3rd ACS Workshop and advanced course ESO Garching Headquarter, January 15-19, 2006 Atmospheric Transmission at Microwaves (ATM) C++ implementation within ALMA TelCal Subsystem Juan R. Pardo 1 (1) Consejo superior de Investigaciones Científicas (Spain) 1. Physical model to implement (described last Monday) 2. Current C++ implementation 3.Architecture and design review

1. Physical model to implement: Atmospheric Refractivity at ALMA frequencies 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 1a. Imaginary Part (absorption) 1b. Real Part (phase delay)

1a. ALMA needs related to this component Able to Guess atmospheric T, P,  gas profiles from available site data (T ground, P ground, local humidity, complementary soundings) Given an atmospheric profile is known, then able to obtain: Atmospheric opacities sorted out by component (dry, wet, individual molecules, continuum-like terms, etc..). Phase delays sorted out by component, but specially those related to H 2 O. Simulate atmospheric brightness temperatures along a given propagation path (the easy-to-get observable) Inversion capabilities. Given atmospheric brightness temperatures can be measured, then it should be able to: Retrieve atmospheric parameters (mainly the H 2 O column). Retrieve hardware implementation parameters such as the coupling to the sky of water vapor radiometers. Use the retrieved information to provide correction parameters at the frequencies of the current astronomical observation. At all ALMA 's

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++ interface developed specifically for ALMA needs. Updated via CVS (TelCal subsystem) Doxygen documented. Test examples provided using real FTS and WVR data. Work done within the TelCal working group. 2. C++ implimentation history

ATM_telluric INI_singlefreq RT_telluric ATM_st76 ATM_rwat ABS_h2o ABS_o2 ABS_co ABS_o3_ ABS_h2o_v2 ABS_o2_vib ABS_n2o ABS_o3_ ABS_hdo ABS_16o17o ABS_o3 ABS_o3_nu1 ABS_hh17o ABS_16o18o ABS_o3_ ABS_o3_nu2 ABS_hh18o ABS_cont ABS_o3_ 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) 3. Architecture and design review: Old ATM fortran code

Class AtmProfile: Profiles of physical conditions & chemical abundances Class AbsorptionPhaseProfile: Profiles of refractive index for an array of frequencies Class WaterVaporRadiometer: Water Vapor Radiometer system in place for phase correction Class SkyStatus: Relevant atmospheric information for antenna operations 3. Architecture and design review: Basic C++ structure: Collaboration diagram between the most important classes

3. Architecture and design review: Comments Class SpectralGrid: replicates essentially what would a Class of the receiver or autocorrelator components. Class Temperautre Class Pressure Class NumberDensity, Class Length... Classes for the physical parameters relevant to ATM have been created within this component with a namespace atm to avoid confussion. Interfaces with other components need to take this into account. Standard classes for this physical parameters within the whole software? Let's have a look to the documentation

3. Architecture and design review: Tests Using real atmospheric transmission curves measured with a Fourier Transform Spectrometer

Taking an average Precipitable Water Vapor amount of 0.5 mm, we have: 23 mk/μm 60 mk/μm 173 mk/μm 3. Architecture and design review: Tests 183 GHz water vapor radiometry (preferred method for phase correction in ALMA)

GOES-10 Water vapor 350  m opacity meter

a Observing Frequency: GHz, PWV to phase conversion factor: deg/  m Time since the beginning of the observation (min) on Nov. 25, Architecture and design review: Tests 183 GHz water vapor radiometry with actual phase correction