Space Station Sensor To Capture 'Striking' Lightning Data

Janet Anderson and Jessica Eagan, NASAs Marshall Space Flight Center

Keeping a spare on hand simply makes sense. Just as drivers keep spare tires on hand to replace a flat or blowout, NASA routinely maintains spares, too. These flight hardware backups allow NASA to seamlessly continue work in the unlikely event something goes down for a repair. When projects end, these handy spares can sometimes find second lives in new areas for use.

Researchers at NASAs Marshall Space Flight Center in Huntsville, Ala., developed a sophisticated piece of flight hardware called a Lightning Imaging Sensor (LIS) to detect and locate lightning over the tropical region of the globe. Launched into space in 1997 as part of NASAs Tropical Rainfall Measuring Mission (TRMM), the sensor undertook a three-year baseline mission, delivering data used to improve weather forecasts. It continues to operate successfully aboard the TRMM satellite today.

The team that created this hardware in the mid-1990s built a spare and now that second unit is stepping up to contribute, as well. The sensor is scheduled to launch on a Space Exploration Technologies (SpaceX) rocket to the International Space Station in February 2016. Once mounted to the station, it will serve 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. STP-H5 is integrated and flown under the management and direction of the DoDs STP.

NASA selected the LIS spare hardware to fly to the space station in order to take advantage of the orbiting laboratorys high inclination. This vantage point gives the sensor the ability to look farther towards Earths poles than the original LIS can aboard the TRMM satellite. Once installed, the sensor will monitor global lightning for Earth science studies, provide 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.

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

The sensor consists of an optical imager enhanced to locate and detect lightning from thunderstorms within its 400-by-400-mile field-of-view on the Earths surface. The station travels more than 17,000 mph as it orbits our planet, allowing the LIS to observe a point on the Earth, or a cloud, for almost 90 seconds as it passes overhead. Despite this brief viewing duration, it is long enough to estimate the lightning-flashing rate of most storms.

Since more than 70 percent of lightning occurs during the day, daytime detection drove the technical design of the LIS. From space, lightning appears like a pool of light on the top of a thundercloud. During the day, sunlight reflected from the cloud tops completely masks the lightning signal, making it difficult to detect. However, LIS creates a solution by applying special techniques that take advantage of the differences in the behavior and physical characteristics of lightning and sunlight signals. These allow LIS to extract the strikes from bright background illumination.

As a final step in processing, a real-time event processor inside the LIS electronics unit removes the remaining background signal, enabling the system to detect the lightning signatures and achieve 90-percent detection efficiency.

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Space Station Sensor To Capture 'Striking' Lightning Data