Antenna Gain and Source calibration

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Antenna Gain and Source calibration

• Jim Gibson and Jack Welch

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Antenna gain Measurement using Standard Horn

• Horn Gain from Shelkunoff and Frijs
• Horn at Edge of 6m BIMA Antenna
• Transfer Switches Between Feed and Horn
• Jupiter is the Signal Source
• Used BIMA 6m Antenna in Array

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Jupiter Flux Measured with Calibrated Antenna

• Temperature Scale from Ambient and LN Loads
• Many On/Off Measurements of Jupiter
• Many Tipping Curves for Extinction
• Tb 145.12K /-2K
• Corrected for Synchrotron Emission Tb143.7/-2K

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Calibrating ALMA Images

• Calibrate Planets as often as Necessary
• Transfer Planetary Fluxes to Phase Calibrators.
  Use 2 or 3.
• Accurate Extinction Needed Here
• Scale ALMA Images to the Phase Calibrator Images.
  Little Extinction Correction Needed

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Future Plans

• Transfer 28.5 Jovian Flux to Mars and MWC349
• Repeat the Calibration at 90 GHz with Mars/Venus
• Generate Overall Scale for MWC349
• Test the Accuracy of Tipping Curves
• Test Stephanes Idea at 90 GHz

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Tipping Experiments

• Compare with an Interferometric Extinction Curve
  on a Stable Day
• Compare with Model Atmospheric Calculations
• Try it with the Standard Gain Horn Its Pattern
  is Cleaner and can be Calculated

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