Proposed Schedule for the Week
DAY 1: Monday 9 July INTRODUCTION to Millimeter Wavelength Interferometry 9-10 am Introduction. (Melvyn) . Course outline -- Day 1 : Basics to get you going. -- Day 2-4: Radio antennas, arrays, aperture synthesis, receivers and correlators. Observing techniques, scheduling, calibration, data inspection, imaging -- Day 5: Data analysis, future developments, VLBI. . Source characteristics, instrumentation, and observing techniques together define a matched filter to possible observations with millimeter wavelength interferometers. . Astronomy from comets to cosmology -- emission mechanisms: thermal and non-thermal -- source selection: astronomy, frequency, size, brightness sensitivity . Atmospheric windows at optical, IR, and radio frequencies . CARMA site characteristics 10-11 am APERTURE SYNTHESIS BASICS (Melvyn) . Radio antennas: collecting area and resolution . Aperture arrays . response of a 2-element interferometer to point source. . coordinate systems: (u,v,w), u,v tracks for different arrays. . CARMA array characteristics. antennas, Rx bands, correlator. . Aperture sysnthesis imaging. . Mapping extended sources. resolving out extended structures . Calibration, Imaging and Deconvolution. 11-12 am. Antenna tour (DaveW & Dick) . Visit to telescopes. Intro to antenna hardware. -- antenna structure -- drive system -- manual, computer control -- limits and switches -- cable wraps 12am - 1pm Lunch. 1-2 pm Intro to CARMA computers. (Marc) . computers. data flow. archiving - control computer: roadmap of machines, disks, directories and subdirectories . school data reduction and analysis space. login, passwords. . basic observing procedures, on-line monitors and data inspection - key programs: 2-3 pm Basic demos (students) -- observe a point source (maser or quasar) and a planet. -- plot amplitude and phase vs. uvdistance -- constant amplitude for point source, Bessel function (with phase flips) for planet -- set up correlator in various modes, take spectra of Orion 3-4 pm OBSERVING PROCEDURES (Melvyn) . Calibrations: -- gain(t,f,p) - gain, bandpass, polarization, pointing. . calibration intervals. V' = gain(t,f,p) x V + noise . Observing scripts . selecting suitable observations for the target sources. -- sensitivity -- source size; mosaicing. . CARMA correlator capabilities; selecting a correlator settup. . choosing calibrators for gain, bandpass, flux and pointing. 4-5 pm group discussion selecting student projects. (Douglas) 5-6 pm Intro to preparing CARMA observing scripts (Marc) 6 pm Dinner at the CARMA site. Student projects observed on CARMA array overnight. DAY 2: Tues 10 July 9-10 am DATA INSPECTION AND ANALYSIS (Melvyn) . overview of data reduction procedure . introduction to MIRIAD data reduction package. . basic Miriad data format: header, history, uvdata, gains, bandpass . inspecting uvdata: uvindex, uvlist, uvplt, uvspec . selecting uvdata: keywords select= and line= . flagging bad data with uvflag . antenna based calibration; selfcal and mfcal. gpplt. gains bandpass polcal . rewriting edited data sets with uvaver, uvcat, uvcal 10-11 IMAGING (Melvyn) . Review of basic math: brightness distribution is FT of visibility data. . FFT requires convolving onto a grid; choosing the pixel and image size. -- mosaicing . invert; choice of natural, uniform, robust weighting, effect on the synthesized beam . deconvolution algorithms: clean, maxen, mossdi, mosmem, restor 11-12 am Laptop tutorial reduction and analysis of student data (Melvyn) 12 - 1 pm Lunch at the CARMA site 1-2 pm. CARMA hardware - I. Receivers and Calibration (Dick) - introduce system block diagram; receiver, cal load, local osc, phaselocks, fiber, downconverter, correlator - compute energy collected if observing 20 Jy source for 1 yr; would need to observe for 10^5 yrs to heat 1 drop of water by 1 C - receiver types: - bolometers: not suitable for interferometry because they don't preserve phase - HEMT amplifiers: not yet competitive at 1mm - heterodyne rcvr: downconvert to lower freq in a nonlinear device - SIS mixers: photon-assisted tunneling; not a Josephson effect - cryogenics; closed-cycle refrigerators, compressors - local oscillator: Gunn oscillator - must be synchronized between all antennas; discuss in lecture 2 - both USB and LSB are downconverted to IF; can be separated with 90 degree phase switch; also defer to lecture 2 - combining LO and signal: mylar beamsplitter - receiver and system temperature - calibration: - ideally, calibrate on loads outside the earth's atmosphere - the chopper wheel method - CARMA sensitivity calculator 2-3 pm. Demos on CARMA system 3-4 pm Planning observations and preparing observing scripts 4-5 pm Source selection and script preparation for student projects 5-6 pm students prepare observing scripts, analyze data. Dinner at the CARMA site. Student projects observed on CARMA array overnight. DAY 3: Wed 11 July 9-10 am CALIBRATION (Melvyn) . Calibrations - gain, bandpass, polarization, pointing. . Antenna based calibrations: amplitude and phase closure . Atmospheric and instrumental phase characteristics . Tsys and Jy/K . Pointing . correlator calibration techniques. 10-12 am calibration and analysis of student projects (all) 12 - 1 pm Lunch at the CARMA site 1-2 pm special topics in mapping (Melvyn) - the missing short spacing problem; importance for getting correct answers for spectral index, etc; negative sidelobes due to extended structure; filling in missing spacings with larger single dish or Ekers-Rots scheme - mosaicing: setting up grid files, linear and nonlinear mosaicing schemes - heterogeneous array imaging 2-3 pm CARMA software system (Marc) -- monitor system -- computers -- data flow -- archiving 2-4 pm Laptop tutorial data reduction and analysis of student data 4-6 pm students prepare observing scripts, and analyze data. Dinner at the CARMA site. Student projects observed on CARMA array overnight. DAY 4: Thurs 12 July 9-10 am CARMA hardware lecture 2 - local oscillators, phaselocks (Dick) - review system block diagram, heterodyne system, local oscillator - independent oscillators, 100 GHz, synchronized to fraction of one cycle over periods of hours (sounds hard) - basic phaselock: mix with reference, low pass filter, generate correction voltage; keeps phase relationship fixed - CARMA phaselock chain; synth, YIG, Gunn, 10 MHz, 50 MHz - numerical example: synth = xxx, YIG = yyy, LO = zzz - fiber system; linelength correction - lobe rotation - compute differential doppler shift due to earth's rotation for 100 GHz signal incident on 2 antennas 10-m apart: 0.24 Hz - lobe rotators - interferometer response for a double sideband conversion system - need to offset freq of 1st LO as well as insert delays; can be understood as removing differential doppler shift due to earth's rotation - phaselocks; the LO system - cable length measurement system - phase switching; Walsh functions - sideband separation by phase switching; note that only signals common to an antenna pair can be separated; noise appears in both sidebands - fiber optic hardware 10-11 am calibration (Dick) - converting to flux density; aperture efficiency; source flux table 12 - 1 pm Lunch at the CARMA site DAY 5: Fri 13 July 9-10 am CARMA hardware lecture 3 - correlator; software control (James) - review system block diagram - correlator is detector and spectrometer for the array - XF vs FX - delays, 2nd LO lobe rotation, sideband separation - correlator modes - FPGA's - noise source - basic architecture of computer control system, CAN nodes observer's everyday responsibilities (Douglas) - creating and running the master observing script - data quality reports - data archiving and disk management polarization measurements (Melvyn) - interferometer response LR, RL, etc in terms of Stokes parameters - Walsh function polarization switching schemes - instrumental leakage terms and how to solve for them - mapping procedures troubleshooting (Dick, Marc) - generator, air conditioning - the anticollision system - cryogenics - rcvr tuning - computer hangups - clocks; resetting the time - rebooting procedure: moving the antennas and calibrating a new array configuration (DaveW, Marc) - changing IFLO connections in the pits - running tilt, shimming the antennas - entering new station coordinates - finding pointing offsets. - finding the delay centers - TV and radio pointing - finding a baseline - entering new pointing offsets or baselines 12 - 1 pm Lunch at the CARMA site - atmospheric phase fluctuations and what we plan to do about them - like floppy backup structure on a big telescope; causes decorrelation, ruins aperture efficiency - show results at long and short baselines - phase structure function - calibrating by rapid switching; put calibrator in grid file; observe weak nearby calibrator often, strong faraway calibrator less often - calibrating by observing the total power; need for extreme gain stability; typical results CARMA future plans (Douglas) - A-configuration - Carlstrom's 1 cm system - wideband receivers - 23-antenna CARMA array . analysis of student data Dinner at the CARMA site. Student projects observed on CARMA array overnight. DAY 6: Sat 14 July hike and go home.