1. Infrared heterodyne interferometry at Calern Observatory Jean GAY Astronome émérite à l’Observatoire de la Côte d’Azur With help of Yves Rabbia Astronome à l’Observatoire de la Côte d’Azur

2. summary The state of science on seventeens Heterodyne interferometry Initial experiments Atmospheric absorption SOIRDETE experiment bilan

3. summary The state of science on seventeens Heterodyne interferometry Initial experiments Atmospheric absorption SOIRDETE experiment bilan

4. what science for the seventies ? extensive surveys from ground-based facilities strongly emitting sources Stars embedded in dust (IRC 10076) What size of IR sources? no telescope able to reach a 1 arcsec angluar resolution in thermal IR no adaptive optics device no IR-ccd camera yet available by this time

5. The state of science on seventeens Heterodyne interferometry Initial experiments Atmospheric absorption SOIRDETE experiment bilan

6. Principle of infrared heterodyne

7. heterodyne current, an example, for reluctant pupils, illustrating the interest of knowing (a+b)^2

8. only frequencies accepted by the detector are transmitted to the amplifier

9. electrical bandpass imposed by the detector's response

10. electrical bandpass limited by the amplifier

11. Narrow bandwidth,so large coherence length

12. but limited SNR (proportional to the wavelength, no pb in radio-astronomy and millimeter, but disastrous in visible) exploitable in thermal infrared

13. summary The state of science on seventeens Heterodyne interferometry Initial experiments Atmospheric absorption SOIRDETE experiment bilan

14. 1

15. 2

18. solar fringes for different base-lines

19. Fringes visibility on the sun at 11  m

21. Expected interferometric SNR on Betelgeuse with two 1 m telescopes

22. Heterodyne detection of Arcturus at OHP april 1973 3

23. summary The state of science on seventeens Heterodyne interferometry Initial experiments Atmospheric absorption SOIRDETE experiment bilan

27. summary The state of science on seventeens Heterodyne interferometry Initial experiments Atmospheric absorption SOIRDETE experiment bilan

28. evocative scents program for Grace, perfume city

30. SOIRDETE in winter 1973

31. 2 one meter telescopes for a 15 m baseline

33. First heterodyne fringes at SOIRDETE (August 3 1978)

34. summary The state of science on seventeens Heterodyne interferometry Initial experiments Atmospheric absorption SOIRDETE experiment bilan

35. BILAN Jitter of the laser? Capricious telescopes tracking? Too small bandwidh? Poor quality telescope mirrors? Atmospheric turbulence not enough corrected? (tilt only) Direct interferometry is easier!

36. First direct fringes in K band

37. First fringes in N band and frequency analysis of the interferogramm (lower, see ozone absorption)