1、ERC REPORT 46 7 Eurom Radiocommunications Committee IWC) -* within the European Conference of Postai and Telecommunications Adhnistrations (CEFT) FURTHER SHARING STUDY BETWEEN THE FIXED SERVICE AND EARTH EXPLORATION-SATELLITE SERVICE IN THE BAND 55.22 - 55.78 GHz Sesimbra, January 1997 STDnCEPT ERC
2、REPORT Lib-ENGL 3997 232b434 0035656 T58 W Copyright 1997 the European Conference of Postai and Telecomrmuiications Administrations (CEPT) STD-CEPT ERC REPORT Lib-ENGL 3997 2326414 0015657 794 m ERC REPORT 46 TABLE OF CONTENTS 1 INTRODUCTION . 1 2 PASSIVE SENSO Rs 1 2.1 INTRODUCTION . 1 AROUND 60 G.
3、 . 1 CURRENT AND FUTURE SATELLITE SYSTEMS AND INSTRUMENTATION . 2 2.3.1 Satellite systems . 2 2.3.2 Instrumentation 2 2.3.3 2.4.1 2.4.2 2.2 2.3 SIGNIFICANCE OFPASSIVE MEASUREMENTS PERFJORMED BY THE mss NEAR THE RESONANCEFREQUENCIES Typical characteristics of microwave sounders . 3 ZNTE“CE CRITIBIAFO
4、R PASSIVE SENSORS. AND VULNWABILITY TOINTERFERENCE . 3 Current intetference criteria definition . 3 Vulnerability to interference . 3 2.5 -CE crlssrncno . 4 2.6 SHARING CONDITIONS . 5 REQUIREMENTS FOR FMED SERVICES . 7 3.1 INTRODUCIION . 7 3.2 TERRESTRIAL PROPAGATION IN THE MILUMETRIC WAVEBANDS . 7
5、3.3 CURRWTAND FREUSEFTHEOYGENABON BANDBY THFIXD SRVICE . 8 3.4 ETSI STANDARDS UNDER Dveoparr 8 3.5 FIxE!D SERVICE SYSTEMPARAMETERS 9 3.6 PS TRANSMITTEX OUTPUTPOWI?R 9 3.7 POSSIBLE MEANS OF SHARING . 9 IMPLICATIONS FOR SHARING IN THE BAND 55.22 . 55.78 GHZ 10 2.4 3 4 . 4.1 4.2 4.3 Dmcr INTERFERENCE P
6、ROPAGATION PATH 10 INDIRECT INTERFERENCE PROPAGATION PATH . 12 EFFECT OF ANTENNAELEVATION 13 5 . CONCLUSIONS 14 STD-CEPT ERC REPORT 4b-ENGL 3997 m 2326414 0015658 820 ERC REPORT 46 Page 1 SHARING BETWEEN TEE FIXED SERVICE AND EARTH EXPLORATION SATELLITE SERVICE IN THE BAND 55.22 - 55.78 GHz 1 INTROD
7、UCTION ERC Report 45 contains an examination of the feasibility of sharing between the fixed service (FS) and Earth exploration- satellite service (EESS) in the range 50.2 to 58.2 GHz. This report concludes that sharing between passive remote sensors and the fixed service is feasible between 55.78 a
8、nd 58.2 GHz, but not feasible between 50.2 and 55.22 GHz; in the initial study there was no definitive conclusion on the feasibility of sharing in the range 55.22 - 55.78 GHz. The following report contains the results of further studies focusing in particular on the band 55.22 - 55.78 GHz 2 PASSIVE
9、SENSORS 2.1 Introduction The electromagnetic spectrum contains many frequency bands where, due to molecular resonances, absorption mechanisms by certain atmospheric gases are taking place. Frequencies at which such phenomena occur characterise the gas. The absorption coefficient depends on the natur
10、e of the gas, on its concentration, and on its temperature. A combination of passive measurements around these frequencies can be performed from spacehe platforms, to retrieve temperature and/or concentration profiles of absorbing gas. Of particular significance to the EESS below 200 GHz are the oxy
11、gen resonance frequencies between 50 and 70 GHz, and at 118.75 GHz, and the water vapour resonance frequencies at A general view of the atmospheric attenuation due to oxygen and water vapour at frequencies up to 350 GHz is shown in Figure 1. Detailed oxygen absorption spectrum in the vicinity of 60
12、GHz is shown in Figure 2. The two neighbouring absorbing peaks which limit the frequency slot under consideration in this document are also indicated. 22.235 GHz andat 183.31 GHz. 2.2 60 GHz Significance of passive measurements performed by the EESS near the resonance frequencies around Spaceborne m
13、icrowave passive sounders making passive measurements near the resonance frequencies around 60 GHz are deployed, particularly by the meteorological services. Their purpose is to provide on a worldwide basis “all weather” three dimensional measurements of the temperature profiles, key parameters whic
14、h describe the status of the atmosphere. Temperature profiles are among the few essential parameters describing the status of the atmosphere, which are fed directly into the operational Numerical Weather Prediction models (”) operated by the meteorological services. Weather forecasting is a Rblic Se
15、rvice” which leads to significant economic benefits for most human activities such as agriculture, transport, construction, energy production etc, and contributes also to protect human lives and properties. There is a strong demand for improvements of this service, particularly in accuracy and in re
16、liability. All weather atmospheric temperature profiles are also essential for scientific applications such as climate and environment monitoring (“Global change” for example). They are also the key auxiliary parameter, which is necessary to extract the concentration profiles of radiatively and chem
17、ically important atmospheric gases (such as ozone), from radiometric measurements in their specific absorption bands. Compared to infra-red (R) techniques, the all-weather capability (the ability for a spacebome sensor to “look” through most clouds) is probably the most important feature that is off
18、ered by microwave techniques. This is fundamental for operational weather forecast and atmospheric science applications, because more than 60% of the earths surface, on average, is totally overcast by clouds, and only 5% of all 20x20 km pixels (corresponding to the typical STD-CEPT ERC REPORT 46-ENG
19、L 1997 232b4L4 00LSb59 7b ERC REPORT 46 Page 2 spatial resolution of the IR sounders) are completely cloud-free. This situation severely hampers operations of IR sounders, which have very little or no access to large, meteorologically active regions. High resolution all-weather temperature profiles
20、can only be obtained by passive measurements from low-earth polar orbiting satellites within the oxygen absorption spectrum around 60 GHz. High vertical resolution is rendered possible by the multi-lhe structure of the absorption spectrum. Because of its specific absorption level, the 55.22 - 55.78
21、GHz sub-band is the oniy suitable one in the spectrum where tropopause information can be collected, as for example by the AMSU-A channel 8 (as shown in Figure 3). This is a unique natural resource for which no alternative exists. 2.3 Current and future satellite system and instrumentation 2.3.1 Sat
22、ellite systems Meteorological services operate essentially two complementary types of satellite systems: Systems based on satellites in low sun-synchronous polar orbits are used to acquire high resolution environmental data on a global scale. The repeat rate of measurements is limited by the orbitai
23、 mechanics. A maximum of two global coverages are obtained daily, with one single satellite. Two low orbiting meteorological satellites in coordinated orbits (“morning” and “afternoon”) are currently operated by NOM (NOAA-KAJM”, USA). This network yields one complete coverage every 6 hours on averag
24、e. NOM-M, to be launched in 1999, will be the last “morning” satellite of the series. Consequently, Europe (ESA and EUMETSAT) has accepted to take up the responsibility of a “morning” satellite system, METOP, which will be developed in Europe. The first satellite of this European series is planned t
25、o be iaunched in 2002; Systems involving satellites in geostationary orbit are used to gather low to medium resolution data at regional scale. The repeat rate of measurements is lidted only by hardware technology, and is typically one regional coverage every 30 minutes or less. Five to six geostatio
26、nary meteorological satellites regularly spaced around the earths equator are deployed. The European component, METEOSAT, is positioned at O” longitude. 23.2 Instrumentation Since 1978, the Meteorological Satellite Service has used sectim of the oxygen absorption spectrum around 60 GHz for passive m
27、icrowave sounding of the atmosphere. These measurements are provided by the Microwave Sounding Unir (MSV) instrument which is flown on the operational series of polar-orbiting weather satellites operated by NOM. MSU is a 4 channel radiometer. On the basis of experience gained with the MSU data, NOAA
28、 is going to upgrade the microwave sounding capability on its operational polar-orbiting satellites in the near future. This capability will be provided by two new instruments: The Advanced Microwave Sounding Unit -A (AMSU-A), for determining atmospheric temperature The AdvancedMicrowave Sounding Un
29、it - B (AMSU-B, supplied by the UK), for determining profiles, has 15 channels of which 12 channels fall within the 50.2 - 58.2 GHz band; atmospheric water vapour profiles, has 5 channels of which 3 channels fall around 183.31 GHz. The first flight of the AMSU-A and AMSU-B instruments, on the NOM-WI
30、IMI” series, is currently scheduled for the end of 1996. The AMSU-A is also going to fly on the European satellite series METOP. Further upgrading of the microwave sounding capability will be achieved: - In the 2005 timeframe, “stratospheric” channels in the frequency range 60.3 - 61.3 GHz, will be
31、added to the AMSU-A instrument. Such channels will increase the maximum height at which the atmospheric temperature is retrieved from approximately 45 km to approximately 70 km. This technique relies on a special interaction between the Earths magnetic field and particular 02 absorption lines (“Zeem
32、an splitting”). STD-CEPT ERC REPORT 4b-ENGL 1997 2326414 0015bb0 489 = ERC REPORT 46 Page 3 - In the 2002 timeframe, on the METOP satellite, the water vapour sounding capability will be ensured by the Microwave Humidity Sounder (MHS), an improved version of the AMSU-B, which is being developed in Eu
33、rope. The MHS may replace the AMSU-B on the NOM-N and N “afternoon“ satellites. A number of other microwave sounding instruments using similar frequency bands are also in operation, in particular on US military weather satellites, and on Russian weather satellites. Due to technological constraints,
34、no microwave sounder has been flown as yet on a geostationary meteorological satellite. This is however envisaged on future systems. Microwave sounders for geostationary platforms will have channels around 183.31 GHz for water vapour profiling, as for the instruments in low earth orbits. For tempera
35、ture profiling, the 118.75 GHz region is preferred over the 60 GHz in order to minimise the size of the antenna. 2.3.3 Typical characteristics of microwave sounders Antenna diameter : IFOV 3dB points : FOV (cross-track) : Antenna gain : Side lobes : Beam efficiency : Radiometric resolution : Swath w
36、idth : Pixel size (nadir) : Number of pixeldine : Orbit altitude (circular) : Orbit inclination (sun-synchronism) : Present : 15 cm 3.3“ 4- 50“ 36 dBi - 1OdBi 95% 0.3 K 23oO km 49 km 30 850 km 98.8 Future : 45 cm 1.1“ +I- 50“ 45 dl3i -10 dBi 95 % 0.1 K 2300 km 16 km 90 850 km 98.8 O 2.4 Interference
37、 criteria for passive sensors, and vulnerability to interference 2.4.1 Current interference criteria definition Recommendation ITU-R SA 1029 sets the permissible interference threshold as follows: - In the 50 to 66 GHz frequency band: -161 dBW for a scanning sensor and -166 dBW for a pushbm sensor,
38、in a reference bandwidth of 100 MHz. These levels are equivalent to brightness temperature increases of 0.06 K and 0.02 K respectively; - The recommendation mentioned above indicates also that These levels may be exceeded for less rhan 5% measurement cells where interference occurs randomly, and for
39、 less than 1 % measurement cells where interference occurs systematically at the same Eocations“. These criteria may be unsuitable for protection of passive sensors in these bands when considering the use of the data in Numerical Weather Prediction models. 2.4.2 Vulnerability to interference Passive
40、 sensors integrate all natural (wanted) and man-made (unwanted) emissions. They cannot in general differentiate ERC REPORT 46 Page 4 between these two kinds of signals because the atmosphere is naturally a fast changing medium, spatially and temporally. If undetected, corrupted data propagate dramat
41、ically in the numerical weather prediction models (”), rendering the whole forecast useless. Recently, the European Centre for Medium-range Weather Forecasting (Em demonstrated that as few as 0.1 % of contaminated satellite data could be sufficient to generate unacceptable errors in Nwp forecasts, t
42、hus destroying confidence in these unique all weather passive measurements. On the contrary, if corrupted data can be detected and then are systematically rejected over areas where the probability for interference is suspected to be high, important natural warnings are likely to remain ignored and t
43、he consequence may be also negative. The systematic deletion of data could postpone or render impossible the recognition of new developing weather systems, and vital indications of rapidly developing potentially dangerous storms may be missed. The possible presence of undetected errors for some poin
44、ts would make this situation worse and add the possibility that false predictions of severe weather could be produced. For climatological studies and particularly “global change monitoring, interference could be interpreted as artificial Warming of the atmosphere. Concerning passive microwaves calib
45、ration and atmospheric retrieved profiles (temperature and humidity), it is necessary to correlate microwave measurements and conventional radiosonde measurements, each 12 hours. This is often done near large cities where interference could lead to wrong calibration, retrievals, and statistics for N
46、WP. 2.5 Interference classification interference can be broadly classified as follows. a- Undetectable : An interfering signal of up to the interference threshold contributes normally to the expected error budget of the instrument, but would not endanger the required quality of measurements. Interfe
47、rence at this level would make sharing possible without restriction. b- Likely to cause misinterpretation : An interfering signal causing an apparent warming of up to around 5 K cannot be detected at the data processing level, because it does not differentiate from the values which are normally expe
48、cted. ECMWP simulation demonstrates that the 5-days forecast over Europe can be completely changed by small perhubations (typically a few cells per thousand) compared to the analysis over North America 5 days earlier. If the location of such interference sources is perfectly known worldwide, the con
49、taminated measurements can be systematically rejected without significant consequences provided that rejected measurements are evenly distributed worldwide, because large patches of missing data could have severe impact on the model forecast (longwave effects). Furthermore, the total data loss should be limited to around 1%. If the location of interfering sources is unknown, contaminated data would cause an incorrect adjustment to the numerical weather prediction model and hence would significantly degrade analysis and forecast. Interference within this range o
