Baseline Fit of the Interferometer: What Is Happening

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Baseline Fit of the Interferometer: What Is

Happening

Baseline Fit of the Interferometer: What Is

HappeningBy: Michelle Simon

W.M. Keck ObservatoryMentor: Jorg-Uwe Pott, Ben BerkeyHome Institution: Pacific Lutheran

University

By: Michelle Simon

W.M. Keck ObservatoryMentor: Jorg-Uwe Pott, Ben BerkeyHome Institution: Pacific Lutheran

University

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What You Will See Today

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

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

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VocabularyVocabulary

Interferometer

Baseline bFitPython

Script

Interferometer

Baseline bFitPython

Script

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Why this project is needed and what an Interferometer does

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.

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.

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How the program bFit Works

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.

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.

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What is Happening (Physically)

What is Happening (Physically)

• The rotation of each telescope is imprecise and has yet to be predicted.

1. The azimuth motion can be repeated for each telescope but is not the same.

2. The rotation axis can change from night to night.

3. The up portion of the baseline vector may depend on the thickness of the azimuth oil bearing.

• The rotation of each telescope is imprecise and has yet to be predicted.

1. The azimuth motion can be repeated for each telescope but is not the same.

2. The rotation axis can change from night to night.

3. The up portion of the baseline vector may depend on the thickness of the azimuth oil bearing.

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What is Happening(Programming)

What is Happening(Programming)

1. Incorrect measurements that are extremely off.

2. bFit as is, is not designed for detailed monitoring of the interferometer baseline.

1. Incorrect measurements that are extremely off.

2. bFit as is, is not designed for detailed monitoring of the interferometer baseline.

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What I have doneWhat 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.

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.

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Graphs Showing the Impact of Different Baseline Fits

Graphs Showing the Impact of Different Baseline Fits

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What can cause bFit to go bad in a single

night

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.

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.

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What's next...What's next...

The team will further investigate what exactly causes the baseline to vary.

See if the baseline variation can be predicted.

The team will further investigate what exactly causes the baseline to vary.

See if the baseline variation can be predicted.

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Acknowledgments: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)

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)