ENHANCED COLUMBIA PICTURE AIDS PROBE.

Byline: Charles F. Bostwick Staff Writer

Aviation Week and Space Technology magazine has computer-enhanced a photograph of space shuttle Columbia's re-entry over California that reveals a sudden expansion and color change in its trail - then a bright spot - at roughly the time NASA noted unusual readings from the spacecraft's sensors.

The time-lapse photograph was taken by Daily News freelance photographer Gene Blevins from north of Bishop at 5:54 a.m. Feb. 1, about two minutes after NASA said sensors on the left wing showed an unusual rise in temperature.

``That's one of the mysteries to be solved - what happened early. It points you in the direction to look,'' NASA Johnson Space Center spokesman Greg Jurls said Friday.

Trying to determine what happened to the shuttle, National Aeronautics and Space Administration officials asked for and received copies of Blevins' time-lapse photographs - one taken digitally, one on traditional film.

The space agency has received thousands of still and video images from professional and amateur photographers, some of them showing bright spots like Blevins' photo and others showing what appear to be objects breaking off the spacecraft, which disintegrated, killing all seven on board.

``It's got to be some piece of tile or structure. The question is what actually fell off where and why,'' said Craig Covault, a senior editor for Aviation Week and Space Technology magazine, which is publishing Blevins' photo in its edition that comes out today.

Aviation Week, an aerospace industry publication, enlarged and filtered Blevins' digital photograph to bring out the change in color in Columbia's trail. The enhanced photograph clearly shows a bright spot.

``That's right where I started seeing some stuff breaking off,'' Blevins said Friday of the color change.

After he turned off his camera, but before Columbia passed out of sight over Nevada, Blevins said he watched a bright spot detach from the larger image he knew was Columbia.

``It looked like it was dropping a flare out of a bomb bay,'' Blevins said.

Because so many amateur astronomers had been out before dawn, watching the re-entry from throughout the Western United States, NASA set up a special e-mail address for citizens to send it images.

``No other aviation accident has been witnessed by as many people as this one ... certainly thousands of people across six states, and quite a few of those were pointing all sorts of cameras,'' Covault said.

The images will give investigators more information to analyze about what might have gone wrong, he said.

Speculation has centered on possible damage to the heat-resistant silica tiles that cover much of the shuttles' exterior, protecting it from 3,000-degree temperatures as it re-enters the earth's atmosphere.

NASA officials are examining whether foam insulation that fell off the external fuel tank during liftoff on Jan. 16 might have damaged tiles on the shuttle's left wing.

Officials say they have reached no conclusions, but the unusual sensor readings occurred on the left wing and are consistent with tile damage allowing heat through to the wing structure, weakening it.

NASA said sensors on the left wing's landing gear brake line showed an unusual rise in temperature at 5:52 a.m. PST last Saturday, as Columbia flew over California at about 220,000 feet and 15,000 mph. Left-wing temperature readings ceased entirely five minutes later.

Amateur astronomer Paul Maley, who in 1984 took the first photograph of a shuttle re-entry and who has worked for private companies at NASA's Johnson Space Center for more than 30 years, cautioned against making quick assumptions about what the photographs show.

Earlier shuttle re-entry trails also showed variations as the spacecraft traveled through the various layers of the earth's atmosphere, he said.

But Maley said he saw a video taken from western Nevada, at about the same time Blevins was photographing the shuttle, that appears to show an object detaching.

``No one really knows for sure what was going on up there,'' Maley said.

The western Nevada video was shot near Reno, by amateur astronomer Jay Lawson, who estimates Columbia was a few miles inside the Nevada border when a bright flash occurred, then an object dropped away.

``In my video you can see a real bright flash and it's incredibly obvious something went horribly wrong,'' Lawson said.

CAPTION(S):

2 photos

Photo:

(1 -- 2 -- color -- ran in Valley edition only) Daily News freelance photographer Gene Blevins shot the space shuttle Columbia streaking across the sky, above, not long before the ship broke apart over Texas. Aviation Week and Space Technology magazine enhanced the photo, top, to show the unusual pink trail starting on top of the normal white trail.

Gene Blevins/Special to the Daily News