NSA/MPL/C1 - laser head failure

On 2002-04-28 the laser energy was observed to decrease throughout the day.  Although low 
clouds continued to be detected, by the end of the day the output laser energy was about 
10% of nomimal.  This decrease continued throughout 2002-04-29 to the extent that clouds 
were no longer detected.  The source of failure was eventually determined to be the laser 
head, requiring the MPL to be shipped for repair.  The MPL was reinstalled on 2002-08-28 
at about 01:00 UTC.  

MPL NSA data from 2002-04-29 through 2002-08-27 (inclusive) should not be used.

• Heights
• MPL Cloth et al. Algorithm Cloud Mask(CloudMaskMplCloth)
• time_offset
• base_time

NSA/MPL/C1 - Laser Q-Switch Problem

At about 22:52 UTC on 2004/01/19, the NSA MPL appears to have suffered a temporary failure 
of the laser Q-Switch.  This results in a complete loss of lidar data immediately 
thereafter.  The problem was resolved (at least for the time being) by disconnecting and 
reconnecting the Q-Switch cable on 2004/01/24 at about 00:16 UTC.  Data after this time appears 
good.

• Heights
• MPL Cloth et al. Algorithm Cloud Mask(CloudMaskMplCloth)
• time_offset
• base_time

NSA/MPL/C1 - Hardware Failure/Missing Data

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

• Heights
• MPL Cloth et al. Algorithm Cloud Mask(CloudMaskMplCloth)
• time_offset
• base_time

NSA/MPL/C1 - Frost on Viewport Window

During periods of extremely cold outside temperatures (-30 C or below), the MPL may suffer 
from reduced sensitivity due to obscuration of its viewport window with frost or 
condensation.  

During the winter of 1998-1999, on-site observers noted frost or condensation obscuring 
part or all of the viewport window.  A fan providing blowing heated air on the viewport had 
failed.  Although replacement of this fan reduced the degree of obscuration, the problem 
was not entirely eliminated.  During the summer of 1999 a more robust  forced-air system 
was installed and the problem was essentially solved except for during isolated cases of 
extremely cold weather.  Under these extreme conditions partial or complete obscuration 
of the window is still possible with the result that cloud detection sensitivity will be 
reduced depending on the fraction of the window surface obscured.  Even with significant 
obscuration, the MPL may still detect clouds and the cloud base heights of detected 
clouds will be reported correctly.  This problem is one of detection sensitivity only and does 
not affect the range scale in any way.

• Heights
• MPL Cloth et al. Algorithm Cloud Mask(CloudMaskMplCloth)