1、 Report ITU-R RS.2194(10/2010)Passive bands of scientific interestto EESS/SRS from 275 to 3 000 GHzRS SeriesRemote sensing systemsii Rep. ITU-R RS.2194 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use of the radio-frequency spectru
2、m 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 Sector are performed by World and Regional Radiocommunication Co
3、nferences 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 ITU-R 1. Forms to be used for the submission of patent statement
4、s 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 can also be found. Series of ITU-R Reports (Also available onl
5、ine 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 Mobile, radiodetermination, amateur and related satellite services
6、 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 management Note: This ITU-R Report was approved in English by the
7、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. Rep. ITU-R RS.2194 1 REPORT ITU-R RS.2194 Passive bands of scie
8、ntific interest to EESS/SRS from 275 to 3 000 GHz (2010) TABLE OF CONTENTS Page 1 Introduction 2 2 Primary EESS measurement classes 2 2.1 Meteorology/climatology . 2 2.2 Atmospheric chemistry . 4 2.3 Specificities of the 1 000 to 3 000 GHz range 6 2.4 Ground-based and balloon-based sensors . 7 3 Com
9、patibility with active service systems . 7 3.1 Atmospheric absorption 8 3.2 Sharing in the 1 000-3 000 GHz Region 10 3.4 Conclusion 14 4 Consolidated tables . 14 5 Summary . 14 Annex 1 Passive bands of scientific interest for EESS between 275 and 1 000 GHz 15 Annex 2 Passive bands of scientific inte
10、rest for terrestrial sensors between 275 and 3 000 GHz . 19 2 Rep. ITU-R RS.2194 1 Introduction This Report provides relevant passive bands of interest to Earth exploration-satellite service (passive) (EESS(passive) and space research service (passive) (SRS (passive) in the 275-3 000 GHz frequency r
11、ange and the corresponding scientific rationale. It also provides information on EESS (passive) systems that are currently operating or planned to operate in the 275 to 3 000 GHz frequency range. Information on current and planned spaceborne passive remote sensing systems was reviewed for applicable
12、 information. Scientific literature and personnel were surveyed and consulted to determine currently known frequency bands of interest. In addition, studies were conducted to examine possible interference to the Earth observing passive sensors from stations that may operate in the active services, b
13、oth terrestrial and space-based, in the 1 000-3 000 GHz band. 2 Primary EESS measurement classes There are two primary EESS measurement “classes”, namely meteorology/climatology and atmospheric chemistry. The meteorology/climatology measurements mainly focus around the water vapour and oxygen resona
14、nce lines and the associated windows to retrieve necessary physical parameters, such as humidity, pressure, cloud ice and temperature (there is a direct correlation between the temperature and the sub-millimetre emissions from oxygen). The atmospheric chemistry sensing measures the many smaller spec
15、tral lines of the various atmospheric chemical species. An important difference between the two classes is in the geometry of the measurement. Most meteorology/climatology measurements are performed using vertical nadir sounders at lower frequencies (typically below 600 GHz) and limb sounders at hig
16、her frequencies whereas atmospheric chemistry measurements are mostly performed using limb sounding across the whole frequency range. In some cases, apparent redundant coverage (a single molecule is observed in several different bands) is needed for several reasons, such as different bands being sen
17、sitive to different altitudes. 2.1 Meteorology/climatology Figure 1 shows the sensitivity of millimetre and sub-millimetre frequencies to atmospheric temperature and water vapour variations between 2 and 1 000 GHz. The water vapour and oxygen resonance spectral lines are indicated in the figure as w
18、ell. The figure shows the increasing atmospheric attenuation at higher frequencies and the sizable variability of the attenuation due to water vapour. For this reason the low frequencies (below 200 GHz) are the most suitable for vertical nadir measurements of the lower layers of the atmosphere, whil
19、e the higher frequencies are better suited for the higher layers of the atmosphere. Above 600 GHz the oxygen lines are only visible over regions with very dry atmosphere. Measurements at these frequencies are therefore typically from limb sounders and, in any case, exclusively for the top atmospheri
20、c layers. Rep. ITU-R RS.2194 3 FIGURE 1 The sensitivity of millimetre and sub-millimetre frequencies to atmospheric temperature and water vapour variations1Among these bands, it has to be stressed that ranges around the water vapour resonance at 325 and 380 GHz and the oxygen at 424 and 487 GHz are
21、unique in their opacity and high enough in frequency to permit practical antennae to be used at geosynchronous altitudes, yet low enough for technology to provide practical, sensitive instrumentation. Use of the 380 GHz water vapour band helps avoid false alarms over super-dry air masses. Adding cha
22、nnels in the 380 GHz band to operational polar-orbiting satellites allows the retrieval of precipitation over snow-covered mountains and plains and in the driest polar areas where even the most opaque 183 GHz channels become transparent. The only remedy for transparency is a more opaque water vapour
23、 band and 380 GHz seems to be a uniquely good choice. Among oxygen lines, one can also note that the resonance line at 368 GHz is not considered since it is masked by the nearby 380 GHz water vapour resonance line. Cloud ice and water vapour are two components of the hydrological cycle in the upper
24、troposphere, and both are currently poorly measured. The hydrological cycle is the most important subsystem of the climate system for life on the planet and its understanding is of the utmost importance. The use of passive sub millimetre-wave measurements to retrieve cloud ice water content and ice
25、particle size was suggested years ago by Evans and Stephens (Evans KF, Stephens GL. 1995. Microwave radiative transfer through clouds composed of realistically shaped ice crystals. Part II: Remote sensing of ice clouds. J. Atmos. Sci. 52: 20582072) and refined in subsequent publications. Since then,
26、 a number of missions have been proposed that focus on this technique to measure cloud ice water path, ice particle size and cloud altitude to US and European Space Agencies. 1The sensitivity of millimeter and sub-millimeter frequencies to atmospheric temperature and water vapour variations. Journal
27、 of Geophysical Research-Atmospheres, 13, from A.J. GASIEWSKI and M. KLEIN. 4 Rep. ITU-R RS.2194 Currently, these measurements focus on the 183 GHz, 243 GHz, 325 GHz, 340 GHz, 380 GHz, 425 GHz, 448 GHz, 664 GHz and 874 GHz. The vertical water vapour and oxygen sounding measurements are typically per
28、formed using a set of channels, composed of so-called “wings” and associated “window”. The “window” corresponds to a frequency range where the effect of the resonance line is minimal. Corresponding measurements are used to determine the component that are not linked to the specific resonance line un
29、der investigation and that will then be eliminated from the “wings” measurements. The vertical sounding measurements along the “wings” of the resonance curve under investigation are performed in frequency slots (with a given bandwidth BW) at symmetrical distance (Offset) from the central resonance f
30、requency. This allows characterizing the resonance curve slope at the various atmospheric heights and providing therefore the water vapour and oxygen vertical profiles. The measurements on the wings around the main resonance lines are sometimes presented individually, while in other cases the freque
31、ncy requirement is expressed as the whole range needed to cover all the individual measurements. Indeed, for a given resonance curve, there is not always consistency in the definition of the offsets needed for these wing measurements, depending on the different instruments characteristics (bandwidth
32、, offset and number of slots) or investigation strategies. To cover all cases, the required total frequency band can hence be defined as the maximum bandwidth (BW) plus twice the maximum offset, centred on the resonance frequency. It should be noted that the frequency band corresponding to the “wing
33、s” measurements is not necessarily contiguous to the associated “window”. The retrieval of atmospheric properties (e.g., ice cloud content, ice cloud altitude, rain rate, rain profiles, etc.) requires the use of simultaneous multiple frequency observations for better accuracy as demonstrated in Jime
34、nez et al. (Performance simulations for a sub-millimetre wave cloud ice satellite instrument, Q.J.R. Meteorol. Soc , Vol. 133, No. S2, p. 129-149, 2007), Mech et al. (Information content of millimetre observations for hydrometeor properties in mid-latitudes, IEEE Trans. Geosci. Remote Sens., 45, 228
35、7-2299, 2007) or Defer et al. (Development of precipitation retrievals at millimetre and sub-millimetre wavelengths for geostationary satellites, J. Geophys. Res., 113, D08111, doi:10.1029/2007JD008673, 2008). 2.2 Atmospheric chemistry Atmospheric chemistry measurements are typically made with limb
36、sounders, scanning the atmosphere layers at the horizon as viewed from the satellite orbital position. These measurements relate to a large number of chemical species in the atmosphere and refer to spectral lines that are much narrower and larger in numbers than the water vapour and oxygen resonance
37、 lines. Among others, the following ones represent a subset of important species to be studied: HNO3: Nitric acid The most important reservoir for odd nitrogen in the atmosphere is nitric acid. It plays an important role in heterogeneous chemistry in polar stratospheric clouds. It comprises 90% of N
38、Oyin the lower stratosphere. HNO3plays role in air quality, atmospheric oxidation efficiency and stratospheric ozone depletion. This acid also shows a strong latitudinal gradient and is a useful tracer of stratospheric dynamics. Rep. ITU-R RS.2194 5 SO2: Sulphur dioxide A key species in formation of
39、 sulphate particles is sulphur dioxide. It is produced from the oxidation of biogenic compounds and emitted directly by volcanoes. SO2is an important tropospheric pollutant involved in rainfall acidification, smog formation and aerosol formation. Monitoring mid-upper tropospheric concentrations is i
40、mportant in understanding trans-national pollutant transport. Anthropogenic emissions stem mainly from fossil-fuel combustion. They continue to be globally very large despite the effective desulphurisation technology developed and applied in most developed countries. CH3Br: Methyl bromide Methyl bro
41、mide has both natural and anthropogenic sources and accounts for about 50% of the global organic bromine emissions. There are large uncertainties in the global trend of total organic bromine in the troposphere. It plays role in the stratospheric ozone layer depletion. CH3Cl: Methyl chloride Methyl c
42、hloride is important halogen source which plays a role in atmospheric ozone layer depletion. NO, NO2: Nitric oxide, nitric dioxide These two reactive nitrogen species are often referred to as NOx, play a critical role in atmospheric chemistry. NOx is released into the troposphere by biomass burning,
43、 combustion of fossil fuels and lightning. In troposphere NOx is a dominant factor in the in situ photochemical catalytic production of O3. Nitric oxide. BrO: Bromine monoxide BrO is an active halogen compound. Its principal importance is in the stratosphere where it participates in chain reactions
44、which destroy ozone. The details of the variation of BrO are essential in the verification of the models used to describe the atmosphere, and to obtaining accurate picture of the state of the atmosphere, particularly the dynamics in the stratosphere. N2O: Nitrous oxide There are natural land-surface
45、 sources and anthropogenic sources of nitrous oxide. It is a greenhouse gas with a tropospheric mean residence time of 120 years. Its concentration is increasing in the atmosphere at a rate of 0.25% per year. There are major unknowns in its global cycle that remain to be resolved. N2O is often used
46、as a tracer for stratospheric dynamics and stratospheric/tropospheric exchange studies. CO: Carbon monoxide The origin of CO is predominantly anthropogenic. It is mainly being produced by the combustion of fossil fuel. CO has a direct influence on the greenhouse gas concentrations of CO2and O3. HCl/
47、HOCL: Hydrochloric acid / Hypochlorous acid HCl is a major reservoir compound for inorganic stratospheric chlorine, which plays a role in ozone depletion. Current observations show that the total column abundances of HCl are currently starting to decrease. These results provide robust evidence of th
48、e impact of the regulation of the Montreal protocol and its subsequent amendments on the inorganic chlorine loading of the stratosphere. HOCl is also a chlorine reservoir. Reservoir forms of chlorine (HCl, ClONO2and 6 Rep. ITU-R RS.2194 HOCl) are converted to ClO by heterogeneous reactions on polar
49、stratospheric clouds. ClO: Chlorine monoxide ClO is the main trace gas involved in the catalytic destruction of stratospheric ozone at high latitudes. ClO is an active halogen compound. Its principal importance is in the stratosphere where it participates in chain reactions which destroy ozone. The details of the variation of ClO are essential in the verification of the models used to describe the atmosphere, and to obtaining accurate picture of the state of the atmosphere. O3: Ozone The 623-661 GHz band (technically, a set of 3 bands with gaps between them) is view
