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B L A S T The Balloon‐borne Large Aperture Submillimeter Telescope Reaction Wheel NSF: GK‐12 Research Program Brown University By: Herminia Collado Contents The BLAST Background – Developed by Brown University, University of Pennsylvania, University of Toronto, University of Miami, University of British Columbia, Cardiff University, and INAOE. Motivation: – Observe the earliest galaxies that formed in the universe. – Study star formation regions in our galaxy. The BLAST Balloon 1000 ft Equipped with a two‐meter telescope that is sensitive to three wavelengths. Gondola Gondola Pivot Telescope Star camera Computers Reaction Wheel Reaction Wheel Shaft Weight Weight support The Reaction Wheel • Purpose of the reaction wheel – Pointing the telescope • Features of the reaction wheel – Lightweight aluminum honeycomb – Diameter of two meters – 48 balancing brass weights around the edge – Spins at a rate of 1 Hz. Reaction Wheel Comparing an Unbalanced Wheel to a Balanced Wheel Balancing the Reaction Wheel The process has two major components: – Adjustment and calibration of the wheel’s total structure – Balancing the reaction wheel on the structure Wheel Reaction Wheel Structure Weight Support Pivot Shaft Linear motion sensor Pivot Arm Motion Sensor Bracket Rotary Encoder Balancing the Structure of the Wheel – Calibration of the pivot – Adjustment of motion sensor – Design and construction of a structure to place the motion sensor. This allows greater access to the reaction wheel’s axle and increased precision in data collection – Design and construction of a new pivot arm and its calibration Old Pivot Arm New Pivot Arm Balancing the Reaction Wheel – Weigh each object that is to be used on the wheel – Spin the wheel without adding any weight. – Add a weight support in a position on the wheel, spin it, and run a comparison analysis. – Move each weight support on the wheel to the opposite position on the wheel. – Read the graphs and data, and depending on the results, make the necessary adjustments. LabVIEW Screen Using this program, we read the graphs and data, and, depending on the results, make the necessary adjustments. Graph of angular displacement Linear Position Angle Phase Where Are We Now? – The wheel is balanced within a 5 gram margin of error on the circumference. – The reaction wheel is tilted by 0.1 degrees due to construction deformation of the wheel. Acknowledgements – NSF: “GK‐12 ‐ Physical Processes in the Environment.” – Observational Cosmology Lab Personnel at Brown University: Dr. Gregory Tucker, Andrei Korotkov, John Macaluso, Ryan Michney, and Melanie Finn References – M. D. P. Truch, P. A. R. Ade, J. J. Bock, E. L. Chapin, M. J. Devlin, S. Dicker, M. Griffin, J. O. Gundersen, M. Halpern, P. C. Hargrave, D. H. Hughes, J. Klein, G. Marsden, P. G. Martin, P. Mauskopf, C. B. Netterfield, L. Olmi, E. Pascale, G. Patanchon, M. Rex, D. Scott, C. Semisch, C. Tucker, G. S. Tucker, M. P. Viero, and D. V. Wiebe. (2008) The Balloon‐ borne Large Aperture Submillimeter Telescope (BLAST) 2005: Calibration and Targeted Sources. The Astrophysical Journal 681:1, 415‐427 Online publication date: 1‐Jul‐2008. – Wright, Edward L. “Cosmic Microwave Background”. 15 Aug 2007. < http://www.astro.ucla.edu/~wright/CMB.html > 21 July 2008.
