1、 Report ITU-R SA.2167(09/2009)Factors affecting the choice of frequency bands for space research service deep-space (space-to-Earth) telecommunication linksSA SeriesSpace applications and meteorologyii Rep. ITU-R SA.2167 Foreword The role of the Radiocommunication Sector is to ensure the rational, e
2、quitable, 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 Radiocommunica
3、tion 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/ISO/IEC referenced in Annex 1 of Resolu
4、tion 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/IEC and the ITU-R patent information da
5、tabase 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
6、 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 fixed-satellite and fixed service systems SM Spectr
7、um management 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
8、 ITU. Rep. ITU-R SA.2167 1 REPORT ITU-R SA.2167 Factors affecting the choice of frequency bands for space research service deep-space (space-to-Earth) telecommunication links (2009) TABLE OF CONTENTS Page 1 Introduction 2 2 Spectrum requirements for future deep-space missions . 2 3 Factors considere
9、d in the choice of frequency bands . 4 3.1 Link applications 4 3.2 Propagation impairments 4 3.3 Available bandwidth . 9 3.4 Technology maturity and equipment availability . 9 3.5 Ground infrastructure considerations . 10 3.6 Compatibility with the recommended frequency plan for the Mars region 10 3
10、.7 Incompatible services . 11 3.8 Feasibility of frequency sharing . 12 4 Spectrum that could be considered for possible allocations . 12 5 Conclusions 14 TABLES TABLE 1 Primary SRS (deep-space) allocations . 2 TABLE 2 Users of science instruments requiring high downlink data rates 3 TABLE 3 Atmosph
11、eric attenuation around the Goldstone area for a 20 elevation angle . 9 TABLE 4 Summary of frequency bands for communications in the Mars region . 11 TABLE 5 Interference from a deep-space downlink to an Earth orbiter 13 TABLE 6 Frequencies between 8-40 GHz for possible deep-space applications 14 FI
12、GURES FIGURE 1 Zenith gaseous absorption due to oxygen and water vapour as a function of frequency. . 5 FIGURE 2 Atmospheric noise temperature as a function of frequency . 6 FIGURE 3 Rain attenuation at zenith as a function of percent of time exceeded 7 FIGURE 4 Atmospheric noise temperature due to
13、rain at zenith . 8 2 Rep. ITU-R SA.2167 1 Introduction There are a number of primary space research service (SRS) allocations that can be used by deep-space missions for telecommand, telemetry, and radiometric data collection. Some of these allocations are designated specifically for deep-space SRS
14、missions and are not available to non-deep-space SRS missions, while other allocations are available to both deep-space and non-deep-space SRS missions. The deep-space SRS allocations are given in Table 1. TABLE 1 Primary SRS (deep-space) allocations Earth-to-space space-to-Earth 2 110-2 120 MHz 2 2
15、90-2 300 MHz 7 145-7 190 MHz 8 400-8 450 MHz 34.2-34.7 GHz 31.8-32.3 GHz The above primary SRS allocations are restricted to deep-space missions and are not available to non-deep-space missions. These allocations together provide a total of 555 MHz in the Earth-to-space direction and 560 MHz in the
16、space-to-Earth direction. In addition to these primary deep-space allocations in Table 1, there are two other general primary SRS allocations of 37-38 GHz (space-to-Earth) and 40-40.5 GHz (Earth-to-space). Since the 37.5-38 GHz part of the 37-38 GHz band is shared with FSS, it is not especially usab
17、le for deep-space missions, especially for manned planetary missions. The use of the 2 110-2 120 MHz (Earth-to-space) band will be limited in the future at NASAs Madrid Deep-Space Communication Complex due to potential interference to IMT-2000 users. The 8 400-8 450 MHz (space-to-Earth) band is very
18、 congested, since it is being extensively used by all deep-space missions. The 34.2-34.7 GHz (Earth-to-space) and 31.8-32.3 GHz (space-to-Earth) allocations are not yet crowded, but deep-space missions have started using these bands. Currently, there are no known deep-space missions planning to use
19、the 37-38 GHz (space-to-Earth) and the 40-40.5 GHz (Earth-to-space) allocations, and the ground infrastructure needed to support these frequencies has yet to be developed. 2 Spectrum requirements for future deep-space missions The amount of spectrum needed to support the space-to-Earth links of deep
20、-space missions is expected to increase within the next 15 to 30 years, as the number of future missions and the data rate of each mission are expected to increase. More and more space agencies are expected to send missions to explore the solar system and beyond. Furthermore, all these future deep-s
21、pace missions are expected to send the data collected by the on-board instruments using a much higher data rates, perhaps in excess of hundreds of megabits per second. On-board instruments require very high data rates. For example, a radar may require a data rate of 100 Mbit/s and a hyperspectral im
22、ager may require data rates between 150 Mbit/s and 600 Mbit/s (EO-1, Moon Mineralogy Mapper, EnMAP). These instruments can be flown on both robotic and human missions. Examples of possible future spacecraft flying these high-rate science instruments are shown in Table 2. Rep. ITU-R SA.2167 3 TABLE 2
23、 Users of science instruments requiring high downlink data rates User spacecraft Instrument Data rate (Mbit/s) Robotic rovers Surface radar Hyperspectral imaging 100 150-600 Science orbiters Orbiting radar Hyperspectral imaging 100 150-600 Human transports Hyperspectral imaging 150-600 The return of
24、 science data from deep-space missions is limited by the capacity of the space-to-Earth links. Often, the amount of science data returned to Earth from a deep-space mission during its lifetime is only a small fraction of what it is capable of producing. A deep-space mission sometimes may take months
25、 or years to reach its destination, but may have only a limited time, measured in weeks or even in days, to explore its target. Increasing the amount of data returns is important scientifically and economically. This increase is already taking place in the planned deep-space missions, which have sta
26、rted taking advantage of the 31.8-32.3 GHz (space-to-Earth) band capability to increase data returns. The Mars Reconnaissance Orbiter (MRO), for example, has a 32.2 GHz downlink capable of sending telemetry at 6 Ms/s. While this link is experimental, the MRO project plans to use it to return science
27、 data once it has been successfully demonstrated. The data rate of MRO is about 5 times higher than the telemetry rates of all existing deep-space missions, except SIRTF, which has a downlink rate of 4.4 Ms/s. Another planned Mars mission, Mars Telecom Orbiter (MTO) would have an even higher downlin
28、k rate. In one option, the MTO telecom system was designed to support a telemetry data rate of 40 Ms/s using a 34-m ground antenna. MTO was initially planned for launch in 2009, but had recently been postponed due to budgetary constraints. Two developments considered by NASA will enable to increase
29、the downlink data rate and accelerate the trend towards higher and higher data returns. First, NASA is considering to implement a large array of antennas with a G/T 10 times higher than the existing 70-m antennas in the NASAs Deep-Space Network (DSN). This will enable spacecraft to transmit at a muc
30、h higher rate than they presently can, without requiring a large EIRP from the spacecraft. Second, NASA is also considering to use nuclear power technology to power the spacecraft, making ample power available for sending data to the Earth. The Prometheus programme has studied large EIRP missions to
31、 Jupiter. The requirement for the Jupiter Icy Moons Orbiter (JIMO) mission is a data rate of 10 Mbit/s at a range of 6.5 AU into a 70-m equivalent aperture. To achieve this data rate, the current design has a 3 m 32 GHz band high-gain antenna with a 1 kW 32 GHz band transmitter. A similar spacecraft
32、 at Mars range would support a data rate of 62 Mbit/s at Mars maximum range (2.6 AU) and 1.1 Gbit/s at Mars minimum range. The supportable data rate would be 10 times higher using the full antenna array. These developments together will enable future deep-space missions to send science data to the E
33、arth at a much higher data rate than they presently can. Previous studies indicated a possible 1 000 fold increase in mission data reception throughput by 2030 for deep-space missions based on a JPL analysis. A 2009 internal JPL study estimated a downlink throughput data rate of 125 Mbit/s, 150 Mbit
34、/s, and 1500 Mbit/s for the highest data rate user in the 2010, 2020 and 2030 time-frame, respectively. While there is a large uncertainty in these estimates, they do point to a trend toward higher and higher data rates for deep-space missions. They indicate that the bandwidth required to support fu
35、ture deep-space missions will far exceed the capacity of all existing allocations, even after accounting for possible use of bandwidth-efficient modulation schemes. Interests among various 4 Rep. ITU-R SA.2167 space agencies in exploring Mars through robotic or human missions increase the likelihood
36、 that there may be multiple spacecraft operated by different space agencies exploring Mars at the same time. This will further increase the needed spectrum because the frequency used by one Mars mission cannot in general be reused by another. Factoring the needs for future Mars missions and allowing
37、 some spectrum for non-Mars missions, a total allocated spectrum of 2 to 3 GHz in addition to existing allocations appears to be sufficient to meet the anticipated long-term spectrum needs. For example, with 3 GHz of additional spectrum, two spacecraft at Mars would be able to send data simultaneous
38、ly to Earth at the highest anticipated data rate. 3 Factors considered in the choice of frequency bands There are many factors that can constrain the choice of frequency bands for future high-rate deep-space missions. In allocating appropriate spectrum and identifying suitable frequency bands, we ne
39、ed to consider the following factors. Note that some of these factors are more constraining than the others. 3.1 Link applications The intended application of a telecommunication link can have an impact on the choice of its operating frequency. A link operating at a frequency not suitable for its ap
40、plication can experience poor link performance. In general, a communications link having a broadbeam antenna at both ends of the link would perform better at a lower frequency than at a higher one. Links with a broadbeam antenna perform much better at 400 MHz, 1 GHz, or 2 GHz bands than, for example
41、, at 32 GHz or 79 GHz bands. A broadbeam antenna has the advantage of not requiring accurate antenna pointing, making it best for certain mission events such as propulsive maneuvers, landing, or loss of spacecraft attitude. On the other hand, a link with a narrow-beam antenna at both ends would perf
42、orm better at a higher frequency than at a lower frequency, assuming that the antennas can be accurately pointed. For the specific application of sending data to Earth at extremely high rates, it is not suitable to use a broadbeam low-gain antenna at either end of the link. Instead, a highly directi
43、ve narrow-beam antenna is needed at both ends of the link. Everything else being equal, a higher frequency would be preferable over a lower frequency. 3.2 Propagation impairments A space-to-Earth link is adversely affected by the atmosphere and weather conditions on Earth, due to increased system no
44、ise temperature, signal attenuation, scintillation, and depolarization. Figure 1 gives the zenith atmospheric gaseous absorption up to 100 GHz for a water-vapour density of 12 g/m3, exceeded approximately 1% of the time for the area around Goldstone, California. The attenuation generally increases w
45、ith increasing frequency. For any other elevation angle (), the attenuation will be higher by a factor of 1/sin() than the attenuation at zenith. For receiving systems such as the deep-space receivers operating with a very low system noise temperature, increased atmospheric noise temperature due to
46、water vapour and light clouds (without rain) can degrade the link performance significantly. Figure 2 gives the zenith atmospheric noise temperature as a function of frequency for various elevation angles. The noise temperature was calculated for a rainfall region with a moist atmosphere and light c
47、louds. The curves are derived assuming a water-vapour density of 15 g/m3and moderate cloud columnar liquid-water content of 0.5 kg/m2(both are exceeded 1% of time). Figure 2 shows that the noise temperature generally increases as the operating frequency increases. Note that Fig. 2 is applicable to t
48、he DSN site at Goldstone, California. The noise temperature for the DSN site in Canberra, Australia is somewhat higher. Rep. ITU-R SA.2167 5 FIGURE 1 Zenith gaseous absorption due to oxygen and water vapour as a function of frequency Report 2167-01Zenith attenuation of oxygen and water vapor for Gol
49、dstone, CA(Density 12 g/m , approximately 1% of time exceeded)for a zenith path (1-100 GHz)31021011010110210310310 101102Frequency (GHz)Zenithattenuation(dB)TotalOxygenWater vapor6 Rep. ITU-R SA.2167 FIGURE 2 Atmospheric noise temperature as a function of frequency Report 2167-02Frequency (GHz)CLOUD + CLEAR AIR, AH = 15 g/m , BASE = 1 km, TOP = 3 km, LWC = 0.25 g/m3 32,COLUMNAR LIQUID = 0.5 kg/m3203002802602402202001801601401201008060402000 5 10 15 20 25 30 35 40 450.51235101520304590Atmosphericnoisetemperature,(K)The rain, which does not ha
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