1. Turbulence profiler MASS: First tests and plans A. Tokovinin CTIO http://www.ctio.noao. edu/edu/~atokovin/profiler

2. MASS = Multi-Aperture Scintillation Sensor Need for a simple, cheap profile monitor: single-star profiler Presursor: “Scintillometer” of Ochs et al. MASS: better hardware, theory and signal processing (polychromatic scintillation; photon counting; de- biasing)

3. The principle

4. Weighting functions

5. Profile restoration Six fixed layers (0.5,1,2,4,8,16 km) Least-squares solution: Cn2 can be negative… -> Min. Chi-squared with sign constraint! Three “floating” layers: free intensities and altitudes (6 parameters) Direct computing of moments

6. Simulations: one layer

7. Simulations: two layers

8. The instrument Detector box (4 PMTs, 1 stepper motor, 7 microprocessors) Feeding telescope (14 cm, off-axis) PC + RT Linux (RS-485 interface) Software Guiding TV Auto-guiding

9. Real-time data processing

10. Generalized mode Add “virtual propagation” of 0.5 km to sense low turbulence Constraints: <4 arcsec. guiding, good optics Extensive computer simulations Tested: seeing worse than DIMM… Ground layer? Conclusion: do not use gen. mode!

11. One night of data: May 2-3, 2002 Profile: fixed layers Profile: floating layers Comparison with DIMM Residuals

12. More profiles… May 20 and 21

13. A night with good seeing: April 17-18

14. Comparison with DIMM

15. Two MASS instruments

16. Immediate plans (2002) Accumulate data for Cerro Tololo Move to Cerro Pachon SCIDAR calibrations (La Silla, Mauna Kea)

17. Instrument development (2003) Optimization: smaller outer apertures Simplify the instrument (no gen-mode) Simplify data acquisition (no RT Linux) Couple with DIMM in a single instrument Make it all robotic ( pointing !!! )

18. MASS +DIMM

19. Pointing