SGP/MFRSR/E9 - Large night-time offsets

Some channels (415, 673 and 940) are flatlining in the early morning and late afternoon.  
This is not an instrument problem per se, but a result of the new data calibration 
procedure combined with the way the instrument operates. This problem is noticeable when an 
instrument has an unusually large negative nighttime offset.  The new data calibration 
procedure adds back the offset to daytime data.  The problem arises because the MFRSR, in 
banding mode, doesn't allow for values less than 0.  So the large offset gets added back to 
the global and diffuse data producing the "flatline" until raw values exceed zero. It is 
most noticeable on very overcast days.

• Narrowband Direct Normal Irradiance, Filter 1(direct_normal_narrowband_filter1)
• Direct normal narrowband irradiance, filter 4, offset corrected(direct_normal_narrowband_filter4)
• Offset subtracted from hemispheric filter1 data(offset_filter1)
• Offset subtracted from direct normal filter4 data(offset_filter4)
• Narrowband Direct Horizontal Irradiance, Filter 4, cosine corrected(direct_horizontal_narrowband_filter4)
• Narrowband Direct Horizontal Irradiance, Filter 6, cosine corrected(direct_horizontal_narrowband_filter6)
• Offset subtracted from hemispheric and diffuse filter6 data(offset_filter6)
• Alltime Narrowband Hemispheric Irradiance, Filter 4(alltime_hemisp_narrowband_filter4)
• Alltime narrowband hemispheric irradiance, filter 1(alltime_hemisp_narrowband_filter1)
• Alltime Narrowband Hemispheric Irradiance, Filter 6(alltime_hemisp_narrowband_filter6)
• Ratio of direct_normal_narrowband_filter6 to diffuse_hemisp_narrowband_filter6(direct_diffuse_ratio_filter6)
• Ratio of direct_normal_filter4 to diffuse_hemisp_filter4(direct_diffuse_ratio_filter4)
• Ratio of direct_normal_filter1 to diffuse_hemisp_filter1(direct_diffuse_ratio_filter1)
• Diffuse Narrowband Hemispheric Irradiance, Filter 6, offset corrected(diffuse_hemisp_narrowband_filter6)
• Narrowband hemispheric irradiance, filter 4, offset and cosine corrected(hemisp_narrowband_filter4)
• Direct horizontal narrowband irradiance, filter 1(direct_horizontal_narrowband_filter1)
• Diffuse Narrowband Hemispheric Irradiance, Filter 4(diffuse_hemisp_narrowband_filter4)
• Narrowband Hemispheric Irradiance, Filter 1, offset corrected(hemisp_narrowband_filter1)
• Direct normal narrowband irradiance, filter 6, offset corrected(direct_normal_narrowband_filter6)
• Diffuse Narrowband Hemispheric Irradiance, Filter 1, offset corrected(diffuse_hemisp_narrowband_filter1)
• Narrowband hemispheric irradiance, filter 6, nominal wavelength is 935 nm(hemisp_narrowband_filter6)

• Diffuse Narrowband Hemispheric Irradiance, Filter 1, offset corrected(diffuse_hemisp_narrowband_filter1)
• Diffuse Narrowband Hemispheric Irradiance, Filter 6, offset corrected(diffuse_hemisp_narrowband_filter6)
• Offset subtracted from hemispheric filter1 data(offset_filter1)
• Diffuse Narrowband Hemispheric Irradiance, Filter 4(diffuse_hemisp_narrowband_filter4)
• Offset subtracted from direct normal filter4 data(offset_filter4)
• Direct horizontal narrowband irradiance, filter 1(direct_horizontal_narrowband_filter1)
• Offset subtracted from hemispheric and diffuse filter6 data(offset_filter6)
• Narrowband Hemispheric Irradiance, Filter 1, offset corrected(hemisp_narrowband_filter1)
• Narrowband hemispheric irradiance, filter 4, offset and cosine corrected(hemisp_narrowband_filter4)
• Narrowband hemispheric irradiance, filter 6, nominal wavelength is 935 nm(hemisp_narrowband_filter6)
• Narrowband Direct Horizontal Irradiance, Filter 4, cosine corrected(direct_horizontal_narrowband_filter4)
• Alltime Narrowband Hemispheric Irradiance, Filter 6(alltime_hemisp_narrowband_filter6)
• Narrowband Direct Horizontal Irradiance, Filter 6, cosine corrected(direct_horizontal_narrowband_filter6)
• Alltime Narrowband Hemispheric Irradiance, Filter 4(alltime_hemisp_narrowband_filter4)
• Alltime narrowband hemispheric irradiance, filter 1(alltime_hemisp_narrowband_filter1)

• percentage of initial points used in final linear fit for the Direct Narrowband
  Filter6(barnard_good_fraction_filter6)
• percentage of initial points used in final linear fit for the Direct Narrowband
  Filter4(barnard_good_fraction_filter4)
• optical depth for the Direct Narrowband Filter1(michalsky_optical_depth_filter1)
• error in optical depth (slope) of final linear fit for the Direct Narrowband
  Filter4(barnard_error_slope_filter4)
• error in optical depth (slope) of final linear fit for the Direct Narrowband
  Filter6(barnard_error_slope_filter6)
• optical depth for the Direct Narrowband Filter6(michalsky_optical_depth_filter6)
• optical depth for the Direct Narrowband Filter4(michalsky_optical_depth_filter4)
• percentage of initial points used in final linear fit for the Direct Narrowband
  Filter1(barnard_good_fraction_filter1)
• rejection flag for Direct Narrowband Filter4(michalsky_badflag_filter4)
• rejection flag for Direct Narrowband Filter6(michalsky_badflag_filter6)
• standard deviation around regression line for the Direct Narrowband Filter4(michalsky_standard_deviation_filter4)
• standard deviation around regression line for the Direct Narrowband Filter6(michalsky_standard_deviation_filter6)
• rejection flag for Direct Narrowband Filter1(michalsky_badflag_filter1)
• standard deviation around regression line for the Direct Narrowband Filter1(michalsky_standard_deviation_filter1)
• number of points used in final linear fit for the Direct Narrowband Filter1(barnard_number_points_filter1)
• number of points used in final linear fit for the Direct Narrowband Filter6(barnard_number_points_filter6)
• number of points used in final linear fit for the Direct Narrowband Filter4(barnard_number_points_filter4)
• rejection flag for Direct Narrowband Filter1(barnard_badflag_filter1)
• number of points used in final linear fit for the Direct Narrowband Filter6(michalsky_number_points_filter6)
• optical depth for the Direct Narrowband Filter1(barnard_optical_depth_filter1)
• number of points used in final linear fit for the Direct Narrowband Filter4(michalsky_number_points_filter4)
• rejection flag for Direct Narrowband Filter6(barnard_badflag_filter6)
• rejection flag for Direct Narrowband Filter4(barnard_badflag_filter4)
• optical depth for the Direct Narrowband Filter6(barnard_optical_depth_filter6)
• optical depth for the Direct Narrowband Filter4(barnard_optical_depth_filter4)
• percentage of initial points used in final linear fit for the Direct Narrowband
  Filter6(michalsky_good_fraction_filter6)
• percentage of initial points used in final linear fit for the Direct Narrowband
  Filter4(michalsky_good_fraction_filter4)
• percentage of initial points used in final linear fit for the Direct Narrowband
  Filter1(michalsky_good_fraction_filter1)
• error in optical depth (slope) of final linear fit for the Direct Narrowband
  Filter1(barnard_error_slope_filter1)
• error in final linear fit for the Direct Narrowband Filter6(barnard_error_fit_filter6)
• number of points used in final linear fit for the Direct Narrowband Filter1(michalsky_number_points_filter1)
• error in final linear fit for the Direct Narrowband Filter1(barnard_error_fit_filter1)
• error in final linear fit for the Direct Narrowband Filter4(barnard_error_fit_filter4)

• log(irradiance) for the Direct Narrowband Filter1, Barnard(barnard_lnI_filter1)
• log(irradiance) for the Direct Narrowband Filter4(barnard_lnI_filter4)
• log(irradiance) for the Direct Narrowband Filter6(barnard_lnI_filter6)
• rejected points for the final fit for the Direct Narrowband Filter6(barnard_rejected_filter6)
• rejected points for the final fit for the Direct Narrowband Filter4, Barnard(barnard_rejected_filter4)
• rejected points for the final fit for the Direct Narrowband Filter1, Michalsky(michalsky_rejected_filter1)
• rejected points for the final fit for the Direct Narrowband Filter6, Michalsky(michalsky_rejected_filter6)
• rejected points for the final fit for the Direct Narrowband Filter4, Michalsky(michalsky_rejected_filter4)
• log(irradiance) for the Direct Narrowband Filter6, Michalsky(michalsky_lnI_filter6)
• log(irradiance) for the Direct Narrowband Filter4, Michalsky(michalsky_lnI_filter4)
• log(irradiance) for the Direct Narrowband Filter1(michalsky_lnI_filter1)
• rejected points for the final fit for the Direct Narrowband Filter1(barnard_rejected_filter1)