A New Home for LIS

Though LIS burned up with TRMM in 2017, the LIS instrument lives on attached to the ISS. The flight spare LIS unit was launched to the ISS for a second deployment to extend the LIS record in latitude and time.

The International Space Station (ISS) is an orbital scientific laboratory that is continuously manned and hosts a wide array of scientific payloads and experiments. Construction on the ISS began in 1998, and it is expected to remain in service until 2030. The ISS has a low Earth orbit with an altitude of 400 km and an inclination of 51 degrees.

One of the ISS hosted payloads is the flight spare Lightning Imaging Sensor (LIS) from the TRMM mission. The ISS has a similar orbit to TRMM, but with a higher inclination. This allows LIS to sample subtropical lightning at a similar spatial resolution to its previous deployment on TRMM.

ISS-LIS extends the TRMM-LIS record to 2017 and beyond while providing total lightning snapshots from around the world in near real time. It has also proven useful for calibrating and validating NOAA's new Geostationary Lightning Mapper (GLM) that is built on the LIS-heritage design and provides continuous real-time observations of lightning across the Americas.

I use ISS-LIS to examine coincident observations of optical pulses detected by both LIS and GLM. The fine LIS pixels provide additional details on the evolution of a given flash. However, GLM can resolve more optical pulses than LIS due to a combination of sensitivity differences and trigger thresholds. For example, photons arriving in 1 large GLM pixel may cause a GLM trigger. But if the photons are split between 2 small LIS pixels, neither pixel could get bright enough to trigger LIS, and LIS would miss the entire pulse.