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27 May 1998 Results of the STRV-2 lasercom terminal evaluation tests
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The STRV-2 lasercom terminal (LCT) was designed and developed by AstroTerra Corporation of San Diego, California, under funding from the Ballistic Missile Defense Organization (BMDO). Scheduled for launch in late 1998 it will be used to demonstrate, for the first time, high data rate bi-directional satellite-to-ground optical communications. Concurrently with the development of the STRV-2 lasercom NASA/JPL was assembling the lasercom test and evaluation station (LTES), a high quality test platform for pre-flight characterization of optical communications terminals. The respective development schedules allowed evaluation of the STRV-2 LCT using LTES, for a month, prior to integration of the LCT with the spacecraft palette. Final co-alignment of the transmitter lasers to within plus or minus 20 (mu) rads with respect to the receive axis was achieved. This in turn allowed the specified 76 (mu) rad transmit beam divergence to be realized. However, subjecting the LCT to expected on-orbit temperatures revealed that the co-alignment deteriorated causing beam spreading, a finding which prompted the recommendation to operate the lasers warmed up during ground encounters. The 'bent-pipe' operation bit-error rates (BER) at 155, 194 and 325 Mbps were less than or equal to 1E - 10 over an approximately 20 dB range of irradiance measured at the receive telescope aperture. At 500 Mbps BER's of 1E-6 were achieved over an approximately 6 dB irradiance range, suggesting greater vulnerability to atmosphere induced fades. A pointing offset between the acquisition receivers and transmitter lasers of 1 mrad was measured. The impact of this offset will be to limit acquisition camera framing rates to 87 and 251 Hz, thus limiting the tracking loop bandwidth. Tracking performance test of the lasercom terminal, though planned could not be carried out because the software was not ready at the time of testing with LTES. The test results obtained for STRV-2 lasercom terminal will be used for designing the ground receiver.
© (1998) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Abhijit Biswas, George Williams, Keith E. Wilson, Harel Hakakha, Ron Stieger, and Eric J. Korevaar "Results of the STRV-2 lasercom terminal evaluation tests", Proc. SPIE 3266, Free-Space Laser Communication Technologies X, (27 May 1998);

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