SGP/MFR10M/C1 - Data discontinuities

There is a discontinuity in the data (all channels) just after 1500 UTC on June 27, 2003 
and again, just before 1930 UTC on Jan 20, 2005.  There is nothing unusual in the temp or 
volt data.

At these times the tower was lowered for cleaning so the initial assumption was the 
instrument was dirty, and a cleaning resulted in the discontinuity.  This theory doesn't hold 
up well though as the tower is lowered for instrument cleaning regularly and these are the 
only two times in the past few years that a discontinuity coinciding with a lowering of 
the tower has resulted.  

Also, down pointing instruments are also not prone to collecting dust and dirt.  This 
instrument is located on the E13 SIRS tower and the down pointing PSP does not show a 
discontinuity at either time, which further discounts the dirty instrument theory.  Site 
operations were asked to check the instrument mount to see if it was loose possibly causing the 
instrument to change its position, and they reported that the mount seemed secure and 
stable.  So as of now, the cause of this issue is a mystery.

Compare with other down pointing instruments to help ascertain if data on one side of the 
discontinuity or the other are "better."  Perform an error analysis to determine if this 
would introduce a significant error in the role the data stream plays in a user's research.

• 3 meter upwelling broadband hemispheric irradiance(up_hemisp_broadband)
• 10 meter Narrowband Upwelling Hemispheric Irradiance, Filter 6(up_hemisp_narrowband_filter6)
• 3 meter upwelling narrowband hemispheric irradiance, filter 4(up_hemisp_narrowband_filter4)
• 25 meter upwelling narrowband hemispheric irradiance, filter 5, offset corrected(up_hemisp_narrowband_filter5)
• 3 meter upwelling narrowband hemispheric irradiance, filter 2, offset corrected(up_hemisp_narrowband_filter2)
• 3 meter upwelling narrowband hemispheric irradiance, filter 3, offset corrected(up_hemisp_narrowband_filter3)
• 10 meter upwelling narrowband hemispheric irradiance, filter 1(up_hemisp_narrowband_filter1)

• 10 meter upwelling narrowband hemispheric irradiance, filter 1(up_hemisp_narrowband_filter1)
• 3 meter upwelling broadband hemispheric irradiance(up_hemisp_broadband)
• 3 meter upwelling narrowband hemispheric irradiance, filter 3, offset corrected(up_hemisp_narrowband_filter3)
• 3 meter upwelling narrowband hemispheric irradiance, filter 2, offset corrected(up_hemisp_narrowband_filter2)
• 25 meter upwelling narrowband hemispheric irradiance, filter 5, offset corrected(up_hemisp_narrowband_filter5)
• 3 meter upwelling narrowband hemispheric irradiance, filter 4(up_hemisp_narrowband_filter4)
• 10 meter Narrowband Upwelling Hemispheric Irradiance, Filter 6(up_hemisp_narrowband_filter6)