OLSG Report_Final_06_05_12 - Interagency Operations Advisory ...
OLSG Report_Final_06_05_12 - Interagency Operations Advisory ...
OLSG Report_Final_06_05_12 - Interagency Operations Advisory ...
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Optical Link Study Group (<strong>OLSG</strong>) <strong>Final</strong> <strong>Report</strong><br />
IOAG.T.<strong>OLSG</strong>.20<strong>12</strong>.V1<br />
LEO DOW NLINK BUDGET<br />
INPUT PARAM ETERS<br />
LINK BUDGET<br />
Range 1.30E+03 km Tx Ave Power 26.99 dBm<br />
Elevation 20 deg<br />
Tx Antenna Gain<br />
100.<strong>12</strong> dBi<br />
TRANSMITTER<br />
Tx Transmission Loss<br />
-3.01 dB<br />
Modulation Type OOK Tx Pointing Loss -0.04 dB<br />
EIRP<br />
94.<strong>05</strong> dBW<br />
Tx Wavelength 1.55 µm Isotropic Space Loss -260.46 dB<br />
Tx Ave Power 0.5 W Atmospheric Loss -2.65 dB<br />
Tx Data Rate 10.0E+09 Hz Irradiance at g/s 1.20E-04 W/m^2<br />
Rx system 117.11<br />
Tx Aperture Diam 0.<strong>05</strong> m Rx Antenna Gain <strong>12</strong>0.<strong>12</strong> dBi<br />
Tx Angular Diam 8.14 arcsec Array Gain 0.00 dB<br />
Tx Footprint Diam 5.13E+01 m Rx Transmission Loss -3.01 dB<br />
Tx Optical Transmission 50.0 % Rx Pointing Loss 0.00 dB<br />
Tx Depointing 0.40 arcsec Total Optical Path Loss -48.93 dB<br />
ATMOSPHERIC LOSSES<br />
Ave Power at Rx Detector<br />
-21.94 dBm<br />
Atm Zenith Transmittance 95.0 %<br />
Relative Airmass 2.90 Required Power -26.00 dBm<br />
Atm Transmission Along LOS 86.2 % Link M argin 4.<strong>06</strong> dB<br />
Scintillation Loss -2.0 dB<br />
RECEIVER<br />
Rx Aperture Diam 0.50 m<br />
Rx FOV 5.00 arcsec<br />
Rx Depointing 1.00 arcsec<br />
Rx Optical Transmission 50.0 %<br />
Rx Array Size 1 apertures<br />
Code Rate 1.00<br />
Figure 27: Example downlink budget for the LEO Scenario.<br />
3.1.5.2 Uplink Budget<br />
A sample uplink beacon budget for the LEO scenario is reported in Figure 28. The<br />
transmitter consists of four 5 cm apertures, which provide a beam divergence of about 40<br />
μrad (8.14 arcsec). The average power per aperture is 0.<strong>12</strong>5 W, for a total transmitted<br />
power of 0.5 W. In the calculation, the scintillation loss (or turbulence loss) is computed as<br />
the Strehl ratio 2 and accounts for spread loss and beam wandering, under the assumptions<br />
of a seeing of 2 arcsec (Fried parameter r 0 of 5 cm, at zenith, at a wavelength of 500 nm).<br />
The irradiance required at the receiver aperture is based on the acquisition procedure of<br />
LLCD. The link budget shows that the average transmitted power could be reduced by<br />
about 26 dB, which corresponds to 0.3 mW per aperture.<br />
2 L. C. Andrews, R. L. Phillips, R. J. Sasiela, R. R. Parenti, Strehl ratio and scintillation theory for uplink Gaussian<br />
beam waves: beam wander effects (Opt. Eng. 45[7], 20<strong>06</strong>).<br />
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