Progress on active tracking at the Starfire Optical Range (SOR) has been significant in the years 2003-2004. We have obtained laser returns from a number of retro-reflector and also unaugmented satellite objects, and compared the signal returns to theories presented in previous SPIE papers (ref. 1-3). These results have concentrated on very low-power, sinusoidally-modulated lasers and a large-aperture, phase-sensitive detection receiver to discriminate the return signal from background and noise. This year, we have installed and used a much higher average power, high-repetition-rate pulsed laser in order to increase the signal-to-noise ratio. Results from these laser engagements will be presented along with simulation and theoretical comparisons. Techniques for diagnosing the laser uplink and the receiver systems will be discussed.
In the fall of 1996, we had the opportunity to mneasure the atmospheric coherence length (Fried's r0 parameter) at the STarfire Optical Range using three instruments. Each instrument measured r0 using a different theory and technique. The first instrument, designed and built by Dr. Donald Walters of the Naval Postgraduate School, is based on measuring the MTF of the atmosphere using a stellar image on a one dimensional detector. The second instrument, designed and built by Lockheed Martin engineers at White Sands Missile Range, is based on measuring the differential motion of stellar images. The third technique in this study used short exposure star images taken through the 1.5m telescope and processed by matching the images to shrot exposure theory values of r0. All of the instruments were located at the STarfire Optical Range and data were collected during both day and night hours. This paper presents the results of these measurements and discusses the different techniques in terms of the results obtained.
Since 1987, we have measured the transverse coherence length (Fried's r<SUB>o</SUB> parameter) and the isoplanatic angle, (theta) <SUB>o</SUB>, using optical instruments at the Starfire Optical Range (SOR). Through the end of December 1994, we have accumulated 160, 653 r<SUB>o</SUB> measurements and 185,488 (theta) <SUB>o</SUB> measurements. The transverse coherence length, r<SUB>o</SUB>, was determined by measuring the short exposure modulation transfer function of the atmosphere using a 35.5 cm Celestron transfer observing bright stars. The isoplanatic angle was obtained using a stellar scintillation technique on bright stars with a 10 cm Meade telescope. Prior to 1992, a 20 cm Celestron telescope with an apodized aperture was used. Means and frequency distributions of r<SUB>o</SUB> and (theta) <SUB>o</SUB> have been determined for the period 1987 through December 1994, for each individual year and for each month using measurement from all years. In addition, for the period November 1993 to December 1994, we used Albuquerque National Weather Service rawinsonde wind data and a model of the C<SUB>n</SUB><SUP>2</SUP> profile to estimate the Greenwood frequency f<SUB>G</SUB>. These estimates generally compare well with measured Greenwood frequency data obtained from the high speed wavefront sensor in the 1.5 m adaptive optics system. The summaries presented are a first attempt to characterize the optical turbulence at the SOR and may be used to plan experiments during months of statistically low atmospheric turbulence and Greenwood frequency.