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ALMA Calibration Plan

Detailed calibration examples and observation sequences from ALMA ASAC Meeting in Florence, September 2006. Evolution of calibration types into hardware and software sequences for ALMA operations.

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ALMA Calibration Plan

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  1. ALMA Calibration Plan Jeff Mangum (NRAO) Robert Lucas (IRAM) Baltasar Vila Vilaro (NAOJ) ALMA ASAC Meeting Florence September 2006

  2. ALMA Calibration Development Roadmap ALMA ASAC Meeting Florence September 2006

  3. Calibration Examples • Atomic-level descriptions of each type of calibration. • Derive from science and system requirements and characteristics coupled with experience. • Evolve into hardware and software observation sequences which implement each type of calibration. ALMA ASAC Meeting Florence September 2006

  4. Calibration Examples Green = Complete; Blue = Reviewed / In Revision; Red = Draft ALMA ASAC Meeting Florence September 2006

  5. HW/SW Observation Sequences • Method-level descriptions of each type of calibration. • Detailed descriptions of how hardware is commanded by software to effect each calibration measurement. ALMA ASAC Meeting Florence September 2006

  6. Observing Modes • Integration of HW/SW Observation Sequences into scheduling blocks ALMA ASAC Meeting Florence September 2006

  7. Calibration Matrix ALMA ASAC Meeting Florence September 2006

  8. Phase Calibration • Target Sequence: Over a period of 15 to 30 seconds the following measurement sequence is observed involving the target and phase calibration source located typically less than or equal to 2 degrees away from the target source: • Tune to the calibration frequency if cross-band calibration required. • Phase calibrator measurement (tint ≤ 1 second). • Tune to the source frequency if cross-band calibration required. • Target source measurement (tint ≤ 25 seconds). • Tune to the calibration frequency if cross-band calibration required. • Phase calibrator measurement (tint ≤ 1 second). • Instrumental Sequence: This cycle of measurements is required for cross-band calibration of dual-frequency fast switching measurements. Over a period of 10 to 25 seconds a strong phase calibrator source which can be detected at both the target and calibration frequency is used to provide the phase scaling from the target (usually higher) frequency to the calibration (usually 90 GHz) frequency: • Tune to calibration frequency. • Phase calibrator measurement (tint ≤ 1 second). • Tune to target frequency. • Phase calibrator measurement (tint ≤ 1 second). • Repeat this sequence. ALMA ASAC Meeting Florence September 2006

  9. Phase Calibration Sequence ALMA ASAC Meeting Florence September 2006

  10. Absolute Amplitude Calibration • Research topic • Absolute Amplitude Calibration Focus Group recently formed • Bryan Butler (NRAO) • Mark Gurwell (SAO) • Jack Welch (Berkeley) • Charter: • Develop list of potential primary and secondary flux calibration sources • Planets (Mars, Uranus, etc.) • Asteriods • Stars (Main Sequence, Giant, Supergiant) • Large Ice Bodies (Titan, Galilean Satellites, Triton, etc.) • For each candidate define measurements or calculations required to define status as a primary or secondary flux calibrator • Initiate measurement program where appropriate (CARMA, SMA, ALMA, etc.) ALMA ASAC Meeting Florence September 2006

  11. Operations/Maintenance Calibration Pointing Polarization Antenna Location Antenna and Electronic Delay Optics Primary Beam User Calibration Reference Pointing Amplitude Phase Bandpass Polarization Calibration and ALMA Operations ALMA ASAC Meeting Florence September 2006

  12. Calibration and ALMA Operations • How does calibration planning get incorporated into ALMA Operations? Example: Pointing • Pointing calibrator list development and maintenance • Required interval • Monitoring requirements for antenna/array vital signs • Weather monitoring analysis and requirements • Antenna-based behavior and trends ALMA ASAC Meeting Florence September 2006

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