1. Radio Aeronomy at Onsala Space Observatory Peter Forkman forkman@oso.chalmers.se

3. Infrared OH-airglow instrument

5. Pressure broadening Sky switched H 2 O at 22 GHzFrequency switched CO at 115 GHz

6. CO at 115.27 GHz

7. CO receiver

8. H 2 O at 22.2 GHz

9. T cold can be estimated assuming constant T rec

10. Sky as cold load

11. T eff is estimated from radiosonde data Traditionally T eff = 0.95T ground

12. H 2 O at 22.2 GHz

13. 21/31.4 GHz radiometer

14. Syntetic spectra 18-34 GHz

15. Stand alone calibration using skydip method

16. Optical depth from skydip and dual channel radiometer

17. Elevation and tropospheric opacity change at 22 GHz

19. Radio Aeronomy at Onsala Space Observatory Peter Forkman forkman@oso.chalmers.se