SGP/SIRS/E19 - Instrument mux problem

Beginning 7/31, the upwelling_longwave_hemispheric data were intermittent with periods of 
erratic and missing data typically during daylight hours. A multiplexer was found to be 
the problem and replaced 8/31 1630GMT.

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• Instantaneous Upwelling Pyrgeometer Dome Thermistor Resistance Pyrgeometer(inst_up_long_dome_resist)
• Instantaneous Upwelling Pyrgeometer Case Thermistor Resistance, Pyrgeometer(inst_up_long_case_resist)
• Instantaneous Upwelling Pyrgeometer Thermopile Pyrgeometer(inst_up_long_hemisp_tp)

• Upwelling Longwave Hemispheric Irradiance, Pyrgeometer, Minima(up_long_hemisp_min)
• Upwelling (10 meter) Longwave Hemispheric Irradiance, Ventilated Pyrgeometer,
  Standard Deviation(up_long_hemisp_std)
• Instantaneous Upwelling Longwave Hemispheric Irradiance, Pyrgeometer(up_long_netir)
• Upwelling longwave hemispheric irradiance, pyrgeometer, maxima(up_long_hemisp_max)
• Instantaneous upwelling pyrgeometer case thermistor temperature, pyrgeometer(inst_up_long_case_temp)
• 10 meter Upwelling Longwave Hemispheric Irradiance, Pyrgeometer(up_long_hemisp)
• Instantaneous Dome Temperature(inst_up_long_dome_temp)