DSN TELECOMMUNICATIONS INTERFACES:
34-METER BEAM WAVEGUIDE ANTENNAS

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1.1 Purpose

This module describes capabilities of the Deep Space Network 34-meter diameter BWG (beam-waveguide) and HSB (high-speed beam-waveguide) antennas. Information herein is sufficient to enable the nominal design of a telecommunications link using these antennas.

1.2 Scope

Presented are the uplink EIRP and downlink gain, noise temperature, and pointing capabilities of these antennas. Also given are geographic locations, expected implementation dates, and configuration descriptions. For ease of use, design expectation performance values for antennas not yet constructed are given; although these values are properly shown in 810-5, Volume II (Proposed Capabilities), TCI-31 (34-Meter Beam-waveguide Antennas).

1.3 Contents

2. General Information

2.1 Description

The 34-meter diameter BWG (beam-waveguide) and HSB (high-speed beam-waveguide) antennas are the new generation of antennas being built for use in the DSN. These antennas differ from more conventional antennas (e.g., the 34-meter HEF antennas, c.f., TCI-30) in the fact that a series of small mirrors (approximately 2.5 meters diameter) direct microwave energy from the region above the main reflector to a location at the base of the antenna, typically in a pedestal room, which may be located below ground level. The pedestal room is located below the azimuth track of the antenna, although other beam-waveguide designs (not utilized by the DSN) locate the microwave equipment in an alidade room above the azimuth track, but below the main reflector. All antennas described in this module are of the pedestal room design. The microwave equipment is contained in the pedestal room. In this configuration, numerous stations of microwave equipment can be accessed by rotation of an ellipsoidal mirror located on the floor of the pedestal room. This enables great versatility of design and allows tracking while equipment maintenance is carried out. Since cryogenic low-noise amplifiers (LNAs) do not tip (as they do when located in a cone above the elevation axis), certain state-of-the-art ultra low noise amplifier (ULNA) and feed designs can be implemented.

The HSB antennas differ from the BWG antennas in that the optics design is slightly different and the subreflector does not focus automatically for the purpose of maintaining gain as the elevation angle of the antenna changes. The HSB antennas have higher tracking rates than do the BWG antennas, thus they are the appropriate antennas to use when tracking earth-orbiting satellites.

Those antennas with two LNAs at a particular frequency (S-band or X-band) will be capable of receiving simultaneous RCP and LCP downlink signals. Not all antennas will have two LNAs installed for the same frequency band. If an uplink capability exists at a particular frequency, the antenna will be capable of transmitting through the diplexer in one polarization and receiving in the low-noise (non-diplexed) path with the opposite polarization. If uplink and downlink are at the same polarization, then reception must be through the diplexed path, with subsequent higher noise and lower gain. Typically the following modes are available for transmission and reception:

  1. downlink non-diplexed path (RCP or LCP) to LNA-1, with uplink of opposite polarization
  2. downlink non-diplexed path (RCP or LCP) to LNA-2, with uplink of opposite polarization
  3. downlink diplexed path (RCP or LCP) to LNA-1, with uplink of same polarization
  4. downlink diplexed path (RCP or LCP) to LNA-2, with uplink of same polarization
For those antennas with dual-band capabilities (e.g., DSS 25) and dual LNAs, each of the above four modes can be used in a single-frequency or dual-frequency configuration. Thus for those antennas with the most complete capabilities, there will be sixteen possible ways to receive at a single frequency (2 polarizations [RCP or LCP], 2 waveguide paths [non-diplexed or diplexed], 2 LNAs [LNA-1 or LNA-2], and 2 single/dual frequency modes [f1-only or f1/f2 simultaneously]).

The receiving frequency bands are S-band (2200-2300 MHz), X-band (8400-8500 MHz), and Ka-band (31800-32300 MHz).

2.2 Geographic Location

Table 1 gives the geographic locations (geodetic coordinates) of the BWG and HSB antennas. These positions are sufficiently accurate for the user to generate nominal elevation vs. time profiles for a spacecraft of known right ascension (RA) and declination (DEC). The elevation angles thus found will allow accurate calculation of antenna gain and noise temperature from formulas, tables, and figures presented in this module. The precision of these positions is left purposely coarse, at 0.1 degree in latitude and longitude. More accurate positions of these antennas (to better than 0.001 degree) are given in module GEO-10, Coverage and Geometry, of this handbook.

Table 1. Geographic Locations of BWG and HSB Antennas


Antenna Location Longitude Latitude Height, MSL (Deg.) (Deg.) (m)
BWG Antennas DSS 24 Goldstone W 116.9 N 35.3 956 DSS 25 Goldstone W 116.9 N 35.3 971 DSS 26 Goldstone W 116.9 N 35.3 981 DSS 34 Canberra E 149.0 S 35.4 672 DSS 54 Madrid W 004.2 N 40.4 787 HSB Antennas DSS 27 Goldstone W 116.8 N 35.2 1050 DSS 28 Goldstone W 116.8 N 35.2 1050

2.3 Implementation Schedule

Table 2 presents the implementation schedule for the BWG and HSB antennas effective as of January 5, 1996. A more recent schedule may be obained by clicking in the image of the table.

Table 2. Operational Schedule for BWG and HSB Antennas

2.4 Microwave Configurations

Table 3 presents the BWG and HSB microwave transmitter and LNA configurations for both uplink and downlink implementations. The listed transmitter powers are nominal values at the output of the transmitter. Block diagrams for the antennas are shown in Figures 1 through 7.

Table 3. BWG and HSB Antenna Configurations


Antenna Band- S-Up S-Down X-Up X-Down Ka-Down Ka-Up Up/Down Power(1) LNA-1 LNA-2 Power LNA-1 LNA-2 LNA Power
DSS 24 BWG S-Up/Down 20 kW HEMT(2) N/A N/A Maser N/A N/A N/A Goldstone X-Down DSS 25 BWG X-Up/Down N/A N/A N/A 4 kW Maser HEMT(2) HEMT(3) 800 W(4) Goldstone Ka-Up/Down DSS 26 BWG X-Up/Down N/A N/A N/A 4 kW HEMT(2) HEMT(2) N/A N/A Goldstone DSS 34 BWG S-Up/Down 20 kW HEMT(2) N/A 4 kW HEMT(2) N/A N/A N/A Canberra X-Up/Down DSS 54 BWG S-Up/Down 20 kW HEMT(2) N/A 4 kW Maser N/A N/A N/A Madrid X-Up/Down DSS 27 HSB S-Up/Down 200 W HEMT(5) N/A N/A N/A N/A N/A N/A Goldstone DSS 28 HSB X-Up/Down N/A N/A N/A TBD Maser N/A N/A N/A Goldstone
NOTES: 1. Transmitter power refers to nominal power available at transmitter output. Exact powers are given in Table 5. S-band uplink is limited to 5 kW transmitter power in the frequency range 2070-2090 MHz. 2. All BWG antennas use cooled HEMTs. 3. Cooled HEMT utilizing cooled feed with aperture load. 4. Uses Ka/Ka dichroic plate as diplexer. 5. DSS 27 HSB uses room temperature S-band HEMT.

Figure 1. DSS 24 BWG (Goldstone) Functional Block Diagram


Figure 2. DSS 25 BWG (Goldstone) Functional Block Diagram


Figure 3. DSS 26 BWG (Goldstone) Functional Block Diagram


Figure 4. DSS 34 BWG (Canberra) Functional Block Diagram


Figure 5. DSS 54 BWG (Madrid) Functional Block Diagram


Figure 6. DSS 27 HSB (Goldstone) Functional Block Diagram


Figure 7. DSS 28 HSB (Goldstone) Functional Block Diagram

Table 4a presents the expected noise temperatures of operational LNAs used in the BWG and HSB antennas and Table 4b presents the nominal noise temperature values used in modeling. It can be seen from these tables that the nominal noise temperature values used in performance modeling (see Section 2.6.6) may vary significantly from the actual value of an operational LNA.

Table 4a. Operational LNA Input Noise Temperatures


Band Type LNA & Model Minimum(K) Maximum(K)
BWG Antennas S-Band HEMT, S2 4.5 7.0 X-Band TWM/CCR, BLK IIA 3.0 5.0 HEMT, X1 7.0 15.0 HEMT, X2 5.0 6.5 HEMT, X3 4.0 5.0 Ka-Band HEMT 28.0 (at feedhorn aperture, 10/98) 21.0 (at feedhorn aperture, 5/01) HSB Antennas S-Band HEMT, room temp. 25.0 45.0 X-Band TWM/CCR, BLK I 4.0 9.0
Table 4b. LNA Noise Temperatures Used in Modeling

Band Type LNA Nominal Temperature(K)
BWG Antennas S-band Cooled HEMT 5.7 (at LNA input) X-band BLK II-A Maser 3.43 (at LNA input) X-band Cooled HEMT 9.7 (at LNA input) Ka-band Cooled HEMT and Feed 28.0 (at feedhorn aperture) HSB Antennas S-band Room Temperature HEMT 45.0 (at LNA input) X-band BLK I Maser 4.5 (at LNA input)

2.5 Uplink Performance Characteristics

Tables 5a and 5b present uplink performance characteristics for the BWG and HSB antennas. The uplink frequency bands are S-band (2025-2120 MHz), X-band (7145-7190 MHz), and Ka-band (34200-34700 MHz). Calculated gain and net transmitter power at the horn aperture are given. The effective isotropic radiated power (EIRP) at the horn aperture is calculated from the product of gain (ratio) and power (watts), both referenced to the horn aperture. From knowledge of the gain falloff at 10 and 80 degrees elevation relative to the assumed peak gain at 45 degrees elevation, the EIRP at those elevations is also calculated. S-band uplink is limited to 5 kW transmitter power in the frequency range 2070-2090 MHz.

Table 5a. Uplink Performance Characteristics for BWG Antennas


Parameter DSS 24 DSS 25 DSS 26 DSS 34 DSS 54 S-band X-band Ka-band X-band S-band X-band S-band X-band
Gain at horn aperture (dBi) 56.12 66.92 78.01 66.92 56.14 66.92 56.14 66.92 @ 45-Deg. Elevation Power at horn aperture (W) 16991 3565 TBD 3565 16991 3565 16991 3565 Power at horn aperture (dBm) 72.30 65.52 TBD 65.52 72.30 65.52 72.30 65.52 EIRP at horn aperture (dBm) 128.43 132.44 TBD 132.44 128.44 132.44 128.44 132.44 Gain Falloff (dB) -0.01 -0.04 -0.64 -0.04 -0.01 -0.04 -0.01 -0.04 @ 10 and 80 Deg. Elevation EIRP @ aperture (dBm) 128.42 132.40 TBD 132.40 128.43 132.40 128.43 132.40 @ 10 and 80 Deg. Elevation
Note: S-band uplink is limited to 5 kW transmitter power in the frequency range 2070-2090 MHz.
Table 5b. Uplink Performance Characteristics for HSB Antennas

Parameter DSS 27 DSS 28 S-band X-band
Gain at horn aperture (dBi) 54.36 66.76 @ 45-Deg. Elevation Power at horn aperture (W) 170 TBD Power at horn aperture (dBm) 52.30 TBD EIRP at horn aperture (dBm) 106.67 TBD Gain Falloff (dB) -0.01 -0.04 @ 10 and 80 Deg. Elevation EIRP @ aperture (dBm) 106.66 TBD @ 10 and 80 Deg. Elevation

2.6 Downlink Performance Characteristics

This section presents both measured and modeled gain and noise temperature performance for the BWG and HSB antennas. A somewhat "conservative" (not optimistic) estimate of the tolerances for gain and noise temperature is as follows:

   GAIN

      S-band:   favorable tolerance, +0.1 dB       
                adverse tolerance,   -0.2 dB
                triangular PDF

      X-band:   favorable tolerance, +0.1 dB
                adverse tolerance,   -0.2 dB
                triangular PDF

      Ka-band:  favorable tolerance, +0.2 dB
                adverse tolerance,   -0.4 dB
                triangular PDF

   NOISE TEMPERATURE

      S-band:   favorable tolerance, -1.0 K
                adverse tolerance,   +2.0 K
                triangular PDF

      X-band:   favorable tolerance, -1.0 K
                adverse tolerance,   +2.0 K 
                triangular PDF

      Ka-band:  favorable tolerance, -1.0 K
                adverse tolerance,   +2.0 K
                triangular PDF

A triangular PDF (probability density function) implies that there is no chance the gain or noise temperature will be found outside of the limits indicated.

Gain and noise temperature values presented in tables or calculated by use of equations should be considered to be design values, or design expectations. For a triangular distribution, the mean (M) and variance (V) of the distribution can be calculated from the design value (D) and the favorable (F) and adverse (A) tolerances by:

     M = D + (F+A)/3

     V = (F2 + A2 - AF)/18

2.6.1 Gain (DSS 24 BWG Antenna) - Figures 8 and 9 show DSS 24 (Goldstone) gain performance (referenced to the LNA input), based on measurements, for a vacuum condition (no atmosphere) and with additional atmospheric losses for various weather conditions as given in module TCI-40, Atmospherics, of this handbook. Because weather effects at S-band do not change significantly from 0% (minimum effect) to 90% (exceeded 10% of the time), the gain (and noise temperature) curves for 0%, 25%, 50%, 80%, and 90% lie nearly on top of one another. At X-band, the weather effects are somewhat more spread out, which results in distinct weather-effect curves.


Figure 8. DSS 24 (Goldstone) Measured S-band Gain; S/X Mode, Non-diplexed


Figure 9. DSS 24 (Goldstone) Measured X-band Gain; S/X Mode, Non-diplexed

For S-band (Figure 8), in the S/X, non-diplexed mode, with the S/X dichroic plate over the S-band horn, the DSS 24 vacuum gain as a function of elevation angle (el, degrees) is given by:

     Gvac(el) = 56.80 - 0.000032(el-90)2   dBi

     Notes 
     1.  Peak vacuum gain occurs at 90-degrees elevation angle.
     2.  For the S/X diplexed mode, subtract 0.10 dB.

S-band is always received with the S/X dichroic plate over the S-band horn. This is called the S/X mode. There is no S-band solid plate reflector; so there is no higher-gain configuration available for S-band.

For X-band (Figure 9), in the S/X-mode, with the S/X dichroic plate in place and a flat plate over the X-band horn, non-diplexed, the DSS 24 vacuum gain is given by:

     Gvac(el) = 68.06 - 0.000027(el-51.483)2   dBi

     Note: For the X-only mode, with the S/X dichroic plate retracted,
           add 0.05 dB.

There is no X-band uplink at DSS 24, thus there is no diplexed mode available.

Table 6a shows measured DSS 24 antenna gain (referenced to the LNA input) at various elevation angles for Goldstone average clear weather (CD=0.25) as given in module TCI-40, Atmospherics, of this handbook.

Table 6a. DSS 24 (Goldstone) Measured Antenna Gain with 25% Average Clear Weather


Band-MHz Mode Diplex LNA Elevation (deg.) 90 80 60 45 30 20 15 10
S - 2295 S/X No HEMT 56.77 56.77 56.74 56.69 56.63 56.56 56.51 56.43 S/X Yes HEMT 56.67 56.67 56.64 56.59 56.53 56.46 56.41 56.33 X - 8420 X-Only No maser 68.03 68.05 68.07 68.06 68.03 67.98 67.94 67.86 S/X No maser 67.98 68.00 68.02 68.01 67.98 67.93 67.89 67.81

2.6.2 Gain (DSS 25, 26, 34, 54 BWG Antennas) - For all other BWG antennas, the following modeled vacuum gains apply, assuming a main reflector panel setting of 0.25 mm at DSS 25 and 0.50 mm at DSS 26, 34, and 54:

     S-band:        Gvac(el) = 56.74 - 0.00000267(el-45)2   dBi
     (DSS 34, 54)

     X-band:        Gvac(el) = 68.23 - 0.000036(el-45)2   dBi
     (DSS 25)

     X-band:        Gvac(el) = 68.14 - 0.000036(el-45)2   dBi
     (DSS 26, 34, 54)

     Ka-band:       Gvac(el) = 78.80 - 0.00052(el-45)2   dBi 
     (DSS 25)

The S- and X-band coefficients of the elevation terms are modeled by frequency-squared from the Ka-band coefficient of 0.00052.

The following configurations apply to the above equations:

     S-band:        S/X mode (S/X dichroic in place), non-diplexed, LNA-1 path
     (DSS 34, 54)

     X-band:        X-only mode (S/X dichroic retracted), non-diplexed, LNA-1 path
     (DSS 25, 26, 34, 54)

     Ka-band:       Ka-only (X/Ka dichroic retracted), non-diplexed, LNA-1 path
     (DSS 25)

Figure 10 shows the modeled Ka-band gain performance for DSS 25 (Goldstone) referenced to the feed aperture for a vacuum condition (no atmosphere) and with additional atmospheric losses for various weather conditions. This figure assumes a main reflector panel setting of 0.25 mm, rms and illustrates the additional effects of weather for Ka-band when compared to the lower frequency bands.


Figure 10. DSS 25 (Goldstone) Modeled Ka-band Gain; Ka-only Mode, Non-diplexed

Table 6b shows gain values as a function of elevation angle, for 25% CD average-clear weather, as given in module TCI-40, Atmospherics, of this handbook, for all frequencies and configurations of the other BWG antennas. At S- and X-bands, the gain is referenced to the LNA input; at Ka-band it is referenced to the feedhorn aperture.

Table 6b. BWG Modeled Antenna Gains with 25% Average Clear Weather


Band-MHz Mode Diplex LNA Elevation (deg.) 90 80 60 45 30 20 15 10
DSS 25 (Goldstone)
X - 8420    X-Only    No   maser   68.12   68.15   68.18   68.18   68.15   68.11   68.06   67.98
            X-Only    No    HEMT   68.05   68.08   68.11   68.11   68.08   68.04   67.99   67.91
            X-Only   Yes   maser   67.95   67.98   68.01   68.01   67.98   67.94   67.89   67.81
            X-Only   Yes    HEMT   67.88   67.91   67.94   67.94   67.91   67.87   67.82   67.74
             X/Ka     No   maser   68.11   68.14   68.17   68.17   68.14   68.10   68.05   67.97
             X/Ka     No    HEMT   68.04   68.07   68.10   68.10   68.07   68.03   67.98   67.90
             X/Ka    Yes   maser   67.94   67.97   68.00   68.00   67.97   67.93   67.88   67.80
             X/Ka    Yes    HEMT   67.87   67.90   67.93   67.93   67.90   67.86   67.81   67.73

Ka - 32000  Ka-Only   No    HEMT   77.63   78.05   78.55   78.64   78.45   78.14   77.89   77.50
            Ka-Only  Yes    HEMT   77.53   77.95   78.45   78.54   78.35   78.04   77.79   77.40
              X/Ka    No    HEMT   77.57   77.99   78.49   78.58   78.39   78.08   77.83   77.44
              X/Ka   Yes    HEMT   77.47   77.89   78.39   78.48   78.29   77.98   77.73   77.34
DSS 26 (Goldstone)
X - 8420    X-Only    No   HEMT-1  68.03   68.06   68.09   68.09   68.06   68.02   67.97   67.89
            X-Only    No   HEMT-2  67.96   67.99   68.02   68.02   67.99   67.95   67.90   67.82
            X-Only   Yes   HEMT-1  67.86   67.89   67.92   67.92   67.89   67.85   67.80   67.72
            X-Only   Yes   HEMT-2  67.79   67.82   67.85   67.85   67.82   67.78   67.73   67.65
DSS 34 (Canberra)
S - 2295     S/X      No    HEMT   56.71   56.71   56.71   56.70   56.68   56.64   56.62   56.56
             S/X     Yes    HEMT   56.61   56.61   56.61   56.60   56.58   56.54   56.52   56.46

X - 8420    X-Only    No    HEMT   68.02   68.05   68.08   68.08   68.05   68.00   67.95   67.85
            X-Only   Yes    HEMT   67.85   67.88   67.91   67.91   67.88   67.83   67.78   67.68
             S/X      No    HEMT   67.97   68.00   68.03   68.03   68.00   67.95   67.90   67.80
             S/X     Yes    HEMT   67.80   67.83   67.86   67.86   67.83   67.78   67.73   67.63
DSS 54 (Madrid)
S - 2295     S/X      No    HEMT   56.71   56.71   56.71   56.70   56.68   56.64   56.62   56.56
             S/X     Yes    HEMT   56.61   56.61   56.61   56.60   56.58   56.54   56.52   56.46

X - 8420    X-Only    No   maser   68.02   68.05   68.08   68.08   68.05   68.00   67.95   67.85
            X-Only   Yes   maser   67.85   67.88   67.91   67.91   67.88   67.83   67.78   67.68
             S/X      No   maser   67.97   68.00   68.03   68.03   68.00   67.95   67.90   67.80
             S/X     Yes   maser   67.80   67.83   67.86   67.86   67.83   67.78   67.73   67.63

The X-only mode for all antennas implies that there is a solid (flat) reflector over the X-band horn. For an X-only antenna (DSS 26), this is the normal configuration. For an S/X antenna (DSS 24, 34, and 54), this implies that the S/X dichroic plate is retracted. For an X/Ka antenna (DSS 25), and possibly future S/X/Ka antennas, X-only implies an optimum performance configuration for X-band in which the X/Ka dichroic is replaced by a solid plate. Use of an X/Ka dichroic over the X-band horn (rather than a flat plate) will reduce the X-band gain by 0.01 dB as shown for DSS 25 in Table 6b.

For Ka-band gain in the X/Ka-mode, with an X/Ka dichroic in the microwave path, subtract 0.06 dB from the Ka-only gain values. For a diplexed mode, using a Ka/Ka dichroic plate as the diplexer, subtract 0.10 dB from the non-diplexed gain values.

2.6.3 Gain (DSS 27, 28 HSB Antennas) - Figure 11 shows the DSS 27 (Goldstone) gain performance (referenced to the LNA input) at S band, based on measurements, for a vacuum condition (no atmosphere) and with additional atmospheric losses for various weather conditions as given in module TCI-40, Atmospherics, of this handbook.


Figure 11. DSS 27 (Goldstone) Measured S-band Gain; S-only Mode, Diplexed

The equation for the elevation component of gain in this figure is:

     Gvac(el) = 55.06 - 0.00205 (90-el)     dBi 

     Note: Peak vacuum gain occurs at 90-degrees elevation angle.

The S-band gain for the DSS 27 HSB antenna as a function of elevation angle with 25% CD average-clear weather, as given in module TCI-40, Atmospherics, of this handbook is shown in Table 7. DSS 27 operates only in an S-band diplexed configuration.

Table 7. DSS 27 (Goldstone) Measured S-band Antenna Gain with 25% Average Clear Weather


Band-MHz Mode Diplex LNA Elevation (deg.) 90 80 60 45 30 20 15 10
S - 2295 S-Only Yes HEMT 55.04 55.01 54.97 54.93 54.88 54.84 54.80 54.73

Figure 12 shows the modeled DSS 28 (Goldstone) gain performance (referenced to the LNA input) at X-band for a vacuum condition (no atmosphere) and with additional atmospheric losses for various weather conditions as given in module TCI-40, Atmospherics, of this handbook.


Figure 12. DSS 28 (Goldstone) Modeled X-band Gain; X-only Mode, Non-diplexed

The equation for the elevation component of gain in this figure is:

     Gvac(el) = 67.99 - 0.000138(el-45)2     dBi

The X-band gain for the DSS 28 HSB antenna as a function of elevation angle with 25% CD average-clear weather, as given in module TCI-40, Atmospherics, of this handbook, in the non-diplexed and diplexed configurations is shown in Table 8.

Table 8. DSS 28 (Goldstone) Modeled X-band Antenna Gain with 25% Average Clear Weather


Band-MHz Mode Diplex LNA Elevation (deg.) 90 80 60 45 30 20 15 10
X - 8420 X-Only No maser 67.68 67.79 67.92 67.94 67.89 67.80 67.73 67.62 X-Only Yes maser 67.51 67.62 67.75 67.77 67.72 67.63 67.56 67.45

2.6.4 Atmosphere Adjustment to Vacuum Gain - To account for atmospheric effects on net gain for all antennas, attenuation at the elevation angle (el) of interest should be subtracted from the vacuum gains as given above.

     attenuation(el) = Az/sin(el)   dB

     where Az = zenith atmospheric attenuation as given in 810-5,
                TCI-40, for the appropriate antenna location, 
                frequency, and weather cumulative distribution (CD).

Thus, the net effective antenna gain G(el) is given by

     G(el) = Gvac(el) - attenuation(el)    dBi

2.6.5 Noise Temperature (DSS 24) - Figures 13 and 14 show DSS 24 (Goldstone) noise temperature performance based on measurements, for a vacuum condition and with additional noise contributions for various weather conditions as given in module TCI-40, Atmospherics, of this handbook. The S-band performance (Figure 13) is for the non-diplexed S/X mode whereas the X-band performance (Figure 14) is for the X-only mode with the S/X Dichroic Plate retracted.


Figure 13. DSS 24 (Goldstone) Measured S-band Noise Temperature; S/X Mode, Non-diplexed

The curve for S-band vacuum-condition noise temperature as a function of elevation angle (Figure 13) is given by:

     Tvac(el) = 28.34 + 5.0 e-0.05el   K

A measured value of 6.45 K must be added to the non-diplexed value to get the diplexed performance.


Figure 14. DSS 24 (Goldstone) Measured X-band Noise Temperature; X-only Mode, Non-diplexed

The curve for X-band vacuum-condition noise temperature (Figure 14) is flat and is given by

     Tvac(el) = 23.18 + 0.0 e-0.0el   K

For the non-diplexed S/X mode, with the S/X dichroic plate in place, add 1.4 K (based on measurements). There is no X-band uplink at DSS 24, thus there is no diplexed mode.

Table 9a shows measured DSS 24 antenna noise temperature (referenced to the LNA input) at various elevation angles for Goldstone average clear weather (CD=0.25) as given in module TCI-40, Atmospherics, of this handbook.

Table 9a. DSS 24 (Goldstone) Measured Operating Noise Temperature with 25% Average Clear Weather


Band-MHz Mode Diplex LNA Elevation (deg.) 90 80 60 45 30 20 15 10
S - 2295 S/X No HEMT 30.20 30.26 30.67 31.41 33.05 35.41 37.60 41.62 S/X Yes HEMT 36.65 36.71 37.12 37.86 39.50 41.86 44.05 48.07 X - 8420 X-Only No maser 25.35 25.38 25.68 26.24 27.49 29.46 31.46 35.47 S/X No maser 26.75 26.78 27.08 27.64 28.89 30.86 32.86 36.87

2.6.6 Noise Temperature (DSS 25, 26, 34, 54 BWG Antennas) - For all other BWG antennas, the following equations for modeled vacuum noise temperature apply:

     S-Band:     Tvac(el) = 27.2 + 3.2 e-0.029el   K
     (DSS 34, 54)

     X-Band:     Tvac(el) = 20.0 + 3.5 e-0.011el   K
     (DSS 25, 54 with masers)

     X-Band:     Tvac(el) = 26.3 + 3.5 e-0.011el   K
     (DSS 26, 34 with HEMTs)

     Ka-band:    Tvac(el) = 39.0 + 2.8 e-0.013el   K
     (DSS 25)

The following configurations apply to the above equations:

     S-band:        S/X mode (S/X dichroic in place), non-diplexed, LNA-1 path
     (DSS 34, 54)

     X-band:        X-only mode (S/X dichroic retracted), non-diplexed, LNA-1 path
     (DSS 25, 26, 34, 54)

     Ka-band:       Ka-only (X/Ka dichroic retracted), non-diplexed, LNA-1 path
     (DSS 25)

The X-only mode for all antennas implies that there is a solid (flat) plate over the X-band horn. For an X-only antenna (DSS 26), this is the normal configuration. For an S/X antenna (DSS 24, 34, 54), this implies that the S/X dichroic plate is retracted. For an X/Ka antenna (DSS 25), and possibly future S/X/Ka antennas, X-only implies an optimum performance configuration for X-band in which the X/Ka dichroic is replaced by a solid plate.

The LNA and follow-on noise temperatures used in the above models are as follows:

     S-Band:   6.0 K HEMT plus 0.3 K follow-on, referenced to LNA input

     X-Band:   3.43 K maser + 0.3 K follow-on, referenced to LNA input

               9.7 K HEMT + 0.3 K follow-on, referenced to LNA input

     Ka-band:  28.0 K HEMT with cooled feed,  including follow-on noise,
               referenced to feedhorn aperture

The modeled diplexer and additional waveguide noise contribution at S-band is 6.45 K, based on DSS 24 measurements. At X-band it is 10.6 K.

Table 9b shows modeled system noise temperature values as a function of elevation angle, for 25% CD average-clear weather as given in module TCI-40, Atmospherics, of this handbook, for all frequencies and configurations of all other BWG antennas.

Table 9b. BWG Modeled Operating Noise Temperatures with 25% Average Clear Weather


Band-MHz Mode Diplexed LNA Elevation (deg.) 90 80 60 45 30 20 15 10
DSS 25 (Goldstone)
X - 8420    X-Only    No   maser   23.40   23.58   24.22   25.08   26.65   28.89   30.98   34.97
            X-Only    No    HEMT   33.90   34.08   34.72   35.56   37.11   39.31   41.37   45.30
            X-Only   Yes   maser   34.00   34.17   34.79   35.61   37.13   39.28   41.29   45.12
            X-Only   Yes    HEMT   44.55   44.73   45.33   46.14   47.63   49.75   51.73   55.50
             X/Ka     No   maser   23.78   23.96   24.60   25.46   27.03   29.27   31.36   35.35
             X/Ka     No    HEMT   34.28   34.46   35.10   35.94   37.49   39.69   41.75   45.68
             X/Ka    Yes   maser   34.38   34.55   35.17   35.99   37.51   39.66   41.67   45.50
             X/Ka    Yes    HEMT   44.93   45.11   45.71   46.52   48.01   50.13   52.11   55.88

Ka - 32000  Ka-Only   No    HEMT   46.90   47.13   48.38   50.41   54.64   60.99   67.14   78.93
            Ka-Only  Yes    HEMT   47.90   48.13   49.38   51.41   55.64   61.99   68.14   79.93
              X/Ka    No    HEMT   50.61   50.84   52.09   54.11   58.33   64.66   70.79   82.55
              X/Ka   Yes    HEMT   51.61   51.84   53.09   55.11   59.33   65.66   71.79   83.55
DSS 26 (Goldstone)
X - 8420    X-Only    No   HEMT-1  29.67   29.85   30.49   31.35   32.92   35.16   37.25   41.24
            X-Only    No   HEMT-2  33.90   34.08   34.72   35.56   37.11   39.31   41.37   45.30
            X-Only   Yes   HEMT-1  40.27   40.44   41.06   41.88   43.40   45.55   47.56   51.39
            X-Only   Yes   HEMT-2  44.55   44.73   45.33   46.14   47.63   49.75   51.73   55.50
DSS 34 (Canberra)
S - 2295     S/X      No   HEMT    29.45   29.58   30.10   30.84   32.24   34.45   36.44   40.16
             S/X     Yes   HEMT    35.90   36.03   36.55   37.29   38.69   40.90   42.89   46.61

X - 8420    X-Only    No   HEMT    30.03   30.22   30.91   31.86   33.65   36.23   38.66   43.34
            X-Only   Yes   HEMT    40.63   40.81   41.48   42.39   44.13   46.62   48.97   53.49
             S/X      No   HEMT    33.26   33.45   34.14   35.08   36.88   39.45   41.88   46.56
             S/X     Yes   HEMT    43.73   43.92   44.58   45.49   47.23   49.71   52.06   56.58
DSS 54 (Madrid)
S - 2295     S/X      No   HEMT    29.45   29.58   30.10   30.84   32.24   34.45   36.44   40.16
             S/X     Yes   HEMT    35.90   36.03   36.55   37.29   38.69   40.90   42.89   46.61

X - 8420    X-Only    No   maser   23.76   23.95   24.64   25.59   27.38   29.96   32.39   37.07
            X-Only   Yes   maser   34.36   34.54   35.21   36.12   37.86   40.35   42.70   47.22
             S/X      No   maser   26.99   27.18   27.87   28.81   30.61   33.18   35.61   40.29
             S/X     Yes   maser   37.46   37.65   38.31   39.22   40.96   43.44   45.79   50.31

Figure 15 illustrates the estimated DSS 25 (Goldstone) noise temperature performance for Ka-band in a non-diplexed, Ka-band only configuration. Use of an X/Ka dichroic over the X-band horn (rather than a flat plate) will result in 0.38 K noise temperature increase as shown for DSS 25 in Table 9b.


Figure 15. DSS 25 (Goldstone) Modeled Noise Temperature; Ka-only Mode, Non-diplexed

2.6.7 Noise Temperature (HSB Antennas) - Figure 16 shows system noise temperature for the DSS 27 (Goldstone) S-band HSB antenna, based on measurements. This antenna operates in a diplexed mode only and employs a 45 K room temperature HEMT as its LNA. The vacuum noise temperature curve is shown, in addition to curves for five different Goldstone atmosphere conditions.


Figure 16. DSS 27 (Goldstone) Measured Noise Temperature; S-only Mode, Diplexed

For the DSS 27 S-band vacuum curve, the noise temperature is given as:

     Tvac(el) = 101 + 27 e-0.061el   K

Figure 17 shows system noise temperature for the DSS 28 (Goldstone) X-band HSB antenna, based on a model. The vacuum curve is shown, in addition to curves for five different Goldstone atmosphere conditions.


Figure 17. DSS 28 (Goldstone) Modeled Noise Temperature; X-only Mode, Non-diplexed

For the DSS 28 X-band vacuum curve, the noise temperature is given as:

     Tvac(el) = 24.0 + 20.0 e-0.088el   K

The LNA used in this noise temperature model is a 4.5 K Block-I maser.

Table 10 shows S-band and X-band noise temperatures as a function of elevation angle for 25% CD average clear weather as given in module TCI-40, Atmospherics, of this handbook for all frequencies and configurations of the DSS 27 and DSS 28 HSB antennas.

Table 10. HSB Operating Noise Temperatures with 25% Average Clear Weather


Band-MHz Mode Diplexed LNA Elevation (deg.) 90 80 60 45 30 20 15 10
DSS 27 (Goldstone) Measured data
S - 2295   S-Only   Yes    HEMT    102.92  103.04  103.78  105.28  108.92  114.20  118.71  125.92
DSS 28 (Goldstone) Modeled data
X - 8420   X-Only    No    maser    26.18   26.22   26.60   27.44   29.74   33.72   37.62   44.59
           X-Only   Yes    maser    36.78   36.82   37.20   38.04   40.30   44.32   48.22   55.19

2.6.8 Atmosphere Adjustment to Vacuum Noise Temperature - To account for atmospheric effects on total operating system noise temperature (T-op) for all antennas, atmosphere contributions at the elevation angle (el) of interest should be added to the vacuum expressions given above.

       Tatm(el) = Tz/([sin(el)]B)   K

where  Tz = zenith atmosphere noise contribution as given in 810-5,
            TCI-40, for the appropriate antenna location, frequency,
            and weather cumulative distribution (CD).

       B = 1 - 0.27Az   (dimensionless)

       Az = zenith atmospheric attenuation, dB, as given in 810-5,
            TCI-40,  for the same antenna location, frequency, and 
            weather cumulative distribution (CD).

Thus, the operating system noise temperature Top(el) is given by:

       Top(el) = Tvac(el) + Tatm(el)    K

2.6.9 Pointing Losses - Table 11 gives half-power beamwidth (full width) and pointing loss to be expected for BWG and HSB antenna pointing errors at S-, X-, and Ka-bands, for both uplink and downlink.

Table 11. 34-m BWG and HSB Loss due to Pointing Errors


Band S-Up S-Down X-Up X-Down Ka-Down Ka-Up Freq.(MHz) 2115 2295 7145 8420 32000 34000 HPBW (Deg.)* 0.250 0.231 0.074 0.063 0.017 0.016
Pointing Pointing Loss (dB) Error (Deg)
0.000 0.00 0.00 0.00 0.00 0.00 0.00 0.001 0.00 0.00 0.00 0.00 -0.04 -0.05 0.002 0.00 0.00 -0.01 -0.01 -0.18 -0.20 0.003 0.00 0.00 -0.02 -0.03 -0.40 -0.45 0.004 0.00 0.00 -0.04 -0.05 -0.70 -0.79 0.005 0.00 -0.01 -0.05 -0.08 -1.10 -1.24 0.006 -0.01 -0.01 -0.08 -0.11 -1.58 -1.79 0.007 -0.01 -0.01 -0.11 -0.15 -2.16 -2.43 0.008 -0.01 -0.01 -0.14 -0.19 -2.82 -3.18 0.009 -0.02 -0.02 -0.18 -0.25 -3.56 -4.02 0.010 -0.02 -0.02 -0.22 -0.30 -4.40 -4.97 0.012 -0.03 -0.03 -0.32 -0.44 -6.34 -7.15 0.014 -0.04 -0.04 -0.43 -0.60 -8.62 -9.74 0.016 -0.05 -0.06 -0.56 -0.78 -11.26 -12.72 0.018 -0.06 -0.07 -0.71 -0.99 -14.26 -16.09 0.020 -0.08 -0.09 -0.88 -1.22 -17.60 -19.87
* Half-power Beamwidth (HPBW = full width at half-power)

Table 12 provides the expected blind-pointing performance in various wind conditions. Pointing errors are given in terms of Rayleigh distribution, assuming equal pointing performance in the elevation (EL) and cross-elevation (X-EL) directions (equal Gaussian standard deviations). The mean pointing error for the Rayleigh distribution equals 1.25 times the standard deviation of the EL and X-EL pointing error distributions.

Table 12. Accuracy and Pointing Loss in Various Wind Conditions


Wind Speed Mean Pointing Range 0-3 Loss at Mean Pointing Error (dB) (m/s) (mph) Error (mdeg) sigma (mdeg) S-Band X-band Ka-band
<4.5 <10 1.67 0-4 0.001 0.009 0.123 <8.9 <20 3.33 0-8 0.003 0.034 0.489 <13.4 <30 5.00 0-12 0.006 0.076 1.101

An optional conical scanning technique for maintaining the antenna on point (CONSCAN) is available at S-band and X-band. A discussion of this technique is contained in module TRK-10, Angle Tracking, of this handbook. CONSCAN is not available at Ka-band because of the difficulty of moving the antenna structure at extremely small scan radii and the effect of atmospherics on the CONSCAN algorithm. Expected gain reduction due to CONSCAN are:

     S-band:  0.01 dB when using X-band CONSCAN reference set for
              0.1 dB loss at X-band

     X-band:  0.1 dB when using X-band CONSCAN reference
2.6.10 Wind Loading Loss - In addition to pointing errors, wind causes a structural deformation of the antenna surface. This results in a reduced gain as shown in Table 13 for X and Ka-bands. The gain reduction at S-band is negligible for wind speeds up to 20 m/s (45 mph). Cumulative probability distributions of wind velocity at Goldstone are given in module TCI-40, Atmospherics, of this handbook.

Table 13. Loss due to Wind Loading


Wind Speed Wind Loading Loss (dB)* (m/s) (mph) X-band Ka-band
4.5 10 0.2 TBD 13.4 30 0.3 TBD 20.1 45 0.4 TBD
NOTE: * Worst case, with most adverse wind-antenna orientation.

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Initial Release: May 1, 1996
DSN Document 810-5, Module TCI-31/Jet Propulsion Laboratory/stephen.d.slobin@jpl.nasa.gov