1. Ground Target kHz Laser Ranging with Submillimeter Precision Lukas Kral, Karel Hamal, Ivan Prochazka (1) Georg Kirchner, Franz Koidl (2) presented at kHz SLR Meeting, Graz, Austria 27–29 October 2004 (1) Czech Technical University in Prague, Czech Republic (2) Satellite Laser Station Graz Lustbuehel, Graz, Austria

2. L.Kral, K. Hamal, I. Prochazka, G. Kirchner, F. Koidl, Graz, October 2004 Goal & Philosophy n Goal: to achieve precision of <1 mm RMS together with high return rate during ground target calibration (purpose: investigation of atmospheric turbulence influence on the ranging jitter) n Method: target selection and placing adjusting return energy level adjusting beam divergence etc. n Based on the authors’ personal experience from the SLR station Graz

3. L.Kral, K. Hamal, I. Prochazka, G. Kirchner, F. Koidl, Graz, October 2004 Target Selection & Placing n The best target for the ground calibration turned out to be a single cube-corner retroreflector: u does not spread the reflected laser pulse in time u provides high return energy n Must be distant enough to include the effects of pass through the turbulent atmosphere (in our case 4.3 km from the observatory)

4. L.Kral, K. Hamal, I. Prochazka, G. Kirchner, F. Koidl, Graz, October 2004 Influences of Return Energy optimum

5. L.Kral, K. Hamal, I. Prochazka, G. Kirchner, F. Koidl, Graz, October 2004 Ground Target Laser Ranging Energy Spectrum Graz, May 5, 2004, 2 kHz, 8 ps laser, C-SPAD, PET2k dark counts prepulses 1 m ground target 1 - 10 PE, 15 ps rms 4 km ground target ~ 1000 PE, 6 ps rms

6. L.Kral, K. Hamal, I. Prochazka, G. Kirchner, F. Koidl, Graz, October 2004 Adjusting Divergence and FOV Field-proven procedure at Graz observatory: 1.Set the minimum beam divergence (~ 50 urad) to concentrate the energy and make the target easily visible 2.Adjust laser/telescope to point exactly to the target (visual + CCD control of the reflected light intensity) 3.Set the maximum beam divergence (1 mrad) to stabilize the return rate (reduces the atmospheric fluctuation of returned light intensity) 4.Attenuate the laser beam to adjust the proper return energy (-> low jitter + high return rate)

7. The 4.3 km distant retro illuminated by the laser

8. Example of Results dataset suitable for atmospheric influence extraction Single shot RMS = 0.8 mm (2.2-sigma) Return rate = 1.2 kHz

9. L.Kral, K. Hamal, I. Prochazka, G. Kirchner, F. Koidl, Graz, October 2004 Conclusion n Ground target 2–4 km ranging to a corner retro reflector became routine with <1 mm instrumental precision at a signal strength ~ 1ooo phot/echo n Standard procedure developed and documented n Atmospheric fluctuation contribution to the laser ranging jitter budget extracted from this data for the first time PROCHÁZKA, I. – HAMAL, K. – KRÁL, L. Atmospheric fluctuation induced laser ranging jitter. In Laser Radar Techniques for Atmospheric Sensing: Proceedings of SPIE, vol. 5575. ISBN 0-8194-5522-9.