SGP/IRT/E13 - Missing data

Data are missing and unrecoverable.

• IR Brightness Temperature(sky_ir_temp)
• alt
• sky_ir_temp_max
• samples_in_average
• base_time
• lon
• sky_ir_temp_std
• lat
• sky_ir_temp_min
• time_offset
• time
• ref_ir_temp
• ref_ir_temp_std

• alt
• IR Brightness Temperature(sky_ir_temp)
• time
• lat
• time_offset
• ref_ir_temp
• lon
• base_time

SGP/IRT/E13 - Reprocess: Sky temperature bias

Measurements of sky temperature, especially those <250K,, were positively biased compared 
with AERI because there was no compensation for the effect of the emissivity and 
temperature of the gold mirror. The problem was corrected by changing the IRT emissivity from 
1.000 to 0.987, adding an RTD and transmitter electronics to measure the temperature of the 
mirror, and changing the ambient temperature measurement for internal reference to 
external mirror temperature.

Use sky temperature measurements less than 230K with caution. Biases as large as 30K have 
been observed when the actual temperature, as measured by AERI, is less than 210 K.

• IR Brightness Temperature(sky_ir_temp)
• sky_ir_temp_max
• sky_ir_temp_min

• IR Brightness Temperature(sky_ir_temp)

SGP/IRT/E13 - Reprocess: Sensor Calibration

The measurements are greater than AERI, especially when sky temperature is less than -40C. 
The lens and mirror was cleaned on 11/21/2008 and the mirror was replaced on 1/28/2009 
but these actions did not correct the problem. It was learned that the internal 
calibration factor was not changed by the manufacturer after the unit was repaired and recalibrated 
on 9/6/2007. The calibration factor was corrected from 1.2172 to 1.4100 on 2/12/2009.

• IR Brightness Temperature(sky_ir_temp)
• sky_ir_temp_max
• sky_ir_temp_std
• sky_ir_temp_min

• IR Brightness Temperature(sky_ir_temp)

SGP/IRT/E13 - Reprocess: wrong units

While diagnosing serial communication problems, the IRT configuration was reset to factory 
defaults so the temperature unit parameter was set to C instead of K.

• IR Brightness Temperature(sky_ir_temp)
• ref_ir_temp
• sky_ir_temp_max
• sky_ir_temp_min

• ref_ir_temp
• IR Brightness Temperature(sky_ir_temp)

SGP/IRT/E13 - Response time

The time response of the temperature measurement was changed from 1.0 to 0.1 sec to 
accommodate the 5Hz sample rate. This caused a 370% decrease in the resolution (to 1.85C at a 
sky temperature of -50C) and a significant decrease in the signal-to-noise ratio.

• ref_ir_temp_std
• sky_ir_temp_std

• ref_ir_temp
• IR Brightness Temperature(sky_ir_temp)

SGP/IRT/E21 - Missing data

Data are missing and unrecoverable.

• samples_in_average
• ref_ir_temp
• alt
• time_offset
• base_time
• IR Brightness Temperature(sky_ir_temp)
• lat
• lon
• sky_ir_temp_max
• time
• sky_ir_temp_min
• ref_ir_temp_std
• sky_ir_temp_std

SGP/IRT/E13 - Instrument output invalid

The signal was missing for 25 min and then changed to a constant values of 
sky_ir_temp=262.22K and ref_ir_temp=313.10K. The problem was corrected when the intrument was 
power-cycled.

• IR Brightness Temperature(sky_ir_temp)
• ref_ir_temp
• sky_ir_temp_max
• ref_ir_temp_std
• sky_ir_temp_std
• sky_ir_temp_min

• ref_ir_temp
• IR Brightness Temperature(sky_ir_temp)

SGP/IRT/E21 - TimeCheck Error

The EF data system lost communication with the GPS likely starting on or around June 7th; 
the max time offset for E21 was -5.04 sec. Then it began increasing steadily:

Jun 8  Offset:	  -267.449039
Jun 9  Offset:	  -541.038624
Jun 10 Offset:	  -814.469141
Jun 11 Offset:	  -1076.862114
Jun 12 Offset:	  -1350.330223
Jun 13 Offset:	  -1623.639335
Jun 14 Offset:	  -1897.047754
Jun 15 Offset:	  -2170.552312
Jun 16 Offset:	  -2422.130746
Jun 17 Offset:	  -2684.607495
Jun 18 - Jun 22 (unknown)
Jun 23 Offset:	  -4204.730579

If the system clock drifts the irt_comm program will get the same incorrect time. IRT 
temperature data will be correct but the corresponding time stamp cannot be accurately known 
or simply corrected for.

• time
• time_offset
• base_time

SGP/IRT/E12 - Reprocess: Calibration error

The measured sky temperature was lower than other SGP facilities because the original 
calibration, as set be the vendor, was wrong. The IRT was replaced and returned to the vendor.

• sky_ir_temp_min
• sky_ir_temp_max
• IR Brightness Temperature(sky_ir_temp)