antenna gain and source calibration jim gibson and jack welch

21
Antenna Gain and Source calibration Jim Gibson and Jack Welch

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Page 1: Antenna Gain and Source calibration Jim Gibson and Jack Welch

Antenna Gain and Source calibration

Jim Gibson and Jack Welch

Page 2: Antenna Gain and Source calibration Jim Gibson and Jack Welch

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

Page 3: Antenna Gain and Source calibration Jim Gibson and Jack Welch
Page 4: Antenna Gain and Source calibration Jim Gibson and Jack Welch
Page 5: Antenna Gain and Source calibration Jim Gibson and Jack Welch
Page 6: Antenna Gain and Source calibration Jim Gibson and Jack Welch
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Page 10: Antenna Gain and Source calibration Jim Gibson and Jack Welch

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: Tb=143.7+/-2K

Page 11: Antenna Gain and Source calibration Jim Gibson and Jack Welch
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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

Page 18: Antenna Gain and Source calibration Jim Gibson and Jack Welch

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 Stephane’s Idea at 90 GHz

Page 19: Antenna Gain and Source calibration Jim Gibson and Jack Welch

Tipping Experiments

• Compare with an Interferometric Extinction Curve on a Stable Day

• Compare with Model Atmospheric Calculations

• Try it with the Standard Gain Horn; It’s Pattern is Cleaner and can be Calculated

Page 20: Antenna Gain and Source calibration Jim Gibson and Jack Welch
Page 21: Antenna Gain and Source calibration Jim Gibson and Jack Welch