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Proceedings Paper

How to measure a femtometer
Author(s): Jan R. Nijenhuis; Huib Visser; Bob Kruizinga
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Paper Abstract

Measuring the wind speed from a satellite is not new. However measuring with great precision is by far not trivial. Various methods are available for that. A common method is to use the Doppler effect. A UV-laser on board of the satellite is used to "fire" to the earth atmosphere. Some photons will be reflected back to the satellite. Because of the speed of the particles in the air the photons will experience a small Doppler shift. Wind speeds of 1 m/s are hereby equivalent to a wave length shift of 1 femtometer. The paper presents the patented method of how to measure these small wavelength shifts without running into trouble concerning the mechanical design. It will understood that such instrument will be very sensitive to thermal variations (a challenging requirement was that a temperature change of 0.2° in 7 seconds was specified at the interface surfaces). The optical system makes use of a modified Michelson interferometer while the mechanical system automatically compensates for thermal expansion effects. Originally the idea was to make a complete Zerodur structure to eliminate the thermal effects. However it appeared to be possible to use a titanium structure with certain elements made from invar and aluminium. No need to say that this reduced risk and cost of the instrument drastically.

Paper Details

Date Published: 27 October 2003
PDF: 8 pages
Proc. SPIE 5176, Optomechanics 2003, (27 October 2003); doi: 10.1117/12.509127
Show Author Affiliations
Jan R. Nijenhuis, TNO (Netherlands)
Huib Visser, TNO (Netherlands)
Bob Kruizinga, TNO (Netherlands)

Published in SPIE Proceedings Vol. 5176:
Optomechanics 2003
Alson E. Hatheway, Editor(s)

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