TWP/VCEIL/C2 - poor receiver

The receiver optical cross-talk compensation was poor and could not be adjusted. It 
appeared the receiver had failed so the instrument was replaced.

• Vertical visibility(vertical_visibility)
• Aerosol volume backscattering coefficient at 355 nm(backscatter)
• Lowest cloud base height detected(first_cbh)
• Second lowest cloud base height(second_cbh)
• Third cloud base height(third_cbh)