TWP/VCEIL/C2 - occasional communication fault

Beginning August 30, 2005, the Nauru Ceilometer periodically went into a strange 
operational mode where the backscatter data exhibits vertical stripes.  Looking at the backscatter 
data - there are high amplitude oscillations occuring in the backscatter as a function 
of time at a given height.  The phenomenon appears to be more common at night.  Dates 
include: 30 Aug, 31 Aug, 1 Sep, 9 Sep, 15 Sep, 20 Oct, 22 Oct, 8 Dec, and others.

The fiber optic link to the ceilometer was faulty and causing periodic data corruption. 
The problem was corrected when the fiber optic line was replaced with a hard wired RS232 
link.

• Aerosol backscatter coefficient at 355 nm(backscatter)
• Flag indicating aeri retrieval status(status_flag)
• Percentage of nominal factory setting (0 to 999%)(laser_pulse_energy)
• Third cloud base height(third_cbh)
• Time offset of tweaks from base_time(time_offset)
• base time(base_time)
• Lowest cloud base height detected.(first_cbh)
• Warning and alarm status bits(status_string)
• range(range)
• lon(lon)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• Vertical visibility(vertical_visibility)
• Laser temperature(laser_temperature)
• Altitude of highest signal(alt_highest_signal)
• 6 character string describing instrument measurement parameters(measurement_parameters)
• Second lowest cloud base height(second_cbh)
• GPS raw data filename(filename)
• Degrees from vertical (0 to +90)(tilt_angle)
• Detection status. See details(detection_status)
• lat(lat)
• Dummy altitude for Zeb(alt)
• Millivolts at internal ADC input(window_contamination)
• Backscatter sum(sum_backscatter)

TWP/VCEIL/C2 - Vceil computer disconnected

VCEIL computer was disconnected during this time period.

• Aerosol backscatter coefficient at 355 nm(backscatter)
• Flag indicating aeri retrieval status(status_flag)
• Percentage of nominal factory setting (0 to 999%)(laser_pulse_energy)
• Third cloud base height(third_cbh)
• Time offset of tweaks from base_time(time_offset)
• base time(base_time)
• Lowest cloud base height detected.(first_cbh)
• Warning and alarm status bits(status_string)
• range(range)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• Vertical visibility(vertical_visibility)
• Laser temperature(laser_temperature)
• Altitude of highest signal(alt_highest_signal)
• 6 character string describing instrument measurement parameters(measurement_parameters)
• Second lowest cloud base height(second_cbh)
• GPS raw data filename(filename)
• Degrees from vertical (0 to +90)(tilt_angle)
• Detection status. See details(detection_status)
• Millivolts at internal ADC input(window_contamination)
• Backscatter sum(sum_backscatter)

TWP/VCEIL/C2 - Time offset

On 7/14/2006, I found that the ceilometer time was 8m 36s slow, the PC time display (lower 
right taskbar) was frozen at "22:24", and AboutTime was not running. Corrected it on 
7/17 by running AboutTime so that 19:03:29 became 19:12:05. This also corrected the frozen 
display on the Windows98 taskbar. 

I am not sure of the start time of this problem but there were several other Windows 
related issues that had to be corrected on 5/14 with indications of inappropriate access via 
Remote Administrator on 5/13. I do not know if the time offset was a sudden or gradual 
change.

• Aerosol backscatter coefficient at 355 nm(backscatter)
• Flag indicating aeri retrieval status(status_flag)
• Percentage of nominal factory setting (0 to 999%)(laser_pulse_energy)
• Third cloud base height(third_cbh)
• Time offset of tweaks from base_time(time_offset)
• base time(base_time)
• Lowest cloud base height detected.(first_cbh)
• Warning and alarm status bits(status_string)
• range(range)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• Vertical visibility(vertical_visibility)
• Laser temperature(laser_temperature)
• Altitude of highest signal(alt_highest_signal)
• 6 character string describing instrument measurement parameters(measurement_parameters)
• Second lowest cloud base height(second_cbh)
• Degrees from vertical (0 to +90)(tilt_angle)
• Detection status. See details(detection_status)
• Millivolts at internal ADC input(window_contamination)
• Backscatter sum(sum_backscatter)

TWP/VCEIL/C2 - optical cross-talk compensation

The ceilometer gave frequent optical cross-talk compensation warnings, was insensitive to 
high clouds, and the tropics window was deteriorated. The instrument was replaced with a 
spare.

• Aerosol backscatter coefficient at 355 nm(backscatter)
• Vertical visibility(vertical_visibility)
• Altitude of highest signal(alt_highest_signal)
• Third cloud base height(third_cbh)
• Second lowest cloud base height(second_cbh)
• Millivolts at internal ADC input(window_contamination)

TWP/VCEIL/C2 - Receiver failure

The receiver failed and the instrument was replaced.  Data during the specified period are 
not valid.

• Aerosol backscatter coefficient at 355 nm(backscatter)
• Vertical visibility(vertical_visibility)
• Altitude of highest signal(alt_highest_signal)
• Third cloud base height(third_cbh)
• Second lowest cloud base height(second_cbh)
• Lowest cloud base height detected.(first_cbh)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• Backscatter sum(sum_backscatter)