Time-stamped coding on the tape, which engineers could see as they copied it, showed that there is some kind of imprint of data until 18 seconds past 9 a.m. EST (1400 GMT), the independent board investigating the tragedy said in a statement released Thursday.

That's about 14 seconds later than the final two-second burst of telemetry radioed from Columbia, according to the latest official timeline released by NASA.

"After that time, the tape is blank," the statement said.

After copying the tapes today, KSC workers are to ship the tapes to JSC by tomorrow and work to analyze the data will begin this weekend.

"It will be Monday before we know whether or not it's giving us good, valid data that is of a useable nature for the investigation," Hartsfield said.

The data and the way it is handled is more complicated than the way stream of information are radioed to Earth during a shuttle mission, he said.

"In Mission Control we have flight controllers that can tell you in a split second whether it's valid data and what it means. It's much more tedious than that."

If all goes according to the anticipated schedule, it will be the end of next week before the tape's data will be understood and deemed valid enough to begin adding its contents into the official timeline.

Scott Hubbard of the Columbia Accident Investigation Board said Wednesday that the OEX tape offered a potential "gold mine" of information about the shuttle's last minutes.

Hubbard said that in "a perfect world" the recorder will have stored 721 various measurements from sensors that were installed all over Columbia to support the ship's early test flights, which began in 1981.

The measurements would supplement those radioed to Mission Control that come from a different set of sensors.

Unfortunately the sensor wiring in the left wing follows the same path as the other sensors that stopped working in the minutes before Columbia's loss, Hubbard said.

So it's possible the amount of useful information could be limited if those wires also were melted by the breach in the wing.

"If all the data were there that I described of course this would be a gold mine of information that could lead us to a much, much better understand of what happened throughout the vehicle, and particularly on the left wing," Hubbard said.

A breach of still unknown origin allowed dangerous hot gases inside the left wing, which caused sensor wires and the aluminum structure within the wing to melt. That, in turn, led to the loss of Columbia's structural integrity and disaster ensued.

Late last week, the recently found recorder was taken to the Imation Corporation's Discovery Technology Center in Oakdale, Minnesota -- a firm specializing in data storage and handling. Throughout last weekend, a team of NASA officials and company experts completed cleaning and stabilization of the recorder's magnetic tape.

According to Imation, in opening the recorder it was found that most of the tape was still intact on both the supply reel and the take-up reel inside the device. The tape, however, had broken between the two.

A portion of the tape was stretched or wrinkled on both ends of the take-up and supply reels.

According to Imation, most of the tape was in fairly good condition on visual inspection. There was some contamination inside the recorder from dirt and water that had accumulated on the tape from its impact on the ground.

The tape is one-inch wide #799 instrumentation tape, which is a magnetic data recording tape made specifically for aerospace and government applications.

The tape was mounted on two 14-inch reels, one supply reel of unrecorded tape and a take-up reel for tape that had recorded information.

Using a non-destructive process, Imation experts were able to pinpoint the place on the tape where it had stopped.

Working with a NASA-approved approach that would minimize any chance of data loss, a team began cleaning the tape by hand-immersing the tape multiple times in a filtered de-ionized water bath.

The tape was then dried with a lint free cloth and nitrogen, allowed to air-dry overnight, and wound to the appropriate tension on the original hub with new flanges.

The recorder and its tape were then shipped to Florida for copying.