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SN User's Guide - ESC Home - NASA

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Appendix A. Example Link Calculations<br />

A.1 General<br />

This appendix contains example link calculations for forward and return services. All<br />

link calculations are based on the TDRSS telecommunications services defined in<br />

Sections 5 (MA), 6 (SSA), 7 (KuSA), and 8 (KaSA).<br />

NOTE:<br />

The calculations in this appendix are provided for example<br />

only, and no data should be extracted from them for specific<br />

use. For specifics on preparing necessary RFICD's, contact<br />

GSFC Code 450.<br />

A.2 Customer Platform-to-TDRS Range<br />

All forward and return service link calculations are based upon example customer<br />

platform-to-TDRS ranges of 42,510 km for S-band and 45,890 km for K-band (Ku and<br />

Ka). Figure A-1 illustrates the example communications range positions for a 2000-km<br />

customer platform orbit. The maximum communications ranges for particular customer<br />

platforms can differ from these values as a result of the actual orbit, Power Flux Density<br />

(PFD) constraints (refer to Appendix D), or other customer mission requirements and<br />

constraints.<br />

A.3 Forward Service Link Calculations<br />

A.3.1<br />

Forward service performance is expressed in terms of having a sufficient data Bit<br />

Energy to Noise Spectral Density Ratio (Eb/No) at the customer platform receiving<br />

system for the desired link operating point (e.g., command data channel BER of 10 -5 ).<br />

Forward service performance is determined by calculating a predicted (Eb/No) and<br />

comparing it against the required (Eb/No).<br />

Revision 10 A-1 450-<strong>SN</strong>UG

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