The Landsat 4 satellite is returning the best photographs of Earth ever taken from space, providing geologists, farmers and environmentalists with new information about mineral deposits, crop yields and sources of air and water pollution.
The photographs being beamed back by Landsat 4, which was put into orbit last fall, have 10 times the clarity of the three previous Landsats, which were launched in 1972, 1975 and 1978. From an altitude of 438 miles, the new Landsat also can distinguish four times as many shades of color, such as the subtle color difference between snow and clouds, and with its three infrared cameras can identify objects on the ground by gauging temperature differences.
"Our new Landsat can distinguish very nicely between rice fields and soybean fields that lie right next to each other," Vincent Salomonson, Landsat project scientist at the Goddard Space Flight Center, told a news conference yesterday. "The older satellites could never do that."
Landsat 4's seven cameras (compared with four on the older Landsats) can resolve details on Earth that are no more than 90 feet wide, meaning they can pick out individual buildings and landmarks in any city. In a photograph of Washington displayed at the news conference, the Washington Monument, the Capitol, the Tidal Basin, the Reflecting Pool and the Pentagon could be discerned easily with the naked eye.
The same photograph also took in the entire city of Baltimore, parts of Chesapeake Bay and made the Capital Beltway in Virginia distinguishable from the same road in Maryland because of the paving material: concrete in Maryland and asphalt in Virginia. Office buildings with gravel roofs could be distinguished from office buildings with metal roofs.
Fall-colored trees were distinguishable from trees that were still green. Silt and sediment pouring from rivers into the Atlantic Ocean were so discernible that scientists could tell if they were polluted with chemicals. Scientists could also see whether smoke pouring from factories was polluted.
The satellite's scanners detected changes in the clay minerals near the Earth's surface that often are telltale clues to the whereabouts of buried mineral deposits.
Mark Settle, Landsat program scientist, said, "It's going to be a great boon to geologists. This satellite can even discriminate the ages of most rocks on the Earth."