TWP/VCEIL/C2 - Installation

The Nauru ARCS was installed during the period September-November
1998.  Data were being collected by the end of October, but for the
first several weeks of November, the site was undergoing considerable
change, so data from that period should be used with caution.  The
official site dedication occured on November 20.  Most on-site
activity ended following the dedication so we will consider November
20 to be the beginning of the Nauru operations.  The last members of
the installation team left Nauru on November 24.

• null(Raw data stream - documentation not supported)

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

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

TWP/VCEIL/C2 - Nauru Vceil data suspect

During this period the ceilometer began producing a cross-talk warning. Since it is a 
warning, some of the data are OK. However, the instrument began to be limited to detecting 
clouds only about 2 km above the ground.

• Aerosol backscatter coefficient at 355 nm(backscatter)
• Flag indicating aeri retrieval status(status_flag)
• Third cloud base height(third_cbh)
• Lowest cloud base height detected.(first_cbh)
• Warning and alarm status bits(status_string)
• range(range)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• Vertical visibility(vertical_visibility)
• Altitude of highest signal(alt_highest_signal)
• Second lowest cloud base height(second_cbh)
• Backscatter sum(sum_backscatter)

• Altitude of highest signal(alt_highest_signal)
• Flag indicating aeri retrieval status(status_flag)
• Backscatter sum(sum_backscatter)
• range(range)
• Warning and alarm status bits(status_string)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• Vertical visibility(vertical_visibility)
• Detection status. See details(detection_status)
• Third cloud base height(third_cbh)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• Second lowest cloud base height(second_cbh)

TWP/VCEIL/C2 - Power outage in I-Van resulted in Missing Data

I forgot to put in the daily report that we took the I van down yesterday to replace the 
fans in the Clary UPS. This was from 2300z on 24May03 to 0010z on 25May03. Instruments 
affected :

MPL
Ceilometer
MWR
WSI
TSI

Rex

• null(Raw data stream - documentation not supported)

• Aerosol backscatter coefficient at 355 nm(backscatter)
• Warning and alarm status bits(status_string)
• lon(lon)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• 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)
• Detection status. See details(detection_status)
• lat(lat)
• Dummy altitude for Zeb(alt)
• Flag indicating aeri retrieval status(status_flag)
• Percentage of nominal factory setting (0 to 999%)(laser_pulse_energy)
• Third cloud base height(third_cbh)
• base time(base_time)
• Lowest cloud base height detected.(first_cbh)
• range(range)
• Millivolts at internal ADC input (0 to 2500)(background_light)

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

TWP/VCEIL/C2 - Ceilometer failure

Large data gaps began occurring frequently at the TWP Nauru site 26 February at 06Z.  
Prior to 25 February, optical cross talk errors had been observed.  Beginning on 25 February, 
data errors were observed.  By 26 February, these errors were exhibiting themselves as 
extended data gaps.  These gaps became increasingly frequent between 2/26 and 3/4.  All 
data are missing after 20050304.1550.

The instrument was replaced on 29 March and after some subsequent configuration work, the 
instrument was revived just after 00Z on 1 April.

• null(Raw data stream - documentation not supported)

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

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)

Calibration interruption at TWP Nauru

The ceilometer was tipped horizontal for a calibration check

• null(Raw data stream - documentation not supported)

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

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