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--> Executive Summary The National Oceanic and Atmospheric Administration (NOAA) asked the National Research Council (NRC) to assess the adequacy of planned geostationary and polar meteorological satellite coverages in terms of system continuity and backup. This report, prepared by the NRC's National Weather Service Modernization Committee (NWSMC), responds to that request. The NWSMC has not investigated the Defense Meteorological Satellite Program (DMSP) of the Department of Defense except peripherally, as it relates to the proposed National Polar-Orbiting Operational Environmental Satellite System (NPOESS) program and as a backup to the polar-orbiting operational environmental satellites (POES). The National Weather Service (NWS) is charged with providing forecasts of the weather for the United States and the adjoining oceans and with providing warnings of severe weather conditions in advance and as they occur. Satellite observations have been essential inputs in the provision of these services for more than 20 years. In addition, satellite data in many forms are used by NOAA, other government agencies, and the private and academic sectors in a broad range of applications, such as monitoring climate, planning land-use, and research. The National Environmental Satellite, Data, and Information Service (NESDIS) operates two satellite systems: the geostationary operational environmental satellite (GOES) system, which observes the same area of the Earth continuously; and the POES system, which observes the full area of the Earth in north-south strips, with the orbit height set so that each strip is observed at the same local time. The committee's findings and recommendations are summarized in this Executive Summary, and details are provided in the report. In general, the findings show that NOAA's satellite systems are adequate and the strategy for satellite replenishment and scheduling of launches is sound. However, the committee made
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--> no attempt to evaluate the impact of incorporating improved sensors and new technology or other factors not presently included in planned programs. The committee does recognize the importance of these other factors, particularly the long lead time required for developing and integrating new sensors and other new technology. This lead time must be taken into account in planning follow-on replenishment programs for environmental satellites. Reliable and continuous service from the operational satellites remains a dominant national requirement. Completely redundant systems and sensors are not provided aboard each satellite; therefore, a sufficient number of GOES and POES must be launched to provide the necessary redundancy in orbit at all times. The committee's analysis of NWS requirements for satellite data led to the following findings and recommendations. Finding 1a. At least one operational POES is needed in orbit at all times to provide data vital to global numerical-prediction models. A backup POES in orbit also is required to ensure that unacceptable degradation of service does not occur when the operational POES fails. The backup satellite may also be operated simultaneously with the first satellite, thus providing global coverage four times a day. A replacement must be available for launch in case either of the orbiting spacecraft fails. Finding 1b. At least two operating GOES satellites are needed in orbit at all times to provide the necessary coverage from the central Pacific Ocean eastward to the coast of West Africa. Recommendation 1. To meet NWS high priority requirements for satellite coverage in support of weather forecasts and warnings, NOAA must ensure that the requisite data are available at all times from at least one POES and two GOES in orbit. To ensure this continuity, a backup POES and a backup GOES need to be available in orbit. Finding 2. The GOES-8 and GOES-9 offer an opportunity to establish the operational utility of deriving soundings and upper air winds from GOES data and implement new operational techniques. Field office staff visited by the committee would like to have access to sounding and wind data from GOES. Recommendation 2. NWS/NOAA should fully support efforts to develop and demonstrate techniques for using GOES soundings and winds to improve warnings and forecasts. It is essential that the NESDIS and the NWS (particularly the National Centers for Environmental Prediction) devote adequate personnel to processing, evaluating, and applying newly available satellite data as soon as possible. Science operations officers and other field staff could also contribute to this effort.
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--> In response to a presidential decision directive, steps are being taken to merge the present POES system and the DMSP into a single system, the NPOESS. The first NPOESS launch is planned for 2008. Negotiations are under way between the NOAA and the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT); the latter will provide a replacement for one of the two POES satellites currently in orbit. The European satellites, called “meteorological operational” (METOP) satellites, will be introduced about 2002. Cooperation between NOAA and EUMETSAT is expected to continue in the NPOESS era, during which two of the nominal three satellites in orbit will be provided by NOAA. EUMETSAT will provide the third. Examination of the launch and in-orbit performance of the POES and GOES satellites, schedules for future satellites, possible backups to POES and GOES, spacecraft availability, and ground system vulnerabilities led the committee to the following additional findings and recommendations. Finding 3. The polar program, as presently planned, depends on the availability of European METOP satellites in polar orbit from 2002 to 2010 and the availability of NPOESS beginning about 2008. Recommendation 3. NOAA should closely coordinate the POES program with the progress of the NPOESS and METOP satellite programs so that “gap-filler” satellites are not needed. Finding 4. In the longer term, the replenishment strategy depends on the new NPOESS for polar-orbiting satellites and on the procurement of additional GOES satellites. (NOAA plans to procure a new design beginning with GOES-R.) Longer lead times than normal are required when new designs, which are planned for GOES-R, METOP, and NPOESS, are introduced. Recommendation 4. When considering ways to develop new spacecraft and incorporate major new improvements in technology, NOAA should carefully consider the lead times dictated by the required launch schedules and the very long procurement cycle. NOAA should develop schedules for the transition from current designs to new ones, such as NPOESS and GOES-R, that adequately account for the necessary lead times for funding approval, procurement, design and development, fabrication, and verification. The POES ground system appears to be adequate for the foreseeable future. However, the Wallops command and data acquisition (CDA) station is a potential single point of failure for the GOES system. Any phenomenon that could shut down the station, such as a hurricane, flooding, major fire, or explosion, would result in a complete cutoff of data from GOES satellites. Minimum prudent backup would require—at a location geographically remote from the Wallops
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--> facility—an antenna subsystem and the necessary receiving, transmitting, data formatting, and processing subsystems to command a GOES satellite, receive telemetry, and acquire and distribute data from the sounding and imaging instruments. Finding 5. The Wallops CDA station is a potential single point of failure for the GOES system. Shutdown of the station would result in a complete cutoff of data from the GOES satellites. Recommendation 5. NOAA should implement an adequate backup system to the Wallops CDA station to ensure the uninterrupted operation of GOES satellites and the acquisition of sufficient data to generate basic image and sounding products to meet NWS mission requirements. An agreement exists between NOAA and EUMETSAT whereby, under certain circumstances, one organization may provide backup of the other's operational geostationary meteorological satellite system. At the present time, the agreement appears to offer backup of GOES that is of limited value. This supports the following findings and recommendations. Finding 6. Although arrangements have been made for a European geostationary meteorological satellite, METEOSAT, to provide backup to GOES under certain conditions, the coverage by METEOSAT or its successor is very limited compared to the coverage provided by GOES. Recommendation 6. NOAA should ensure that a replacement GOES satellite can be launched and operated as soon as an operational GOES fails to continue the full level of coverage expected of this series of satellites. Finding 7. One additional GOES is needed in orbit as a ready spare to protect against a dangerous, protracted loss of full, two-satellite coverage if one operational GOES fails. Even more severe, although far less likely, would be an outage of continual, real-time coverage if both satellites in orbit should fail before a replacement could be made operational. Dependence on commercial launches for GOES can lead to delays of well over a year, even if a spacecraft is available for launch. Recommendation 7. To ensure the continuity of two-GOES coverage, NOAA should store a standby GOES in orbit, rather than on the ground, if this is technically and operationally feasible and cost effective. Consideration of factors that determine continuity of service has led to a launch-decision process in which a group of senior managers of the NWS and
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--> NESDIS regularly review the status of the satellites in orbit, satellite production, the availability of launch times, the readiness of the next satellite in the short range, and the replenishment strategy in the long range. They also review and update satellite availability prediction studies on a regular basis. Finding 8a. The launch-decision process used by NWS and NESDIS is appropriate. Finding 8b. The planned GOES, POES, METOP, and NPOESS procurements are adequate to provide continuity of the NOAA geostationary and polar-orbiting satellites for at least the next 15 years, if they are funded and carried out on the current schedule. Recommendation 8. To ensure continuity, NOAA should fund and procure the planned block of four GOES-Next spacecraft in a timely fashion and should avoid further delays in the METOP and NPOESS programs.
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