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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 2:25 |
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Conference: Bucharest University Faculty of Physics 2024 Meeting
Section: Atomic and Molecular Physics. Astrophysics. Applications. Optics, Spectroscopy, Plasma and Lasers
Title:
CONSTELATION ACQUISITION SENSOR SPOT CENTROIDING
Authors:
Georgiana SIMIONESCU(1,2), Eugeniu Mihnea POPESCU (1), Florin Adrian POPESCU(1), Gabriel CHIRITOI(1)
*
Affiliation:
1)Institute of Space Science
2)Faculty of Physics, University of Bucharest
E-mail
georgiana.simionescu22@gmail.com
Keywords:
CAS, LISA, CoG
Abstract:
LISA (Laser Interferometer Space Antena) is a NASA-ESA space mission aimed at observing sources of gravitational waves in a low frequency range. The Constellation Acquisition Sensor helps to maintain the positioning and the alignment of the three satellites.
The CAS configuration, with a laser spot size on the sensor of ~ 100 µm, two centroiding methods have been studied and implemented, namely: the simple 5x5 pixels centroiding window CoG (Center of Gravity) method, a modified CoG method with a 5x5 pixels centroiding window and a 7x7 pixels border for background subtraction.
The precision testing method in this case consisted of placing the laser spot at different locations on CAS sensor (by mechanically displacing the sensor and keeping the laser direction fixed) and taking 10 successive images of the spot at a one location. All two centroiding methods were applied to each such set of 10 images, and for each centroiding method the average centroid position was calculated as well as centroid position standard deviation, and the latter was compared to the reference centroiding resolution of 0.2 µrad in the sky (which translates into a 3.41 μm resolution on the sensor in the CAS experimental configuration).
The displacement measurement accuracy testing method is an extension of the precision testing. The sensor was displaced mechanically, with the help of the micrometer stage and starting from its approximate center, in the vertical and the horizontal direction with respect to the optical axis of the CAS, in steps of 500 µm. At each spot position on the sensor, 10 successive spot images were taken, each of the two centroiding methods was applied to these image sets to estimate the spot position on the sensor by averaging, the distance between such consecutive centroids was calculated using simple Euclidean geometry and the resulting estimated spot displacement was compared to the reference micrometer displacement of 500 μm.
References:
[1] M. Born, E. Wolf, “Principles of Optics”, Cambridge University Press, Cambridge New York Oakleigh, 1997
[2] William H. Press, Saul A. Teukolsky, William T. Vetterling, Brian P. Flannery,
”Numerical Recipes”, Third Edition.
[3] J. W. Goodman, ”Introduction to Fourier Optics”
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