NSA/MPL/C1 - Hardware Failure/Missing Data

Data are missing during this extended period due to a hardware failure.

• MPL Cloth et al. Algorithm Significance Mask(SigniMaskMplCloth)
• Range Heights (center of radar sample volume)(Heights)
• Time offset from base_time(base_time)
• Time offset of tweaks from base_time(time_offset)

• Raw data stream - documentation not supported(Raw data stream - documentation not supported)

• Range Heights (center of radar sample volume)(Heights)
• MPL Clothiaux et al. Algorithm Cloud Mask Occurrence(CloudMaskMplCloth)
• Time offset of tweaks from base_time(time_offset)
• Time offset from base_time(base_time)

• Angle of orientation with respect to true geographic north(transceiver_azimuth_angle)
• Amount of time the actual laser pulse lags behind the sync trigger(laser_sync_offset)
• Number of laser pulses summed during measurement interval(shots_summed)
• Time offset from base_time(base_time)
• Background signal(background_signal)
• Amount of time the scalar lags behind the sync trigger(scalar_sync_offset)
• Aerosol volume backscattering coefficient at 355 nm(backscatter)
• required to correct raw counts for detector deadtime prior to all other
  corrections.(deadtime_correction)
• Maximum altitude retrieved from multichannel scalar card.(max_altitude)
• Laser temperature(laser_temp)
• Number of laser pulses summed during measurement interval(shots_sum)
• Distance from leading edge of first range bin to the center of each bin.(range_bins)
• Preliminary cloud base height above ground level(preliminary_cbh)
• Voltage level which operates the A/D card and the detector(voltage_05)
• value represents date when configuration is first applicable as YYYYMMDD(property)
• Height of bins above ground level for the temperature, retrieved water vapor,
  and pressure profile(height)
• Time offset from midnight of date of file. For CO data, this is identical to
  time_offset and is included for compatibility.(time)
• north latitude for all the input platforms.(lat)
• Repetition rate, or Trigger Frequency of the laser(trigger_freq)
• Time in nanoseconds for each range bin of multichannel scalar card.(range_bin_time)
• Time offset of tweaks from base_time(time_offset)
• effective range offset due to poor sync between laser firing and A/D trigger.(range_offset)
• Detector temperature(detector_temp)
• altitude above sea levelaltunits(alt)
• Voltage level which operates the energy monitor(voltage_15)
• Sum of raw backscatter counts per bin prior to ANY corrections.(total_counts)
• Voltage level which operates the thermistor(voltage_10)
• Amount of time laser pulse lags behind the scalar trigger(laser_scalar_sync_offset)
• Filter temperature(filter_temp)
• Instrument temperature(instrument_temp)
• Width of range-bins calculated from range_bin_time(range_bin_width)
• Repetition rate, or Trigger Frequency of the laser(pulse_rep)
• east longitude for all the input platforms.(lon)
• Energy output per pulse of transmitted laser beam at 523 nm (Doubled Nd-YLF)(energy_monitor)
• Angle of inclination with respect to horizontal(transceiver_altitude_angle)
• distance to center of range bin after correcting for offset in sync(range)

NSA/MPL/C1 - MPL clock drift

The MPL PC clock was noted to be off (slow) by more than an hour over a several day 
period.  It has previously been noted that the time synchronization program "D-4" fails to 
update the PC clock under certain circumstances.  As a result, the program "D-4" was replaced 
by "AboutTime" on 2/5/2004.  

The specifics of this problem are not well understood.  It turns out that the instrument 
has TWO clocks on the instrument computer display - one being displayed by the MPL 
software and the other being the PC clock displayed in the lower right-hand corner of the 
screen. The MPL software clock was the one that is noted on daily rounds and was never off by 
any amount. Apparently the only clock that was off was the computer clock.

What is clear is that between the time the MPL computer was installed on 11-11-2003 and 
the CM log on 1-06-2004 the MPL clock exhibited a discrepancy of over 1 hour and 20 
minutes.  What is not clear is whether this clock discrepancy was also applied to the data time 
stamps.  Furthermore, seven days later the MPL clock exhibited only a 1.77 second drift.  
Not exceptional at all, and not in line with the previous discrepancy of more than 4800 
seconds over a span of 57 days.

Attempts to identify gradual correctible clock drift in the MPL data were not successful.  
As a worst-case scenario, the MPL data may be inappropriately time-stamped by as much a 
1 hour 20 minutes and 41 seconds slow relative to UTC between the dates of 2003-11-11 and 
2004-01-06.  After this time until 2004-02-05 time synchronization was maintained within 
a few seconds a day with local observer assistance.

• Time offset from midnight of date of file. For CO data, this is identical to
  time_offset and is included for compatibility.(time)
• Time offset of tweaks from base_time(time_offset)
• Time offset from base_time(base_time)

• Time offset of tweaks from base_time(time_offset)
• Time offset from base_time(base_time)
• Time offset from midnight of date of file. For CO data, this is identical to
  time_offset and is included for compatibility.(time)