design judgment is required. 9.3.6.3 Typical Down-Link Power Budget. A link budget is a tabular method of calculating space communication system parameters. The approach is very similar to that used for LOS microwave links (see Section 9.2.3.4). We start with the EIRP of the satellite for the downlink or the EIRP of the earth station for the uplink. The bottom line is C/No and the link margin, all calculated with decibel notation. C/No is the carrier-to-noise ratio in 1 Hz of bandwidth at the input of the LNA. (Note: RSL or receive signal level and C are synonymous). Expressed as an equation: (other losses) + G/TB/K - k, (9.23) where FSL is the free-space loss to the satellite for the frequency of interest and k is Boltzmann's constant expressed in dBW. Remember in Eq. (9.9) we used Boltzmann's constant, which gives the thermal noise level at the output of a "perfect" receiver operating at absolute zero in 1 Hz of bandwidth (or No). 15 Its value is -228.6 dBW/Hz. "Other losses" may include: Polarization loss (0.5 dB) Pointing losses, terminal and satellite (0.5 dB each) Off-contour loss (depends on satellite antenna characteristics) Gaseous absorption loss (varies with frequency, altitude, and elevation angle) Excess attenuation due to rainfall (for systems operating above 10 GHz) The loss values in parentheses are conservative estimates and should be used only if no definitive information is available. The off-contour loss refers to spacecraft antennas that provide a spot or zone beam with a footprint on a specific geographical coverage area. There are usually two contours, one for G/T (uplink) and the other for EIRP (downlink). Remember that these contours are looking from the satellite down to the earth's surface. Naturally, an off-contour loss would be invoked only for earth stations located outside of the contour line. This must be distinguished from satellite pointing loss, which is a loss value to take into account that satellite pointing is not perfect. The contour lines are drawn as if the satellite poin