Background

The Earth is changing in ways that are not fully understood.

It will never be possible to comprehend the meaning of these changes without a clear and consistent record of observable surface phenomena.

In 1992, Congress directed the Department of the Interior to establish a permanent Government archive containing satellite remote sensing data of the Earth's land surface -- and to make these data easily accessible and readily available for study. Residing in the U.S. Geological Survey's (USGS) EROS Data Center near Sioux Falls, South Dakota, this collection of information is known legally as the National Satellite Land Remote Sensing Data Archive (NSLRSDA). It is a comprehensive, permanent, and impartial record of the planet's land surface derived from 40+ years of satellite remote sensing.

Only with satellites, which can cover large areas of the globe at regular intervals, is it practical to quickly understand such developments as deforestation, desertification, some kinds of environmental contamination, and natural hazards. Comparisons of satellite images from different times can make these phenomena quite clear.

Aside from the larger question of change at the global scale, NSLRSDA permits scientists to study water, energy, and mineral resource problems; to help protect environmental quality; and to contribute to prudent, orderly management and development of our Nation's natural resources.

NSLRSDA Holdings

Over the past three decades the Nation has invested money to acquire and distribute data worldwide from the Landsat series of satellites -- more than 630,000 gigabytes of which are held at the EROS Data Center. This collection from Landsats 1 through 5 and 7, including image data from both the Thematic Mapper (TM) and Multispectral Scanner (MSS) sensors, forms the core of NSLRSDA but does not complete it.

The archive includes more than 28,000 gigabytes of data from the Advanced Very High Resolution Radiometer (AVHRR) carried aboard National Oceanic Atmospheric Administration's polar orbiting weather satellites and more than 880,000 declassified intelligence satellite photographs.

In addition to these data, the planned archive holdings include data from:

• NASA's MODIS instrument, part of the Mission to Planet Earth's Earth Observing System
  
• ASTER, a cooperative effort between NASA and Japan's Ministry of International Trade and Industry
  
• The Shuttle Radar Topography Mission (SRTM), a joint venture of NASA and the National Imagery and Mapping Agency
  
• DeClass II

The total holdings by the year 2005 are projected to be 1,400,000 gigabytes of data -- an ocean of information stored as bits and bytes on computer media.

Challenge

Managing the exponential growth of the data holdings is a daunting task in itself, but just the beginning of the challenge emerging over the coming decade or so. This is because a primary objective of NSLRSDA is to distribute data on demand to a worldwide community of scientific users.

The USGS EROS Data Center is a world leader not only in techniques of archiving remotely sensed data, but also in getting the data to end users quickly, in forms they can use, at costs they can bear. Every advance in on-line distribution, in storage media, in applications research, or in cost-saving delivery technologies means more people can use the data. As demand increases, user expectations about delivery times and efficiency rise. One important element of the USGS response will surely be to establish external partnerships with other government agencies, the private sector, and international organizations.

Data Access