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Equation A-5
Predicted Required Prec = Ideal Required Prec - L - Lp - LI - Lnc
where:
L = pointing loss (in dB) due to the inability of the customer platform to
point its antenna directly at the TDRS (L 0 dB).
Lp = polarization loss (in dB) due to mismatch of the customer platform
radiated polarization and that of the TDRS receiving antenna (LP 0
dB).
LI, Lnc = RFI and customer platform incompatibility factors (in dB) as
determined by CLASS (refer to paragraph 3.5.2) (LI 0 dB, Lnc 0
dB).
A.4.4
By extension, the minimum customer platform EIRP, (EIRP)min, required to produce the
predicted required Prec is as follows:
Equation A-6
(EIRP)min = Predicted Required Prec - Ls
where: Ls is space loss as defined in paragraph A.3.2.
A.4.5
The return service performance margin M (in dB) is a customer decision that should be
coordinated with GSFC Code 450 and should consider long-term performance
degradation of the customer platform throughout its operational lifetime. M is defined as
follows:
Equation A-7
M = EIRP - (EIRP)min (M > 0 dB)
A.4.6
The return service performance curves in Figure A-8 through Figure A-42 show ideal
required (Prec) versus ADR for selected services, type of tracking and/or field of view,
codings, modes, data rates and channels. Figure A-43 shows an example ADR versus
customer platform EIRP for a hypothetical customer platform, for an assumed
performance margin, M, as illustrated in Equation A-7. The service, coding, mode, and
channel in Figure A-43 are assumed to be those given in Figure A-15, so as to illustrate
how the predicted required Prec is realized, (or alternatively, how the ideal required Prec
plus performance margin is realized).
Revision 10 A-12 450-SNUG