TWP/VCEIL/C3 - ceilometer lost sensitivity

ceilometer sesitivity decreased suddenly and only very strong cloud reflections are 
observed in the first kilometer.

null

• Vertical visibility(vertical_visibility)
• Aerosol volume backscattering coefficient at 355 nm(backscatter)
• Third cloud base height(third_cbh)
• Second lowest cloud base height(second_cbh)
• Detection status.(detection_status)
• Flag indicating aeri retrieval status(status_flag)
• Sum of detected and normalized backscatter(sum_backscatter)
• Warning, alarm, and internal status information(status_string)
• Distance to the center of the corresponding range bin(range)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• Lowest cloud base height detected(first_cbh)