1、STD.ITU-R RECMN SAmh39b-ENGL L999 4855212 053b395 822 Rec. ITU-R SA.1396 1 RECOMMENDATION ITU-R SA.1396. PROTECTION CRITERIA FOR THE SPACE RESEARCH SERVICE IN THE 37-38 GHZ AND 40405 GHZ BANDS (Question ITU-R 21 117) (1999) The ITU Radiocommunication Assembly, cornidering that limiting interference
2、criteria for telecommunication links for space research are determined by the a) technical considerations examined in Annex 1; b) that two-way communication is required for many space research missions, and is vital for manned missions; c) that space research systems will be implemented in the 37-38
3、 GHz and 40-40.5 GHz bands; d) that these systems will serve inter alia lunar and planetary manned and unmanned missions and space very long baseline interferometry (S-VLBI) missions having bandwidth requirements that cannot be accommodated in lower frequency bands allocated to the space research se
4、rvice; e) that the lunar and planetary space stations planned for these bands will spend ail or a part of their mission lifetimes within the ITU-defined deep space limit of 2 X lo6 km from the Earth and thus cannot be accommodated within other space research bands restricted to deep space; 0 -211 dB
5、W/Hz) in the 37-38 GHz band; that overall system operating noise temperatures of earth stations may be as low as 60 K (equivalent to g) -193 dB(W/20 Hz) in the 40-40.5 GHz band; that overall system operating noise temperatures of space stations may be as low as 200 K (equivalent to h) j) k) link; t
6、hat link margins for space-to-Earth links are small, typically between 2 and 4 dB; that link margins for Earth-to-space links are typically between 6 and 9 dB; that an increase of 1 dB in overall system noise due to interference is considered harmful to a space-to-Earth 1) link that an increase of 3
7、 dB in overall system noise due to interference is considered harmful to an Earth-to-space m) n) 0) interference; that a noise to interference ratio of about 6 dB results in 1 dB increase in overall system operating noise; that a noise to interference ratio of about O dB results in 3 dB increase in
8、overall system operating noise; that technical andor regulatory limitations restrict increases in spacecraft power as a means of minimizing P) that space research protection criteria and required bandwidths can be found in Recommen- dations ITU-R SA.609, ITU-R SA.1157 and ITU-R SA.1015, * This Recom
9、mendation should be brought to the attention of Radiocommunication Study Groups 4 and 9. STD-ITU-R RECMN SA.139b-ENGL 3999 4855232 053b39b 769 2 Rec. ITU-R SA.1396 noting the potential difficulties to be expected in frequency sharing between stations in the space research service and a) certain type
10、s of stations in other services, recommends 1 that protection criteria (see Note 1) for earh stations in the space research service be established as follows: 1.1 -217 dB(W/Hz) at the input terminals of the receiver, in the 37-38 GHz band; 1.2 that calculation of interference to a space research ear
11、th station that may result from atmospheric and precipitation effects should be based on weather statistics for 0.001% of the time for manned missions and for 0.1% of the time for unmanned missions; 2 that protection criteria (see Note I) for space research space stations be established as follows:
12、193dB(W/20Hz) at the input terminals of the receiver, for 0.1% of the time for both manned and unmanned spacecraft, for the 40-40.5 GHz band. NOTE 1 - These protection critena are intended to protect unique operations during critical mission events in the space research service from unexpected inte
13、rference. Levels in excess of the protection critena may be acceptable on a case by case basis. ANNEX 1 Protection criteria relating to space research systems in the 37-38 GHz and 40-40.5 GHz bands 1 Introduction Lunar and planetary and other stations will be implemented in the 37-38 GHz and 40-40.5
14、 GHz bands allocated to the space research service on primary busis worldwide. These systems will be used infer alia for high-rate digital data transfer of telemetry, voice, and video between the Earth and other planetary bodies such as the Moon and Mars to support manned exploration. Further, the 3
15、7-38 GHz band will be used for high-rate data transfer from an Earth-orbiting S-VLBI station. The digital data transfer will enable operations such as infomation management for the safe conduct of human exploration missions, coordination and status of planned activities, updating of data files, and
16、relay of scientific data. Data rates on the order of 100 Mbit/s from planetary ranges, 500 MbWs from lunar range and 1 O00 MbiVs from S-VLBI station to Earth will be implemented. 2 Protection criteria In a communication link, the permissible ratio of interference to system noise may be determined by
17、 the portion of design margin allocated to external interference. In space-to-Earth links, the incentive is to minimize link margins in order to save weight and power, to comply with emission limits, and in the interest of economy. Typical link design margins to allow for the effects of non-ideal co
18、nditions from all causes are generally in the range of 2 dB to 4 dB. Considering these low link margins, interference can be harmful to a typical earth station in the space research service if the link performance is decreased by more than 1 dB. This corresponds to a required ratio of system noise s
19、pectral density to interference spectral density (N/I) of about 6 dB. Considering that margins are higher for the Earth-to-space links, interference can be harmful to a typical space station in the space research service if the link performance is degraded by more than 3 dB. This corresponds to a re
20、quired NI of about O dE3. Rec. ITPR SA.1396 3 2.1 Reference bandwidth The reference bandwidth in which a protection level must be specified depends upon the smallest bandwidth likely to be employed. For earth-station receivers, phase-locked loops may employ bandwidths as low as 1 Hz. The detection b
21、andwidth of space stations is usually greater (20 Hz or more) due to the need for rapid, automatic acquisition of signals from the Earth. Thus, recommended values for the reference bandwidths for space research receivers are: - earth-station receivers: 1 Hz; - space-station receivers: 20 Hz. 2.2 Ref
22、erence percentage of time When considering interference to space research earth stations, it is necessary to note that sporadic interference from man-made sources can be expected due to trans-horizon propagation, fluctuating weather conditions, and the changing gain in the link between the interferi
23、ng station and the receiving station due to the relative motions of the antenna, etc. Therefore, any criterion of interference which is established must be stringent enough to minimize the possibility of this type of interference. Further, as propagation data are usually presented in the form of a p
24、ercentage of time that certain conditions are exceeded, it is necessary to relate outage time with propagation data. For manned space missions, a loss of more than 5 min of communication during critical periods would seriousiy affect the mision. However, it is usual that propagation conditions are s
25、uch that the lowest transmission loss between two stations will persist for much longer periods than 5 min. Therefore, to provide protection which will prevent interference for longer than 5 min per day, it is necessary not only to consider the worst hour in the year, but also the worst 5 min within
26、 that hour. This is approximately 0.001% of the time. For unmanned missions, where safety of life is not a factor, the reference percentage of time is 0.1%. 2.3 Required protection levels 2.3.1 Earth-station receivers In the 37-38 GHz region, the total noise temperature of receiving earth stations m
27、ay be as low as 60 K. This total is a function of antenna elevation angle, existing meteorological conditions and other factors. Therefore, based on the established NI ratio of 6 dB, and a receive noise temperdture of 60 K, the following criterion is the most directly appropriate for the protection
28、of earth stations: In the frequency range 37-38 GHz, harmful interference can occur if the total time during which the power density of noise-like interference or the total power of CW-type interference in any single band or in all sets of bands 1 Hz wide, is greater than -217 dB(W/Hz) at the input
29、terminah of the earth station receiver for a period exceeding 0.001% of the time for manned missions, and 0.1% of the time for all other space research missions. 2.3.2 Spacestation receivers The total noise temperature of a 40 GHz space-station receiver is generally 200 K when viewing cold space bac
30、kground. Based on the established NI of O dB, the following criterion is most directly appropriate for the protection of space stations: In the frequency range 4040.5 GHz, harmful interference can occur if the power density of noise-like interference or the total power of CW-type interference in any
31、 single band or in all sets of bands 20 Hz wide, is greater than -193 dB(W/20 Hz) at the input terminals of the space station receiver. Due to the motion of low-orbit spacecraft, which can be susceptible to this level of interference, the amount of time of exposure to the interference is limited to 0.1% of the time for both manned and unmanned missions.
