Experiment

Global Lightning and sprIte MeasurementS on JEM-EF (JEM-GLIMS) obtained its first observation data

Global Lightning and sprIte MeasurementS on JEM-EF (JEM-GLIMS) is the equipment onboard the Multi-mission Consolidated Equipment (MCE), installed on the Exposed Facility (EF) of the Japanese Experiment Module Kibo on the International Space Station (ISS).

JEM-GLIMS was launched to the ISS on July 21, 2012, aboard the H-II Transfer Vehicle (HTV) KOUNOTORI3 and installed on the Exposed Facility (EF) of Kibo on August 9. After the installation, JEM-GLIMS successfully obtained its first observation data.

JEM-GLIMS was collaboratively developed by Osaka University, Hokkaido University, Kinki University, Stanford University, National Institute of Polar Research, Osaka Prefecture University, Tohoku University, the University of Electro-Communications and JAXA. JEM-GLIMS, composed of a CMOS camera with high spatial resolution, photometers with high temporal resolution, and VLF/VHF radio wave receivers, lead the world in the continuous observation of the lightning and sprites from just above.

By doing the just-above observations, a detailed study for the horizontal spatial distribution and temporal development process of lightning and sprites which has been difficult to derive from the on-ground observation data becomes possible. Further, since the just-above observation from space receives little impact from absorption and scattering by the Earth's atmosphere, it is possible to acquire precise data of the luminescence intensity. Initial checkout of each instrument of JEM-GLIMS was completed; and the observation equipment had been verified working normally.

The figure below is an image data captured by the CMOS camera of a just below, a lightning that occurred over Malaysia, which JEM-GLIMS observed at 11:51 p.m. and 44.408 second on November 27, 2012 (Japan time). From the figure, the lightning emissions show a non-uniform, complicated spatial distribution of an approximately 20km wide. In addition, a strong light of near-ultraviolet ray has been detected with a wavelength of 150-280nm. The light of near-ultraviolet ray is mostly absorbed to the ozone in the atmosphere and rarely reaches the ISS flying at 400km altitude. For this reason, detection of near-ultraviolet ray suggests that the occurrence of a transient luminous event (TLE) in the upper-atmosphere. The data will be validated in near future. As such, JEM-GLIMS conducts the world's first, just-above observation of lightning and TLE in the upper-atmosphere.

[Fig. 1] Image data taken by the CMOS camera

This example of observation is a data before it is validated. Research teams and JAXA will conduct the continuous observation and aims to detect the luminous phenomena, such as sprites. In addition, by a comparison with the observational data of lightning obtained on the ground, we will clarify the electrical characteristics of lightning that caused upper-atmospheric luminous phenomena. In addition, in collaboration with the researchers from around the world, we are planning to carry out a simultaneous observation of an upper-atmospheric luminous event using a ground-based optical observation instrument and this JEM-GLIMS.

【Remarks from PI, Tomoo Ushio, Associate Professor, Osaka University】

JEM-GLIMS experiment was chosen as one of the JAXA's port sharing utilization mission onboard Kibo-Exposed Facility of the ISS. It was launched this July without trouble. I'd like to express my gratitude to all the concerned people. This first observation proved the equipment was working normally, and interesting data was included in the obtained data. I expect to obtain important findings in the near future.

See also: JEM GLIMS website by Hokkaido University

Supplemental reading

Observation data by JEM-GLIMS

CMOS camera images captured the upper-atmospheric lightning that occurred over Malaysia. From left, three consecutive images are data captured sequentially every 33 milliseconds (1,000 milliseconds equal to 1 second). Time rate of change and spatial extension are identified. The brightest lightning area has about 10km in diameter, with the overall lightning area of more than 20km.

[Fig. 2] Observation data of the high-speed photometer

Waveform based on the time sequence of the lightning strength observed by a photometer. The photometer comprises 6 channels from PH1 to PH6.Each channel measures the emission strength of different wavelength. Because a strong signal at the channel of wavelength 150-280nm was observed, it suggested the occurrence of a luminous event in the upper-atmosphere. Validity of the occurrence of the lightning in the upper-atmosphere will be conducted in comparison with the lightning observation network data gained on the ground.

[Fig. 3] Observation data by the VHF interferometer

VHF pulse waveforms measured by the two sets of VHF antennas (A-Unit, B-Unit) installed apart 1.5 meters from the bottom of MCE. By identifying the arrival timing of each pulse waves, direction of arrival and the origin of the radio emission can be determined, so that the time and spatial range of upper-atmosphere lightning current can be learned in detail.

[Fig. 4]　ISS location when captured the lightning

ISS location at 11:51 p.m. and 44.408 second on November 27, 2012 (Japan time). The lightning was captured over Malaysia. Yellow square shows the field of the CMOS camera while the red circle shows the field of the photometer.

About JEM-GLIMS

• Observation target

JEM-GLIMS aims to observe the lightning that occurs at an altitude of 10 km or below and the upper-atmospheric lightning such as sprites, elves, and gigantic jets that occur at altitudes between 20-90 km in connection with the lightning.

Upper-atmospheric lightning was discovered about 20 years ago. Occurrence condition and the mechanisms are still remain a mystery such as the causes of discharge type differences of columns or carrots, vertical occurrence location gap between a thunder and a sprite, and factors that determine the number of sprite discharge(s). The most effective means to solve these is a method to observe an upper-atmosphere lightning from right above from space. By doing so, spatial distribution, time development, and relationships with the parent thunders are expected to be easily clarified, which has been difficult by the optical observation on the ground.

Furthermore, JEM-GLIMS' sweep observation alongside the ISS movements, which covers the area of latitudes 51 degree in north and south enables to obtain precise data of occurrence distribution and the frequency of the upper-atmospheric lightning can be measured. This is expected to become a key for the quantitative inference of how upper-atmospheric lightning affect the change of the atmosphere constitution of the Earth and the ozone chemistry.




[Fig. 5] Representation of upper-atmospheric lightning phenomena

• Observation equipment for JEM-GLIMS



[Fig. 6] JEM-GLIMS observation equipment
PH (Photometer), LSI (Lightning and Sprite Imager), VLFR (VLF Receiver)




[Fig. 7] Antennas of VHF radio receivers
Attached 1.5 meters away from the bottom of MCE




[Fig. 8] System configuration of JEM-GLIMS


*All times are Japan Standard Time (JST)