NSA/VCEIL/C1 - Degraded window

The ceilometer continuously gave warnings for window contamination because the window had 
deteriorated. Cloud base height detection did not appear to be significantly affected. 
The window conditioner was replaced on 8/11/09 but this did not clear the warning. The 
instrument was replaced.

• Vertical visibility(vertical_visibility)
• Warning, alarm, and internal status information(status_string)
• Flag indicating aeri retrieval status(status_flag)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• Aerosol volume backscattering coefficient at 355 nm(backscatter)
• Lowest cloud base height detected(first_cbh)
• Third cloud base height(third_cbh)
• Second lowest cloud base height(second_cbh)
• Sum of detected and normalized backscatter(sum_backscatter)
• Window contamination(window_contamination)
• Altitude of highest signal(alt_highest_signal)