1. 3rd ACS Workshop and advanced course ESO Garching Headquarter, January 15-19, 2006 Atmospheric Transmission at Microwaves (ATM): ALMA software on atmospheric effects and their correction Juan R. Pardo 1 Col.: J. Cernicharo 1, E. Serabyn 2,, F. Viallefond 3, M. Wiedner 4, R. Hills 5, J. Richer 5 (1) Consejo superior de Investigaciones Científicas (Spain), (2) California Institute of Technology (USA), (3) LERMA- Observatoire de Paris, (4) Köln University (Germany), (5) Cavendish Laboratory (UK), 1. Atmospheric mm/submm refractivity a.Imaginary Part (absorption spectrum) b.Real Part (Phase delay terms) c.Scattering by hydrometeors 2. The atmospheric problem for ALMA 3. ATM: Atmospheric software for ALMA

2. 1. Atmospheric mm/submm Refractivity 1.0 + Gas-phase contribution + Hydrometeros contribution 1a. Imaginary Part (absorption) 1b. Real Part (phase delay) 1c. Scattering. Polarization must be included K: 2x2 matriz de extinción  : vector de emisión S: 2x2 scattering matrix K=2   S+  I= ( IQIQ ) « Intensity vector » Chajnantor zenith transmission for 0.5 mm H2O / Water lines / Oxygen lines / ozone lines / H 2 O-foreign / N 2 -N 2 + N 2 -O 2 + O 2 -O 2 Impact approximation  collision << 1 / Van-Vleck-Weisskopf line profile 1a. Imaginary Part (absorption)

3. "Line" spectrum: rotational transitions of H 2 O, O 2, O 3, N 2 O, CO, and other trace gases. "Hydrometeor" contribution: absorption & scattering by liquid, ice and other particles. Collision-induced absorption by N 2 -N 2, O 2 -O 2 and N 2 - O 2, H 2 O-N 2, H 2 O-O 2 mechanisms 1a. Atmospheric absorption

4. Accurately measure the shape of the terrestrial longwave spectrum. Solve the « excess of continuum » problem. Input to build an state-of-the-art absorption models: ARTS (Bremen University) AM (CfA, Harvard) ATM (CalTech, CSIC) 1a. Atmospheric absorption: Direct measurements with FTS experiments at Mauna Kea, Chajnantor & Sout Pole Schematics of FTS experiment Characteristics of CSO-FTS Mounted on Cassegrain focus of telescope for dedicated obs. runs. Detector: 3 He cooled Bolometer Moving arm: 50 cm ~ 200 MHz resolution Filters: 7 different (165 to 1600 GHz)

5. a Frecuency (GHz) Zenith Transmission CSO-FTS: Some of the best data sets, subsequently used to study the collision-induced non-resonant absorption ALMA overlap

6. a Serabyn, Weisstein, Lis & Pardo, Appl. Optics, 37:2185, 1998 Matsushita, Matsuo, Pardo, & Radford, PASJ, 51:603, 1999. Pardo, Serabyn & Cernicharo, JQSRT, 68:419, 2001 Pardo, Cernicharo & Serabyn, IEEE TAP, 49:1683, 2001 Pardo, Wiedner, Serabyn, Wilson, Cunningham, Hills & Cernicharo, Ap. J. Suppl., 153:363, 2004 Pardo, Serabyn, Wiedner & Cernicharo, JQSRT, 96:537, 2005 Absorption lines taken out in the analysis. Remaining absorption due to collision- induced non-resonant mechanisms Very important result for submm astronomy The collision-induced non-resonant absorption

7. Resulting model Example 1: Opacity terms in wet atmospheric conditions at Mauna Kea

8. Model (0.5 mm H2O) CSO data 3/98 CSO data 7/99 Atacama data 6/98 Frequency (GHz) Transmission 0.0 1.0 0.2 0.4 0.6 0.8 Example 2: Atmospheric transmission at high frequencies in dry Mauna Kea conditions

10. 1. Atmospheric mm/submm Refractivity 1.0 + Gas-phase contribution + Hydrometeros contribution 1a. Imaginary Part (absorption) 1b. Real Part (phase delay) 1c. Scattering. Polarization must be included K: 2x2 matriz de extinción  : vector de emisión S: 2x2 scattering matrix K=2   S+  I= ( IQIQ ) « Intensity vector » Impact approximation  collision << 1 / Van-Vleck-Weisskopf line profile 1b. Real Part (phase delay)

11. 1b. Atmospheric phase delay (wet component)

12. 1. Atmospheric mm/submm Refractivity 1.0 + Gas-phase contribution + Hydrometeros contribution 1a. Imaginary Part (absorption) 1b. Real Part (phase delay) 1c. Scattering. Polarization must be included K: 2x2 matriz de extinción  : vector de emisión S: 2x2 scattering matrix K=2   S+  I= ( IQIQ ) « Intensity vector » Impact approximation  collision << 1 / Van-Vleck-Weisskopf line profile 1c. Scattering. Polarization must be included High cirrus (ice particles)

13. a ~ 20 m  atm (baseline, wind, atmospheric status) 2. The atmospheric problem for ALMA

14. Atmospheric water vapor fluctuations  gas,i (x,y,z,t) P(x,y,z,t) T(x,y,z,t) Refractive index field n(x,y,z,t) t=t 0 ;  nd  Atmospheric brightness temperature T B (x,y)  T B (R xy ) Delay autocorrelation function A  (R xy )  : Line of sight coordinate 2D FT Power spectrum of delay P  (q xy )  P  (q xy ) Radiative transfer along coordinate  at t=t 0 Wavefront delay  (x,y)   (R xy ) T B autocorrelation function A T B (R xy ) 2D FT Power spectrum of T B P T B (q xy ) Frozen screen; y=0 x=vt A  (  t) A T B (  t) P  (  ) P T B (  ) 1D FT Flat ground for interferometry Antennae positions: ( x i,y i )  (R xy ) i Temporal autocorrelation functions All functions are  dependent

15. Example of atmospheric water vapor field: Kolmogorov Screen With one antenna we can measure  T B (t), from which we obtain: P T B,  (  ) Chose  very sensitive to H 2 O so that we track P H 2 O (  ) With an interferomerter and a reference point source P  (q xy ) at  astro With two antennas: P  (  ) at  astro P T B,  (  )  P H 2 O (  )  P  (  )  y (m)

16. 1000s100s10sTime d for v=5 m/s 5km500m50m Outer sc. -8/3 3D -5/3 2D Instr. Temporal Power Spectra: P x (  ) The slope informs on the scale of phenomena -8/3 3D Kol -5/3 2D 0 outer 70m 6km P T B,  (  ) measured on Nov/25/2001 at Mauna Kea  1 = 183.31  7.8 GHz  2 = 183.31  3.0 GHz  3 = 183.31  1.3 GHz P  (  ) measured on Nov/25/2001 at Mauna Kea at  astro = 230.5 GHz Target source: Uranus Base line: 48 m P T B,  (  )  P H 2 O (  )  P  (  ) OK / 70 m - 6 km : 2D Kolmogorov screen

17. Assuming 0.4 K noise in 1 s in all three channels of the Water Vapor Radiometer Taking an average Precipitable Water Vapor amount of 0.5 mm, we have: 23 mk/μm 60 mk/μm 173 mk/μm Uncertainty in determining the PWV: 2.3 μm 8.47 μm pathlength / μm PWV 6.65 μm/μm 10.41 μm/μm 612 μm462 μm353 μm The goal of 15 μm pathlength correction accuracy for ALMA should be reachable with this technique in time scales of the order of 1 s. CURRENT PROTOTYPES ALREADY MEET THESE REQUIREMENTS Phase correction can be performed using water vapor radiometry at frequencies sensitive to H2O

18. Phase fluctuations: Correction using 183 GHz water vapor radiometers a Observing Frequency: 230.5 GHz, PWV to phase conversion factor: 1.944 deg/  m Time since the beginning of the observation (min) on Nov. 25, 2001

19. Starting point: Fortran code developed during 20 years. Contract with ESO to develop ATM for alma. Fortran library created to encapsulate "fundamental" physics of the problem (C++). C++ interface developed specifically for ALMA needs. Updated via CVS. Doxygen documented. Test examples provided using real FTS and WVR data. Work done withing the TelCal working group. 3. ATM: Atmospheric software for ALMA

20. ATM_telluric INI_singlefreq RT_telluric ATM_st76 ATM_rwat ABS_h2o ABS_o2 ABS_co ABS_o3_161618 ABS_h2o_v2 ABS_o2_vib ABS_n2o ABS_o3_161816 ABS_hdo ABS_16o17o ABS_o3 ABS_o3_nu1 ABS_hh17o ABS_16o18o ABS_o3_161617 ABS_o3_nu2 ABS_hh18o ABS_cont ABS_o3_161716 ABS_o3_nu3 INTERFACE LEVEL DEEP LEVEL(LIBRARY) I/O Parameters Ground Temperature Tropospheric Lapse Rate Ground Pressure Rel. humidity (ground) Water vapor scale height Primary pressure step Pressure step factor Altitude of site Top of atmospheric profile 1st guess of water vapor column Layer thickness (NPP) Number of atmospheric layers, NPP Layer pressure (NPP) Layer temperature (NPP) Layer water vapor (NPP) Layer_O3 (NPP) Layer CO (NPP) Layer N2O (NPP) User Frequency ABSORPTION COEFS. kh2o_lines (NPP) kh2o_cont (NPP) ko2_lines (NPP) kdry_cont (NPP) kminor_gas (NPP) PHASE FACTORS total_dispersive_phase (NPP) total_nondisp_phase (NPP) kabs (NPP) DATA_xx_lines DATA_xx_index xx all species Air mass Bgr. Temp. Atmospheric radiance Other sources to obtain atmospheric parameters Applications: INV_telluric for WVR and FTS data (available in current release) Old ATM fortran code

21. ALMA-ATM C++ structure: Collaboration diagram between the most important classes Class AtmProfile: Profiles of physical conditions & chemical abundances Class AbsorptionPhaseProfile: Profiles of refractive index for an array of frequencies Class WaterVaporRadiometer: WVR system in place for phase correction Class SkyStatus: Relevant atmospheric information for antenna operations Design workshop: Tuesday afternoon