NSA/MWR/C1 - Temperature Stabilization of Noise Diode Impaired

On 1/17 we had a big spike in the data and lost temperature stabilization. The instrument 
had problems maintaining the Noise Diode (ND) temperature since. At ambient temperatures 
under about -20 C the ND was not maintaining the set temperature of 30 C. This problem 
was reported in P010122.1.

Fred Solheim recommended on 1/22 that we powercycle the instrument as it looked like the 
instrument CPU had lost the temperature reference.

So we powercycled the instrument on 1/22 @ 20:30 and lost all comumnication to it; after a 
second powercycling the instrument came back on line and the temperature stabilized 
quickly (within a couple of minutes) to the set temperature (30 C)

Fred Solheim reported after the system was restored:
"I've never seen this behavior before. I don't think it was due to the RF deck physically 
hanging temperature, because the recorded temp dropped about 30 C in one observation 
cycle. If this happens again, send the MWR down along with data files for us to look at."

Data collected in the periode 1/17/2001 6:00 to 1/22/2001 21:45 are questionable since it 
is uncertain whether the temperature really was unstable and what really caused the 
problem.

• tbsky31_sdev
• tbsky23_sdev
• Total liquid water along LOS path(liq)
• ir_temp_sdev
• num_obs_irt
• liq_sdev
• num_obs
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)
• Temperature, brightness, longwave(ir_temp)
• Total water vapor along LOS path(vap)
• water_flag_fraction
• vap_sdev
• 31.4 GHz sky brightness temperature(tbsky31)

• bb31
• tnd_nom23
• 31.4 GHz sky brightness temperature(tbsky31)
• tnd23
• Total liquid water along LOS path(liq)
• Total water vapor along LOS path(vap)
• bbn31
• tkair
• tkxc
• sky23
• bb23
• tkbb
• sky31
• tnd31
• tc23
• tnd_nom31
• Temperature, brightness, longwave(ir_temp)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)
• tc31
• bbn23
• tknd
• wet_window

• 31.4 GHz sky brightness temperature(tbsky31)
• Total water vapor along LOS path(vap)
• wet_window
• Total liquid water along LOS path(liq)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)
• Temperature, brightness, longwave(ir_temp)

NSA/MWR/C1 - negative sky brightness temperatures

The data exhibit occasional negative sky brightness temperatures.
The problem was corrected when the site operator cleaned the cable connectors and coated 
the terminals with dielectric grease.

• 31.4 GHz sky brightness temperature(tbsky31)
• Total liquid water along LOS path(liq)
• tkxc
• Total water vapor along LOS path(vap)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)

• 31.4 GHz sky brightness temperature(tbsky31)
• Total water vapor along LOS path(vap)
• Total liquid water along LOS path(liq)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)

NSA/MWR/C1 - negative sky brightness temperatures

The data exhibit occasional negative sky brightness temperatures.
The problem was corrected when the computer was reconfigured following a virus infection.

• 31.4 GHz sky brightness temperature(tbsky31)
• Total liquid water along LOS path(liq)
• tkxc
• Total water vapor along LOS path(vap)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)

• 31.4 GHz sky brightness temperature(tbsky31)
• Total water vapor along LOS path(vap)
• Total liquid water along LOS path(liq)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)

NSA/MWR/C1 - Reprocess: calibration change

The thicker (1/2-inch) insulation was installed on the RF deck and the reference 
temperature was reduced from 50 C to 30 C to prevent thermal instability in winter. A change in 
the mixer temperature affects the instrument's calibration. A new calibration was 
automatically derived and applied after 1500 valid tip curves were acquired. During the period 
after the temperature was reset and before the calibration was updated, the previous 
calibration was used.

• 31.4 GHz sky brightness temperature(tbsky31)
• Total liquid water along LOS path(liq)
• Total water vapor along LOS path(vap)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)

• 31.4 GHz sky brightness temperature(tbsky31)
• Total water vapor along LOS path(vap)
• Total liquid water along LOS path(liq)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)

NSA/MWR/C1 - incorrect flagging of data

The wet window flag is set high more than expected.

• wet_window

• wet_window

• wet_window

NSA/MWR/C1 - incorrect flagging of data

The wet window flag is set high more frequent than expected.

• wet_window

• wet_window

• wet_window

NSA/MWR/C1 - Reprocess: calibration change

The computer was replaced but not configured correctly for the MWR.

• tnd_nom23
• 31.4 GHz sky brightness temperature(tbsky31)
• tc23
• tnd_nom31
• Total liquid water along LOS path(liq)
• Total water vapor along LOS path(vap)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)
• tc31

• 31.4 GHz sky brightness temperature(tbsky31)
• Total liquid water along LOS path(liq)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)
• Total water vapor along LOS path(vap)

• tnd_nom31
• tnd_nom23
• tipsky31
• tc31
• tc23
• tipsky23

NSA/MWR/C1 - Reprocess: wrong calibration

Moisture was found inside the lens of the MWR. Removal of the moisture caused a 
significant change in the calibration, especially in the 23.8 GHz channel. The calibration was 
updated automatically.

• 31.4 GHz sky brightness temperature(tbsky31)
• Total liquid water along LOS path(liq)
• Total water vapor along LOS path(vap)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)

• 31.4 GHz sky brightness temperature(tbsky31)
• Total liquid water along LOS path(liq)
• Total water vapor along LOS path(vap)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)

NSA/MWR/C1 - Contamination or Calibration Effect

A short period of odd data occurs in PWV and the LWP.  Its a sudden offset in the data 
values.  Vic Morris suggests it could be a calibration issue as seen before at SGP.  Data 
make a marked change after the events (suggesting the data were questionable prior to this 
time).  No obvious changes in other instruments occur. Some of these effects may coincide 
with operator's preventive maintenance but others are in the middle of the night local 
time and can not be explained by cleaning.

• Total liquid water along LOS path(liq)
• Total water vapor along LOS path(vap)

• Total liquid water along LOS path(liq)
• Total water vapor along LOS path(vap)

NSA/MWR/C1 - Frosting

Spike in PWV and LWP
. Operator reports instrument is frosted. Instrument teflon window was cleaned by 
operator.

• Total liquid water along LOS path(liq)
• Total water vapor along LOS path(vap)

• Total liquid water along LOS path(liq)
• Total water vapor along LOS path(vap)

NSA/MWR/C1 - Instrument maintenance

Installed cold weather insulation on radiometer, required time to thermally stabilize.

• skyn31
• 31.4 GHz sky brightness temperature(tbsky31)
• tnd23
• Total liquid water along LOS path(liq)
• Total water vapor along LOS path(vap)
• IR Brightness Temperature(sky_ir_temp)
• tair
• tkxc
• sky23
• skyn23
• bb23
• tkbb
• tc23
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)
• Temperature, brightness, longwave(ir_temp)
• unoise23
• tc31
• bbn23
• bb31
• tnd_nom23
• unoise31
• bbn31
• tkair
• losn
• sky31
• tnd31
• tnd_nom31
• tknd
• wet_window

• 31.4 GHz sky brightness temperature(tbsky31)
• IR Brightness Temperature(sky_ir_temp)
• sky23
• tkxc
• Total water vapor along LOS path(vap)
• tkbb
• bbn23
• tkair
• bb23
• sky31
• tnd_nom31
• Temperature, brightness, longwave(ir_temp)
• bbn31
• tnd23
• tknd
• tnd_nom23
• bb31
• wet_window
• Total liquid water along LOS path(liq)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)
• tnd31
• tc23
• tc31

NSA/MWR/C1 - MWR moved

The MWR data are unreasonable during this period, because it was shutdown and moved by 
operations at this time.

• skyn31
• 31.4 GHz sky brightness temperature(tbsky31)
• tnd23
• Total liquid water along LOS path(liq)
• Total water vapor along LOS path(vap)
• IR Brightness Temperature(sky_ir_temp)
• alt
• tair
• actaz
• tkxc
• sky23
• skyn23
• bb23
• tkbb
• tc23
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)
• Temperature, brightness, longwave(ir_temp)
• unoise23
• lat
• tc31
• base_time
• bbn23
• bb31
• tnd_nom23
• time_offset
• unoise31
• bbn31
• tkair
• losn
• sky31
• tnd31
• tnd_nom31
• actel
• tknd
• wet_window
• lon

• 31.4 GHz sky brightness temperature(tbsky31)
• sky23
• IR Brightness Temperature(sky_ir_temp)
• tkxc
• Total water vapor along LOS path(vap)
• alt
• tkbb
• bbn23
• base_time
• tkair
• bb23
• sky31
• tnd_nom31
• Temperature, brightness, longwave(ir_temp)
• bbn31
• lon
• tnd23
• tknd
• tnd_nom23
• bb31
• time_offset
• wet_window
• lat
• Total liquid water along LOS path(liq)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)
• tnd31
• tc23
• actel
• tc31
• actaz

NSA/MWR/C1 - negative PWV (bad calibration?)

During this time, the PWV drops to slightly negative values.  This could be related to 
calibration issues.

• Total water vapor along LOS path(vap)

• Total water vapor along LOS path(vap)

NSA/MWR/C1 - Heater/blower removed

Note that the heater/blower was removed from the MWR during this time.  This may impact 
snow removal from teflon window, thereby affecting the quality of the data between 
cleanings.

• tnd_nom23
• skyn31
• 31.4 GHz sky brightness temperature(tbsky31)
• tnd23
• Total liquid water along LOS path(liq)
• Total water vapor along LOS path(vap)
• IR Brightness Temperature(sky_ir_temp)
• unoise31
• tkair
• tair
• losn
• sky23
• tkxc
• skyn23
• tkbb
• tnd31
• sky31
• tc23
• tnd_nom31
• Temperature, brightness, longwave(ir_temp)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)
• unoise23
• tc31
• tknd
• wet_window

• 31.4 GHz sky brightness temperature(tbsky31)
• tnd23
• tknd
• tnd_nom23
• sky23
• IR Brightness Temperature(sky_ir_temp)
• tkxc
• Total water vapor along LOS path(vap)
• tkbb
• wet_window
• tkair
• Total liquid water along LOS path(liq)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)
• tnd31
• tc23
• sky31
• tnd_nom31
• tc31
• Temperature, brightness, longwave(ir_temp)

NSA/MWR/C1 - Data spikes, possibly due to cleaning events

Unreasonable spikes occurred, which may be due to cleaning of 
the instrument by the operator.  Other cleaning events did
not result in obvious data spikes and have not been included 
in this report.

• 31.4 GHz sky brightness temperature(tbsky31)
• Total liquid water along LOS path(liq)
• Total water vapor along LOS path(vap)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)

• 31.4 GHz sky brightness temperature(tbsky31)
• Total liquid water along LOS path(liq)
• Total water vapor along LOS path(vap)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)

SGP/MWR/C1 - Intermittent Negative Sky Brightness Temperatures

Several related and recurring problems with the MWRs have been reported
dating back to 1999.  These problems were due to the occurrence of
blackbody signals (in counts) that were half of those expected. The
symptoms included noisy data, spikes in the data, negative brightness
temperatures, and apparent loss of serial communication between the
computer and the radiometer, which results in a self-termination of the
MWR program.

Because these all initially appeared to be hardware-related problems,
the instrument mentor and site operations personnel (1) repeatedly
cleaned and replaced the fiber optic comm. components, (2) swapped
radiometers, (3) sent radiometers back to Radiometrics for evaluation
(which did not revealed any instrument problems), and (4) reconfigured
the computer's operating system.  Despite several attempts to isolate
and correct it, the problem persisted.

It became apparent that some component of the Windows98 configuration
conflicted with the DOS-based MWR program or affected the serial port
or the contents of the serial port buffer. This problem was finally
corrected by upgrading the MWR software with a new Windows-compatible
program.

• 31.4 GHz sky brightness temperature(tbsky31)
• Total liquid water along LOS path(liq)
• Total water vapor along LOS path(vap)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)

• 31.4 GHz sky brightness temperature(tbsky31)
• Total water vapor along LOS path(vap)
• Total liquid water along LOS path(liq)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)

NSA/MWR/C1 - min/max/delta values incorrect

The values of valid_min, valid_max, and valid_delta for fields tkxc and tknd were 
incorrect. They should be 303, 333, and 0.5 K, respectively.

• tkxc
• tknd

NSA/MWR/C1 - software upgrade (version 3.28)

The MWR operating program was upgraded to version 3.28 on 3 February 1999. This version 
includes a beam width correction as well as providing the capability to automatically level 
the elevation mirror (that is, to automatically detect and correct offsets in the 
elevation angle stepper motor position.)

The improvement in the quality of the tip curves resulting from the auto-
leveling has been dramatic: differences in the brightness temperatures at
3 airmasses (19.5 and 160.5 degrees) have been reduced from +/- 5 K to
+/- 0.5 K.  In order to take full advantage of this improvement to detect and reject 
cloudy tip curves, the minimum value of the goodness-of-fit coefficient for a valid tip curve 
has been increased from 0.995 to 0.998.

• 31.4 GHz sky brightness temperature(tbsky31)
• Total liquid water along LOS path(liq)
• Total water vapor along LOS path(vap)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)

• 31.4 GHz sky brightness temperature(tbsky31)
• Total water vapor along LOS path(vap)
• Total liquid water along LOS path(liq)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)

NSA/MWR/C1 - Missing data

Data are missing and unrecoverable.

• 31.4 GHz sky brightness temperature(tbsky31)
• IR Brightness Temperature(sky_ir_temp)
• sky23
• tkxc
• Total water vapor along LOS path(vap)
• alt
• tkbb
• bbn23
• tkair
• base_time
• bb23
• sky31
• tnd_nom31
• Temperature, brightness, longwave(ir_temp)
• bbn31
• lon
• tnd23
• tknd
• tnd_nom23
• bb31
• time_offset
• wet_window
• lat
• Total liquid water along LOS path(liq)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)
• tnd31
• tc23
• actel
• tc31
• actaz

• lat
• tnd_nom23
• bb31
• tnd31I
• liqtip
• wet_window
• bbn31
• r31
• tkair
• tnd_nom31
• tknd
• lon
• tc23
• r23
• bbn23
• tnd23
• tkxc
• tc31
• actel
• tkbb
• alt
• tbskytip31
• actaz
• vaptip
• bb23
• tnd23I
• tipsky31
• time_offset
• tipsky23
• base_time
• tbskytip23
• tnd31