GMT Milestone Entry Event Remarks

February 1st 2003

13:10:39 TIG-5 APU 2 Start - Low Press

13:15:30 TIG OMS TIG

13:18:08 OMS End of Burn

13:26:09 FRCS Dump Start

13:27:12 FRCS Dump Complete

13:31:25 EI-13 APU 1 Start - Low Press

13:31:29 APU 3 Start - Low Press

13:31:57 APU 1 Norm Press

13:31:59 APU 2 Norm Press

13:32:01 APU 3 Norm Press

13:32:29 SSME Engine Stow sequence start Sequence was completed with closure of TVC Iso Vlv 1 at 13:33:30 GMT.

13:39:09 EI-5 (304 PRO) Mach 24.40

13:39:11 Speedbrake close & Rudder cmded to zero

13:44:09 EI Entry Interface (400,000 Ft) Mach 24.57

13:46:48 Qbar 0.5 psf Mach 24.66

13:47:52 Qbar 2.0 psf Elevon, BF active Mach 24.66

13:49:07 ISELECT = 2 Closed-Loop Guidance

13:49:16 Qbar 10 psf Roll Jets Deactivated Mach 24.57

13:49:32 Initial Roll Mach 24.51

13:50:00 / 43 Five events of unexpected Return link comm drop-out.

Event 1 - 13:50:00 (1 sec);

Event 2 - 13:50:04 / 06;

Event 3 - 13:50:16/22:

Event 4 - 13:50:25/28;

Event 5 - 13:50:42 (1 sec)

On upper left aft antenna (TDRS 171/W). S-Band comm drop-outs considered out-of-family based on comparison with previous 102 flight data at 39 degrees, into KSC, descending node and similar look angles to TDRS.

13:50:30 1st Entry Heating Indication Nominal Rise in Center Line Bond Temp (1) due to Entry Heating Aft fuselage center bottom bond line

13:50:53 Start of Peak Heating Determined by analysis

13:51:19 / 13:52:49 Remote sensors indicate off-nominal external event - earliest known event Note:

L2L jet firing at 13:51:45.38 / 51.45.62.

L3L jet firing at 13:51:45.36 / 41.45.60.

R2R/R3R jet firings between 13:52:08 / 52:15 during data loss (firings determined by inj temp). R2R/R3R jet firings between 13:52:24 / 52:32 during data loss (firing determined by inj temps). (RCS data taken from Atlas analysis and plotted data).

13:51:46 Inertial sideslip angle (Beta) goes and stays Negative until LOS While the magnitude of the observed Beta is not outside the flight history (41G & 42), the almost linear negative ramp prior to the first roll reversal is not consistent with other flights reviewed. This is consistent with a negative rolling and yawing torque on the vehicle.

13:52:05 First clear indication of off-nominal aero increments Delta yawing moment coefficient only (as compared to nominal aero). Derived by analysis.

13:52:09 / 15 Unexpected Return link comm drop-out (Event 6) On upper left aft antenna (TDRS 171/W). S-Band comm drop-out considered out-of-family based on previous flt data (same remarks as seq # 20.3 above).

13:52:15 2nd Entry Heating Indication Nominal Rise in Center Line Bond Temps (2) due to Entry Heating Mid Fus Lower "Mid" Skin Temp

Mid Fus Bottom Center Bond Line Temp X1214

13:52:17 Approx Vehicle Ground Location:

39.0 N / -129.2 W Altitude 236,800 ft / Mach 23.6 - Over the Pacific Ocean, approx 300 miles West of California Coastline Approx vehicle position when first off-nominal data was seen; Data source: STS-107 GPS Trajectory Data

13:52:17 LMG Brake Line Temp D - On wheel well inbd sidewall (aft of sw vlvs) - Start of off nominal trend Initiation of temp rise - off nominal based on rise rate comparison with flight experience.

13:52:25 / 31 Two events of unexpected Return link comm drop-out

Event 7 - 13:52:25/26;

Event 8 - 13:52:29/31

On upper left aft antenna (TDRS 171/W). S-Band comm drop-out considered out-of-family based on previous flt data (same remarks as seq # 20.3 above).

13:52:32 Supply H2O dump Nozzle temps A/B show temporary increase in temp rise rate (15 second duration of high rise rate). High rise rate is bounded by data loss. Increase in rise rate not observed on previous flights. GMT shown indicates start of initial rise duration. Reference event seq no. 26.6 for termination of event.

13:52:32 Vacuum vent temp shows temporary increase in temp rise rate (23 second duration of high rise rate). High rise rate is bounded by data loss. Increase in rise rate not observed on previous flights. GMT shown indicates start of initial rise duration. Reference event seq no. 26.65 for termination of event.

13:52:41 LMG Brake Line Temp A - On strut facing MLG door - start of off nominal trend Initiation of temp rise - off nominal based on rise rate comparison with flight experience.

13:52:41 Left Main Gear Brake Line Temp C - Start of off nominal trend Unusual Temp Rise

13:52:47 Supply H2O dump Nozzle temps A/B return to typical rise rates. High rise rate is bounded by data loss. GMT shown indicates end of initial rise duration. Temp took additional 48 seconds to return to nominal temp rise (53:35 GMT).

13:52:49 / 55 Unexpected Return link comm drop-out (Comm event 9) On upper left aft antenna (TDRS 171/W). S-Band comm drop-out considered out-of-family based on previous flt data (same remarks as seq # 20.3 above).

13:52:55 Vacuum vent temp returns to typical rise rate. High rise rate is bounded by data loss. GMT shown indicates end of initial rise duration. Temp took additional 40 seconds to returns to nominal temp rise (53:35 GMT).

13:52:56 Left INBD Elevon Lower Skin Temp - Start of off nominal trend Temp trending down

13:52:59 Left INBD Elevon Lower Skin Temp - OSL

13:53:01 First clear indication of off-nominal rolling moment increment Start of steady (-) growth in roll moment, derived by analysis

13:53:02 Hyd Syst 1LH INBD Elevon Actr Ret Ln Temp - start of off nominal trend

Hyd Syst 3 LOE Ret LN Temp - start of off nominal trend Temp trending down

13:53:10 Hyd Syst 3 LOE Ret LN Temp - OSL OSL was preceded by Nominal Temp rise

13:53:11 Hyd Syst 1LH INBD Elevon Actr Ret Ln Temp - OSL OSL was preceded by Nominal Temp rise

13:53:24 Alpha Modulation Angle of attack modulation active

13:53:26 Approx Veh Grd Location:

38.7 N / -123.5 W Altitude 231600 ft / Mach 23.0 - Crossing the California Coastline Data source: STS-107 GPS Trajectory Data

13:53:31 / 53:34 Hyd Syst 1 LOE Return Line Temp - OSL OSL was preceded by Nom Temp rise plus data loss 3 sec's prior to event

13:53:32 / 34 Unexpected Return link comm drop-out (Comm event 10) On upper left aft antenna (TDRS 171/W). S-Band comm drop-out considered out-of-family based on previous flt data (same remarks as seq # 20.3 above).

13:53:34 / 55:57 3rd Entry Heating Indication Nominal Rise in Center Line Bond Temps (3) due to Entry Heating 13:53:34 - V09T1016A (Mid Fus Bot Port BL T X 620);

13:54:00 - V09T1022A (Mid Fus Bot Port BL T X 777);

13:55:57 - V09T1624A (Fwd Fus Lwr Skin Bot CL T)

13:53:34 Hyd Sys 2 LIE Return Ln Temp - Start of Off Nominal Trend Temp trending down

13:53:36 Hyd Sys 2 LIE Return Ln Temp - OSL

13:53:44 / 48 Debris #1 - First report of debris observed leaving the Orbiter Seen just aft of Orbiter envelope. No evidence of RCS jet firings (ref Atlas data and plots).

13:53:46 / 50 Debris #2 - Second report of debris observed leaving the Orbiter Seen just aft of Orbiter envelope. No evidence of RCS jet firings (ref Atlas data and plots).

13:53:46 LMG Brake Line Temp A - On strut facing MLG door - Start of off nominal trend (temp rise rate change) Temp rise rate change from 1.4 F/min to 5.5 F/min and increasing to LOS

13:53:54 / 58 Debris #3 - Third report of debris observed leaving the Orbiter. Event followed by momentary brightening of plasma trail. Seen just aft of Orbiter envelope. No evidence of RCS jet firings (ref Atlas data and plots).

13:54:00 / 04 Debris #4 - Fourth report of debris observed leaving the Orbiter Seen just aft of Orbiter envelope. No evidence of RCS jet firings (ref Atlas data and plots).

13:54:07 / 11 Debris #5 - Fifth report of debris observed leaving the Orbiter Seen just aft of Orbiter envelope. No evidence of RCS jet firings (ref Atlas data and plots).

13:54:10 LMG Brake Line Temp B - Start of off nominal trend Temp Increase

13:54:14 / 22 Unexpected Return link comm drop-out (Comm event 11) On upper left aft antenna (TDRS 171/W). S-Band comm drop-out considered out-of-family based on previous flt data (same remarks as seq # 20.3 above).

13:54:20 Start of slow aileron trim change GMT is approximate (13:54:20 +/- 10 seconds)

13:54:20 Reversal in growth trend of derived roll moment coefficient Observed moment changed from a negative slope to positive slope. Derived by analysis.

13:54:22 M-FUS LT BL Temp at x1215 - start of off nominal trend (increased rise rate) Unusual Temp Rise (Rise rate higher than STS-109 & 87). Rise rate increased from 1 F/min (typical) to 7.6 F/min.

13:54:22 LH Aft Fus Sidewall Temp at x1410 - start of off nominal trend (increased rise rate) Unusual Temp Rise (Rise rate higher than STS-109 & 87). Rise rate increased from 2.7 F/min (typical) to 5.5 F/min.

13:54:24 Sys 3 Left Main Gear Strut Actuator Temp - start of off nominal trend Unusual Temp Rise

13:54:25 Approx Veh Grd Location:

38.3 N / -119.0 W Altitude 227400 ft / Mach 22.5 - Crossing the California / Nevada State Line Data source: STS-107 GPS Trajectory Data

13:54:26 S-Band switched from upper left aft antenna to upper right aft antenna TDRS 171/W

13:54:33.3 / 33.9 Flash #1 - Orbiter envelope suddenly brightened (duration 0.3 sec), leaving noticeably luminescent signature in plasma trail

Note: R3R and R2R 0.24 sec jet firings occurred at 13:54:33.52 / 33.76 and 13:54:33.54 / 33.78 respectively (ref: RCS Atlas analysis and plots).

13:54:35 / 37 Debris #6 - Very bright debris seen leaving the Orbiter Seen just aft of Orbiter envelope. Also, reference RCS jet firing note in item # 36.5 above. Debris events 6 and 14 are visually the biggest, brightest events and therefore may indicate the most significant changes to the Orbiter of the western debris events.

13:54:53 MLG LH Outbd Wheel Temp - start of off nominal trend 2 bit flips up (ref #56.5 when temp starts to trend down)

13:55:04 / 10 Debris #7 - Seventh report of debris observed leaving the Orbiter Seen just aft of Orbiter envelope. No evidence of RCS jet firings (ref Atlas data and plots).

13:55:12 Sys 3 LMG Brake Sw Vlv Ret Line Temp (FWD) - start of off nominal trend Temp Increase

13:55:21 Drag 11 fps2 Drag Measurement Incorporation Mach 21.nn

13:55:21 / 27 Debris #8 - Eighth report of debris observed leaving the Orbiter. Event was followed by momentary brightening of plasma trail. Seen just aft of Orbiter envelope. No evidence of RCS jet firings (ref Atlas data and plots).

13:55:25 / 29 Debris #9 - Ninth report of debris observed leaving the Orbiter. Event was followed by multiple secondary plasma trails. Seen just aft of Orbiter envelope. No evidence of RCS jet firings (ref Atlas data and plots).

13:55:26 / 30 Debris #10 - Tenth report of debris observed leaving the Orbiter Seen well aft of Orbiter envelope. No evidence of RCS jet firings (ref Atlas data and plots).

13:55:30 Remote sensors indicate off-nominal external event GMT is approximate. Preliminary match to debris shedding seen in video from Ivins, UT (Debris #10). Strong confidence that this is an off-nominal event. No evidence of RCS jet firings (ref Atlas data and plots).

13:55:32 Approx Veh Grd Location:

37.4 N / -114.1 W Altitude 223400 ft / Mach 21.8 - Crossing the Nevada / Utah State Line Data source: STS-107 GPS Trajectory Data

13:55:33 / 35 Return link comm drop-out (Comm event 12) First comm drop out after switched to upper right aft antenna (TDRS 171/W). While uncommon to have a drop out at this point, inconclusive if drop-out is off-nominal based on previous flt data.

13:55:36 / 42 Debris #11 - Eleventh report of debris observed leaving the Orbiter Seen well aft of Orbiter envelope. No evidence of RCS jet firings (ref Atlas data and plots).

13:55:41 Mid Fus Port (Left) Sill Longn Temp at x1215 - start of off nominal trend Unusually high temp rise with respect to STS-87 & 109. Went to 2.6 F/min from 0 F/min.

13:55:45 / 49 Debris #12 - Twelfth report of debris observed leaving the Orbiter. Event was preceded and followed by secondary plasma trails. Seen aft of Orbiter envelope. No evidence of RCS jet firings (ref Atlas data and plots).

13:55:55 Approx Veh Grd Location:

37.0 N / -112.4 W Altitude 222100 ft / Mach 21.5 - Crossing the Utah / Arizona State Line Data source: STS-107 GPS Trajectory Data

13:55:55 / 59 Debris #13 - Thirteenth report of debris observed leaving the Orbiter. Event was followed by momentary brightening of plasma trail adjacent to debris. Seen well aft of Orbiter envelope. No evidence of RCS jet firings (ref Atlas data and plots).

13:55:58 / 56:00 Debris #14 - Very bright debris observed leaving the Orbiter. Seen just aft of Orbiter envelope. Debris events 6 and 14 are visually the biggest, brightest events and therefore may indicate the most significant changes to the Orbiter of the western debris events.- No evidence of RCS jet firings (ref Atlas data and plots).

13:56:00 / 03 Return link comm drop-out (Comm event 13) On upper right aft antenna (TDRS 171/W). While uncommon to have a drop out at this point, inconclusive if drop-out is off-nominal based on previous flt data.

13:56:02 Qbar 40 psf Aft RCS Pitch Jets Deactivated

13:56:03 Left Lower Wing Skin Temp - start of off nominal trend Temp reading trending down (potential sensor/wire damage)

13:56:09 / 13 Debris #15 - Fifteenth report of debris observed leaving the Orbiter. Seen just aft of Orbiter envelope. Nearest jet firings: R2R jet firing at 032:13:56:17.30 / 56:17.54 for 0.24 seconds, & R3R jet firing at 032:13:56:17.28 / 56:17.52 for 0.24 seconds. (Ref: RCS Atlas data analysis and plots).

13:56:16 Hyd Sys 1 LMG UpLK Actr Unlk Ln Temp - Temp rise rate change Temp rise rate change from 0.7 F/min (nominal) to 3.9F/min and increasing to LOS

13:56:17 Sys 3 LMG Brake Sw Vlv Ret Line Temp (FWD) - Temp rise rate change Temp rise rate change from 1.5 F/min to 8.8 F/min (stayed at this rate to LOS)

13:56:20 LMG Brake Line Temp C - Temp rise rate change Temp rise rate change from 1.3 F/min to 9.9 F/min (stayed at this rate to LOS)

13:56:22 LMG Brake Line Temp B - Temp rise rate change Temp rise rate change from 2.1 F/min to 9.1 F/min increasing to LOS

13:56:24 Left Upper Wing Skin Temp - start of off nominal trend Temp reading trending down (potential sensor/wire damage)

13:56:30 1st Roll Reversal Initiation Mach 21.13

13:56:45 Approx Veh Grd Location:

36.1 N / -109.0 W Altitude 219000 ft / Mach 20.9 - Crossing the Arizona / New Mexico State Line Data source: STS-107 GPS Trajectory Data

13:56:53 Sys 3 Left Main Gear Strut Actuator Temp - Temp rise rate change Temp rise rate change from 1.7 F/min to 12.9 F/min (stayed at this rate to LOS)

13:56:55 Roll Reversal #1 1st Roll Reversal Complete Mach 20.76

13:56:55 / 57 Return link comm drop-out (Comm event 14) On upper right aft antenna (TDRS 171/W). While uncommon to have a drop out at this point, inconclusive if drop-out is off-nominal based on previous flt data.

Note: No further comm drop-out events are listed in the timeline thru LOS, since they are not considered out-of-family at this time.

13:56:58 IMU Velocity Increase Reflects accelerations imparted during roll reversal. Same signature observed on STS-109. Nominal event.

13:57:nn Bodyflap deflection up 3 degrees Matches nominal aero simulation

13:57:19 / 29 Debris # 16 - Very faint debris observed leaving just aft of Orbiter (occurred over NM) Observations by personnel from the Starfire Optical Range (Kirtland Air Force Base, NM).

Note: nearest jet firings:

L2L jet firing at 032:13:56:54.71 / 57:01.12 & 032:13:57:46.35 / 57:53.12 &

L3L jet firing at 032:13:56:54.66 / 57:01.07 & 032:13:57:46.33 / 57:53.10 (all 4 occurred during data dropouts & were determined based on injector temps alone).

Also, R2R at 032:13:57:43.94 / 57:44.42 & R3R at 032:13:57:43.92 / 57:44.40 for 0.48 secs ea. (Ref Atlas data analysis and plots.)

13:57:19 MLG LH Outbd Tire Pressure 1 - start of off nominal trend Bit flip up - off nominal thru comparison with previous flights

13:57:24 MLG LH Outbd Tire Pressure 2 - start of off nominal trend Bit flip up - off nominal thru comparison with previous flights

13:57:43 Left Upper Wing Skin Temp - OSL

13:57:54 Sys 2 LH Brake Switching Vlv Return Temp (AFT) - start of off nominal trend Temp increase

13:57:53.7 / 55.7 Flare 1: Asymmetrical brightening of Orbiter shape observed (occurred over NM) Observations by personnel from the Starfire Optical Range (Kirtland Air Force Base, NM).

Note: nearest jet firings:

Same as seq no. 49.55 plus

L2L at 032:13:58:00.50 / 01.46 & L3L at 032:13:58:00.48 / 01.44 (in both cases there was no start up data, but good tail off/shutdown) - 0.96 sec pulse each.

Also, R2R at 032:13:58:03.18 / 09.16 & R3R at 032:13:58:03.18 / 09.16 - (in both cases firings occurred during data dropouts and were determined by injector temps). (Ref Atlas analysis and plots.)

13:57:59.5 / 58:01.5 Flare 2: Asymmetrical brightening of Orbiter shape observed (occurred over NM) Observations by personnel from the Starfire Optical Range (Kirtland Air Force Base, NM).

Note: same jet firing information as for event seq no.s 49.55 & 53.5. (Ref Atlas analysis and plots.)

13:58:03 Start of "sharp" aileron trim increase Mach 19.79; GMT is approximate (13:58:03+/-10 seconds)

13:58:09 Increase in derived rolling and yawing moment increments Sustantial increase in observed growth rate of both roll and yaw moment increments. Derived by analysis.

13:58:16 LMG Brake Line Temp D - Temp rise rate change Temp rise rate change from 0.9 F/min to 11.7 F/min (stayed at this rate to LOS)

deleted

13:58:20 Approx Veh Grd Location:

34.2 N / -103.1 W Altitude 209800 ft / Mach 19.5 - Crossing the New Mexico / Texas State Line Data source: STS-107 GPS Trajectory Data

deleted

13:58:32 MLG LH Outbd Tire Pressure 1 - pressure trending down (to OSL) Trending to OSL following 7 sec LOS (initiation time not exact) - ref #60

13:58:32 MLG LH Inbd Tire Pressure 1 - pressure trending down (to OSL) Trending to OSL following 7 sec LOS (initiation time not exact) - ref #64

13:58:32 MLG LH Outbd Wheel Temp - temperature trending down (to OSL) Trending to OSL following 7 sec LOS (initiation time not exact) - ref #62

13:58:32 / 59:22 Sys 2 LH Brake Switching Vlv Return Temp (AFT) - temp rise rate change Temp rise rate change from 2.5 F/min to 40.0 F/min until 13:59:22 (temp peak) - ref #70.5

13:58:36 MLG LH Inbd Wheel Temp - start of temperature trending down (to OSL) Start of trend to OSL - ref #66

13:58:39 MLG LH Outbd Wheel Temp - OSL

13:58:39 MLG LH Outbd Tire Pressure 2 - start of pressure trending down (to OSL) Start of trend to OSL - ref #68

13:58:40 BFS Fault Msg (4) - Tire Pressures - First Message 32/13:58:39.94 - SM0 Tire P LOB

32/13:58:41.84 - SM0 Tire P LIB

32/13:58:49.54 - SM0 Tire P LIB

32/13:58:56.26 - SM0 Tire P LOB

13:58:40 MLG LH Inbd Tire Pressure 1 - OSL

13:58:41 MLG LH Inbd Tire Pressure 2 - start of off nominal trend Press rose ~3.5 psia in 2 sec's

13:58:43 MLG LH Inbd Tire Pressure 2 - start of pressure trending down

13:58:48 MLG LH Inbd Wheel Temp - OSL

13:58:48 MLG Inbd Tire Pressure 2 - OSL

13:58:54 MLG LH Outbd Tire Pressure 2 - OSL

13:58:56 BFS Fault Msg (4) - Tire Pressures - Last Message

13:59:06 Left Main Gear Downlocked Indication - Transferred ON Uplock indicated no change

13:59:23 Loss of MCC real-time data to the workstations in the FCR and MER

13:59:22 Sys 2 LH Brake Switching Vlv Return Temp (AFT) - start of sharp downward temperature trend Temp trending down until loss of signal - ref #81

13:59:30.66 Start of R2R yaw firing Last pulse before LOS (stayed on to end of first 5-sec period of recon data at 032/13:59:37.4 GMT)

13:59:30.68 Start of R3R yaw firing Last pulse before LOS (stayed on to end of first 5-sec period of recon data at 032/13:59:37.4 GMT)

13:59:31 Observed elevons deflection at LOS Left: -8.11 deg (up); Right: -1.15 deg (up)

13:59:31.400 FCS Channel 4 Aerosurface position measurements start trending towards their null values Indicates worsening failure of transducer excitation via a wiring short conditions

13:59:31.478 All FCS Channel 4 Bypass valves close (indicating bypassed) Leading indicator of ASA fail (high-rate data)

13:59:31.7 Speedbrake channel 4 OI position measurement indicated successively 19, 20, 24 degrees over last three samples prior to LOS (should be closed / 0º). Speedbrake was commanded to "overclose" (-10 degrees), position measurements for Channels 1 thru 3 were 0 degrees. Secondary delta pressure on Ch 4 went to zero, which indicates that the channel was bypassed. This is real data and the ASAs were responding appropriately.

13:59:32 Observed aileron trim at LOS Trim: -2.3 deg (V96H2045C - V90H1500C)

13:59:32 M-FUS LT BL Temp at x1215 - LOS LOS

13:59:32 LH Aft Fus Sidewall Temp at x1410 - LOS LOS

13:59:32 LMG Brake Line Temp A - LOS LOS at 172.2 F

13:59:32 LMG Brake Line Temp B - LOS LOS at 154.2 F

13:59:32 LMG Brake Line Temp C - LOS LOS at 104.8 F

13:59:32 LMG Brake Line Temp D - LOS LOS at 88.3 F

13:59:32 Left Main Gear Strut Actuator Temp - LOS LOS at 76.3 F

13:59:32 Hyd Sys 1 LMG Uplk Actr Unlk Ln Temp - LOS LOS at 52.2 F

13:59:32 Sys 2 LH Brake Sw Vlv Return Temp (AFT) - LOS LOS at 62.8 F

13:59:32 Sys 3 LMG Brake Sw Vlv Return Line Temp (FWD) - LOS LOS at 67.3 F

31:59:32 Approx Veh Grd Location:

32.9 N / -99.0 W Altitude ~200700 ft / Mach ~18.1 - Near Dallas TX Approximate Vehicle Ground Location at Loss of Signal based on GMT; Data source: STS-107 GPS Trajectory Data

13:59:32.130 FCS Channel 4 fail flags raised (1 Hz) on all aerosurface actuators Lagging indicator of ASA position measurement discrepancy

13:59:32.136 LOS

(Loss of Signal) Last valid downlink frame accepted by ODRC - OI / BFS / PASS

(This time has been referred to as "LOS" thoughout the investigation.)

Start of reconstructed data Upper Right Aft (URA) Quad Antenna was selected by BFS antenna management S/W to communicate with TDRS-W. The pointing angle to TDRS-W was off the Orb tail at -65 degs and trending further into blockage. Prev experience / eng calcs predict probable loss of comm at elevation angles greater than -60 degrees. Loss of comm at this GMT is therefore considered nominal.

13:59:32.598 Left Outboard bypass valve reopens. A force fight between channels 1/2/3 and channel 4 begins, resulting in a difference of up to 0.5 degrees observed between the left outboard and inboard elevons Indicates a short in bypass valve has grown sufficient to drop below voltage threshold of valve; RPC B is current limiting.

13:59:33.680 BFS Fault Message annunciation (1) - FCS CH 4 TDRS-E Data. Error is detected by ATVC/ASA hardware when sensed delta pressure across actuator exceeds a limit indicating the FCS channel is no longer driving the actuator. FCS CH 4 failure will annunicate for any of the following: LIB / LOB / RIB / ROB elevon actutor 4, rudder actuator 4, speedbrake actuator 4, SSME 1/2/3 P/Y Actuator D, & L/R SRB R/T actuator D.

13:59:33.863 PASS Fault Message annunciation (1) - FCS CH 4 TDRS-E Data

13:59:33.976 Master Alarm noted. D&C analysis is continuing to determine cause of alarm.

13:59:34.518 Left Outboard force fight ends, driver currents go to zero.

(RPC B trip indication). Leading indicator of RPC B trip / ASA power down. I.e., indicates opening of all bypass valves (due to RPC B trip removing power) on ASA 4. Force fight goes away since actuators are already at the last commanded position (so channel 4 has no hyd load on the servo asking for position change).

13:59:34.561 Speedbrake force fight begins (continues to LOS) Indicates opening of all bypass valves (due to RPC B trip removing power) on ASA 4. Since the speedbrake is at zero but is being commanded to "over-close" position (-10) this results in a force fight between channels 1,2,3 and channel 4.

13:59:35/36 Sideslip on vehicle changes sign. The event occurred between the two times listed. Just prior to initial LOS the magnitude of the negative Sideslip started to decrease and between 59:34 and 59:37 sideslip grew from -.6 to +.8 deg. With this change, the normal roll and yaw moments on the vehicle would change sign. Aerodynamic forces due to sideslip are now reinforcing aerodynamic asymmetry.

13:59:36 Growth in Bank attitude error Up until this time the flight control had been able to maintain the Bank error around 5 deg. Aerojet DAP drops left wing to compensate for increasing aerodymanic moments, creating a bank attitude error.

13:59:36.8 Aerojet DAP Requests Third Right Yaw RCS Jet (R4R) This additional jet is required to counteract the increasing aerodynamic moments on the vehicle. The RCS jet fired, as expected and stayed on to end of first 5-sec period of recon data at 032/13:59:37.4 GMT.

13:59:37.3 Aerojet DAP Requests Fourth Right Yaw RCS Jet (R1R) This additional jet is required to counteract the increasing aerodynamic moments on the vehicle. The RCS jet fired, as expected and stayed on to end of first 5-sec period of recon data at 032/13:59:37.4 GMT.

13:59:37.n Last aileron data The aileron position is now approx -5.2 deg with approx -2.5 deg of aileron trim. The rate of change of aileron trim had reached the maximum allowed by the flight control system.

13:59:37.396 End of 5 second period of reconstructed data End of first 5-seconds of the 32-second period of post-LOS data. Start of approximately 25 seconds of no data available GMT derived by MER data personnel

13:59:46.347 PASS Fault Message annunciation - ROLL REF Message retrieved from "fault message buffer" received between 14:00:04 and 14:00:05. The ROLL REF message is triggered when Roll command req'd to fly reference profiile falls below 37 degs. Message generation less than 10 secs (5 guidance cycles) after start of 4 yaw jets firing suggests rapid change in Lift to Drag ratio.

Note: BFS does not have this message in the Fault message stack. It is likely that BFS annunciated this message during the 25 second gap of no data, but that if it was annunciated it was pushed out of the downlist stack by additional fault messages (at least 5) annunciated during the gap.

13:59:52.114 PASS Fault Message annunciation - L RCS LEAK Data located in PASS fault message buffer. Data is potentially error prone.

14:00:01.540* BFS Fault Message annunciation - L RCS LEAK Data located in BFS fault message buffer. Data is potentially error prone.

*Time info corrupted.

14:00:01.900* BFS Fault Message annunciation - L RCS LEAK Data located in BFS fault message buffer. Data is potentially error prone.

*Time info corrupted.

14:00:02/06 Debris A observed leaving the Orbiter - Large debris seen falling away from the Orbiter envelope.

14:00:02.654 PASS Fault Message annunciation - L RCS LJET Data is potentially error prone.

14:00:02.660 Beginning of 2 second period of reconstructed data Start of last 2-seconds of the 32 second period of post-LOS data. GMT derived by MER data personnel.

CAUTION: Data from this period is suspect because multiple bit errors were evident in this reconstructed data. Many of the parameters were 1 Hz data and therefore only one data sample was available. Where possible, high rate data and/or corroborating data were used to draw subsystem performance conclusions. However, some of the conclusions drawn below may be in error or misinterpreted.

During this final 2 second period of reconstructed data, the data indicates the following systems werenominal: APUs were running and WSB cooling was evident (although potentially overcooling). MPS integrity was still evident. Fuel cells were generating power and the PRSD tanks/lines were intact. Comm and navaids systems in the forward fuselage were performing nominally. RSB, Body Flap, main engine, and right wing temps appeared active. With the exception of an apparent FES shutdown, ECLSS performance was nominal.

During this final 2 second period of reconstructed data, the data indicates the following systems wereoff-nominal: All three Hyd systems were lost (zero pressure/zero rsvr qty's). The left inbd/outbd elevon actuator temps were either OSL or no data exists. WSB's appeared to be overcooling APU lube oil. The FES appeared to have shutdown. Majority of left OMS pod sensors were either OSH or OSL or no data exists. Multiple BFS and PASS fault message annunciations for left pod hardware were found in the buffer. Elevated temps at bottom bondline centerline skin forward and aft of the wheel wells and at the port side structure over left wing were observed. EPDC shows general upward shift in Main Bus amps and downward shift in Main Bus volts. AC3 phase A inverter appeared disconnected from the AC Buss.

GNC data suggests vehicle was in an uncommanded attitude and was exhibiting uncontrolled rates. Yaw rate was at the sensor maximum of 20 deg/sec. The flight control mode was in AUTO. (Note that all Nav-derived parameters (e.g., alpha) are suspect due to high rates corrupting the IMU state.)

Based on the nominal and off-nominal system performance described above, it appears that the fwd/mid/aft fuselage, right wing, and right pod were still intact.

14:00:03.470* BFS Fault Message annunciation - L OMS TK P Data located in BFS fault message buffer after acquisition of data. Data is potentially error prone. *Time info corrupted.

Note: Error is annunciated when left OMS oxidizer tank ullage pressure (V43P4221C) or fuel tank ullage pressure (V43P4321C) is out of limits high or low. Oxidizer limits - High: 288 psi; Low 234 psi; Fuel limits - High: 288 psi; Low: 234 psi.

14:00:0n.nnn BFS Fault Message annunciation - In-determinant

14:00:0n.nnn* BFS Fault Message annunciation - SM1 AC VOLTS Occurred after L OMS TK P message. Data is potentially error prone. *Time info corrupted. Note: Error message indicates that AC Bus 3 phase A, B, or C voltage (V76V1700A, V75V1701A, V76V1702A) is out of limits high or low. Low limit for all 3 parameters is 108VAC; High limit is 123VAC.

14:00:03.637 PASS Fault Message annunciation - L RCS PVT Data is potentially error prone.

14:00:03.637 PASS Fault Message annunciation - DAP DNMODE RHC The software process which logs the PASS message runs every 1.92 seconds, so event could have occurred as early as 14:00:01.717 GMT. The fault message was corroborated by an initialization flag for the aerojet DAP roll stick function. However, during the 2 sec period, available vehicle data indicates RHC was in detent & DAP was in AUTO. Data is potentially error prone.

Note: BFS downlist bits indicating CSS mode are initialized to "ON" for entry because BFS does not have an "Auto" mode, is always CSS, and will drive the eyebrow panel lights ON if engaged. These bits are always on in BFS through all of OPS 3 until touchdown.

14:00:04.826 End of 2 second period of reconstructed data Last identifiable OI Downlink frame GMT derived by MER data personnel. Last recognizable Downlist frame (BFS & PASS) was approx 60 ms earlier.

14:00:17/21 Debris B observed leaving the Orbiter Time is for debris first seen well aft of Orbiter envelope.

14:00:18/22 Debris C observed leaving the Orbiter Time is for debris first seen well aft of Orbiter envelope.

14:00:21/25 Vehicle Main Body break-up Onset of vehicle main body break-up

14:00:53 End of Peak Heating Determined by analysis

nn = data still needed

Summary: Mission Management Decision Making

Discovery and Initial Analysis of Debris Strike

In the course of examining film and video images of Columbia’s ascent, the Intercenter Photo Working Group identified, on the day after launch, a large debris strike to the leading edge of Columbia’s left wing. Alarmed at seeing so severe a hit so late in ascent, and at not hav¬ing a clear view of damage the strike might have caused, Intercenter Photo Working Group members alerted senior Program managers by phone and sent a digitized clip of the strike to hundreds of NASA personnel via e-mail. These actions initiated a contingency plan that brought together an interdisciplinary group of experts from NASA, Boeing, and the United Space Alliance to analyze the strike. So concerned were Intercenter Photo Working Group personnel that on the day they discovered the debris strike, they tapped their Chair, Bob Page, to see through a request to image the left wing with Department of Defense assets in anticipa¬tion of analysts needing these images to better determine potential damage. By the Board’s count, this would be the first of three requests to secure imagery of Columbia on-orbit during the 16-day mission.

IMAGERY REQUESTS

1. Flight Day 2. Bob Page, Chair, Intercenter Photo Working Group to Wayne Hale, Shuttle Pro¬gram Manager for Launch Integration at Kennedy Space Center (in person).

2. Flight Day 6. Bob White, United Space Alliance manager, to Lambert Austin, head of the Space Shuttle Systems Integration at Johnson Space Center (by phone).

3. Flight Day 6. Rodney Rocha, Co-Chair of Debris Assessment Team to Paul Shack, Manager, Shuttle Engineering Office (by e-mail).

MISSED OPPORTUNITIES

1. Flight Day 4. Rodney Rocha inquires if crew has been asked to inspect for damage. No re¬sponse.

2. Flight Day 6. Mission Control fails to ask crew member David Brown to downlink video he took of External Tank separation, which may have revealed missing bipod foam.

3. Flight Day 6. NASA and National Imagery and Mapping Agency personnel discuss possible request for imagery. No action taken.

4. Flight Day 7. Wayne Hale phones Department of Defense representative, who begins identify¬ing imaging assets, only to be stopped per Linda Ham’s orders.

5. Flight Day 7. Mike Card, a NASA Headquarters manager from the Safety and Mission Assur¬ance Office, discusses imagery request with Mark Erminger, Johnson Space Center Safety and Mission Assurance. No action taken.

6. Flight Day 7. Mike Card discusses imagery request with Bryan O’Connor, Associate Adminis¬trator for Safety and Mission Assurance. No action taken.

7. Flight Day 8. Barbara Conte, after discussing imagery request with Rodney Rocha, calls LeRoy Cain, the STS-107 ascent/entry Flight Director. Cain checks with Phil Engelauf, and then deliv¬ers a “no” answer.

8. Flight Day 14. Michael Card, from NASA’s Safety and Mission Assurance Office, discusses the imaging request with William Readdy, Associate Administrator for Space Flight. Readdy directs that imagery should only be gathered on a “not-to-interfere” basis. None was forthcoming.

Upon learning of the debris strike on Flight Day Two, the responsible system area manager from United Space Alliance and her NASA counterpart formed a team to analyze the debris strike in accordance with mission rules requiring the careful examination of any “out-of-fam¬ily” event. Using film from the Intercenter Photo Working Group, Boeing systems integration analysts prepared a preliminary analysis that afternoon. (Initial estimates of debris size and speed, origin of debris, and point of impact would later prove remarkably accurate.) As Flight Day Three and Four unfolded over the Martin Luther King Jr. holiday weekend, en¬gineers began their analysis. One Boeing analyst used Crater, a mathematical prediction tool, to assess possible damage to the Thermal Protection System. Analysis predicted tile damage deeper than the actual tile depth, and penetration of the RCC coating at impact angles above 15 degrees. This suggested the potential for a burn-through during re-entry. Debris Assessment Team members judged that the actual damage would not be as severe as predicted because of the inherent conservatism in the Crater model and because, in the case of tile, Crater does not take into account the tile’s stronger and more impact-resistant “densified” layer, and in the case of RCC, the lower density of foam would preclude penetration at impact angles under 21 degrees.

On Flight Day Five, impact assessment results for tile and RCC were presented at an informal meeting of the Debris Assessment Team, which was operating without direct Shuttle Program or Mission Management leadership. Mission Control’s engineering support, the Mission Evalu¬ation Room, provided no direction for team activities other than to request the team’s results by January 24. As the problem was being worked, Shuttle managers did not formally direct the actions of or consult with Debris Assessment Team leaders about the team’s assumptions, uncertainties, progress, or interim results, an unusual circumstance given that NASA managers are normally engaged in analyzing what they view as problems. At this meeting, participants agreed that an image of the area of the wing in question was essential to refine their analysis and reduce the uncertainties in their damage assessment.

Each member supported the idea to seek imagery from an outside source. Due in part to a lack of guidance from the Mission Management Team or Mission Evaluation Room managers, the Debris Assessment Team chose an unconventional route for its request. Rather than working the request up the normal chain of command – through the Mission Evaluation Room to the Mission Management Team for action to Mission Control – team members nominated Rodney Rocha, the team’s Co-Chair, to pursue the request through the Engineering Directorate at John-son Space Center. As a result, even after the accident the Debris Assessment Team’s request was viewed by Shuttle Program managers as a non-critical engineering desire rather than a critical operational need.

When the team learned that the Mission Management Team was not pursuing on-orbit imag¬ing, members were concerned. What Debris Assessment Team members did not realize was the negative response from the Program was not necessarily a direct and final response to their official request. Rather, the “no” was in part a response to requests for imagery initiated by the Intercenter Photo Working Group at Kennedy on Flight Day 2 in anticipation of analysts’ needs that had become by Flight Day 6 an actual engineering request by the Debris Assessment Team, made informally through Bob White to Lambert Austin, and formally through Rodney Rocha’s e-mail to Paul Shack. Even after learning that the Shuttle Program was not going to provide the team with imagery, some members sought information on how to obtain it anyway.

Debris Assessment Team members believed that imaging of potentially damaged areas was necessary even after the January 24, Mission Management Team meeting, where they had re¬ported their results. Why they did not directly approach Shuttle Program managers and share their concern and uncertainty, and why Shuttle Program managers claimed to be isolated from engineers, are points that the Board labored to understand. Several reasons for this communica¬tions failure relate to NASA’s internal culture and the climate established by Shuttle Program management, which are discussed in more detail in Chapters 7 and 8.

A Flawed Analysis

An inexperienced team, using a mathematical tool that was not designed to assess an impact of this estimated size, performed the analysis of the potential effect of the debris impact. Cra¬ter was designed for “in-family” impact events and was intended for day-of-launch analysis of debris impacts. It was not intended for large projectiles like those observed on STS-107. Crater initially predicted possible damage, but the Debris Assessment Team assumed, without theoretical or experimental validation, that because Crater is a conservative tool – that is, it pre¬dicts more damage than will actually occur – the debris would stop at the tile’s densified layer, even though their experience did not involve debris strikes as large as STS-107’s. Crater-like equations were also used as part of the analysis to assess potential impact damage to the wing leading edge RCC. Again, the tool was used for something other than that for which it was designed; again, it predicted possible penetration; and again, the Debris Assessment Team used engineering arguments and their experience to discount the results.

As a result of a transition of responsibility for Crater analysis from the Boeing Huntington Beach facility to the Houston-based Boeing office, the team that conducted the Crater analyses had been formed fairly recently, and therefore could be considered less experienced when com¬pared with the more senior Huntington Beach analysts. In fact, STS-107 was the first mission for which they were solely responsible for providing analysis with the Crater tool. Though post-ac¬cident interviews suggested that the training for the Houston Boeing analysts was of high quality and adequate in substance and duration, communications and theoretical understandings of the Crater model among the Houston-based team members had not yet developed to the standard of a more senior team. Due in part to contractual arrangements related to the transition, the Hous¬ton-based team did not take full advantage of the Huntington Beach engineers’ experience.

At the January 24, Mission Management Team meeting at which the “no safety-of-flight” con¬clusion was presented, there was little engineering discussion about the assumptions made, and how the results would differ if other assumptions were used.

Engineering solutions presented to management should have included a quantifiable range of uncertainty and risk analysis. Those types of tools were readily available, routinely used, and would have helped management understand the risk involved in the decision. Management, in turn, should have demanded such information. The very absence of a clear and open discussion of uncertainties and assumptions in the analysis presented should have caused management to probe further.

Shuttle Program Management’s Low Level of Concern

While the debris strike was well outside the activities covered by normal mission flight rules, Mission Management Team members and Shuttle Program managers did not treat the debris strike as an issue that required operational action by Mission Control. Program managers, from Ron Dittemore to individual Mission Management Team members, had, over the course of the Space Shuttle Program, gradually become inured to External Tank foam losses and on a funda¬mental level did not believe foam striking the vehicle posed a critical threat to the Orbiter. In particular, Shuttle managers exhibited a belief that RCC panels are impervious to foam impacts. Even after seeing the video of Columbia’s debris impact, learning estimates of the size and location of the strike, and noting that a foam strike with sufficient kinetic energy could cause Thermal Protection System damage, management’s level of concern did not change.

The opinions of Shuttle Program managers and debris and photo analysts on the potential severity of the debris strike diverged early in the mission and continued to diverge as the mis¬sion progressed, making it increasingly difficult for the Debris Assessment Team to have their concerns heard by those in a decision-making capacity. In the face of Mission managers’ low level of concern and desire to get on with the mission, Debris Assessment Team members had to prove unequivocally that a safety-of-flight issue existed before Shuttle Program management would move to obtain images of the left wing. The engineers found themselves in the unusual position of having to prove that the situation was unsafe – a reversal of the usual requirement to prove that a situation is safe. Other factors contributed to Mission management’s ability to resist the Debris Assessment Team’s concerns. A tile expert told managers during frequent consultations that strike damage was only a maintenance-level concern and that on-orbit imaging of potential wing damage was not necessary. Mission management welcomed this opinion and sought no others. This constant reinforcement of managers’ pre-existing beliefs added another block to the wall between deci¬sion makers and concerned engineers.

Another factor that enabled Mission management’s detachment from the concerns of their own engineers is rooted in the culture of NASA itself. The Board observed an unofficial hierarchy among NASA programs and directorates that hindered the flow of communications. The effects of this unofficial hierarchy are seen in the attitude that members of the Debris Assessment Team held. Part of the reason they chose the institutional route for their imagery request was that without direction from the Mission Evaluation Room and Mission Management Team, they felt more comfortable with their own chain of command, which was outside the Shuttle Program. Further, when asked by investigators why they were not more vocal about their concerns, De¬bris Assessment Team members opined that by raising contrary points of view about Shuttle mission safety, they would be singled out for possible ridicule by their peers and managers.

A Lack of Clear Communication

Communication did not flow effectively up to or down from Program managers. As it became clear during the mission that managers were not as concerned as others about the danger of the foam strike, the ability of engineers to challenge those beliefs greatly diminished. Managers’ ten¬dency to accept opinions that agree with their own dams the flow of effective communications.

After the accident, Program managers stated privately and publicly that if engineers had a safe¬ty concern, they were obligated to communicate their concerns to management. Managers did not seem to understand that as leaders they had a corresponding and perhaps greater obligation to create viable routes for the engineering community to express their views and receive infor¬mation. This barrier to communications not only blocked the flow of information to managers, but it also prevented the downstream flow of information from managers to engineers, leaving Debris Assessment Team members no basis for understanding the reasoning behind Mission Management Team decisions.

The January 27 to January 31, phone and e-mail exchanges, primarily between NASA engi¬neers at Langley and Johnson, illustrate another symptom of the “cultural fence” that impairs open communications between mission managers and working engineers. These exchanges and the reaction to them indicated that during the evaluation of a mission contingency, the Mission Management Team failed to disseminate information to all system and technology experts who could be consulted. Issues raised by two Langley and Johnson engineers led to the development of “what-if” landing scenarios of the potential outcome if the main landing gear door sustained damaged. This led to behind-the-scenes networking by these engineers to use NASA facilities to make simulation runs of a compromised landing configuration. These engineers – who un¬derstood their systems and related technology – saw the potential for a problem on landing and ran it down in case the unthinkable occurred. But their concerns never reached the managers on the Mission Management Team that had operational control over Columbia.

A Lack of Effective Leadership

The Shuttle Program, the Mission Management Team, and through it the Mission Evaluation Room, were not actively directing the efforts of the Debris Assessment Team. These manage¬ment teams were not engaged in scenario selection or discussions of assumptions and did not actively seek status, inputs, or even preliminary results from the individuals charged with analyzing the debris strike. They did not investigate the value of imagery, did not intervene to consult the more experienced Crater analysts at Boeing’s Huntington Beach facility, did not probe the assumptions of the Debris Assessment Team’s analysis, and did not consider actions to mitigate the effects of the damage on re-entry. Managers’ claims that they didn’t hear the engineers’ concerns were due in part to their not asking or listening.

The Failure of Safety’s Role

As will be discussed in Chapter 7, safety personnel were present but passive and did not serve as a channel for the voicing of concerns or dissenting views. Safety representatives attended meetings of the Debris Assessment Team, Mission Evaluation Room, and Mission Management Team, but were merely party to the analysis process and conclusions instead of an independent source of questions and challenges. Safety contractors in the Mission Evaluation Room were only marginally aware of the debris strike analysis. One contractor did question the Debris As¬sessment Team safety representative about the analysis and was told that it was adequate. No additional inquiries were made. The highest-ranking safety representative at NASA headquar¬ters deferred to Program managers when asked for an opinion on imaging of Columbia. The safety manager he spoke to also failed to follow up.

Summary

Management decisions made during Columbia’s final flight reflect missed opportunities, blocked or ineffective communications channels, flawed analysis, and ineffective leadership. Perhaps most striking is the fact that management – including Shuttle Program, Mission Man¬agement Team, Mission Evaluation Room, and Flight Director and Mission Control – displayed no interest in understanding a problem and its implications. Because managers failed to avail themselves of the wide range of expertise and opinion necessary to achieve the best answer to the debris strike question – “Was this a safety-of-flight concern?” – some Space Shuttle Program managers failed to fulfill the implicit contract to do whatever is possible to ensure the safety of the crew. In fact, their management techniques unknowingly imposed barriers that kept at bay both engineering concerns and dissenting views, and ultimately helped create “blind spots” that prevented them from seeing the danger the foam strike posed.

Because this chapter has focused on key personnel who participated in STS-107 bipod foam debris strike decisions, it is tempting to conclude that replacing them will solve all NASA’s problems. However, solving NASA’s problems is not quite so easily achieved. Peoples’ actions are influenced by the organizations in which they work, shaping their choices in directions that even they may not realize