsville. Credit: NASA