NASA Logo, National Aeronautics and Space Administration
NASA Space Science Data Coordinated Archive Header

Lightning and Airglow Camera (LAC)

NSSDCA ID: 2010-020D-05

Mission Name: Akatsuki

Description

The Lightning and Airglow Camera (LAC) searches for lightning flashes and maps airglow emissions on the nightside of Venus at visible wavelengths. LAC probes the 777.4 nm (OI) atomic oxygen line to observe lightning, if it exists, to study the microphysics of clouds and the dynamics of mesoscale convection. LAC also measures oxygen nightglow emissions at 552.5 nm (O2 Herzberg II) and 557.7 nm (OI) to study the global-scale circulation and small-scale waves in the lower thermosphere.

LAC is designed to detect lightning flashes with an intensity of 1/100 of standard lightning on the Earth when viewed from 1000 km altitude. The LAC utilizes is an 8 x 8 pixel multi-anode silicon avalanche photodiode array with a pixel size of 2 x 2 mm. There is a gap of 0.2 mm between pixels. The angular resolution is 1.84 deg per pixel which yields a total field of view of 16 x 16 deg including the gaps. The spatial resolution is 32 km at 1000 km and 580 km at 3 Rv. The focal length is 61.9 mm (F-number of about 2.5). Instead of a filter wheel, an array bandpass filter consisting of a composite of rectangular bandpass interference filters placed over the detector: 777.4 nm with a 4 x 8 pixel area for lightning detection; 480-605 nm and 557.7 nm with 2 x 8 pixel and 1 x 8 pixel areas, respectively, for airglow; and 545.0 nm covering a 1 x 8 pixel area for an airglow-free background. The LAC optics use a single aspherical quartz lens to save the mass, and there is no shutter. To reduce light and thermal radiation influx, an interference filter that transmits only the observing wavelength range is placed on the front of the optics.

LAC has two observing modes. The lightning observation mode has a sampling frequency of 30 kHz and uses a pre-trigger sampling method that can acquire data from pre- to post-trigger periods depending on the duration of lightning flashes which yields data acquisition times from 2.048 ms to 2.096 s. The data depth is 8 bit/pixel. The airglow observation mode uses numerical integration with integration times of 10, 20, and 90 s. The data depth is 24 bit/pixel.

LAC began lightning search observations in December 2016. During its first 3 years in orbit, LAC conducted 42 low-altitude observing sessions that accumulated 16.8 hours of observations, yielding an area-time product of 81.6 x 10**6 km**2-hr. On March 1, 2020, LAC detected a single optical flash of light that could have been either lightning or a meteorite burning up in the atmosphere (Takahashi, et al., 2020).

Alternate Names

  • Akatsuki/LightningandAirglowCamera(LAC)
  • LAC
  • urn:jaxa:darts:context:instrument:vco.lac

Facts in Brief

Mass: 2.2 kg
Power (avg): 14.4 W

Funding Agency

  • Japan Aerospace Exploration Agency (Japan)

Discipline

  • Planetary Science: Atmospheres

Additional Information

Questions and comments about this experiment can be directed to: Dr. David R. Williams

 

Personnel

NameRoleOriginal AffiliationE-mail

Selected References

  • Takahashi, Y., et al., Lightning detection by LAC onboard the Japanese Venus climate orbiter, Planet-C, Space Sci. Rev., 137, 317-334, doi:10.1007/s11214-008-9400-x, June 2008.
  • Takahashi, Y., et al., Initiation of a lightning search using the lightning and airglow camera onboard the Venus orbiter Akatsuki, Earth Planets Space, 70, 88, doi:10.1186/s40623-018-0836-2, May 2018.
  • Lorenz, R. D., et al., Constraints on Venus lightning from Akatsuki's first 3 years in orbit, Geophysical Research Letters, 46, 7955-7961, doi:10.1029/2019GL083311, July 2019.
  • Takahashi, Y., et al., Optical flash in Venus observed by LAC onboard AKATSUKI, American Geophysical Union, Fall Meeting 2020, abstract #AE002-05, Dec. 2020.
[USA.gov] NASA Logo - nasa.gov