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ALMA Calibration Introduction

ALMA Calibration Introduction. Bryan Butler NRAO. Definition. calibration: 1 : the act or process of calibrating : the state of being calibrated calibrate: 4 : to measure or adjust precisely

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ALMA Calibration Introduction

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  1. ALMA CalibrationIntroduction Bryan Butler NRAO

  2. Definition calibration: 1: the act or process of calibrating : the state of being calibrated calibrate: 4: to measure or adjust precisely so, in the broadest sense, “calibration” includes the effort of measurement (and application) of all instrumental parameters. split into two types: 1 – quantities which must be known when the observation is made (signal adjustments pre-correlation) – these are mostly component values which change only infrequently, or array parameters which change with antenna moves, e.g.; 2 – quantities which can be applied to the data at a later date (but might have to be measured during obsn) – these are mostly instrumental parameters which change with time or ambient conditions. the timescale is important!

  3. The Elements • Antenna • Pointing • Surface & primary beam • subreflector & feed positioning • Amplitude • Fluctuating (opacity, receiver – Tsys; decorrelation) • Flux density scale • Single dish • Delay • Geometric • Atmosphere (the fluctuating part is what we often call “phase”) • Antenna structure • Electronics • Bandpass • Polarization • Miscellaneous (solar, e.g.)

  4. Agenda Amplitude Calibration 13:50 Introduction Guilloteau 14:00 Tests of Dual-Load System Welch 14:10 Tests of S/T-Vane System Pintado 14:20 New Grid System Guilloteau, Lamb 14:40 New Absolute Scheme Welch 15:00 Mod to New Absolute Scheme Guilloteau 15:10 Receiver Gain Stability D’Addario, Guilloteau 15:20 Discussion 15:30 Break Phase Calibration 15:40 Introduction Wootten 15:50 Fast Switching Holdaway 16:00 Discussion

  5. Agenda Bandpass Calibration 16:10 Introduction Guilloteau 16:20 Use of Astronomical Sources Guilloteau 16:40 Discussion Polarization Calibration 16:50 Introduction Butler 17:00 Discussion 17:10 Miscellaneous (Antenna Location, Focus, Delay, etc...) Butler ACA 17:30 Introduction Hasegawa 17:35 Discussion 17:40 Milestones Guilloteau, Wootten, Butler

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