Review of NASA's Distributed Active Archive Centers (1999) / Chapter Skim
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6 Alaska SAR Facility DAAC
6 Alaska SAR Facility DAAC
Pages 109-130
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From page 109... ...
Its mission is to process, distribute, and archive SAR data collected at present exclusively from foreign spacecraft the European Remote Sensing Satellites 1 and 2 (ERS-1, 2~; the Japanese Earth Remote-Sensing Satellite-1 (JERS-1~; and the Canadian RADARSAT-1. As specified in Memoranda of Understanding between NASA and the foreign space agencies, only limited quantities of data are acquired by the Alaska SAR Facility and distributed to NASA-approved investigators.
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From page 110... ...
Its mission is to establish, operate, and maintain a receiving, image processing, analysis, and archiving facility for SAR data, which are collected exclusively by foreign spacecraft. JPL designed and installed the data acquisition and management system, and SAR data have been acquired and distributed since 1991.
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From page 111... ...
These data are essential for answering important scientific questions in a variety of disciplines, as well as for detecting and monitoring natural hazards. Further, SAR data become even more useful when combined with other remotely sensed and ground-based data.
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From page 112... ...
112 REVIEW OF NASA 'S DISTRIBUTED ACTIVE ARCHIVE CENTERS Formats The ASF DAAC uses an international standard developed by the Committee on Earth Observation Satellites, rather than the EOSDIS standard (Hierarchical Data Format [HDFI-EOS) , because SAR data are recorded as complex numbers, a data type not defined in the HDF-EOS standard.
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From page 113... ...
Similarly, the MOU between NASA and the National Space Development Agency of Japan allows NASA-approved investigators to request JERS data within the Alaska station mask. Prior to the failure of the on-board tape recorder, which was turned off in August 1997, limited amounts of data from outside the Alaska mask were also available from the DAAC.
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From page 114... ...
and a source of contention. Processing Strategy SAR data are processed on demand to Level 1 (Table 6.1)
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From page 115... ...
Long-Term Archive The ASF DAAC currently archives two copies of raw signal data, and will
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From page 116... ...
The issue of long-term custody of SAR data is particularly complex in this case because such a large fraction of the data is subject to restrictions imposed by foreign agencies, most of which are under pressure to recover their investment by charging a fee for the data. The contents and structure of any long-term archive holding other data products are tightly coupled with the processing strategy.
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From page 117... ...
The DAAC is quite aware of the problem, and the current reorganization is intended in part to solve it. Because in-mask data are more readily available to study polar processes, scientists at the Alaska SAR Facility and the Geophysical Institute are understandably concentrating on polar studies.
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From page 118... ...
In addition, a tracking and feedback system for monitoring the status of customer requests should be put in place, and statistics accumulated to provide metrics on the efficacy of this system. Software Support for Interferometry The panel praises the efforts of the science team at the Alaska SAR Facility to develop and distribute software for interferometric analysis of SAR data.
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From page 119... ...
researchers in future MOUs or purchases SAR data from foreign space agencies, the ASF DAAC will not be able to satisfy its user community any better in the future. For example, the panel heard numerous anecdotes that the Canadian Space Agency has placed severe restrictions on the amount of data U.S.
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From page 120... ...
data archiving facilities. In evaluating the DAAC's responsibilities within the production facilities, the panel tried to ignore the first component because data acquisition is the role of the Alaska SAR Facility, not the ASF DAAC.
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From page 121... ...
Consequently, the open tape racks will continue to serve as a data archive for at least the next several years. A prototype Level 0 processor has been procured, and the ASF DAAC, JPL developers, and ESDIS are currently determining how many will be necessary to attain a parallel processing capability that exceeds the raw signal data rate.
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From page 122... ...
In addition, browse capabilities would enable timely access to SAR data, thereby allowing their use in near-real-time applications, such as sea-ice forecasting and volcano monitoring. The User Working Group has been unable to get the DAAC management to devote people and resources to the development of a fully functional Web interface, and the panel agrees that greater use of the Web would help build the DAAC's user community.
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From page 123... ...
Organization The Alaska SAR Facility has two components: (1) a satellite-receiving ground station, which is responsible for data acquisition and antenna operation, and (2)
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From page 124... ...
. Responsibility and authority are split between the ASF DAAC and the JPL developers, exacerbating the normal tensions between operations and development.
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From page 125... ...
Nevertheless, the cost per Level 1 product, measured this way, has dropped substantially due to recent major increases in processing volume, which led to a large increase in the number of images flowing through the system. The increases in processing volume were related to the debugging of RADARSAT processing code, system changes and upgrades, and management decisions on the RADARSAT processing workload and user priorities.
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From page 126... ...
For example, scientists using SAR data for interferometry will frequently request digital elevation models (DEMs) from the EDC DAAC, and scientists interested in improving the DEMs may want to use SAR data from the ASF DAAC.
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From page 127... ...
Relation to the,IPL Developers Because the priorities of the ECS contractor have shifted to the AM-1 DAACs, ESDIS asked JPL to build an "interim solution" for processing data and to keep the system going until the ECS arrives. The JPL system, however, is incompatible with the ECS, and JPL developers argue that this is because they were neither required nor funded to make the two systems compatible or to make the ASF DAAC interoperable with the other DAACs.
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From page 128... ...
At present (except for a few airborne and shuttle-based experiments of limited duration) , it is collected exclusively by foreign space agencies, which, by agreement with NASA, allow limited amounts of SAR data to be acquired and distributed to NASA-approved investigators at below-commercial prices.
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From page 129... ...
the ASF DAAC is responsible for operations and for satisfying user needs; (2) the JPL developers are responsible for creating the data acquisition and processing systems; and (3)
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