Other Space Activities

Lightning Sensors

Last updated:May 2, 2024

Instrument Types

Lightning is a transient, high-current electric discharge that occurs when two regions acquire sufficiently different electrical charges. Whilst we will most closely associate lightning with thunder clouds, also known as cumulonimbus clouds, they are not the only source. Lightning can occur within clouds, between clouds, between clouds and earth, between clouds and air, and even in clear air on a bright sunny day 1).

Figure 1: Thunderstorm near Pritzerbe, Germany (Image credit: Mathias Krumbholz)

Lightning strikes are closely correlated with thunderstorms, and as such, are used to monitor the formation, development, tracking, and classification of thunderstorms. The rate at which lightning strikes occur and the changes of this rate are good predictors of severe thunderstorms and heavy precipitation. Real-time information on lightning strikes is also an important tool for those managing electricity infrastructure, to minimise the potential for damage 3).

Global lightning monitoring before satellite observations was only performed in a limited capacity by ground-based radio frequency (RF) sensors. However, due to the poor range of ground-based sensors, oceans and low-population areas were poorly sampled. Since being introduced, Earth-observing satellites with lightning sensors have provided widespread observations across the globe. However, some regions are still being observed more than others due to the Low Earth Orbit (LEO) that many of the satellites are positioned in. This bias is observed in Figure 2. Lightning-observing satellites in a geostationary orbit have the benefit of observing areas more equally, and also being able to observe a storm throughout its entire lifetime 4).

Figure 2: An example of the amount of time that various locations on the Earth are within the field of view of a lightning detector during 24 hours (Image credit: Hugh J. Christian et al 2))

Several different facets of lightning can be studied and measured including electric current, magnetic field and radiation. However, the typical lightning sensors used in Earth-observing satellites are concerned with the time, location, brightness, size, and duration of lightning strikes.

When lightning strikes, atoms in the atmosphere absorb some of the energy, which is then emitted in specific wavelengths (shown in Figure 4). Oxygen atoms emit photons with a wavelength of 777 nm, which is the most intense of the various bands emitted. This is why lightning sensors on satellites exclusively detect near-infrared (NIR) radiation with a wavelength of 777 nm 5).

Figure 3: Spectrum of ball lightning6) (Image credit: Olli Niemitalo)

Essential Climate Variable

Lightning is an Essential Climate Variable (ECV) under the Global Climate Observing System (GCOS), with Schumann Resonances, and Total Lightning Stroke Density identified as required ECV products 7). Schumann Resonances are the frequencies in which electromagnetic waves travel around Earth between its surface and the ionosphere 8). These electromagnetic waves are created by lightning strikes. Total Lightning Stroke Density refers to the number of lightning strikes in some unit of space.

ECV Product	Required Spatial Resolution	Required Temporal Resolution	Required Uncertainty
Schumann Resonances	NA*	30 days	5%
Total Lightning Stroke Density	111 km	30 days	15%

Figure 4: The minimum requirements for the collected data to be useful 7). *One value represents the measurement of the entire globe, so no spatial resolution is required.

Example Products

World Wide Lightning Location Network

The World Wide Lightning Location Network (WWLLN) provides a live lightning map, spectrograms from cities around the globe, and other storm-related data.

Figure 5: World lightning map (Image credit: WWLLN)

The National Oceanic and Atmospheric Administration (NOAA) operates the Comprehensive Large Array-data Stewardship System (CLASS) which has data from the Geostationary Lightning Mapper (GLM) instruments. GLM instruments are hosted on both Geostationary Operational Environmental Satellite (GOES) 16 and 17 and can be accessed here.

Tropical Rainfall Measuring Mission (TRMM) Data

Launched in November 1997, the Tropical Rainfall Measuring Mission (TRMM) was a research satellite jointly developed by the National Aeronautics and Space Administration (NASA) and the Japan Aerospace Exploration Agency (JAXA). Figure 6 shows different aspects of the data collected by its Lightning Image Sensor (LIM) over its 16-year lifespan. It was through the analysis of this data that Earth’s lightning hotspot was discovered, Lake Maracaibo in Venezuela. From August to November, the lake experiences more than 65 flashes/day.

Figure 6: Very high horizontal (0.1°) resolution total lightning climatology from 16 years (1998–2013) of TRMM LIS total lightning observations: (a) FRD (flashes/kilometre/year), (b) local hour of maximum flash rate density, and (c) month of maximum flash rate density. Data shown for the latitude band of ±38° (Image credit: Bulletin of the American Meteorological Society 97, 11; 10.1175/BAMS-D-14-00193.1)

OrbView-1 Data

One of the earliest satellite lightning detectors was onboard the OrbView-1 satellite launched in 1995. The data presented in Figure 7 is an average of all the data collected over its five-year lifespan. The annual average total was found to be 44 ± 5 flashes/s. The highest mean annual flash density was over 80 flashes/km2/year. That area was just west of the town of Kamembe in Rwanda. Kamembe experiences the most days with thunderstorms, 221 days per year.

Figure 7: The annual distribution of total lightning activity (in units of flashes per km squared, per year) (Image credit: Hugh J. Christian et al 2))

Related Missions

Meteosat Third Generation (MTG)

With its first satellite launched in December 2022, MTG is a satellite constellation collaboratively led by ESA and the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) to enhance weather forecasting capabilities. The constellation consists of two imaging satellites (MTG-I1 and MTG-I2) and one sounding satellite (MTG-S1)11). The Lightning Imagers (LIs) on board MTG-I1 and MTG-I2 will observe developing thunderstorms over Europe and Africa with a spatial resolution of less than 10 km. MTG-I1 launched in late 2022, and the first lightning data from its LI were released on 24 March 2024 and can be viewed here. The remaining MTG satellites will be launched in the near future.

Geostationary Operational Environmental Satellite-R (GOES-R) Series

GOES-R is a series of four geostationary meteorological satellites operated by NASA and the National Oceanic and Atmospheric Administration (NOAA). The satellites GOES-R/16, GOES-S/17, and GOES-T/18 were launched in 2016, 2018, and 2022 respectively. The Geostationary Lightning Mapper (GLM) equipped on all of the satellites was the first lightning detector on board a geostationary satellite 12).

FengYun-4 (FY-4)

FY-4 is a series of seven geostationary meteorological satellites operated by the China Meteorological Administration (CMA). FY-4A and FY-4B were launched in 2016 and 2021 respectively, with a further five planned for the future. The Lightning Mapping Imager (LMI) on board five of the seven satellites observes with a spatial resolution of 7 km.

International Space Station (ISS): Atmosphere-Space Interactions Monitor (ASIM)

Equipped by the ISS in April 2018, the Atmosphere-Space Interactions Monitor (ASIM) is an instrument assembly operated by the European Space Agency (ESA). One instrument of this assembly is the Modular Multispectral Imaging Array (MMIA), comprising two optical narrow-band cameras and three photometers. Its purpose is to observe and categorise lightning strikes and Transient Luminous Events (TLEs) such as blue jets, sprites, and elves.

Figure 7: Transient Luminous Events (Image credit: ESA)

International Space Station (ISS): Lightning Image Sensor (LIS)

TRMM’s spare LIS was launched and attached to the ISS in February 2017. The LIS is part of the United States of America’s (USA’s) Department of Defence (DoD) module, specifically their Space Test Program (STP) science and technology development payload9). With the ISS’s inclined orbit of 51.6°, LIS can observe all lightning events that occur on Earth with a latitude of +/- 55°. This coverage, greater than TRMM’s +/- 38° of latitude, allows for near-global lightning observation 10).

Figure 8: Instrument platforms for the LIS (Image credit: NASA/GHRC)

Firefly

Launched in November 2013, Firefly was a nanosatellite mission led by the National Aeronautics and Space Administration (NASA). It aimed to study the relationship between lightning and Terrestrial Gamma-ray Flashes (TGFs). One of its instruments was the Optical Lightning Detector (OLD) which used four photodiodes to detect lightning strikes.

Tropical Rainfall Measuring Mission (TRMM)

Launched in November 1997, the Tropical Rainfall Measuring Mission (TRMM) was a research satellite jointly developed by the National Aeronautics and Space Administration (NASA) and the Japan Aerospace Exploration Agency (JAXA). For the mission, two Lightning Image Sensors (LISs) were designed by the University of Alabama, and developed by the Marshall Space Flight Centre (MSFC). TRMM equipped one sensor, whilst the other was placed in storage for 20 years until it was sent up to the International Space Station (ISS) as part of the ISS:LIS mission9). The TRMM ended in 2015.

Fast On-orbit Recording of Transient Events (FORTE)

Launched in August 1997, FORTE was a satellite operated by the USA’s Department of Energy (DoE) to study the optical and Radio Frequency (RF) emissions of lightning. It was used as a testbed for nuclear detonation detection systems because nuclear detonations also release RF emissions. The satellite was equipped with an RF System, comprised of an RF antenna and receiver, as well as an Optical Lightning System comprised of a Lightning Location System (LLS) and a PhotoDiode Detector (PDD). The LLS observed lightning over a swath of 1200 km with a spatial resolution of 10 km, whereas the PDD picked up on the brightness over all visible (VIS) and near-infrared (NIR) wavelengths.

OrbView-1 (formerly MicroLab-1)

Launched in April 1995, OrbView-1 was a commercial satellite developed by GeoEye (formerly known as Orbital Image Corporation). GeoEye was merged into DigitalGlobe in January 2013. The primary payload of OrbView-1 was its Optical Transient Detector (OTD), a lightning imager provided by NASA’s Marshall Space Flight Center. The OTD observed over a swath of 1300 km with a spatial resolution of 10 km. OrbView-1’s mission ended in 2000.

References

1) Uman, M. A. (2012). Lightning. United States of America: Dover Publications.

2) Christian, H. J., Blakeslee, R. J., Boccippio, D. J., Boeck, W. L., Buechler, D. E., Driscoll, K. T., ... & Stewart, M. F. (2003). Global frequency and distribution of lightning as observed from space by the Optical Transient Detector. Journal of Geophysical Research: Atmospheres, 108(D1), ACL-4.

3) UNSW Canberra. (2021). (rep.). Pre-Phase A Mission Study Report. Retrieved from https://www.unsw.adfa.edu.au/sites/default/files/documents/Australian_Bureau_of_Meteorology_Pre-Phase_A_Mission_Study_Report_0.pdf.

4) Symbios Communications. (n.d.). Lightning Instruments. The Earth Observation Handbook. Retrieved February 27, 2024, from https://www.eohandbook.com/eohb2014/sat_earth_obs_lightning.html.

5) University of Arizona. (2015). Satellite detection and location of lightning [Slide show]. ATMO489 Atmospheric Electricity, Tucson, Arizona, United States of America. http://www.atmo.arizona.edu/students/courselinks/spring15/atmo589/ATMO489_online/lecture_25/lect25_satellite_observations.html.

6) Cen, J., Yuan, P., & Xue, S. (2014). Observation of the optical and spectral characteristics of ball lightning. Physical review letters, 112(3), 035001.

7) World Meteorological Organization, United Nations Environment Programme, International Science Council, & Intergovernmental Oceanographic Commission of the United Nations Educational, Scientific and Cultural Organization. (2022). The 2022 GCOS ECVs Requirements (GCOS 245). In Global Climate Observing System (GCOS-245). World Meteorological Association. Retrieved February 26, 2024, from https://library.wmo.int/viewer/58111?medianame=GCOS-245_2022_GCOS_ECVs_Requirements_#page=85&viewer=picture&o=info&n=0&q=

8) English, T. (2021, January 20). Schumann Resonance: Does Earth’s 7.83 Hz “Heartbeat” Influence Our Behavior? Interesting Engineering. Retrieved February 26, 2024, from https://interestingengineering.com/science/what-is-the-schumann-resonance.

9) Lightning Imaging Sensor (LIS). (n.d.). Global Hydrometeorology Resource Center Distributed Active Archive Center. Retrieved February 27, 2024, from https://ghrc.nsstc.nasa.gov/lightning/overview_lis_instrument.html.

10) Earth Observations: Lightning Imaging Sensor (LIS). (n.d.). Global Hydrometeorology Resource Center Distributed Active Archive Center. Retrieved February 27, 2024, from https://ghrc.nsstc.nasa.gov/home/micro-articles/earth-observations-lightning-imaging-sensor.

11) EUMETSAT. (n.d.). Meteosat Third Generation. European Organisation for the Exploitation of Meteorological Satellites. Retrieved February 27, 2024, from https://www.eumetsat.int/meteosat-third-generation.

12) NASA. (n.d.). GOES Satellite Network. National Aeronautics and Space Administration. Retrieved February 27, 2024, from https://science.nasa.gov/mission/goes.

13) Albrecht, R. I., Goodman, S. J., Buechler, D. E., Blakeslee, R. J., & Christian, H. J. (2016). Where are the lightning hotspots on Earth?. Bulletin of the American Meteorological Society, 97(11), 2051-2068.