SGP/MPL/C1 - Signal degrading

The MPL viewport window was blown off during a storm on 2002/09/25.  The MPL received a 
soaking of rain.  Following this event, although site operations cleaned and dried the 
optics, the lidar performance continued to degrade over the next few months.  Although 
initially suitable for cloud detection, by Dec 10th the lidar was providing useful results only 
during the day (oddly enough).  By Jan 16, the detector was dead.  

It is not recommended to depend on night-time cloud base heights after Dec. 10 2002. 

It is not recommended to use any of the data after 9/25 for aerosol retrievals.

• base time(base_time)
• Preliminary cloud base height(preliminary_cbh)
• Maximum altitude retrieved from multichannel scalar card.(max_altitude)
• Time offset of tweaks from base_time(time_offset)
• Detector Temperature(detector_temp)
• Repetition rate, or Trigger Frequency of the laser(trigger_freq)
• lat(lat)
• range(range)
• Number of laser shots recorded(shots_summed)
• value represents date of last configuration change as yyyymmdd(property)
• Background Signal(background_signal)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• Amount of time the actual laser pulse lags behind the sync trigger(laser_sync_offset)
• Voltage level which operates the thermistor(voltage_10)
• Array of heights for the range gates(height)
• Time in nanoseconds for each range bin of multichannel scalar card.(range_bin_time)
• Number of laser pulses summed during measurement interval(shots_sum)
• Amount of time the scalar lags behind the sync trigger(scalar_sync_offset)
• Laser Temperature(laser_temp)
• Angle of inclination with respect to horizontal(transceiver_altitude_angle)
• Distance from leading edge of first range bin to the center of each bin .(range_bins)
• effective range offset due to poor sync between laser firing and A/D trigger.(range_offset)
• Repetition Rate, or Trigger Frequency of the laser(pulse_rep)
• Angle of orientation with respect to true geographic north(transceiver_azimuth_angle)
• Laser output energy per pulse(energy_monitor)
• Instrument Temperature(instrument_temp)
• Amount of time laser pulse lags behind the scalar trigger(laser_scalar_sync_offset)
• Dummy altitude for Zeb(alt)
• Width of range-bins calculated from range_bin_time(range_bin_width)
• time(time)
• required to correct raw counts for detector deadtime prior to all other
  corrections.(deadtime_correction)
• Voltage level which operates the energy monitor(voltage_15)
• Sum of raw backscatter counts per bin prior to ANY corrections.(total_counts)
• Filter Temperature(filter_temp)
• Voltage level which operates the A/D card and the detector(voltage_05)
• lon(lon)

• Background Signal(background_signal)
• Instrument Temperature(instrument_temp)
• Time offset of tweaks from base_time(time_offset)
• Cloud base height, measured by MPL(cloud_base_height)
• lat(lat)
• Laser output energy per pulse(energy_monitor)
• Cloud mask(cloud_mask_2)
• Array of heights for the range gates(height)
• Number of laser shots recorded(shots_summed)
• Repetition Rate, or Trigger Frequency of the laser(pulse_rep)
• The update time of the historical baseline used for the cloud boundary
  determination of this sample(baseline_update_time)
• cloud top height(cloud_top_height)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• Flag indicating whether the beam was extinguished at indicated cloud top(cloud_top_attenuation_flag)
• Detector Temperature(detector_temp)
• Laser Temperature(laser_temp)
• Cloud mask(cloud_mask_1)
• lon(lon)
• base time(base_time)
• Relative random error in backscatter profiles(random_error)
• Dummy altitude for Zeb(alt)

SGP/MPL/C1 - Metadata errors

The latitude, longitude and altitude of the Micropulse Lidar
(MPL) were incorrectly entered into the ARM database.  The 
correct location of the SGP.C1 MPL is:
   Lat: 36.606N
   Lon: 97.485W
   Alt:    316m

• lat(lat)
• lon(lon)
• Dummy altitude for Zeb(alt)

• lat(lat)
• Dummy altitude for Zeb(alt)
• lon(lon)

Instrument misalignment report

A low-resolution (300 m) MPL system (unit number 04) was installed at the
SGP site in April '97 upon the laser diode failure of the 02 unit in
March.  Calibration of this instrument in August found that the optics
were misaligned causing a near range focusing error in the data.  
Calibration files produced for this data, while acceptable, do not 
completely correct for the problem.  As a result, aerosol property 
retrievals using this data are not suggested.  Cloud boundary heights, 
though appear satisfactory.  This system was removed from SGP in early 
September

• Aerosol backscatter coefficient at 355 nm(backscatter)

Laser Output Energy Monitor at Zero

Energy monitor reading for laser output is at zero for intermittant
one-minute averaged shots during this flagged data period.  From the
lidar equation progressing to normalized relative backscatter the
laser energy is required and is a denominator.  Therefore a value of
zero will render the product as infinite.  Shots where this has taken
place are left as zeros.  It is suggested that the time period
19970425 2123 - 19970428 1459
be avoided for any quantitative analysis.

• Aerosol backscatter coefficient at 355 nm(backscatter)

Laser Output Energy Monitor at Zero

Energy monitor reading for laser output is at zero for intermittant
one-minute averaged shots during this flagged data period.  From the
lidar equation progressing to normalized relative backscatter the
laser energy is required and is a denominator.  Therefore a value of
zero will render the product as infinite.  Shots where this has taken
place are left as zeros.  It is suggested that the time periods 
19970902 2211 - 19970903 1359,
19970907 1445 - 19970908 1544,
and
19970910 2142 - 19970910 2355
be avoided for any quantitative analysis.

• Aerosol backscatter coefficient at 355 nm(backscatter)

SGP/MPL - Missing data due to blown detector

Sometime early 11/11 the detector on the
MPL-004 blew out.  The Detector was replaced by Albert Mendoza.
The instrument was operational on Jan. 23, 1999.

Link this to P981119.2 that reported the blown detector and the
corrective action taken

• base time(base_time)
• Preliminary cloud base height(preliminary_cbh)
• Time offset of tweaks from base_time(time_offset)
• Maximum altitude retrieved from multichannel scalar card.(max_altitude)
• Detector Temperature(detector_temp)
• Repetition rate, or Trigger Frequency of the laser(trigger_freq)
• lat(lat)
• range(range)
• Number of laser shots recorded(shots_summed)
• value represents date of last configuration change as yyyymmdd(property)
• Background Signal(background_signal)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• Amount of time the actual laser pulse lags behind the sync trigger(laser_sync_offset)
• Voltage level which operates the thermistor(voltage_10)
• Array of heights for the range gates(height)
• Time in nanoseconds for each range bin of multichannel scalar card.(range_bin_time)
• Number of laser pulses summed during measurement interval(shots_sum)
• Amount of time the scalar lags behind the sync trigger(scalar_sync_offset)
• Laser Temperature(laser_temp)
• Angle of inclination with respect to horizontal(transceiver_altitude_angle)
• Distance from leading edge of first range bin to the center of each bin .(range_bins)
• effective range offset due to poor sync between laser firing and A/D trigger.(range_offset)
• Repetition Rate, or Trigger Frequency of the laser(pulse_rep)
• Angle of orientation with respect to true geographic north(transceiver_azimuth_angle)
• Laser output energy per pulse(energy_monitor)
• Instrument Temperature(instrument_temp)
• Amount of time laser pulse lags behind the scalar trigger(laser_scalar_sync_offset)
• Dummy altitude for Zeb(alt)
• Width of range-bins calculated from range_bin_time(range_bin_width)
• time(time)
• required to correct raw counts for detector deadtime prior to all other
  corrections.(deadtime_correction)
• Voltage level which operates the energy monitor(voltage_15)
• Filter Temperature(filter_temp)
• Sum of raw backscatter counts per bin prior to ANY corrections.(total_counts)
• Voltage level which operates the A/D card and the detector(voltage_05)
• lon(lon)

• (Development raw data stream - documentation not supported)

• Time offset of tweaks from base_time(time_offset)
• lon(lon)
• lat(lat)
• Dummy altitude for Zeb(alt)
• base time(base_time)
• Preliminary cloud base height above ground level(cbh)

• Background Signal(background_signal)
• Instrument Temperature(instrument_temp)
• Time offset of tweaks from base_time(time_offset)
• Cloud base height, measured by MPL(cloud_base_height)
• Laser output energy per pulse(energy_monitor)
• lat(lat)
• Cloud mask(cloud_mask_2)
• Array of heights for the range gates(height)
• Number of laser shots recorded(shots_summed)
• Repetition Rate, or Trigger Frequency of the laser(pulse_rep)
• The update time of the historical baseline used for the cloud boundary
  determination of this sample(baseline_update_time)
• cloud top height(cloud_top_height)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• Flag indicating whether the beam was extinguished at indicated cloud top(cloud_top_attenuation_flag)
• Detector Temperature(detector_temp)
• Laser Temperature(laser_temp)
• Cloud mask(cloud_mask_1)
• lon(lon)
• base time(base_time)
• Relative random error in backscatter profiles(random_error)
• Dummy altitude for Zeb(alt)