Landsat sale may boost satellites' usefulness

Landsat experts attending a ''results'' conference at NASA's Goddard Space Flight Center were ecstatic. Project scientist Vincent Salomonson called it a ''minor miracle.'' The new high-resolution sensors on Landsat 4 had sent back pictures so sharp you could see boats in the lake off Detroit and trace the taxiways at Dulles Airport outside Washington, D.C.

But for most users of Landsat data, the ''minor miracle'' is irrelevant.

It's not the fact that the radio transmitter serving this instrument has failed, at least temporarily, that disturbs users. They are concerned that its data cannot easily be compared with earlier Landsat images. Moreover, foreign users worry that their ground stations can't process the new kind of data.

What users want is assurance that the older type of Landsat data, upon which they rely, will continue to be available. W. Murray Strome of the Canada Centrecq for Remote Sensing made this clear at the Goddard meeting. Although he says he, too, admires the performance of the new instrument, he told his fellow experts, ''We have to figure out ways to make sure that the satellite . . . data continue to be available.'' He added, ''This is a very difficult problem.''

The Landsat system now owned and operated by the US government offers no such assurance. Happily for users, the Landsat 4 satellite does have an old-style instrument as well as the new sharper-eyed thematic mapper. But there are no follow-up plans.

It is this that concerns users, especially overseas users. Gordon Law, a space analyst with the congressional Office of Technology Assessment, notes that the much admired thematic mapper ''is a new thing.'' He adds, ''It will take at least five years of development to get anything useful. Meanwhile, the question is what will the follow-on be.'' For users, he explains, the name of the game is confidence that resource satellite data useful to them will continue to be available.

France seems ready to try to inspire such confidence. Its SPOT earth-resources satellite system should be inaugurated next year. It can deliver images as sharp as, or sharper than, the thematic mapper. It can produce 3-D stereo images as well. And SPOT data will be compatible with the old-style Landsat data.

Comsat, in its proposal to take over Landsat, also outlines plans for an ongoing resource satellite operation. It is an operation that, Comsat says, would enable the US to meet the expected French competition.

Thus, from a user's point of view, a Comsat's takeover of Landsat is the best prospect that the US will continue to meet Landsat customers' needs.

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