Ozone Radiometer at 142 GHz:Calibration

Yasmine Calisesi

The Stratospheric Ozone Monitoring Radiometer SOMORA

●Developed by the IAP for MeteoSwiss●Tuned to Ozone at 142.175 GHz●Improved version of the GROMOS instrument●Operated at the IAP since January 2000●Moved to Payerne in June 2002

Somora location in Payerne

SOMORA Quasi-Optics

Rotating Planar MirrorHot Load

ColdLoad

Eccosorb CV-3

IF 7.1 Ghz

T = 310 K

T=77K

Fans PT 100HeatingElement

EccosorbCV-3

PT 100

PolystyreneWindow

SOMORA Hot Load

EccosorbCV-3

SOMORA Cold Load

Dewar Vessel

Packaging Foam Material

Liquid N2

InletGaz-phase N2 exhaust

ExpansionVesselP = 0.4 Bar

Total Power Calibration

coldcoldhotcoldhot

coldskysky TTT

PP

PPT

)(

,1

y

yTTT coldhotrec

0

0

PP

PPy

cold

hot

Temperature Definitions

● Physical Temperature● „Planck“ Brightness Temp.:

T :

TP :

)2

1ln(

1

2

3

Pc

hk

hTP

● In the RJ limit (hkT):

P ÷ T P can be replaced by T in RT model

RJP Tk

PcT :

2 2

2

Example: Planck and RJ emission curves at various frequencies

Brightness Temperature [K]

Conclusions:

● SOMORA: Total power radiometer

● P ÷ T in considered T range Total power calibration formula can be used

● TRJ ≠ T

P Radiative transfer

computed in the units of P