Radio Aeronomy

at Onsala Space Observatory

Peter Forkmanforkman@oso.chalmers.se

Infrared OH-airglow instrument

Pressure broadening

22.222 22.224 22.226 22.228 22.23 22.232 22.234 22.236 22.238 22.24

-0.05

0

0.05

0.1

0.15

0.2

Frequency [GHz]

Brig

tnes

s te

mpe

ratu

re [

K]

Sky switched H2O at 22 GHz Frequency switched CO at 115 GHz

115.262 115.267 115.272 115.277-20

-19

-18

-17

-16

-15

-14

Frequency [GHz]B

right

ness

tem

pera

ture

[K

]

CO at 115.27 GHz

CO receiver

H2O at 22.2 GHz

Tcold can be estimated assuming constant Trec

2

11

1

280 1300.25

280 325

280 300.50

280 250

cold rec cold

hot cold hot cold

hot reccold

cold hot cold

rec hot rec

cold

rec

cold

rec

P T TA

P P T T

A T TT

AdT T T

dT A T T

dTCO

dT

dTH O

dT

Sky as cold load

( ) 1

b bg eff

eff b

eff bg

b T hot coldhot cold

eff bgb T hot cold

hot cold eff cold

b T amb eff ambhot cold

T T e T e

T Te

T T

PT z T T e

P P

T TPT z T T

P P T T

PT z T if T T

P P

Teff is estimated from radiosonde data

Traditionally Teff = 0.95Tground

2 2

, 90

0.95, 0.05

0.90, 0.10

5

eff ground b

eff

T T T

H O H O

CO CO

T K

H2O at 22.2 GHz

21/31.4 GHz radiometer

122.2 GHz, 90 21 GHz, 90 , 31 GHz, 90b b bT f T T

Syntetic spectra 18-34 GHz

Stand alone calibration using skydip method

/ sin / sin

/ sin / sin

( ) 1

( , ) ( , )

1

can be calculated

b hot coldhot cold

b bg eff

h lb b b eff bg

h hb hot bg eff

hot cold

PT T T

P P

T T e T e

T T l T h T T e e

PT T T e T e

P P

Optical depth from skydip and dual channel radiometer

196 198 200 202 204 206 208

0.05

0.1

0.15

0.2

0.25

0.3

Day of 2001

Trop

osph

eric

opt

ical

dep

th

Elevation and tropospheric opacity change at 22 GHz

288 289 290 291 292 293 294 295 296 297 2985

10

15

20

25

30

35

Day of 2001

Ele

vatio

n [d

eg]/

optic

al d

epth

[ne

pers

*100

] u/

l

0 50 100 150 200 250 300 350140

150

160

170

180

190

200

210

220

230

240

250

Tem

p. a

t 87

km

[K

]

Day of 2002

Radio Aeronomy

at Onsala Space Observatory

Peter Forkmanforkman@oso.chalmers.se