Satellite-Satellite Laser Links for Future Gravity Missions
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A strong candidate for use in future missions to map time variations in the Earth's gravity field is laser heterodyne measurements between separate spacecraft. At the shortest wavelengths that can be measured in space, the main accuracy limitation for variations in the potential with latitude is expected to be the frequency stability of the laser. Thus the development of simple and reliable space-qualified lasers with high frequency stability appears to be an important goal for the near future.
In the last few years, quite high stability has been achieved by locking the second harmonic of a Nd:YAG laser to a resonant absorption line of iodine molecules in an absorption cell. Such a laser system can be made quite robust, and temperature related frequency shifts can be controlled at a low value. Recent results from laboratory systems are described. The Allan standard deviation for the beat between two such lasers was 2 × 10−14 at 10 s, and reached 7 × 10−15 at 600 s.
KeywordsGravity Field Frequency Stability Resonant Absorption Iodine Molecule Future Mission
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- Bender, P.L.: 1992, ‘Integrated laser Doppler method for measuring planetary gravity fields,’ in From Mars to Greenland: Charting Gravity with Space and Airborne Instruments, IAG Symposium, Vol. 110, Springer-Verlag, pp. 63-72.Google Scholar
- Colombo, O.L. and Chao, B.F.: 1992, ‘Global gravitational change from space in 2001,’ IAG Symposium Vol. 112, Potsdam.Google Scholar
- Danzmann, K.V. et al.: 1998, LISA-Laser Interferometer Space Antenna Pre-Phase A Report, 2nd edn., MPQ 233.Google Scholar
- Ishibashi, C., Ye, J. and Hall, J.L.: 2002, ‘Issues and applications in ultra-sensitive molecular spectroscopy,’ in Methods for Ultrasensitive Detection II, C. W. Wilkerson, Jr., Ed., SPIE Vol. 4634 pp. 58-69.Google Scholar
- LISA Study Team: 2000, ‘LISA Laser Interferometer Space Antenna: a Cornerstone Mission for the Observation of Gravitational Waves,’ ESA-SCI(2000)11, European Space Agency.Google Scholar
- Schumaker, B.L.: 1990, ‘Scientific Applications of Frequency-Stabilized Laser Technology in Space,’ Jet Propulsion Laboratory Pub. 90-50, Caltech, Pasadena, CA, pp. 133-146.Google Scholar
- Watkins, M.M., Folkner, W.M., Chao, B., and Tapley, B.D.: 2000, ‘EX-5: A laser interferometer follow-on to the GRACE mission,’ presented at GGG2000, Banff, Canada, 31 July–5 August, 2000 (unpublished).Google Scholar
- Ye, J., L.-S. Ma, and J. L. Hall: 2001, ‘Molecular iodine clock,’ Phys. Rev. Lett. 87, pp. 270801/1-4.Google Scholar