SGP/MFRSR/E34 - Problem with nighttime offset values

Sensor offset values are calculated each night, and at SGP, are applied at 1900 UTC each 
day.  Typically there is very little variation from night-to-night.  At EF-34 we were 
seeing significant steps in the data at 1900 UTC that were attributed to the offset values 
changing substantially.  The cause looks like it might be the linear heater board that was 
in place during the period covered by this DQR.  Note that we replaced the heater board 
on 20120702 which is a bit more than two months after the end of this DQR.  No steps were 
seen after 20120424.  The reason likely being by the 24th it was well into spring and 
approaching summer, and large air temperature changes from day-to-day were not occurring.

Without getting into the gory details here, nighttime offset values are strongly 
influenced by ambient temperature.  Below is a list of days when a step is seen at 1900 UTC:

201201: 2, 3, 5, 12, 17, 26
201202: 5, 11, 24, 26
201203: 13
201204: 24

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• Direct Horizontal Broadband Irradiance(direct_horizontal_broadband)
• Narrowband hemispheric irradiance, filter 4(hemisp_narrowband_filter4_raw)
• Narrowband Hemispheric Irradiance, Filter 3(hemisp_narrowband_filter3_raw)
• Diffuse Narrowband Hemispheric Irradiance, Filter 4(diffuse_hemisp_narrowband_filter4)
• Narrowband diffuse hemispheric irradiance, filter 5, offset and cosine corrected(diffuse_hemisp_narrowband_filter5)
• Diffuse Narrowband Hemispheric Irradiance, Filter 6, offset corrected(diffuse_hemisp_narrowband_filter6)
• Narrowband Hemispheric Irradiance, Filter 6(hemisp_narrowband_filter6_raw)
• Diffuse narrowband hemispheric irradiance, filter 6(diffuse_hemisp_narrowband_filter6_raw)
• Narrowband hemispheric irradiance, filter 5(hemisp_narrowband_filter5_raw)
• Diffuse Narrowband Hemispheric Irradiance, Filter 5(diffuse_hemisp_narrowband_filter5_raw)
• Diffuse Narrowband Hemispheric Irradiance, Filter 1, offset corrected(diffuse_hemisp_narrowband_filter1)
• Diffuse Narrowband Hemispheric Irradiance, Filter 2, offset corrected(diffuse_hemisp_narrowband_filter2)
• Diffuse Narrowband Hemispheric Irradiance, Filter 3(diffuse_hemisp_narrowband_filter3)
• Hemispheric broadband irradiance(hemisp_broadband_raw)
• Diffuse narrowband hemispheric irradiance, filter 4(diffuse_hemisp_narrowband_filter4_raw)
• Diffuse Hemispheric Broadband Irradiance, offset corrected(diffuse_hemisp_broadband)
• Narrowband Direct Horizontal Irradiance, Filter 5, cosine corrected(direct_horizontal_narrowband_filter5)
• Narrowband Direct Horizontal Irradiance, Filter 6, cosine corrected(direct_horizontal_narrowband_filter6)
• Direct Horizontal Narrowband Irradiance, Filter 3(direct_horizontal_narrowband_filter3)
• Narrowband Direct Horizontal Irradiance, Filter 4, cosine corrected(direct_horizontal_narrowband_filter4)
• Direct horizontal narrowband irradiance, filter 1(direct_horizontal_narrowband_filter1)
• Narrowband Direct Horizontal Irradiance, Filter 2, cosine corrected(direct_horizontal_narrowband_filter2)
• Diffuse narrowband hemispheric irradiance, filter 3(diffuse_hemisp_narrowband_filter3_raw)
• Narrowband Hemispheric Irradiance, Filter 5, offset corrected(hemisp_narrowband_filter5)
• Narrowband hemispheric irradiance, filter 6, nominal wavelength is 935 nm(hemisp_narrowband_filter6)
• Narrowband hemispheric irradiance, filter 3, offset and cosine corrected(hemisp_narrowband_filter3)
• Narrowband hemispheric irradiance, filter 4, offset and cosine corrected(hemisp_narrowband_filter4)
• Narrowband Hemispheric Irradiance, Filter 1, offset corrected(hemisp_narrowband_filter1)
• Narrowband hemispheric irradiance, filter 2(hemisp_narrowband_filter2_raw)
• Narrowband Hemispheric Irradiance, Filter 2(hemisp_narrowband_filter2)
• Diffuse Narrowband Hemispheric Irradiance, Filter 2(diffuse_hemisp_narrowband_filter2_raw)
• Diffuse Hemispheric Broadband Irradiance(diffuse_hemisp_broadband_raw)
• Narrowband hemispheric irradiance, filter 1(hemisp_narrowband_filter1_raw)
• Hemispheric broadband irradiance(hemisp_broadband)
• Diffuse narrowband hemispheric irradiance, filter 1(diffuse_hemisp_narrowband_filter1_raw)

• Direct normal narrowband irradiance, filter 2, offset corrected(direct_normal_narrowband_filter2)
• Narrowband Direct Normal Irradiance, Filter 3, cosine corrected(direct_normal_narrowband_filter3)
• Narrowband Direct Normal Irradiance, Filter 1(direct_normal_narrowband_filter1)
• Direct normal narrowband irradiance, filter 6, offset corrected(direct_normal_narrowband_filter6)
• Direct normal narrowband irradiance, filter 4, offset corrected(direct_normal_narrowband_filter4)
• Narrowband Direct Normal Irradiance, Filter 5(direct_normal_narrowband_filter5)
• Narrowband Hemispheric Irradiance, Filter 1, offset corrected(hemisp_narrowband_filter1)
• Narrowband Hemispheric Irradiance, Filter 2(hemisp_narrowband_filter2)
• Narrowband hemispheric irradiance, filter 3, offset and cosine corrected(hemisp_narrowband_filter3)
• Narrowband hemispheric irradiance, filter 4, offset and cosine corrected(hemisp_narrowband_filter4)
• Narrowband Hemispheric Irradiance, Filter 5, offset corrected(hemisp_narrowband_filter5)
• Narrowband hemispheric irradiance, filter 6, nominal wavelength is 935 nm(hemisp_narrowband_filter6)
• Ratio of direct_normal_broadband to diffuse_hemisp_broadband(direct_diffuse_ratio_broadband)
• Ratio of direct_normal_filter1 to diffuse_hemisp_filter1(direct_diffuse_ratio_filter1)
• Ratio of direct_normal_narrowband_filter3 to diffuse_hemisp_narrowband_filter3(direct_diffuse_ratio_filter3)
• Ratio of direct_normal_filter2 to diffuse_hemisp_filter2(direct_diffuse_ratio_filter2)
• Ratio of direct_normal_filter5 to diffuse_hemisp_filter5(direct_diffuse_ratio_filter5)
• Ratio of direct_normal_filter4 to diffuse_hemisp_filter4(direct_diffuse_ratio_filter4)
• Direct Horizontal Narrowband Irradiance, Filter 3(direct_horizontal_narrowband_filter3)
• Narrowband Direct Horizontal Irradiance, Filter 4, cosine corrected(direct_horizontal_narrowband_filter4)
• Direct horizontal narrowband irradiance, filter 1(direct_horizontal_narrowband_filter1)
• Narrowband Direct Horizontal Irradiance, Filter 2, cosine corrected(direct_horizontal_narrowband_filter2)
• Hemispheric broadband irradiance(hemisp_broadband)
• Narrowband Direct Horizontal Irradiance, Filter 5, cosine corrected(direct_horizontal_narrowband_filter5)
• Narrowband Direct Horizontal Irradiance, Filter 6, cosine corrected(direct_horizontal_narrowband_filter6)
• Diffuse Narrowband Hemispheric Irradiance, Filter 1, offset corrected(diffuse_hemisp_narrowband_filter1)
• Diffuse Narrowband Hemispheric Irradiance, Filter 2, offset corrected(diffuse_hemisp_narrowband_filter2)
• Diffuse Narrowband Hemispheric Irradiance, Filter 3(diffuse_hemisp_narrowband_filter3)
• Direct Horizontal Broadband Irradiance(direct_horizontal_broadband)
• Ratio of direct_normal_narrowband_filter6 to diffuse_hemisp_narrowband_filter6(direct_diffuse_ratio_filter6)
• Diffuse Hemispheric Broadband Irradiance, offset corrected(diffuse_hemisp_broadband)
• Diffuse Narrowband Hemispheric Irradiance, Filter 4(diffuse_hemisp_narrowband_filter4)
• Direct Normal Broadband Irradiance, cosine corrected, broadband scale applied(direct_normal_broadband)
• Narrowband diffuse hemispheric irradiance, filter 5, offset and cosine corrected(diffuse_hemisp_narrowband_filter5)
• Diffuse Narrowband Hemispheric Irradiance, Filter 6, offset corrected(diffuse_hemisp_narrowband_filter6)