1. 1 1 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 By: Michelle Simon W.M. Keck Observatory Mentor: Jorg-Uwe Pott, Ben Berkey Home Institution: Pacific Lutheran University

2. 2 What You Will See Today FThe vocabulary you may need to know FWhat was supposed to happen with the baseline FWhat actually happened before and after I arrived FWhat can be done to make the program work as desired FThe vocabulary you may need to know FWhat was supposed to happen with the baseline FWhat actually happened before and after I arrived FWhat can be done to make the program work as desired

3. 3 Vocabulary  Interferometer  Baseline  bFit  Python Script  Interferometer  Baseline  bFit  Python Script

4. 4 Why this project is needed and what an Interferometer does FAn interferometer provides the ability to resolve objects that may not be resovable in a normal viewing with a single telescope. FA new instrument (ASTRA) is being added to the interferometer and requires more precise measurements of the baseline. FAn interferometer provides the ability to resolve objects that may not be resovable in a normal viewing with a single telescope. FA new instrument (ASTRA) is being added to the interferometer and requires more precise measurements of the baseline.

5. 5 How the program bFit Works FTakes the measured fringes positions for each star which are found when the delay line matches the geometric delay. FThen derives the baseline vector from these positions, assuming a perfect rotation of each telescope. FThe precision of the baseline fit is good enough to find the fringes with in 50 microns. FTakes the measured fringes positions for each star which are found when the delay line matches the geometric delay. FThen derives the baseline vector from these positions, assuming a perfect rotation of each telescope. FThe precision of the baseline fit is good enough to find the fringes with in 50 microns.

6. 6 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.

7. 7 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.

8. 8 What I have done FCreated multiple Python programs to ease the baseline analysis FEach program is documented to allow the future user to explore what has been done. FThe programs help to establish the cause of bad data on the results of bFit, and allow to optimize the data selection. FCreated multiple Python programs to ease the baseline analysis FEach program is documented to allow the future user to explore what has been done. FThe programs help to establish the cause of bad data on the results of bFit, and allow to optimize the data selection.

9. 9 Graphs Showing the Impact of Different Baseline Fits

10. 10 What can cause bFit to go bad in a single night FOnly observing a single star FObserving any number of stars but in small range of azimuth. FThe variation in the up and constant terms of the baseline vector. FOnly observing a single star FObserving any number of stars but in small range of azimuth. FThe variation in the up and constant terms of the baseline vector.

11. 11 What's next... FThe team will further investigate what exactly causes the baseline to vary. FSee if the baseline variation can be predicted. FThe team will further investigate what exactly causes the baseline to vary. FSee if the baseline variation can be predicted.

12. 12 Acknowledgments: FJorg – Uwe Pott FBen Berkey FCfAO FW.M. Keck FSarah Anderson FThe Akamai Internship Program is funded by the Center for Adaptive Optics through its national Science Foundation Science and technology Center grant(#AST-987683) FJorg – Uwe Pott FBen Berkey FCfAO FW.M. Keck FSarah Anderson FThe Akamai Internship Program is funded by the Center for Adaptive Optics through its national Science Foundation Science and technology Center grant(#AST-987683)