1、 Report ITU-R SA.2191(10/2010)Spectrum requirements for future SRS missions operating under a potential new SRS allocation in the band 22.55-23.15 GHzSA SeriesSpace applications and meteorologyii Rep. ITU-R SA.2191 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitab
2、le, 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 and policy functions of the Radiocommunication S
3、ector 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/ISO/IEC referenced in Annex 1 of Resolution I
4、TU-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/IEC and the ITU-R patent information database
5、 can also be found. Series of ITU-R Reports (Also available online at http:/www.itu.int/publ/R-REP/en) Series Title BO Satellite delivery BR Recording for production, archival and play-out; film for television BS Broadcasting service (sound) BT Broadcasting service (television) F Fixed service M Mob
6、ile, 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 fixed-satellite and fixed service systems SM Spectrum man
7、agement Note: This ITU-R Report was approved in English by the Study Group under the procedure detailed in Resolution ITU-R 1. Electronic Publication Geneva, 2010 ITU 2010 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without written permission of ITU.
8、Rep. ITU-R SA.2191 1 REPORT ITU-R SA.2191 Spectrum requirements for future SRS missions operating under a potential new SRS allocation in the band 22.55-23.15 GHz (2010) TABLE OF CONTENTS Page 1 Introduction 2 2 Assessment of spectrum requirements . 3 3 Factors limiting the choice of available chann
9、els . 4 3.1 Data relay satellite compatibility 4 3.2 Sharing with other services . 4 3.3 Coherency requirements for ranging purposes . 5 4 Potential frequency plan taking into account limiting effects 5 5 Conclusions 6 Annex 1 Estimated data rate and spectrum requirements per space agency . 7 2 Rep.
10、 ITU-R SA.2191 1 Introduction WRC-12 Agenda item 1.11 proposes for consideration a companion band to the existing SRS space-to-Earth allocation in the band 25.5-27.0 GHz. This would enable the support of high data rate Earth-to-space links for SRS missions in near-Earth orbits, including missions in
11、 transit to the Moon, near the Moon and missions to Lagrangian points L1 and L2. Existing allocations near 2 and 8 GHz are becoming congested due to the increasing usage requirements of co-primary services and will not provide sufficient bandwidth for remote system management and updates, tele-opera
12、tion, network management, mission data, high resolution imagery/video and maps, interactive management instructions, and command and control links for these future generation missions. Detailed description of spectrum usages, symbol rates and bandwidths is contained in Annex 1 for both unmanned and
13、manned missions. Multinational activities amongst space-faring nations have started in 2005 with the objective to coordinate future programmes for the exploration of the Moon. It is envisioned that these exploration missions will be robotic for the foreseeable future and manned in the long term. In
14、the early phases, extensive robotic missions will be predominant, examining the lunar terrain, environment and potential landing sites. The use of SRS earth stations in this band will focus on support of lunar missions with antenna diameters of around 18 m. In addition, also Lagrangian point mission
15、s are planned to be supported by earth stations with antenna diameters of around 35 m. Low-Earth orbiting missions may also use this band and could generally be supported by antennas of around 10 m diameter. It is anticipated that worldwide, over the next few decades, some 10-15 SRS earth stations o
16、f the various participating space agencies will use this band mainly for support of lunar and Lagrangian missions. The stations are almost exclusively deployed around mid-latitudes for mission specific reasons. Since several systems are expected to operate simultaneously in the vicinity of the Moon
17、and their coincident appearance within an earth station antenna beam, frequency separation will be required between affected missions. Earlier studies performed in the frame of the Space Frequency Coordination Group (SFCG) anticipated that a cumulative total net uplink bandwidth of up to 500 MHz wil
18、l be needed for support of lunar missions only. In addition, this band will also be required for Lagrangian point (L1 and L2) missions. These missions will require less bandwidth than lunar missions but will also need exclusive frequencies as they will all be located within the main beams of antenna
19、s of the various space agencies. Furthermore, detailed studies revealed that for reasons outlined below, it is not practicable to simply add one channel after the other. As explained, it would in practice not be feasible to assign the required channels in one contiguous band. Annex 1 is taken from a
20、n SFCG Report and it presents details, based on the plans of the major space agencies worldwide, demonstrating the types of links that Lunar missions will use, their usage descriptions, the expected types of users, and the associated symbol rates and bandwidth requirements. In summary, the indicated
21、 forward requirements of space agencies for their near-Earth, lunar and Lagrangian exploratory missions reveal that, even with global coordination within bodies such as the SFCG to achieve optimum efficiency in spectrum usage, their aggregate requirements will barely be accommodated in 600 MHz and w
22、ill certainly require careful planning and extensive frequency coordination. Rep. ITU-R SA.2191 3 2 Assessment of spectrum requirements A single space agency will typically have requirements for several frequency channels in order to simultaneously support different applications within an exploratio
23、n venture such as low-Earth orbit check-out, manned or un-manned spacecraft support during transfer phase, crew lander, surface operations, habitat, etc. Frequency reuse is seldom possible as any spacecraft around the Moon will be in the antenna main-beam lobe of other space agencies supporting thei
24、r own lunar missions. Despite large antennas with narrow main beams, the Moon is fully within the main lobe of any antenna pointing there from the Earth. A similar situation applies to Lagrangian points. Bandwidth requirements can vary largely and depend on the mission objectives. Unmanned explorati
25、on missions to the lunar surface and Lagrangian points will involve large scale communication requirements such as transmission of detailed mission plans and instructions, highly detailed mapping and terrain updates for navigation, and software updates. In addition to the unmanned communication requ
26、irements, manned lunar exploration applications will involve communication requirements such as streaming high resolution video, video conferencing, high fidelity plans and maps, software updates, and other such detailed command and control transmissions. These communication requirements are standar
27、d practice in modern scientific work environments and will afford control personnel on Earth to effectively coordinate Lunar exploration activities. Control signals as described above for communications to these unmanned and manned exploration terminals can be transmitted in a multiplexed fashion an
28、d distributed to the individual surface elements by way of a communications terminal on the lunar surface. The communications terminal will relay mission data to the specified surface element. Annex 1 contains specific requirements and data/information rates for both unmanned and manned missions, as
29、 well as explains the data/information rates that need to be supported. The expected information rates as listed in Table 1 of Annex 1, for a user, per channel, is estimated to be 10-20 MSps (Million Symbols per second) for Earth to Lunar orbit communications and 20-25 MSps for Earth-to-Lunar surfac
30、e communication terminal transmissions. These high data rates are required to support the large scale requirements of lunar scientific exploration. Therefore, typical channel bandwidths as listed in Table 1 of Annex 1, for lunar missions are expected to range between 10 and 25 MHz. For one space age
31、ncys lunar exploration program, a requirement of typically 2 25 MHz channels plus one or 2 channels between 10 and 20 MHz, will result in an aggregate requirement of 60-90 MHz for Earth-to-space support of the various lunar mission applications. At least for one of these channels, it is desirable to
32、 have the same centre frequency as a Data Relay System (DRS) channel as explained below. Such channels may be reused in low-Earth orbits but the direct links towards the Moon could not be reused and have to be exclusive. Support of Lagrangian missions is also expected to typically utilize around 2 o
33、r 3 channels, each with a bandwidth of several MHz, so that another 10 MHz of exclusive (non-reusable) bandwidth may be added per space agency. Spectrum for low-Earth orbiting missions can in all likelihood be reused in view of low probabilities of interference so that such requirements would not ha
34、ve to be added to the non-reusable spectrum requirements. There are current plans by at least six space agencies for manned Lunar exploration missions and at least eight space agencies for unmanned Lunar exploration missions. Due to the large distances between SRS earth stations and Lunar and Lagran
35、gian exploration activities, the footprints of even very narrow antenna beams from multiple space agencies will intersect. Since individual missions of one space agency will potentially fall within the beam of another space agency, each individual space agency will require exclusive channels to comm
36、unicate with their respective missions. 4 Rep. ITU-R SA.2191 To mitigate the potential of interference between multiple transmissions among space agencies, guardbands between the various channels will be required which will increase the total spectrum requirement by around 20%. Therefore, a total ne
37、t requirement of 70-100 MHz of spectrum per space agency will in total require around 85-120 MHz per space agency taking into account guard bands. Due to excessive interference, re-use of the guardbands by means of interleaved channels is not possible for missions requiring exclusive bandwidths but
38、can, and actually would be applied for conventional near Earth missions. This would mean that, if 600 MHz is allocated at WRC-12 in the band 22.55-23.15 GHz, hypothetically a total of some 5 to 7 space agencies may be accommodated in the midterm if frequency channels could be freely selected from a
39、contiguous band. However, several factors will limit the choice of available spectrum as explained below. Sharing among Lunar and Lagrange missions is not possible (although sharing between each of these types of missions and low-Earth orbit missions is possible) due to geometric configurations that
40、 would cause missions to be within the main lobe of antennas of other missions. This is also further described in Annex 1. 3 Factors limiting the choice of available channels 3.1 Data relay satellite compatibility The 22.55-23.55 GHz band is already used by Data Relay Satellite (DRS) systems to comm
41、unicate with user satellites (forward links) via an existing primary inter-satellite service allocation. These forward links are paired with inter-satellite return links in the band 25.25-27.5 GHz. It is therefore desirable to select frequencies for support of mission phases in the vicinity of the E
42、arth in accordance with the internationally agreed DRS channels in order to enable global support either via an earth station or via a DRS satellite. This provides a degree of redundancy and flexibility of increased coverage to space agencies by not limiting their communications to direct visibility
43、 from an earth station. This ability to achieve global coverage by any one space agency may prove vital for future missions. The DRS channels are spaced at 60 MHz intervals and are part of international cross-support agreements. Even if a bandwidth for a specific mission is typically around 25 MHz,
44、its centre frequency will have to match a DRS channel centre frequency as otherwise no support via a DRS will be feasible. Re-use of DRS channels for conventional uplinks to low Earth orbiting satellites, as well as for other DRS forward links, is expected to be feasible in view of an allowed interf
45、erence percentage of 0.1% as contained in Recommendations ITU-R SA.609 and ITU-R SA.1155. Availability of sufficient DRS channels below 23.15 GHz would also allow for minimal usage of those DRS channels which currently overlap with HIBLEO-2 channels in the range 23.18-23.38 GHz. Despite meeting gene
46、rally recognized protection criteria in co-channel operations, use of DRS channels below 23.15 GHz would result in even further reduced interference potential for the HIBLEO-2 system. 3.2 Sharing with other services Protection of radio astronomy service (RAS) stations from in-band emissions needs to
47、 be taken into account for the bands 22.81-22.86 GHz and 23.07-23.12 GHz in accordance with RR No. 5.149. This has been shown to be feasible by geographic separation between SRS and RAS stations on the order of 150 km, and by avoiding use of DRS forward channels which could illuminate a radio astron
48、omy site. The unavailability of a DRS forward channel allows the SRS to fit several other Earth-to-space channels into these 2 sub-bands. Rep. ITU-R SA.2191 5 Depending on the location of the SRS earth stations with respect to radio astronomy stations, some frequency sub-bands will not be available
49、on a global basis. Specific examples are Cebreros and Robledo which are both relatively close to the radio astronomy station Yebes. As a consequence, frequencies in the range 22.81-22.86 GHz and 23.07-23.12 GHz cannot be used without causing potentially harmful interference to the radio astronomy observatory. While studies have shown that sharing with fixed service installations is generally feasible with large margins, there may be a few locations in the world where separation distances could be insufficient. In such cases, some frequencies within the 600 MHz band might not be us
