7.2.2 Application
The active service under consideration in this analysis is the ISS. Recommendation ITU-R S.1328 contains satellite system characteristics to be considered in frequency sharing analyses between GSO and non-GSO satellite systems in the FSS including feeder links for the MSS. However, this Recommendation does not contain information on inter-satellite links.
7.2.3 Representation of unwanted emission spectra
The level of unwanted emissions from the active service into the EESS (passive) sensors is estimated by integrating the emission levels falling within the passive band. This integration is based on the active system operational parameters, and an unwanted emission mask for the active system based on the national regulations governing the system or Recommendation ITU-R SM.1541.
7.2.4 Transmitter characteristics
There are currently three operational satellite systems with inter-satellite links in the 22.55-23.5 GHz band.
7.2.4.1 Non-GSO satellite network HIBLEO 2
The major characteristics of the HIBLEO-2/2FL non-GSO MSS satellite system are presented in Table 7-5. Its orbital configuration is described in Table 7-6.
For the overall system, it is difficult to know how many channels operate continuously and simultaneously. The full loading of the system is very uneven, and there are multiple beams going in different directions for each satellite. In a normal operational mode, it can be reasonably assumed that no channels operate continuously.
TABLE 7-5
HIBLEO 2 system specifications
System parameter Value
Number of satellite planes 6 Number of satellites per plane 11
Nominal altitude 780
Orbit type Circular polar (inclination angle of 86.5°)
Orbital period (mn) 100
Frequency range (GHz) 23.183-23.377
Necessary bandwidth for 8 channels 8 × 19 MHz channels (total bandwidth 194 MHz). The necessary bandwidth for one channel is 19 MHz. The channel spacing equals 25 MHz.
Peak transmitter power (per 19 MHz channel) 3 dBW Antenna gain (one antenna per channel) 36.6 dBi e.i.r.p. (one single 19 MHz channel) 39.6 dBW
TABLE 7-6
Mean anomalies for HIBLEO-2 satellites
Plane 1
Right ascending node Ω = 0 Right ascending node Plane 2 Ω = 31.6 Right ascending node Plane 3 Ω = 63.2 Satellite Mean anomaly Satellite Mean anomaly Satellite Mean anomaly
1 100.7752 12 83.1116 23 98.1752 2 68.048 13 50.3844 24 65.448 3 35.3207 14 17.6571 25 32.7207 4 2.5934 15 344.9298 26 359.9934 5 329.8661 16 312.2025 27 327.2661 6 297.1389 17 279.4753 28 294.5389 7 264.4116 18 246.748 29 261.8116 8 231.6843 19 214.0207 30 229.0843 9 198.9571 20 181.2935 31 196.3571 10 166.2298 21 148.5662 32 163.6298 11 133.5025 22 115.8389 33 130.9025 Plane 4
Right ascending node Ω = 94.8
Plane 5
Right ascending node Ω = 126.4
Plane 6
Right ascending node Ω = –22.1 Satellite Mean anomaly Satellite Mean anomaly Satellite Mean anomaly
34 80.5116 45 95.5752 56 77.9116 35 47.7844 46 62.848 57 45.1844 36 15.0571 47 30.1207 58 12.4571 37 342.3298 48 357.3934 59 339.7298 38 309.6025 49 324.6661 60 307.0025 39 276.8753 50 291.9389 61 274.2753 40 244.148 51 259.2116 62 241.548 41 211.4207 52 226.4843 63 208.8207 42 178.6935 53 193.7571 64 176.0935 43 145.9662 54 161.0298 65 143.3662 44 113.2389 55 128.3025 66 110.6389
FIGURE 7-10
Antenna gain pattern of HIBLEO-2 Inter-satellite link
7.2.4.2 GSO satellite network TDRSS parametric characteristics of inter-satellite links Inter-satellite links are also provided over another system in this band. The National Aeronautics and Space Administration operates the tracking and data relay satellite system (TDRSS) that provides inter-satellite communications links between the geostationary TDRSS satellites and low earth orbiting satellites, including the space shuttle and the international space station.
The tracking and data relay satellite system (TDRSS) uses GSO satellites to relay data, telemetry and commands between low earth orbiting satellites, including the space shuttle (STS) and the international space station (ISS), and a central earth station at White Sands, New Mexico in the United States of America, TDRSS satellites are located at 174° W (186° E) and 41° W (319° E). The second generation of TDRSS satellites (designated as TDRSS-H, I and J) operate inter-satellite links in the 22.55-23.55 GHz band to provide the forward link of its Ka-band single access service.
Each of these TDRSS satellites can support two such links, with each link provided through a separate, steerable high gain antenna on board the satellite. The following parameters are applicable for each link:
– Necessary bandwidth = 50 MHz – EIRP = 71 dBW
– Assigned frequency closest to passive band = 23.505 GHz – Peak antenna gain = 58 dBi.
7.2.4.3 Data relay test satellite system
Information about the inter-satellite link of the DRTS (data relay test satellite) system is addressed hereafter, as shown in Fig. 7-11.
FIGURE 7-11 DRTS system
Figure 7-12 shows the DRTS forward ISS link spectrum. As shown, the EESS (passive) band is in the spurious domain of DRTS forward ISS link.
FIGURE 7-12
Channels of DRTS forward ISS link
Table II of RR Appendix 3 specifies that an attenuation value used to calculate maximum permitted spurious domain emission power levels for use with radio equipment is derived as 43 + 10 log (P),
or 60 dBc, whichever is less stringent for the space services (space stations). Accordingly, the spurious attenuation levels of the ISS-link signals are provided in Table 7-7 as follows:
TABLE 7-7 Spurious attenuation
KSA forward data Beacon signal Attenuation level (dBc) 38.5(1) 59.8(2)
(1) 43 + 10 × log (0.36 W) = 38.5 dBc (< 60 dBc) (2) 43 + 10 × log (48 W) = 59.8 dBc (< 60 dBc)
Transmission characteristics of the DRTS satellite differ depending on which user satellite the DRTS communicates with. The Japanese Experiment Module (JEM) attached to the International space station is assumed to be the most appropriate user satellite for this analysis since the DRTS forward link is transmitted toward JEM at 23 GHz.
The DRTS ISS forward signals transmitted in the 22.55-23.55 GHz band are a total of two signals of KSA forward data and the beacon signal as shown in Fig. 7-12. These signals are transmitted for a total of 8 h per day while the JEM is visible from the DRTS satellite.
TABLE 7-8
DRTS satellite system specifications (ISS forward link to JEM)
System parameter Forward data Beacon signal Number of satellites 1
Nominal altitude 35786
Orbit type GEO
Frequency range 23.37-23.40 GHz 23.54 GHz Necessary bandwidth for data channels 30 MHz No modulation
0.004 MHz
(reference bandwidth in RR Appendix 3) Peak transmitter power –4.4 dBW 16.8 dBW Antenna gain (including feeder loss) 55.1 dBi 20.8 dBi
e.i.r.p. 50.7 dBW 37.6 dBW
The DRTS forward data and beacon signal are transmitted by different antennas. Figure 7-13 shows the DRTS ISS antenna gain pattern for the forward data transmission. The beam width is as sharp as 0.23° at a –3 dB gain drop.
Figure 7-14 shows the pattern of the DRTS beacon antenna, which has broad beam width being used as a tracking aid.
FIGURE 7-13
FIGURE 7-14
DRTS beacon antenna gain pattern