Temperature Effects on the Pointing of Antennas at the Submillimeter Array

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• Temperature Effects on the Pointing of Antennas
  at the Submillimeter Array

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Outline
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The Submillimeter ArrayMauna Kea, Hawaii
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Important Project
-Daytime observations -Most temperature
variation -Metal heats up it expands -Variation
of expansion affects pointing -Pointing
important for astronomical data -Other factors
cause pointing errors -Correct for factors that
cause large error -Pointing Model -Too
expensive to correct for all
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Quadrapods
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Primary Reflector
Reflector Mount
Sensor
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Temperature Dataon July 25, 2007
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Snapshotson July 25, 2007

• Snapshot of Jupiter at sunset (732PM)

Snapshot of Jupiter a few hours later (1013PM)
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Arcturus
Altair
Deneb
Jupiter
Vega
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Results
In Azimuth The pixel difference was 1.6
pixels With 1.252 per pixel the pointing error
caused by temperature was 1.878 In
Elevation The pixel difference was 3.5
pixels With 1.252 per pixel the pointing error
caused by temperature was 4.381
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Acknowledgments

• Billie Chitwood
• Nimesh Patel
• Erin Brassfield
• SMA Staff
• Sarah Anderson
• Scott Seagroves
• Hilary OBryan
• This work has been supported by the National
  Science Foundation Science and Technology Center
  for Adaptive Optics, managed by the University of
  California at Santa Cruz under cooperative
  agreement No. AST - 9876783.

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Other Pointing Errors

• ?Az cos(El) Az cos(El) C L sin (El) I
  sin(El) sin(Az) I sin(El) cos(Az)
• I sin(El) sin(2(Az)) I sin(El) cos(2(Az)) M
  cos(El) sin(Az) M cos(El) cos(Az)
• M cos(El) sin(2(Az)) M cos(El) cos(2(Az)) M
  cos(El) sin(3(Az))
• M cos(El) cos(3(Az)) Qaz RMaz