SGP/MFRSR/E4 - Offset contamination at sunrise/sunset

The 415 nm filters, 500 nm filters, & 673 nm filters were flatlining in the morning and 
late afternoon hours.  The flatlining is an artifact of the ingest. Nighttime offsets are 
determined each night and added back to the following day's data. If the offset is large 
negative, it will report the offset value until the data in the day go positive. When the 
instrument is running in shadowband mode negative values are not reported, resulting in 
the flatline behavior.  This issue is generally only seen just after sunrise and just 
before sunset on cloudy/overcast days.

Avoid data when flatline behavior is seen.

• Ratio of direct_normal_filter1 to diffuse_hemisp_filter1(direct_diffuse_ratio_filter1)
• Direct normal narrowband irradiance, filter 2, offset corrected(direct_normal_narrowband_filter2)
• Ratio of direct_normal_filter2 to diffuse_hemisp_filter2(direct_diffuse_ratio_filter2)
• Narrowband Direct Normal Irradiance, Filter 1(direct_normal_narrowband_filter1)
• Ratio of direct_normal_filter4 to diffuse_hemisp_filter4(direct_diffuse_ratio_filter4)
• Direct normal narrowband irradiance, filter 4, offset corrected(direct_normal_narrowband_filter4)
• Alltime narrowband hemispheric irradiance, filter 2(alltime_hemisp_narrowband_filter2)
• Alltime narrowband hemispheric irradiance, filter 1(alltime_hemisp_narrowband_filter1)
• Alltime Narrowband Hemispheric Irradiance, Filter 4(alltime_hemisp_narrowband_filter4)
• Narrowband Direct Horizontal Irradiance, Filter 4, cosine corrected(direct_horizontal_narrowband_filter4)
• Narrowband Direct Horizontal Irradiance, Filter 2, cosine corrected(direct_horizontal_narrowband_filter2)
• Direct horizontal narrowband irradiance, filter 1(direct_horizontal_narrowband_filter1)
• Diffuse Narrowband Hemispheric Irradiance, Filter 4(diffuse_hemisp_narrowband_filter4)
• Diffuse Narrowband Hemispheric Irradiance, Filter 2, offset corrected(diffuse_hemisp_narrowband_filter2)
• Diffuse Narrowband Hemispheric Irradiance, Filter 1, offset corrected(diffuse_hemisp_narrowband_filter1)
• Narrowband Hemispheric Irradiance, Filter 2(hemisp_narrowband_filter2)
• Narrowband Hemispheric Irradiance, Filter 1, offset corrected(hemisp_narrowband_filter1)
• Narrowband hemispheric irradiance, filter 4, offset and cosine corrected(hemisp_narrowband_filter4)

• Narrowband Direct Horizontal Irradiance, Filter 4, cosine corrected(direct_horizontal_narrowband_filter4)
• Diffuse Narrowband Hemispheric Irradiance, Filter 4(diffuse_hemisp_narrowband_filter4)
• Alltime narrowband hemispheric irradiance, filter 2(alltime_hemisp_narrowband_filter2)
• Alltime narrowband hemispheric irradiance, filter 1(alltime_hemisp_narrowband_filter1)
• Alltime Narrowband Hemispheric Irradiance, Filter 4(alltime_hemisp_narrowband_filter4)
• Diffuse Narrowband Hemispheric Irradiance, Filter 2, offset corrected(diffuse_hemisp_narrowband_filter2)
• Diffuse Narrowband Hemispheric Irradiance, Filter 1, offset corrected(diffuse_hemisp_narrowband_filter1)
• Direct horizontal narrowband irradiance, filter 1(direct_horizontal_narrowband_filter1)
• Narrowband Direct Horizontal Irradiance, Filter 2, cosine corrected(direct_horizontal_narrowband_filter2)
• Narrowband Hemispheric Irradiance, Filter 1, offset corrected(hemisp_narrowband_filter1)
• Narrowband Hemispheric Irradiance, Filter 2(hemisp_narrowband_filter2)
• Narrowband hemispheric irradiance, filter 4, offset and cosine corrected(hemisp_narrowband_filter4)