1、 Recommendation ITU-R SA.1862(01/2010)Guidelines for efficient use of the band 25.5-27.0 GHz by the Earth exploration-satellite service (space-to-Earth) and space research service (space-to-Earth)SA SeriesSpace applications and meteorologyRec. ITU-R SA.1862 ii Foreword The role of the Radiocommunica
2、tion Sector is to ensure the rational, equitable, efficient and economical use of the radio-frequency spectrum by all radiocommunication services, including satellite services, and carry out studies without limit of frequency range on the basis of which Recommendations are adopted. The regulatory an
3、d policy functions of the Radiocommunication Sector are performed by World and Regional Radiocommunication Conferences and Radiocommunication Assemblies supported by Study Groups. Policy on Intellectual Property Right (IPR) ITU-R policy on IPR is described in the Common Patent Policy for ITU-T/ITU-R
4、/ISO/IEC referenced in Annex 1 of Resolution ITU-R 1. Forms to be used for the submission of patent statements and licensing declarations by patent holders are available from http:/www.itu.int/ITU-R/go/patents/en where the Guidelines for Implementation of the Common Patent Policy for ITU-T/ITU-R/ISO
5、/IEC and the ITU-R patent information database can also be found. Series of ITU-R Recommendations (Also available online at http:/www.itu.int/publ/R-REC/en) Series Title BO Satellite delivery BR Recording for production, archival and play-out; film for television BS Broadcasting service (sound) BT B
6、roadcasting service (television) F Fixed service M Mobile, radiodetermination, amateur and related satellite services P Radiowave propagation RA Radio astronomy RS Remote sensing systems S Fixed-satellite service SA Space applications and meteorology SF Frequency sharing and coordination between fix
7、ed-satellite and fixed service systems SM Spectrum management SNG Satellite news gathering TF Time signals and frequency standards emissions V Vocabulary and related subjects Note: This ITU-R Recommendation was approved in English under the procedure detailed in Resolution ITU-R 1. Electronic Public
8、ation Geneva, 2010 ITU 2010 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without written permission of ITU. Rec. ITU-R SA.1862 1RECOMMENDATION ITU-R SA.1862 Guidelines for efficient use of the band 25.5-27.0 GHz by the Earth exploration-satellite servi
9、ce (space-to-Earth) and space research service (space-to-Earth) (2010) Scope This Recommendation contains guidelines for optimized use of the frequency band 25.5-27.0 GHz between a number of different space science systems, such as near-Earth and deep-space research networks, Earth exploration syste
10、ms, geostationary-satellite systems and data relay satellite networks. The Recommendation also identifies reduced power flux-density limits for geostationary satellites to offer better protection to space research missions with sensitive space-to-Earth links. It also specifies a power flux-density l
11、imit at the GSO for protection of data relay system satellites. The ITU Radiocommunication Assembly, considering a) that the band 25.5-27.0 GHz is allocated to the Earth exploration-satellite service (EESS) (space-to-Earth) and the space research service (SRS) (space-to-Earth), and the 25.25-27.50 G
12、Hz band is allocated to the inter-satellite service1(ISS); b) that EESS and SRS near-Earth missions in the 25.5-27.0 GHz band may be compatible under certain conditions; c) that the power flux-densities (PFD) at the Earths surface from SRS missions are very low for lunar missions and extremely low f
13、or sun-Earth Lagrange and deep-space missions; d) that, due to the low PFD, deep-space missions are very vulnerable to interference and have stringent protection criteria; e) that multiple administrations are planning to fly manned missions to the lunar environment and beyond; f) that manned mission
14、s have more stringent protection criteria than unmanned missions; g) that due to atmospheric attenuation, specifically rain attenuation and the power flux-density limits specified in Article 21 of the Radio Regulations (RR), it may be difficult to achieve link availabilities greater than 99.9% in th
15、e 25.5-27.0 GHz band; h) that the planned use of the 25.5 to 27 GHz band by SRS and EESS missions is most likely not compatible with manned SRS mission protection criteria specified in Recommendation ITU-R SA.609; j) that the 25.5-27 GHz band is planned to be used by EESS missions for various Earth
16、observing, Earth exploration, and climate monitoring missions; k) that the availability of the 25.5-27.0 GHz band is crucial to near-Earth SRS and EESS missions with high data rate requirements; 1Use of the 25.25-27.5 GHz band by the inter-satellite service is limited to space research and Earth exp
17、loration-satellite applications. Rec. ITU-R SA.1862 2l) that interference from transmitting geostationary satellites has the potential to significantly degrade link margins and even cause loss of sensitive links of SRS missions if these satellites operate near the currently applicable PFD limits (se
18、e Annex 1); m) that RR Article 21 limits the power flux-density at the surface of the Earth to levels between 115 and 105 dB(W/(m2. MHz) depending on the angle of arrival; n) that reducing the PFD limits below the limits specified in RR Article 21 for geostationary satellites would provide necessary
19、 protection to lunar and Lagrange SRS missions; o) that space-to-Earth links of typical non-GSO satellites can always meet the power flux-density limit required to protect a DRS satellite, while non-GSO satellites with orbits above 1 370 km may need some allowance to exceed it for a small percentage
20、 of time, recognizing a) that the space-based collection of global weather and climate data in support of the Global Earth Observation System of Systems (GEOSS) is becoming increasingly important to the worldwide community; b) that the 25.5 to 27.0 GHz band is planned to be used by manned SRS missio
21、ns for data transmissions that do not involve astronauts and vehicle safety; c) that non-GSO satellites should also comply with Recommendation ITU-R SA.1155 Protection criteria related to the operation of data relay satellite systems, recommends 1 that deep-space missions should not use the band 25.
22、5-27.0 GHz SRS (space-to-Earth) unless mission requirements cannot be satisfied in other bands specifically allocated for deep-space operations; 2 that if, for a compelling reason, a deep-space mission requires the use of the 25.5-27.0 GHz band, the mission should not claim interference protection f
23、rom near-Earth missions in excess of the protection criteria of Recommendation ITU-R SA.609 applicable to unmanned missions in the 25.5-27.0 GHz band; 3 that manned SRS missions should not claim interference protection from EESS and unmanned SRS missions in excess of the protection criteria of Recom
24、mendation ITU-R SA.609 applicable to unmanned missions in the 25.5-27.0 GHz band; 4 that to provide additional protection to lunar and Lagrange SRS missions, EESS and SRS missions in geostationary orbits should restrict their PFD levels to 115 dB(W/(m2.MHz) in the band 25.5-27.0 GHz for all angles o
25、f arrival at the surface of the Earth (see Annex 1); 5 that EESS and SRS satellites in non-geostationary orbits with space-to-Earth satellite links should not produce a PFD greater than 133 dB(W/(m2.MHz) at any DRS satellite location on the geostationary orbit. This limit may be exceeded no more tha
26、n 0.1% of the time for non-GSO systems with altitudes greater than 1 370 km (see Annex 2). Rec. ITU-R SA.1862 3Annex 1 Potential impact of geostationary satellites on sensitive links of SRS missions 1 Introduction The 25.5-27.0 GHz band is an important downlink band for the EESS and SRS. This band i
27、s planned to be used for EESS as well as SRS missions. The latter ones could operate at any distance from a low Earth orbit to the sun-Earth Lagrange points. A number of extensive studies addressed compatibility between various types of missions, concluding that all potential applications can share
28、the band 25.5-27.0 GHz without problems except for geostationary satellites operating close to the PFD limits of RR Article 21. This annex provides a summary of the various study results and the background for the corresponding reduced power flux-density limits for geostationary satellites. 2 Charac
29、teristics of potential victim SRS systems The most sensitive SRS missions are satellites near the Lagrangian points L1/L2 and near the moon. Figure 1 illustrates such science applications and the corresponding interference constellation. 1862-01Lagrange points MoonEarth stationsGeostationary satelli
30、teInterfering signalDesired signalFIGURE 1Various mission types with potential deployment in the band 25.5-27.0 GHzTable 1 shows characteristics for lunar systems analysed in one of the detailed studies. As shown in this table, the link margin is equivalent to C0/N0 C0/N0required. These margins are
31、calculated from the system data using standard assumptions related to data rate, coding, and availability. Rec. ITU-R SA.1862 4TABLE 1 Essential characteristics for representative lunar SRS victim systems Parameters Representative 26 GHz satellite victim systems LRO Lunar Cx Lunar, 50 MHz Frequency
32、(MHz) 25 650 26 000 Slant range (km) 401 427 404 943 Tx power (dB(W) 16.0 17.0 Tx power split (dB) 3.0 0.0Tx gain (dBi) 42.9 43.5 Maximum PFD at Earth (dB(W/(m2. MHz) 143.0 141.4 Data rate (Mbit/s) 50.0 25.0 Rx gain (dBi) 71.3 70.4 Link losses (dB) 7.5 9.7 Rain/atmospheric loss (dB) 1.25 2.8 Tempera
33、ture (K) 510.0 446.7 C0/N0(dB) 10.3 13.6 C0/N0 required (dB) 2.9 2.2 Margin (dB) 7.4 11.4 Another detailed study used the James Web Space Telescope (JWST) as a representative example for Lagrangian missions. Two different data rates have been considered with 14 and 56 Ms/s. The adjustable data rate
34、helps to maintain a link in case of heavy rain events. Table 2 shows a summary of the assumptions for Lagrangian SRS victim missions. TABLE 2 Essential characteristics for Lagrangian SRS victim systems JWST-14 JWST-56 SRS satellite orbit height (km) 1 500 000 Power of SRS satellite (dBW) 13.1 Bandwi
35、dth of main lobe with QPSK (MHz) 14 56 SRS satellite antenna diameter (m) 1.05 SRS satellite maximum antenna gain (dBi) 46.2 SRS earth station antenna diameter (m) 34.0 SRS system noise temperature (K) 200 Technical receiver and pointing losses (dB) 3.0 Required Es/N0for QPSK with channel coding (dB
36、) 2.5 Margin for atmospheric attenuation (dB) 20.0 13.9 Rec. ITU-R SA.1862 5For all assessments, the protection criteria as contained in Recommendation ITU-R SA.609 have been taken as the baseline. It specifies an interference density level of 156 dB(W/MHz) not to be exceeded for more than 0.1% of t
37、ime. 3 Assumed characteristics of interfering geostationary systems Relevant link budget characteristics for some potential geostationary systems are shown in Table 3. GSO-1 is representative for the Alpha-Sat mission with a channel bandwidth of 405 MHz. The satellite design is based on a 0.7 m para
38、bolic antenna. For the simulations, an earth station in Madrid has been assumed as a worst case. GSO-1 is expected to be quite representative for several types of geostationary systems planned for deployment in this band. GSO-2 is a hypothetical system and could be representative for a low elevation
39、 system with high availability for a dedicated earth station. The satellite was assumed at a GSO position of 48 E. The elevation angle towards central Spain is 20. GSO-3 may be representative for a high availability system with several smaller earth stations within a subregion. An example could be a
40、 system transmitting to a number of direct data read-out stations. GSO-3 was assumed at 14 E serving a number of smaller user stations in Spain. Even with a 1.4 m on-board parabolic antenna, the main beam covers a rather large region, as shown in Fig. 2. Similar situations may be found with other se
41、nsitive SRS earth station locations. TABLE 3 Key parameters for geostationary-satellite systems GSO-1 GSO-2 GSO-3 Transmit power (dBW) 14.0 20.0 23.0 Satellite antenna gain (dBi) 43.1 46.2 49.7 Satellite EIRP (dBW) 57.3 66.2 72.7 Bandwidth of main lobe for 600 Mbit/s and QPSK (MHz) 600 Maximum PFD a
42、t receive site (dB(W/(m2.MHz) 130.2 121.5 114.6 Assumed link availability (%) 99.90 99.98 Signal attenuation for assumed availability (dB) 8.4 21.5 15.0 Earth station antenna diameter (m) 7.3 10.0 2.0 Rec. ITU-R SA.1862 61862-02MADRID20 15 10 5 0 105153 dB contour16 dB contour20 dB contour3035404550
43、55FIGURE 2Footprint contours towards Madrid, for a geostationary satellite at 14 E4 Assessment of interference to SRS missions One approach, based on an I/N criterion, is typically used to determine if intersystem interference will result in unacceptable interference to any of the available SRS or E
44、ESS systems. Based on Recommendation ITU-R SA.609, the received interference level from all sources should not exceed the following aggregate level: I0/N0not to exceed 6 dB more than 0.1% of the time. This analysis moved beyond the basic I0/N0interference criterion and took into account the relative
45、ly large link margins that many of the SRS and EESS systems have. It looked at the degraded link margin, denoted simply by “margin”: Margin = C0/(N0+ I0)measured C0/N0requiredThe basic criterion for determining whether interference is within acceptable levels was the following: Margin not to fall be
46、low dB more than 0.1% of the time where is a value that is discussed below. A possible value for would be 0, as this is the level below which the link could not be closed. However, it was not considered to be prudent to allow the entire link margin to be consumed by interference from other non-GSO o
47、r GSO systems, so may in fact be a value greater than 0. It should be emphasized that use of this type of interference criterion allows the study to move beyond the traditional I/N interference analysis approach to analyse the degradation to the systems link margins. Some key assumptions used for th
48、e simulation were that victim and interfering sources are assumed to operate using the same centre frequency. Furthermore, the interferers total power is averaged Rec. ITU-R SA.1862 7over its bandwidth, and 3 dB is added to account for the peak density, assuming PSK modulation. High-gain satellite a
49、ntenna patterns follow the reference radiation pattern of Recommendation ITU-R S.672. Earth station antenna patterns follow the pattern in Recommendation ITU-R F.1245. Robledo and Cebreros are two locations in central Spain which support sensitive SRS missions, such as to Lagrangian points or, potentially, to the moon. In view of the long distances to L1 and L2, the power flux-density of the received signals is rather low, requiring large earth stations up to 35 m with a high G/T. As far as interference statistics are concerned, all earth stat
