The Venus probe "PLANET-C" is equipped with five cameras, one of which is the first lightening and airglow camera (LAC) for a planet-probing mission in the world. The LAC can shoot 50,000 times per second using its high-speed mechanism to ensure it captures the precise moment when lightning strikes. (People think that we can see lightening flashes with our naked eyes, but it is actually through persistence of vision.)

The camera also has an "automatic event detection" function to determine if lightening really took place. This function is a unique feature to sort out only "real" lightning data from a large amount of trial image data.

In order to pass very strict weight constraints, the LAC design was modified in the fall of 2004, and we successfully reduced its weight by more than 70 percent (from about 5.2 kilograms to about 1.5 kilograms.) We have been verifying the possibility by using a prototype to change the image-pickup element (pixels) from MCP (Micro Channel Plate) to APD (Avalanche Photodiode), which is a more reliable and durable element.

The development team holds high expectations that the LAC will end a dispute over the "existence of lightning and electric discharging on Venus" which has been debated for more than 20 years.





Outline of the Lightning and Airglow Camera (The latest version, Spring 2005)



1) LAC before design change (left)

2) External view of the LAC after design change (center) and the optical system (right)

As the new design does not have a hood to shield it from sunlight or reflections from clouds over Venus, it will carry out observations only when the PLANET-C is in the night side of Venus.

3) Arrangement of filters on the light receiving side

By dividing the detector's light receiving side in five, five kinds of filters of which each penetrates specific wavelengths of light, are attached directly to the image-pickup elements (pixels) to shoot different observation targets pixel by pixel. In the new design, we do not need the filter rotation mechanism, and that greatly contributed to make the camera lighter.