Shuttle Atlantis has managed to dodge unacceptable weather at her home port of the Kennedy Space Center (KSC) on Wednesday, taking the first of the two Florida landing opportunities, ending in a graceful landing. For what may of been her final day in space, Atlantis continued to be in great shape, with only the observation of two debris events during Flight Day 12 checks requiring the attention of the Mission Management Team (MMT).
The opening landing opportunity called for the deorbit burn to occur at 7:41am Eastern, resulting in a perfect landing on runway 33 at the Shuttle Landing Facility (SLF) at 8:48am.
The second – and final – opportunity would have been available one orbit later, with the deorbit burn at 9:17am for a landing at 10:22am. However, this was not required, along with EOM+1 (End Of Mission plus one day), and “pick em” day on Friday, when the Edwards Air Force Base (Dryden Flight Research Facility) would have been brought into the mix.
Some level of troubleshooting was worked on the Flash Evaporator System (FES), which will control Atlantis’ temperatures after the Payload Bay Doors (PLBDs) are closed, removing the radiator’s ability to cool electronics and other systems on the orbiter. This issue was soon resolved, allowing for the closure of the PLBDs.
It’s been a smooth couple of days since undocking from the International Space Station (ISS), with Late Inspections enjoying a nominal survey – following the EVA work to free the Pan Tilt/Unit (PTU) on the Orbiter Boom Sensor System (OBSS).
With the Damage Assessment Team (DAT) working on both imagery and data taken during the inspections early in the mission – and the completion of coverage that had been missed via the lack of ability to angle the Laser Dynamic Range Imager (LDRI) over parts of the Wing Leading Edges (WLE) – engineers took just over a day to work through the hours of footage.
The results of the Late Inspections showed an extremely clean Atlantis, and a good argument for her being classed as the cleanest orbiter in at least recent history, with only 252 ROIs (Regions Of Interest) – areas that need any checks, such as scuffs and stains – a number which is the lowest since the use of the OBSS, and nearly half the number observed on STS-131.
“LESS/RCC team cleared all late inspection regions of interest. Level 1 review by PRT completed at 5:00 pm (5-24). Level 2 completed at 1:00 am. Final PRT Review completed at 6:52 am (5-25),” noted the DAT findings presentation (L2). “No ROI exhibited any damage characteristics. From all of the early/late inspection LDRI imagery LESS PRT is GO for entry.”
The robotic duo responsible for the survey – the OBSS on the end of the SRMS (Shuttle Remote Manipulator System) – were successfully reberthed in the Payload Bay for the return home, marking the end of their operations for the mission.
“On FD 11 (Flight Day 11), the OBSS and RMS were successfully berthed, latched, and stowed and are in a good configuration for payload bay door closure, entry, and landing,” noted the Mission Evaluation Room (MER) report on L2.
“OBSS BERTH and MRL LATCH. Did not receive the Aft MRL Latch 2 indication (known condition), no further action required. All other indications nominal. Good single motor drive time RMS BERTH and MRL LATCH – All indications nominal, good dual motor drive time.
“RMS MPM STOW – All indications nominal, good dual motor drive time. OBSS MPM STOW – All indications nominal, good dual motor drive time. The OBSS was stowed on the Stbd MPM by the SRMS. RMS Cradled and powered-down.”
Flight Day 12 involved checks to Atlantis Flight Control Surfaces (FCS), ahead of their use during Atlantis dive back into the atmosphere – which was successful from a hardware standpoint.
“FCS C/O (Check Out): All APU 1 (Auxiliary Power Unit) parameters were nominal during the FCS checkout run. APU 1 run time and fuel consumption are listed below,” added the MER report. “Start time: 145/07:47:03. Stop time: 145/07:45:21. Run time: 3:18. Fuel Used/Rate: 12 lbs; 3.64 lb/min.
“FD12 Performance: All APU parameters are nominal. All APU heaters are functioning nominally on the ‘B’ string. The GG heater lower set point shift – unique to OV-104 (Atlantis) position #1 since STS-81 – is evident after about six B heater cycles, exactly the same as on the previous OV-104 mission, STS-129 (31). This heater signature was expected and will be noted in the MER trending database.”
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During the FCS checks, Atlantis’ elevons and Rudder Speed Brake (RSB) were put through their paces, ahead of their use for landing, via the use of hydraulic actuators and valves.
“All Elevon Actuator Switching Valves and the RSB PDU Switching Valve were verified to configure to the proper positions (All Elevon Switching Valves to Standby 1 & the RSB PDU Switching Valve in Primary). Priority valve cracking time was 0.393 seconds (spec ≤1 sec). The HYD System #1 bootstrap accumulator was 2336 psia prior APU #1 start and re-seat pressure was approximately 2832 psia (spec: GT 2675 psia).”
“(Object 1): Object estimated size: 0.46”. Appears to from bottom of FOV (Field Of View – assumed to emerge from inside Payload Bay). Distance from Camera B to sill of payload bay is 32 inches. 32 inch range (max) estimated to object. No extensive dynamic analysis produced,” noted a MMT presentation (L2).
“Object estimated size: 0.44” – Does not emerge into provided FOV from bottom, so there is not evidence as with the other FOD that it emerged from the PLB. However, it is first seen against the wing background (i.e. it’s much closer than the wingtip on first appearance. Estimate above assumes that it did come from PLB. 32 inch range (max) estimated to object.”
“The Flight Controls System Checkout was performed. The procedure was completed with nominal results. The team is not working any issues,” confirmed the MER via their latest shift report, reviewing Flight Day 12’s activities. “Monitored FCS Checkout and RCS Hotfire. Two Foreign Object Debris (FOD) items were observed floating away from the Orbiter during FCS checkout.
“Imagery personnel recorded video of the FODs, and did not feel that they would pose a threat to the Orbiter TPS, since they were small (<1″), appeared to originate from the upper surface of the Orbiter and were floating away from the vehicle.”
Also included in the Flight Day 12 activities were the firing of Atlantis’ Reaction Control System (RCS) thrusters – including the L3D thruster with its failed heater, successfully mitigated via a passive thermal mitigation plan.
“38 of 38 primary thrusters have been fired. Thirteen (13) new Primary thrusters were fired since previous report,” noted the MER. “All thermal systems are performing nominally (except L3D thruster heater) and temperatures are within acceptable limits. The L3D temperatures are currently near 56F.”