USGS shutting down satellites

Although sad to see them go, the U.S. Geological Survey has announced that it is decommissioning two satellites that provide digital images of the Earth after a company operating them determined it could no longer do so for free.

Landsat 4 and Landsat 5, launched in 1982 and 1984, respectively, will be shut down no later than June 30, said USGS spokesman Ray Byrnes. They were part of a series of satellites — the first of which was launched in 1972 — that have compiled hundreds of thousands of images documenting changes to the Earth. The latest satellite, Landsat 7, was launched in 1999. In 1993, Landsat 6 never reached orbit.

Though designed to work for only two years, Landsats 4 and 5 "kept on ticking," Byrnes said. "No one expected to be operating the satellites at this stage."

Although Landsat 4's communications hardware for transmitting data to ground receiving stations failed several years ago, the satellite was still useful for testing software changes intended for Landsat 5, such as those to fix the Year 2000 problem.

Landsat 5 is still able to provide images using several backup subsystems. However, Space Imaging Inc., a Thornton, Colo.-based satellite imagery provider that operated the satellites, notified USGS in February that it could no longer do so without losing money. The commercial market favors imagery more detailed than Landsat satellites can provide, Byrnes said.

"Everyone had hoped 5 would keep flying on Space Imaging's watch," he said. But with the company unable to continue and with no money budgeted to operate the satellites on its own, USGS has no choice but to decommission them, he said.

Having been aloft so long, there's not enough fuel left to bring them down quickly, he said. Instead, they will be moved out of their current orbits — the same track as Landsat 7 — and into a slowly degrading orbit. They should fall into the Earth's atmosphere and burn up in about five years, Byrnes said.

Scientists and others use Landsat images, hundreds of thousands of which are stored at USGS' Earth Resources Observation Systems Data Center in South Dakota, to study natural and human-caused changes to the Earth.

Eventually, all the images collected by Space Imaging will be transferred to the data center, Byrnes said.

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