Table 1a. S-Band Transmit Characteristics, 34-m STD Subnet (Antenna)
Table 1b. S-Band Transmit Characteristics, 34-m STD Subnet (Exciter)
Table 1c. S-Band Transmit Characteristics, 34-m STD Subnet (Transmitter)
Table 2a. S-Band, and X-Band Receive Characteristics, 34-m STD Subnet (Antenna)
Table 2b. S-Band, and X-Band Receive Characteristics, 34-m STD Subnet (Low-noise Amplifiers and Receivers)
Table 3a. X-Band Transmit Characteristics, 34-m HEF Subnet (Antenna)
Table 3b. X-Band Transmit Characteristics, 34-m HEF Subnet (Exciter)
Table 3c. X-Band Transmit Characteristics, 34-m HEF Subnet (Transmitter)
Table 4a. S-Band, and X-Band Receive Characteristics, 34-m HEF Subnet (Antenna)
Table 4b. S-Band, and X-Band Receive Characteristics, 34-m HEF Subnet (Low-noise Amplifiers and Receivers)
The attenuation and noise-temperature effects of weather for five specific weather conditions (for the HEF Antennas) are included so that for those specific conditions this module may be used without reference to Module TCI-40 of Volume I, Atmospheric Effects. More comprehensive and detailed S-, X-, and Ka-band weather effects models (for weather conditions up to 99.8% cumulative distribution) are given in Module TCI-40. The weather-included system temperature and net antenna gain curves presented in this module can be used for a quick estimate of telecommunications link performance; but for detailed design control table use, the weather models presented in TCI-40 (Revisions C and later) should be used.
Antenna gain is specified at the indicated frequency . For operation at other frequencies in the same band, the gain (dBi) scales by .
Structural deformation of the antennas causes a reduction in gain when the antenna operates in a position other than that of peak gain. For a HA-DEC antenna, this effect is a function of the position of both axes. For an AZ-EL antenna, the effect is a function of elevation angle only. Gain values are shown in Figures 1 and 2 for the STD Subnet and 5 and 6 (a and b) for the HEF Subnet. The Standard Subnet figures include the attenuation effect of an average clear atmosphere, whereas the HEF figures include the effects of three different weather conditions. The equations for the curves are presented in Appendix A of this module.
Figure 1. S-Band Gain vs. Hour Angle. All STD Subnet Stations, Non-Diplexed, TWM-1 Input
Figure 2. X-Band Gain vs. Hour Angle. All STD Subnet Stations, Low Loss Path, TWM-1 or -2 Input
Figure 5. S-Band Gain vs. Elevation Angle. All HEF Subnet Stations, Cooled FET Input
Figure 6a. X-Band Gain vs. Elevation Angle. DSS 15, Non-Diplexed Path, TWM-1 Input
Figure 6b. X-Band Gain vs. Elevation Angle. DSS 45 and 65, Non-Diplexed, TWM-1 Input
The operating system temperature varies as a function of elevation angle due to changes in the path length through the atmosphere and the effect of the ground in the sidelobes of the antenna. Figures 3 and 4 for the STD Subnet and 7 and 8 (a and b) for the HEF Subnet show the combined effects of these factors . The Standard Subnet figures include the attenuation effect of an average clear atmosphere, whereas the HEF figures include the effects of three different weather conditions. The equations for the curves are presented in Appendix A of this module.
Figure 3. S-Band System Temperature vs. Elevation Angle. All STD Subnet Stations, Non-Diplexed, TWM-1 Input
Figure 4. X-Band System Temperature vs. Elevation Angle. All STD Subnet Stations, Low Noise Path, TWM-1 or -2 Input
Figure 7. S-Band System Temperature vs. Elevation Angle. DSS 15 and DSS 45 HEF Stations, Cooled HEMT Input
Figure 8a. X-Band System Temperature vs. Elevation Angle. DSS 15 HEF Station, Low Noise Path, TWM-1 Input
Figure 8b. X-Band System Temperature vs. Elevation Angle, DSS 45 and DSS 65 HEF Stations, Low Noise Path, TWM-1 Input
The plotted curves for the HEF antennas represent the gain or operating system temperature of the antenna in a hypothetical vacuum (no atmosphere) condition and with 0%, 50%, and 90% weather conditions, designated as CD (cumulative distribution) = 0.00, 0.50, and 0.90. A value of 0% means minimum weather effect (exceeded 100% of the time); the 90% figure means that effect which is exceeded only 10% of the time. Qualitatively, 0% corresponds to the driest condition of the atmosphere, 25% corresponds to average clear, 50% corresponds to humid air or very light clouds, and 90% corresponds to very cloudy conditions--but with no rain. The equations and parameters for these curves (and for 25% and 80% weather) are presented in Appendix A of this module. The models use a flat-earth, horizontally stratified atmosphere approximation
When two masers are available for use (e.g., Standard Subnet, S-band), the maser in the lowest loss (lowest noise) configuration is considered prime and is designated TWM-1. Under some conditions, TWM-2 may be used, and the higher noise temperature values apply.
When an uplink is used at the STD Subnet antennas, the system must be in the diplexed configuration and the higher system noise temperatures apply (Table 2).
A block diagram of the 34-meter HEF antenna microwave assembly is shown in Figure 9. These antennas have an orthomode junction for X-band that permits simultaneous RCP and LCP operation. If the spacecraft receives and transmits simultaneously with the same polarization, the diplexed path is used, and the higher noise temperatures apply (Table 4). For a spacecraft transmitting and receiving on orthogonal polarizations, the low-noise path (orthomode upper arm) is used for reception, and the lower-noise TWM and HEMT values apply.
Figure 9. Block Diagram of HEF Antenna Microwave Assembly
The gain reduction at S-band and X-band due to wind loading is listed in Table 5. The tabular data are for structural deformation only and presume that the antenna is maintained on-point by conical scan (CONSCAN, discussed in Module TRK-10) or an equivalent process. In addition to structural deformation, wind introduces a pointing error which is related to the antenna elevation angle, the angle between the antenna and the wind (yaw), and the wind speed. Cumulative probability distributions of wind velocity at Goldstone are given in Module TCI-40.
Table 5. Gain Loss Due to Wind Loading
Figures 10/11 and 12/13 show the effects of pointing error on effective antenna gain for the Sband and X-band transmit and receive frequencies These curves are exponential approximations based on measured and predicted antenna beamwidths. Data have been normalized to eliminate elevation and wind loading effects. The equations used to derive the curves are provided in Appendix A.
Figure 10/11. S-Band Gain Reduction vs. Angle Off Boresight
Figure 12/13. X-Band Gain Reduction vs. Angle Off Boresight
Table (a and b) provides the recommended minimum operating signal levels for the two 34meter antenna subnets. These levels are 10 dB above the receiver threshold (design point), based on the nominal zenith system temperatures given in Tables 2 (a and b) and 4 (a and b).
Table 6a. Recommended Minimum Operating Carrier Signal Levels for STD Subnet
Table 6b. Recommended Minimum Operating Carrier Signal Levels for HEF Subnet
Figure 1. S-band Gain, Standard Subnet, Average Clear Weather, DEC =
Figure 2. X-band Gain, Standard Subnet, Average Clear Weather, DEC =
where h = hour angle, degrees, measured west from
local meridian, 0 <= h < 360 (degrees)c = 0 if 0 <= h <= 180
c = -360 if h > 180
Figure 3. S-band System Temperature, Standard Subnet, Average Clear Weather, DEC =
Figure 4. X-band System Temperature, Standard Subnet, Average Clear Weather, DEC =
Figure 5. S-band Gain, HEF Subnet
Figure 6. X-band Gain, HEF
Figure 7. S-band System Temperature, HEF Subnet
Figure 8. X-band System Temperature, HEF
Figure 10/11. S-Band Gain Reduction vs. Angle Off Boresight
where: 0.0 <= x < 0.28 (degrees)
where: 0.0 <= x < 0.27 (degrees)
where: 0.0 <= x < 0.25 (degrees)
where: 0.0 <= x < 0.22 (degrees)
where: 0.0 <= x < 0.28 (degrees)
where: 0.0 <= x < 0.057 (degrees)
where: 0.0 <= x < 0.068 (degrees)