Doc 0.3, v1.0 | May, 2011 ALMA Cycle 0 Technical Handbook Baltasar Vila Vilaro (Editor) ALMA, an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. For further information or to comment on this document, please contact your regional Helpdesk through the ALMA User Portal at www.almascience.org. Helpdesk tickets will be redirected automatically to the nearest ALMA Regional Center at ESO, NAOJ or NRAO. Version Date Editors 1.0 18th May, 2011 Baltasar Vila & Lars Nyman Baltasar Vila Vilaro Stephane Leon William Dent Andreas Lundgren Rüdiger Kneissl Mark Rawlings Lars-Ake Nyman Antonio Hales In publications, please refer to this document as: B. Vila Vilaro, 2011, ALMA Cycle 0 Technical Handbook, Version 1.0, ALMA 2 Table of Contents 1 Introduction .................................................................................................................. 9 2 Receivers ........................................................................................................................ 9 2.1 Local Oscillators and IF ranges ............................................................................................................ 11 2.2 The Cycle 0 Receivers .............................................................................................................................. 12 2.2.1 Band 3 receiver.................................................................................................................................................. 13 2.2.2 Band 6 receiver.................................................................................................................................................. 16 2.2.3 Band 7 receiver.................................................................................................................................................. 20 2.2.4 Band 9 receiver.................................................................................................................................................. 23 2.3 Water Vapor Radiometers ..................................................................................................................... 25 3 Amplitude calibration device ................................................................................ 29 3.1 Atmospheric Calibration Procedure .................................................................................................. 30 4 The Correlator ............................................................................................................ 31 4.1 Correlator data processing – spectral and channel-average .................................................... 34 4.1.1 Final data product – the ASDM ................................................................................................................... 35 4.2 Spectral resolution and smoothing .................................................................................................... 35 4.3 Correlator speed and data rates.......................................................................................................... 36 4.4 Sampling the data ..................................................................................................................................... 36 5 Spectral setups ........................................................................................................... 36 5.1 Spectral setups for multiple lines ....................................................................................................... 38 5.2 Spectral setups for lines near the edge of the bands ................................................................... 38 5.3 Observing lines and continuum .......................................................................................................... 38 5.4 Usable bandwidth ..................................................................................................................................... 39 6 Cycle 0 Configurations ............................................................................................. 39 6.1 Introduction ............................................................................................................................................... 39 6.2 The Two Cycle 0 Configurations .......................................................................................................... 40 6.2.1 The Cycle 0 Compact Configuration .......................................................................................................... 40 6.2.2 The Cycle 0 Extended Configuration ........................................................................................................ 46 6.3 Summary ...................................................................................................................................................... 50 6.4 Basic Plots of Cycle 0 Observing Parameters and Sensitivities................................................ 52 7 Simulations of Cycle 0 observations ................................................................... 56 7.1 Introduction ............................................................................................................................................... 56 7.1.1 The ALMA Simulators ..................................................................................................................................... 56 7.1.2 Basic steps of an ALMA simulation ........................................................................................................... 56 7.2 Simulation Examples for Cycle 0 Configurations .......................................................................... 57 7.2.1 Gaussian functions ........................................................................................................................................... 57 7.2.2 An M51-like Galaxy .......................................................................................................................................... 59 7.2.3 3C288..................................................................................................................................................................... 60 3 8 Field Set-up .................................................................................................................. 62 8.1 Single-Field/Offset Pointings ............................................................................................................... 63 8.2 Square Field ................................................................................................................................................ 64 9 Specific Ephemeris .................................................................................................... 66 10 Observing Projects and Logical Data Structure ........................................... 67 10.1 Observing Preparation ....................................................................................................................... 69 10.2 Program Execution .............................................................................................................................. 69 10.3 Structure of an SB and associated scripts .................................................................................... 70 10.3.1 Observing Groups ............................................................................................................................................. 70 10.3.2 The Standard Interferometry Script ......................................................................................................... 70 10.4 Data and Control Flow ........................................................................................................................ 71 10.5 The ALMA Science Data Model (ASDM) ........................................................................................ 73 11 Calibration and Calibration Strategies ........................................................... 75 11.1 Long-Term Effects ................................................................................................................................ 75 11.1.1 All-Sky Pointing ................................................................................................................................................. 75 11.1.2 Focus Models ...................................................................................................................................................... 76 11.1.3 Baseline................................................................................................................................................................. 76 11.1.4 Cable Delay .......................................................................................................................................................... 76 11.1.5 Surface Measurements/Adjustments ....................................................................................................... 76 11.1.6 Beam Patterns .................................................................................................................................................... 76 11.2 Short-Term Effects ............................................................................................................................... 77 11.2.1 Offset Pointing ................................................................................................................................................... 77 11.2.2 Bandpass .............................................................................................................................................................. 77 11.2.3 WVR Corrections: ............................................................................................................................................. 77 11.2.4 Gain (Amplitude & Phase): ........................................................................................................................... 77 11.2.5 Tsys and Trx ....................................................................................................................................................... 78 11.2.6 Amplitude/Flux ................................................................................................................................................. 78 12 Quality Assurance .................................................................................................. 78 12.1 What is QA0 and how will it be done? ........................................................................................... 79 12.2 What is QA1 and how will it be done? ........................................................................................... 79 12.3 What is QA2 and how will it be done? ........................................................................................... 80 12.4 What is QA3 and how will it be done? ........................................................................................... 80 13 Data Archiving ........................................................................................................ 81 14 Appendix ................................................................................................................... 84 14.1 Antennas .................................................................................................................................................. 84 14.2 Antenna Foundations .......................................................................................................................... 86 14.3 Antenna Transportation .................................................................................................................... 86 14.4 Cryostat .................................................................................................................................................... 88 14.5 The LO and IF System .......................................................................................................................... 92 14.5.1 Overview of the IF and LO systems ........................................................................................................... 92 4 14.5.2 The First Local Oscillator (LO1) ................................................................................................................. 94 14.5.3 The IF switch and IF Processor units ....................................................................................................... 94 14.5.4 Digitization and Transmission .................................................................................................................... 96 14.6 Reference and LO Signal Generation and Distribution ........................................................... 96 14.6.1 Reference Signal generation ........................................................................................................................ 97 14.6.2 LO signal generation ........................................................................................................................................ 97 14.6.3 Optical Signal Distribution ............................................................................................................................ 98 14.6.4 Summary of LO distribution system ......................................................................................................... 98 14.6.5 LO Path Length Corrections ......................................................................................................................... 99 14.7 Delay corrections and Sideband Separation ........................................................................... 101 14.8 Limitations and rules for spectral setups in Cycle 0 ............................................................. 102 5 Acronym Dictionary: ACA Atacama Compact Array ACD Amplitude Calibration Device ACS ALMA Common Software ALMA Atacama Large Millimeter/Submillimeter Array AoD Astronomer on Duty AOS Array Operation Site APDM ALMA Project Data Model AQUA ALMA Quality Assurance software ARC ALMA Regional Center ASC ALMA Sensitivity Calculator ASDM ALMA Science Data Model AZ Azimuth BB Baseband BE Backend BL Baseline CASA Common Astronomy Software Applications package CCA Cold Cartridge Assemblies CCC Correlator Control Computer CDP Correlator Data Processor CFRP Carbon Fiber Reinforced Plastic CLO Central Local Oscillator CLT Chilean Local Time CORBA Common Object Request Broker Architecture CRD CentralReference Distributor CRG Central Reference Generator CSV Commissioning and Science Verification CW Continuous Wave DC Direct Current DEC Declination DGCK Digital Clock DMG Data Management Group within DSO DRX Data Receiver module DSB Double Sideband DSO Division of Science Operations DTS Data Transmission System DTX Data Transmitter module EL Elevation EPO Education and Public Outreach ES Early Science 6 ESO European Southern Observatory FDM Frequency Division Mode FE Frontend FITS Flexible Image Transport System FLOOG First LO Offset Generator FOM Fiber Optic Multiplexer FOV Field of View FPGA Field-Programmable Gate Array FT Fourier Transform FWHM Full Width Half Maximum GPS Global Positioning System HA Hour Angle HEMT High Electron Mobility Transistor IF Intermediate Frequency IFP Intermediate Frequency Processor IRAM Institut de Radioastronomie Millimetrique LFRD Low Frequency Reference Distributor LLC Line Length Corrector LO Local Oscillator LO1 First LO LO2 Second LO LO3 Digitizer Clock Third LO LO4 Tunable Filterbank LO LORR LO Reference Receiver LS Laser Synthesizer LSB Lower Sideband LTA Long Term Accumulator MFS Master Frequency Standard ML Master Laser MLD Master Laser Distributor NGAS New Generation Archive System NRAO National Radio Astronomy Observatory OMC Operator Monitoring and Control OMT Ortho-mode Transducer OSF Operations Support Facility OST Observation Support Tool OT Observing Tool OUS Observing Unit Set PBS Polarization Beam Splitter PDM Propagation Delay Measure PI Principal Investigator PLL Phase Lock Loop PMG Program Management Group within DSO PRD Photonic Reference Distributor PWV Precipitable Water Vapor QA Quality Assurance 7 QA0 Quality Assurance Level 0 QA1 Quality Assurance Level 1 QA2 Quality Assurance Level 2 QA3 Quality Assurance Level 3 QL Quicklook pipeline RA Right Ascension RF Radio Frequency RMS Root Mean Square SAS Sub Array Switch SB Scheduling Block SCO Santiago Central Office SD Single Dish SED Spectral Energy Distribution SIS Superconductor-Insulator-Superconductor Mixer SL Slave Laser SNR Signal-to-Noise Ratio SPW Spectral Window SRON Netherlands Instutute for Space Research SSB Single Sideband 2SB Sideband separating Mixer STE Standard Test Environment STI Site Testing Interferometer TDM Time Division Mode TE Time Event TelCal Telescope Calibration subsystem TFB Tunable Filterbanks TFB LO Local Oscillator at the Tunable Filterbanks T System Temperature sys T Receiver Temperature rx USB Upper Sideband VLA Very Large Array WCA Warm Cartridge Assembly WVR Water Vapor Radiometer XF Correlation-Fourier Transform Type Correlator YIG Yttrium-Iron Garnet Oscillator 8 1 Introduction The Atacama Large Millimeter/Submillimeter Array (ALMA) is an aperture synthesis telescope that will consist of at least 66 antennas arranged in a series of different configurations. It will operate over a broad range of observing frequencies in the millimeter and submillimeter regime. During Cycle 0 only a limited number of antennas, frequencies, array configurations and observing modes will be available. Users should refer to the Capabilities section on the ALMA Science Portal at http://www.almascience.org/ for the latest information. This Technical Handbook describes the Cycle 0 setup of the ALMA system. It is intended to provide additional technical information for ALMA users, to a deeper level than what is described in the ALMA ES Primer, and to provide more information on the limitations of the Cycle 0 setups. Although it contains sections relevant for the preparation of proposals, it should not be necessary to read it in order to prepare a proposal. The Technical Handbook contains information on the receivers, the correlator, creation of spectral setups, field setups and a description of the Cycle 0 array configurations including simulations of observations, which is useful for preparation of proposals. It also gives a brief overview of the structure of observing projects, calibration strategies, data quality assurance and data archiving, which is information more relevant to the preparation of observing projects and the observations. The appendix includes more detailed technical information about the antennas, LO and IF systems as well as generation and distribution of reference signals. The Technical Handbook will be updated each Cycle with information relevant for the capabilities of that Cycle. 2 Receivers The ALMA frontend can accommodate up to 10 receiver bands covering most of the wavelength range from 10 to 0.3 mm (30-950 GHz). In Cycle 0, Band 3, 6, 7 and 9 will be available (see available frequency and wavelength ranges for these bands in Table 1). Each receiver band is designed to cover a tuning range which is approximately tailored to the atmospheric transmission windows. These windows and the tuning ranges are outlined in Figure 1 and the specifications are listed in Table 1. 9 Figure 1. ALMA Bands for Cycle 0 are shown in red superimposed on an atmospheric transparency plot at the AOS for 0.5 mm of PWV. The ALMA receivers in each antenna are situated in a single frontend assembly (see Appendix, Section 14.4). The frontend assembly consist of a large cryostat containing the receiver cold cartridge assemblies (including SIS mixers and LO injections) and the IF and LO room-temperature electronics of each band (the warm cartridge assembly, WCA). The cryostat is kept at a temperature of 4 K through a closed-cycle cooling system. The Amplitude Calibration Device (ACD) is mounted above the frontend. Each receiver cartridge contains two complete receiving systems sensitive to orthogonal linear polarizations. The designs of the mixers, optics, LO injection scheme, and polarization splitting vary from band to band, depending on the optimum technology available at the different frequencies; each receiver is described in more detail in the sections below. Table 1 summarizes the characteristics of the bands available in Cycle 0. To avoid overloading the cryostat cooler, only three bands can be switched on at a time. It takes only about 1.5 seconds to switch between these bands. For bands that are not switched on, the time to fully thermally- stabilise them from an off state is 15 minutes – this is mainly to ensure the optimum flat bandpass shape. All of the receivers are mounted off-axis in order to avoid extra rotating band-selection mirrors, which necessitates an offset of the antenna to change band. This means that only one receiver can be used at a given time. 10