1、 Rec. ITU-R RS.1804 1 RECOMMENDATION ITU-R RS.1804*Technical and operational characteristics of Earth exploration-satellite service (EESS) systems operating above 3 000 GHz (Question ITU-R 235/7) (2007) Scope Instruments have been operating on EESS systems at frequencies above 3 000 GHz for many yea
2、rs. The instruments are comprised of both active and passive devices, are deployed on geostationary orbit (GSO) and non-GSO systems, and utilize narrow-spectral lines as well as widebands. This recommendation summarizes the instruments, spacecraft, spectrum of interest and type of data collected usi
3、ng spectrum above 3 000 GHz. The ITU Radiocommunication Assembly, considering a) that observations at frequencies above 3 000 GHz provide data critical to the study of the characteristics of the Earth and its natural phenomena, including data relating to the state of the environment; b) that the tec
4、hnology for Earth exploration-satellite service (EESS) sensors operating above 3 000 GHz is continuously evolving to provide better accuracy and resolution of measurement data; c) that the spectrum above 3 000 GHz is used for active and passive sensor systems as well as for many telecommunication ap
5、plications; d) that, as these systems are rapidly expanding and increasing in number, the likelihood of harmful interference between sensors in the EESS and other services operating above 3 000 GHz may increase; e) that the Earth-to-space laser radiation used by some optical ground stations to condu
6、ct precise satellite and lunar ranging and to measure atmospheric parameters represents a possible source of interference to, and may potentially damage, sensitive satellite passive sensors; f) that while there are significant differences between the technologies used in this part of the spectrum co
7、mpared with lower frequencies (e.g. counting photons versus integrating power over time), there are also many similarities; g) that protective measures and sharing considerations have to be considered to ensure that EESS sensors can continue to operate at frequencies above 3 000 GHz without harmful
8、interference, *This Recommendation should be brought to the attention of Radiocommunication Study Groups 1, 3, 4, 8 and 9. 2 Rec. ITU-R RS.1804 recommends 1 that operators of EESS systems operating above 3 000 GHz should take into account the possibility of interference from transmitters of the scie
9、nce services (including those of EESS) in their selection of mission requirements and choices of sensor design; 2 that studies of interference to and from EESS systems operating above 3 000 GHz should take into account the technical and operational parameters provided in Annex 1. Annex 1 1 Introduct
10、ion Instruments have been operating on EESS systems at frequencies above 3 000 GHz for many years. These instruments operate in several modes and provide a variety of types of data. The instruments are comprised of both active and passive devices, are deployed on GSO and non-GSO systems, and utilize
11、 narrow-spectral lines as well as widebands. The information contained in the following sections summarizes the instruments, spacecraft, spectrum of interest and type of data collected using spectrum above 3 000 GHz. 2 Instruments The instruments to be described are categorized as the following: ima
12、gers, radiometers/ spectrometers, or LIDAR altimeters. Imagers are instruments whose prime objective is to present two-dimensional representations of physical phenomena such as clouds or the Earths surface. Radiometers/spectrometers are instruments which measure electromagnetic radiative flux. LIDAR
13、 altimeters are instruments which measure the height from the spacecraft to the surface directly underneath via pulses of light emissions. 2.1 Imaging technical characteristics One of the earliest uses of the spectrum above 3 000 GHz for EESS applications is imaging the Earths surface and cloud cove
14、r. More recently imaging systems have been used to gather data on the distribution and frequency of lightning. The three types of imaging systems described below are representative of the general capabilities of EESS systems performing imaging at frequencies above 3 000 GHz. A fourth system describe
15、d below optically senses weather phenomena. Rec. ITU-R RS.1804 3 2.1.1 Multispectral cloud imaging Systems A1 through A3 operate as a single instrument which collects imagery at 14 different wavelengths ranging from 0.5 to 12 m. It is used for long-term cloud monitoring at spatial resolutions of 15
16、to 90 m depending on the wavelength measured. The instrument is divided into three separate systems each with its own telescope monitoring a different set of wavelengths. The systems bands are: Visible/near infrared (VNIR) 0.50 to 0.90 m (600 to 333 THz1). Short-wave infrared (SWIR) 1.6 to 2.43 m (1
17、87.5 to 123 THz). Thermal infrared (TIR) 8 to 12 m (37.5 to 25 THz). With its high-spatial resolution, broad spectral coverage, and stereo imaging capability, this instrument provides essential measurements of cloud amount, type, spatial distribution, morphology, and radiative properties. While many
18、 cloud imagery instruments measure similar parameter sets, the ability to observe with this high-spatial resolution provides data that can be directly related to detailed physical properties. Furthermore, in areas where no cloud cover is present, this instrument provides long-term monitoring of loca
19、l and regional changes to the Earths surface which either lead to, or are in response to, global climatic changes (e.g. land use, deforestation, desertification, lake and playa water-level changes and other changes in vegetation communities, glacial movement and volcanic processes). A summary of the
20、 technical parameters of this instrument is provided in Table 1. TABLE 1 Technical parameters of multispectral cloud imaging systems System A1 A2 A3 Field of view (degrees) 6.09 4.9 4.9 Instantaneous field of view (rad) 21.5 42.6 128 Wavelengths measured (m) 0.52-0.60 0.63-0.69 0.76-0.86 1.60-1.70 2
21、.145-2.185 2.185-2.225 2.235-2.285 2.295-2.365 2.360-2.430 8.125-8.475 8.475-8.825 8.925-9.275 10.25-10.95 10.95-11.65 Spatial resolution (m) 15 30 90 Data rate (Mbit/s) 62 23 4.2 Cross-track pointing (degrees) 24 8.55 8.55 Cross-track pointing (km) 318 116 116 Swath width (km) 60 60 60 Detector typ
22、e Silicon (Si) Platinum Silicide-Silicon (PtSi-Si) Mercury Cadmium Telluride (HgCdTe) Quantization (bits) 8 8 12 11 THz = 1 000 GHz. 4 Rec. ITU-R RS.1804 2.1.2 Multispectral imaging of the Earths surface Systems B1 through B5 operate together as a single instrument to collect imagery at seven narrow
23、 wavelengths ranging from 0.45 to 12.5 m and one panchromatic range from 0.5 to 0.9 m. It is used to characterize and monitor change in land-cover and land-surface processes. The high-spatial resolutions (15 to 60 m depending on wavelength range) and seasonal global coverage of this instrument will
24、allow assessment of both the rates of land-cover change and the local processes responsible for those changes. Deforestation, ecosystem fragmentation, agricultural productivity, glacier dynamics, coastal hazards, and volcano monitoring are representative science targets for this instrument. The inst
25、rument conducts its measurements through a single aperture in four bands: Visible (VIS) 0.45 to 0.69 m (667 to 435 THz). Near infrared (NIR) 0.76 to 0.90 m (395 to 333 THz). SWIR 1.55 to 2.35 m (194 to 128 THz). TIR 10.42 to 12.5 m (28.8 to 24 THz). System B6 is a visible and near-infrared radiomete
26、r for observing land and coastal zones. It is used to provide land coverage maps and land-use classification maps for monitoring regional environment. The instrument has a cross-track pointing capability for disaster monitoring. System B7 is a panchromatic radiometer with 2.5 m spatial resolution. I
27、n order to obtain terrain data including elevation, this instrument has three optical systems for forward, nadir, and backward views. The instrument provides precise geographical information suitable to create 1/25 000 scale global maps. A summary of the technical parameters of these systems is prov
28、ided in Table 2. Rec. ITU-R RS.1804 5 TABLE 2 Technical parameters of multispectral imaging of the Earths surface System B1 B2 B3 B4 B5 B6 B7 Instantaneous field of view (rad) 42.5 42.5 42.5 39.4 42.5 85.0 21.25 18.5 14.28 3.57 Wavelengths measured (m) 0.45-0.52 0.52-0.60 0.63-0.69 0.76-0.90 1.55-1.
29、75 2.08-2.35 10.42-12.50 0.50-0.90 0.45-0.50 0.52-0.60 0.61-0.69 0.76-0.89 0.52-0.77 Spatial resolution (m) 30 30 30 60 15 10 2.5 Data rate Data merged into 150 Mbit/s data stream 160 Mbit/s (after data compression: 120 Mbit/s) 320 Mbit/s 3 telescopes = 960 Mbit/s (after data compression: 240 Mbit/s
30、, 120 Mbit/s) Swath width 185 km (7.5). Each image frame represents a 170 km increment along the satellite track 70 km Up to 70 km Detectors per band 16 16 16 8 32 7 000 40 000 6 Rec. ITU-R RS.1804 2.1.3 Hyperspectral imaging This instrument works in a similar manner as multispectral imagers; howeve
31、r, hyperspectral analysis utilizes contiguous spectral channels, allowing the use of derivatives and sophisticated analysis techniques. A much larger number of bands allows more complex systems to be addressed without the under-sampling inherent in multispectral systems. Hyperspectral imaging has wi
32、de ranging applications in mining, geology, forestry, agriculture, and environmental management. The System C hyperspectral imager utilizes 220 bands over a spectral range, 0.4 to 2.5 m (from 750 to 120 THz). Detailed classification of land assets through System C will enable more accurate remote mi
33、neral exploration, better predictions of crop yield, and assessments, and better containment mapping. A summary of the technical parameters of this system is provided in Table 3. TABLE 3 Technical parameters of a hyperspectral imaging system System C Instantaneous field of view (rad) 43 Wavelengths
34、measured (m) 0.4 to 2.5 (contiguous across 220 bands) Spatial resolution (m) 30 Data rate 250-500 MB over 8-12 second collection periods Image size (km2) 7.6 100 Detectors per band 1 (220 individual detectors) 2.1.4 Lightning sensing System D investigates the global incidence of lightning, its corre
35、lation with convective rainfall, and its relationship with the global electric circuit. This instrument consists of a staring imager that is optimized to locate and detect lightning with storm-scale resolution (from 4 to 7 km) over a large region (600 600 km) of the Earths surface. The system can mo
36、nitor individual storms in its field of view for 80 s, long enough to estimate the lightning flash rate. A combination of four methods is used to extract lightning data from the surrounding image. These methods require the ability to separate spatial, temporal and spectral details from consecutive i
37、mage frames in order to identify lightning signatures from other emissions. Temporal filtering is required to confirm the duration of the emission is approximately that of a lightning flash (typically 400 s). Spectral filtering is required to confirm the presence of energy at the strong OI(1) emissi
38、on multiplet in the lightning spectrum 0.7774 m (385.9 THz). Spatial filtering is then required to identify the location of the lightning flash. Rec. ITU-R RS.1804 7 A summary of the technical parameters of this system is provided in Table 4. TABLE 4 Technical parameters of a lightning sensing syste
39、m System D Field of view (degrees) 80 80 Instantaneous field of view (degrees) 0.7 Wavelengths measured (m) 0.7774 Spatial resolution (km) 5 Data rate (kbit/s) 6 Image size (km) 600 600 Detector 128 128 CCD 2.2 Radiometry and spectrometry Radiometry and spectrometry are unique measurement techniques
40、 which may be performed individually or in combination to monitor atmospheric chemical composition (including pollutants), meteorological profiles, cloud structure, and land surface characteristics. These systems may operate over frequencies ranging from ultraviolet (i.e. wavelengths 10.0 m). These
41、instruments may operate in push-broom, scanning, or fixed pointing modes with targets on the Earths surface as well as the limb. Radiometric measurements usually occur over less than 50 different bands without strict filtering. In contrast, spectrometry measurements may simultaneously collect data o
42、n thousands of narrow bands. Valuable information can be drawn from both measurement techniques not only by examining data in individual bands but also by evaluating differential data derived from data in multiple bands. System E1 is a space-borne instrument designed specifically to measure global c
43、limate change indicators. System E1, with spectral coverage from 3.7 to 15.4 m (from 81 to 19.5 THz), can very accurately measure the amounts of atmospheric water vapour and greenhouse gases and can produce precise 3-D maps of the water vapour and trace greenhouse gas distribution throughout the atm
44、osphere. System E2 plays a vital role in the development of validated, global, interactive Earth system models able to predict global change by measuring parameters such as land, cloud, and aerosol boundaries and temperatures, ocean biogeochemistry, and cloud-top height. This instrument provides hig
45、h radiometric sensitivity (12 bit) in 36 spectral bands ranging in wavelength from 0.4 m to 14.4 m (from 750 to 20.8 THz). System E3 provides global, long-term measurements of key components of the Earths atmosphere, the most important being the vertical distribution of aerosols, ozone, and water va
46、pour in the upper troposphere through the stratosphere. This instrument is a grating spectrometer that measures ultraviolet/visible energy using an 800 element CCD linear array to provide continuous spectral coverage between 0.29 and 1.03 m (from 1 034 to 291 THz). Additional aerosol information is
47、provided by a discrete photodiode at 1.55 m (193.5 THz). This configuration enables the instrument to make multiple measurements of absorption features of target gaseous species and multi-wavelength measurements of broadband extinction by aerosols. 8 Rec. ITU-R RS.1804 System E4 is an optical sensor
48、 that observes the reflected solar radiation from the Earths surface, including land, oceans and clouds and/or infrared radiation with a multichannel system for measuring the biological content, such as chlorophyll, organic substance, and vegetation index as well as temperature, snow and ice, and cl
49、oud distribution. These data are used for understanding climate change and the global circulation of carbon. System E5 is a spectrometer that observes the atmospheric limb absorption spectrum from the upper troposphere to the stratosphere using sunlight as a light source (solar occultation technique). The spectrometer covers the 3-13 m (100 to 23.1 THz) and 0.753 to 0.784 m (398 to 383 THz) spectral regions. It was developed to monitor the high-latitude stratospheric ozone. The objectives of the system are to monit
