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Baseline Fit of the Interferometer: What Is Happening. By: Michelle Simon W.M. Keck Observatory Mentor: Jorg-Uwe Pott, Ben Berkey Home Institution: Pacific Lutheran University. What You Will See Today. The vocabulary you may need to know What was supposed to happen with the baseline
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Baseline Fit of the Interferometer: What Is Happening By: Michelle Simon W.M. Keck Observatory Mentor: Jorg-Uwe Pott, Ben Berkey Home Institution: Pacific Lutheran University
What You Will See Today • The vocabulary you may need to know • What was supposed to happen with the baseline • What actually happened before and after I arrived • What can be done to make the program work as desired
Vocabulary • Interferometer • Baseline • bFit • Python Script
Why this project is needed and what an Interferometer does • An interferometer provides the ability to resolve objects that may not be resovable in a normal viewing with a single telescope. • A new instrument (ASTRA) is being added to the interferometer and requires more precise measurements of the baseline.
How the program bFit Works • Takes the measured fringes positions for each star which are found when the delay line matches the geometric delay. • Then derives the baseline vector from these positions, assuming a perfect rotation of each telescope. • The precision of the baseline fit is good enough to find the fringes with in 50 microns.
What is Happening (Physically) • The rotation of each telescope is imprecise and has yet to be predicted. • The azimuth motion can be repeated for each telescope but is not the same. • The rotation axis can change from night to night. • The up portion of the baseline vector may depend on the thickness of the azimuth oil bearing.
What is Happening(Programming) • Incorrect measurements that are extremely off. • bFit as is, is not designed for detailed monitoring of the interferometer baseline.
What I have done • Created multiple Python programs to ease the baseline analysis • Each program is documented to allow the future user to explore what has been done. • The programs help to establish the cause of bad data on the results of bFit, and allow to optimize the data selection.
What can cause bFit to go bad in a single night • Only observing a single star • Observing any number of stars but in small range of azimuth. • The variation in the up and constant terms of the baseline vector.
What's next... • The team will further investigate what exactly causes the baseline to vary. • See if the baseline variation can be predicted.
Acknowledgments: • Jorg – Uwe Pott • Ben Berkey • CfAO • W.M. Keck • Sarah Anderson • The Akamai Internship Program is funded by the Center for Adaptive Optics through its national Science Foundation Science and technology Center grant(#AST-987683)