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N94-22776 the AGRHYMET Data Communications Project

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N94-22776 the AGRHYMET Data Communications Project N94-22776 The AGRHYMET Data Communications Project G. R. Mah Hughes STX EROS Data Center Sioux Falls, SD 57198, USA D. P. Salpini USAID/Information Resource Management 11O0Wilson Boulevard Arlington, VA 22209, USA ABSTRACT clude supplying food production advice to govern- ment ministries, locust plague prediction and con- The U.S. Geological Survey (USGS) and the trol, and assistance to the Famine Early Warning U.S. Agency for International Development (USAID) System program. To accomplish its mission the are providing technical assistance to the AGRHYMET program has set up the AGRHYMET AGRHYMET program in West Africa. AGRHYMET regional center (ARC) in Niamey, Niger, and na- staff use remote sensing technology to produce sat- tional AGRHYMET centers (NAC) in each of the ellite image maps of the Sahel region of West Af- member nations. A receiving station for satellite im- rica. These image maps may show vegetation ages from NOAA's Advanced Very High Resolution greenness, sea surface temperatures, or processed Radiometer (AVHRR) instrument was installed at weather satellite imagery. The image maps must be the ARC by the French Government as part of its distributed from the AGRHYMET Regional Center in foreign aid program. The U.S. Agency for Interna- Niger to national AGRHYMET centers in the mem- tional Development (USAID), in cooperation with the ber countries of Burkina Faso, Cape Verde, Chad, U.S, Geological Survey's EROS Data Center (EDC), Gambia, Guinea-Bissau, Mali, Mauritania, Niger, have set up a system to process the AVHRR data to and Senegal. After consideration of a number of make image maps that indicate the relative "green- land- and space-based solutions for image map ness" of the area. Greenness maps are derived from distribution, the best solution was determined to be the Normalized Difference Vegetation Index (NDVI) use of International Maritime Satellite Organization computed from AVHRR data. [2] They are distrib- (INMARSAT) land-based terminals. In April 1992, a uted in hard copy format from the ARC to the NAC's field test and proof-of-concept demonstration using via the mail system on 10-day intervals throughout land-mobile terminals produced favorable results. the growing season. At present, the delivery of the greenness maps does not occur in a timely manner The USGS and USAID are setting up a wide to support near-realtime assessment of crop pro- area network using INMARSAT terminals to link the duction for policy decisions. It was proposed that a AGRHYMET sites for image data transfer. The sys- telecommunications system be installed to transfer tem is in the procurement and installation phase and the greenness maps electronically, in near-realtime. initial operating capability may be operational for the 1993 growing season, starting in May 1993. REQUIREMENTS INTRODUCTION The telecommunications system is required to In the middle 1970's, the World Meteorological provide a computer-to-computer communications Organization, in cooperation with nine member na- link to transfer the greenness map data from the tions in the Sahel region of western Africa, organ- ARC to the NAC's and for the NAC's to transfer ized the AGRHYMET program to help the member weather data back to the ARC. The system will op- nations increase agricultural crop production. [1] erate primarily during the growing season and trans- The role of AGRHYMET has since expanded to in- fer data on 10-day intervals (decadal) between the PltliGEL)it,d_ PAGE _LANK l'l{.)r FILMED 235 ARCandthe NAC's. The system technical require- ments are summarized as follows: | 1. The system shall provide operational data transfer of greenness map image files rang- ing up to 4 MB from the ARC to a NAC. Other data sets and files may be added in the future as required. 2. Weather data ranging up to 500 KB shall be transferred from a NAC to the ARC. 3. The system shall be operational for the 1993 growing season and remain opera- tional for 5 years. 4. Equipment installed at the ARC or a NAC Figure 1. A Satellite-Based System shall be supported by ARC personnel for hardware and software maintenance and repair. The vendor will provide warranty Among the satellite systems, most privately owned systems were eliminated due to lack of cov- service for the system's operational life of erage over the Sahel or the uncertainty of continuing 5 years. service for the 5 year project lifetime. This narrowed 5. The transmission channel [or "telephone"] candidate systems to satellites operated by two in- service shall be an operational system, us- ternational consortiums, INTELSAT (the Interna- ing the same provider or service for the full tional Telecommunications Satellite Consortium) 5 years of operation. and INMARSAT (the International Maritime Satellite Organization). Between tl_e [wo systems,the iN- 6. The system shall minimize the annual MARSAT approach was selected on the basis of recurring costs of operation. being appropriate for AGRHYMET requirements, initial cost, recurring costs, and ease of operation 7. The system shall provide moderate and maintenance. A summary of the requirements growth capability to accommodate changing criteria is shown in table 1. AGRHYMET requirements and services. 8. The system shall not require any special INMARSAT System licensing or permits. The INMARSAT system consists of four satel- 9. The system shall provide 99% availability lites in geostationary orbits providing global cover- during the growing season (i.e. - unaffected age (figure 2), INMARSAT provides voice, fax, and by storms, power outages, or fluctuations in data communications services between land-mo- local telephone service quality). bile, maritime, and fixed users. The proposed sys- tem will use land-based fixed terminals. CANDIDATE SOLUTIONS The system was originally set up to provide A number of techniques were examined, rang- ship-to-shore radiotelephone service, but has since ing from point-to-point digital radios to satellite expanded to encompass large numbers of land-mo- communications systems, with a satellite system bile users also. The system operates in a manner being the optimum choice. All ground-based sys- analogous to a long distance carrier, connecting to tems were eliminated from consideration because of either a local phone system or an INMARSAT termi- line-of-sight requirements or low data rate capacity. nal. Access to the system is similar to a telephone A diagram of a typical satellite-based system is system. A user dials the desired destination (phone shown in figure 1. number), and the system connects them. 236 System Configuration terminal electronics unit, the personal computer, and an uninterruptible power supply will be located in the Each site (both ARC and NAC) will use a fixed INMARSAT terminal with an external fixed dish an- site computer room; while the antenna will be lo- tenna (1 to 2 m in diameter). The terminals will be cated outside the building (typically installed on the linked to a dedicated personal computer (provided roof). The extemal antenna must be located within as part of the system) through FAX/modem. The 15 m of the terminal electronics unit. Table 1. Summary of Requirements Analysis Requirement INMARSAT INTELSAT Operational System Yes Yes, some terminal customization may be required Duplex Link Yes Yes Minimize Interaction Between COMSAT/Common Carrier Transponder rental Local P'IT and System pays fees requires fees to each PTT, use of existing INTELSAT terminal in Niamey requires leased lines and coordination with PTT(s) Minimize Licensing License to enter country and Requires coordination with possibly operator's permit, each country's PTT considered to be minimal requirements Supportable by ARC Personnel Vendor will train ARC personnel, Vendor will train ARC provide spares and extended personnel, provide spares warranty, easily maintained and extended warranty, special skills required for maintenance and repair System Life of 5 to 7 Years Yes Yes Sahel Environmental Conditions Terminals designed for operation Can be modified to operate in hostile environments in Sahel environment Initial Operation for 1993 Terminals available from stock System development at Growing Season vendor would take 3 to 6 months Expandability/G rowth Yes, add terminals, add high Yes, add terminals, can data option for 56/64 KBPS link increase data rate to width of channel, rent wider channel bandwidth to increase data rate Easily Interface to Existing Yes, interface looks like phone line Some specialized ARC/NAC Hardware connection equipment may be required Satellite Link Available for Yes, satellite links transparent Yes, may be moved to 5 to 7 Years to user another satellite as current satellite ages Minimize Recurring Costs Pay only 'phone' bill ($20kJyr) Transponder rental, plus PTI- fees 237 i / ,____-_._ ,!_!/ .e,.-!\-.._ _. \ _,_ ! , I "_--tl----..¢_ _ il _t_ _, I .,-,%- r'-"_ "wgr._.__l_ _ I! _Z"fl ,I •lJ ll'oa'anOoeao I'1 III "'q--_,[ _ ___ II Satellite - _acific Ocean..Lt__._."_ Ir_x.-_"_d_J I_ I" I '__.,_E I I S._:ellite I, _'__ "_ m I! I 'f.C.IEW I: I I T_'.q'. 'IZ;_, I ! I .. _"f'_ / _ 11 I / _='_,.,v_'L._il I I : .,t_,//_." I', I!1 'i: (iJ I I I " ........ b ....._" - __--....,'" , . ._.:_._ ".-"" ?atelliteate lite :_ ..._..._<L<"......... Figure 2. Global INMARSAT Satellite System Coverage FIELD TEST DESCRIPTION AND RESULTS A field test with two INMARSAT land-mobile satellite terminals was performed in April 1992. Data was relayed between the ARC in Niamey, Niger, and the NAC in Ougadougou, Burkina Faso, using an INMARSAT coast earthstation to turn the link around (double-bounce through the spacecraft). Transfer rates between 4.8 KBPS and 19.2 KBPS were measured, with the typical rate of 8 KBPS for a large file transfer.
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