Investigators probing the loss of space shuttle Columbia on Feb. 1 at
about 9 a.m. EST during re-entry will probably focus on structural- and
Data sent via telemetry from the orbiter are being scrutinized for
clues that could explain the vehicle's high-altitude break-up.
"We'll be poring over that data 24 hours a day for the foreseeable
future," said Ron Dittemore, NASA's space shuttle program manager.
Although details are still slowly emerging from NASA, it appears that
both voice and telemetry signals were lost shortly after Columbia
emerged from the "blackout" portion of the reentry. Milt Heflin, NASA's
Chief Flight Director, said "all vehicle data" were lost when Columbia
was at 207,135 ft. altitude and Mach 18.3.
At a mid-afternoon press briefing, Heflin
outlined a sequence of sensor readings and the loss of those readings:
- 8:53 a.m.
- Lost left wing inboard and outboard hydraulic temperature
- 8:56 a.m.
Left main tire and brake line temperatures
- 8:58 a.m.
EST - "Bondline"
temperatures from sensors in the vehicle structure were lost. Three of
these were on the left wing's inboard and outboard elevons.
- 8:59 a.m.
- Left main gear tire temperatures and pressures were lost; these
involved eight separate sensor measurements. At about this time, a tire
pressure alert was displayed to the shuttle crew, and was apparently
acknowledged verbally. This was believed to be the crew's last
U.S. officials identified several primary areas for investigators'
- The trajectory flown by the shuttle as it entered the upper
atmosphere. A too-steep approach could cause excessive heating of the
vehicle's structure, which could lead to its failure.
- Integrity of the orbiter's structure throughout the reentry.
- The flight controls, including both the reaction control system
(RCS) small thrusters that let astronauts fly the orbiter in space --
and aerodynamic surfaces, such as elevons on the aft edge of the wing,
which control the vehicle within the atmosphere.
- Possible damage to the thermal protection system (TPS), the white
and black tiles that protect the vehicle from excessive heat. During
Columbia's liftoff, a piece of insulation from the external fuel tank
fell off and hit the orbiter, apparently on the leading edge of the left
wing. Whether this impact significantly damaged protective tiles or not,
and had any effect on the shuttle orbiter's ultimate breakup during
re-entry, is being studied.
"We spent a goodly amount of time reviewing" film of the insulation
falling off, "and then analyzing" it to see "would there be any
consequences," Dittemore told reporters. "It was judged that that event
did not represent a safety concern. As we look at that now in hindsight,
and certainly we have, all the indications were on the left wing. We
can't discount that there might be a connection, but we can't rush to
judgment on it."
Information from several Defense Dept. space-monitoring facilities
will also be key to the investigation. Infrared sensors on U.S. Defense
Support Program (DSP) satellites are believed to have captured data that
could help NASA determine what was happening to Columbia during reentry.
Officials at the North American Aerospace Defense Command (NORAD) said
they are supporting NASA, but declined to comment on specifics.
NORAD provides missile warning and space-object tracking primarily
for defense purposes, but its Space Control Center in Cheyenne Mountain,
Colo., also monitors shuttle launches and on-orbit operations. Using a
number of space surveillance systems, NORAD, Air Force Space Command and
U.S. Strategic Command provide debris-avoidance information to NASA when
the shuttle is in space.