Government

The following material provides brief accounts of all those comets seen between 1800 and 1997 which attained an observed maximum brightness of +2 or greater, together with a few additional objects of special interest. In general, the material covers only the period of the comet's apparition during which the object was visible to the unaided eye. The celestial position, approximate magnitude, and physical appearance of each comet is chronicled. Since meaningful cometary photometry did not begin until shortly after 1900, magnitudes cited prior to that time must be considered rather approximate. In many cases these have been derived from a combination of contemporary physical descriptions of the object, the orbital circumstances, and the compiler's 40 years of comet observing experience.

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.

The Office of Coast Survey is a component of the National Ocean Service which is part of the National Oceanic and Atmospheric Administration, (NOAA). Coast Survey has a long history as the oldest scientific organization in the United States, having its foundation as far back as 1807. Today the Office of Coast Survey is known for the useful and necessary navigational products which are required for the safe and efficient maritime commerce in and out of our Nation's ports.

Digitisation of both printed books and graphic material is well under way. For technical and economic reasons, documents have been processed primarily in image mode to begin with. Most of the texts selected for digitisation are out-of-copyright material making up an encyclopaedic collection on the human and social sciences which includes original material, peer reviews, reference works and a collection of journals which are either major research references or difficult to find elsewhere.

Astronomy Picture of the Day Archive

In October of 1963 the US Air Force launched the first in a series of satellites inspired by a recently signed nuclear test ban treaty. Signatories of this treaty agreed not to test nuclear devices in the atmosphere or in space. These "Vela" (from the Spanish verb velar, to watch) series satellites were part of an unclassified research and development program whose goal was to develop the technology to monitor nuclear tests from space and give the US a means of verifying the conditions of the treaty. The satellites were launched and operated in pairs with two identical satellites on opposite sides of a circular orbit 250,000 kilometers in diameter (about a 4 day orbit) so that no part of the earth was shielded from direct observation.

Following in the footsteps of the famous April 1920 'Great Debate' between Harlow Shapley and Heber Curtis, this series of debates among leaders in the astronomical community highlight major quests in astronomy and astrophysics in an open forum at the turn of the millennium.

On time explores the changing ways we have measured, used, and thought about time ove the past three hundred years.

The Federal Aviation Administration (FAA), National Aeronautical Charting Office (NACO), publishes and distributes United States government civil aeronautical charts and flight information publications. Public sales of these charts and publications are available through a network of Chart Agents conveniently located at or near principal civil airports.

NIMA provides timely, relevant, and accurate Geospatial Intelligence in support of national security.