INTRODUCTION

The GSFC DAAC was created in 1993 to archive and distribute data related to climate change, atmospheric dynamics, global biosphere, hydrology, and upper atmospheric chemistry (Box 3.1). Its roots are in the NASA Climate Data System and the Pilot Land Data System. The first data sets archived by the DAAC included data collected by the Total Ozone Mapping Spectrometer (TOMS) and the Nimbus-7 Coastal Zone Color Scanner (CZCS). Today the DAAC manages data sets from a variety of missions and experiments, supports the Goddard Data Assimilation Office, and also manages some of the hydrology holdings of the Marshall Space Flight Center DAAC, which was closed in 1997. With a staff of 114 and current holdings of 4 TB, the GSFC DAAC is one of the largest DAACs in the EOSDIS system.

In the EOS AM-1 era, DAAC holdings will increase in size by a factor of 500 (Box 3.1). The Sea-Viewing Wide-Field-of-View Sensor (SeaWiFS) and Tropical Rainfall Measuring Mission (TRMM) instruments, which have already been launched, will produce 65 TB of data, and MODIS, which will be launched in early 1999, will produce nearly 2,000 TB. To prepare for these large data streams, the DAAC is staffing up. Approximately 40 EOSDIS Core System (ECS) contractors have been added to process MODIS data, and about 12 permanent staff have been added to manage DAAC operations. The average budget for the DAAC, which includes DAAC personnel and functions, civil servants, ECS contractors, and ECS-supplied hardware, is about $15 million per year.

Managing the enormous MODIS data stream poses daunting managerial and technological challenges for the GSFC DAAC. Of most concern is whether the information system, particularly the ingest system, can be scaled up to accommodate increasing loads (see "Technology," below). To prepare for the new data streams, the DAAC will start "day-in-the-life" exercises and operations rehearsals several months before launch. As of June 1998, the ECS was still not ready for day-in-the-life exercises, but so far, it has been sufficient to test the science algorithms. Delays in the launch of the EOS satellites will provide additional preparation time.

The Panel to Review the GSFC DAAC held its formal site visit on October 20–21, 1997. To ensure that its report and recommendations reflect recent developments, several panel members visited the DAAC again in June 1998. The following report is based on findings from both visits and e-mail discussions with DAAC managers in July and September 1998.

HOLDINGS

Even before the launch of TRMM and AM-1, the GSFC DAAC has been managing and distributing numerous data sets of substantial size. These include in particular the Advanced Very High-Resolution Radiometer (AVHRR) and the



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