Mission Operations Summary
STS-92 will carry a crew of seven on an 11-day mission that includes four spacewalks or EVAs on four consecutive days.
On Flight Day 1 (FD1), the DC-to-DC converter unit (DDCU) heaters and the wireless instrumentation system (WIS) radio frequency (RF) kit will be activated as initial spacewalk preparations begin.
On FD2, the crew will activate and check out orbiter and orbiter-based International Space Station (ISS) hardware, including the extravehicular mobility unit (EMU), the shuttle's robotic arm, or remote manipulator system (SRMS) and the orbiter interface unit (OIU), and assembly power conversion unit (APCU) hardware. After the SRMS checkout, the operator will perform a payload bay survey to inspect the integrity of the cargo.
The orbiter will rendezvous and dock with the ISS on FD3. After the docking, the crew will enter Pressurized Mating Adaptor (PMA) 2 to collect Unity air samples and initiate Unity air scrubbing before entering the ISS the next day.
On FD4, the Z1 element will be unberthed from the orbiter and mated with the zenith port of Unity. The first opportunity to enter the ISS will occur after Z1 has been installed. If the temperature in Unity is acceptable, the crew will enter Zarya,transfer any necessary hardware, install the Z1-to-Unity grounding straps, and remove the CPAs and latches in the Z1 vestibule.
The four spacewalks begin on FD5 and end on FD8 to link the Z1 Truss and PMA-3 to the ISS. The crew will return to the ISS on FD9 to perform tasks that were not completed during the first opportunity.
The orbiter is scheduled to undock from the ISS on FD10 and perform a flyaround, but that day has also been reserved as an unscheduled EVA day.
Two EVA teams, each composed of two crew members, ensure backup support on each EVA day. One team will perform spacewalks on FD5 and FD7, and the other team on FD6 and FD8. FD9 and FD10 are reserved in case an unscheduled EVA is required to properly configure any ISS elements or to perform a contingency undocking. The EVA teams are cross-trained for all assembly activities to accommodate unexpected situations that require shuffling of the EVA teams and crew members.
Z1 Installation
Before Z1 is mated with Unity, the zenith active common berthing mechanism (ACBM) is activated and checked out. This procedure is initiated by applying power to the controllers that control the ACBM. Once power has been applied, the 20 individual controller channels begin a power-on self-test (POST). The POST results are relayed after a master motor controller has been designated during the initialization.
The master controller controls all ACBM functions and reports statuses that it gathers from the slave controllers. The early portable computer system (EPCS) reports the status of the power-up and remote power controller module (RPCM) switches, and the crew reviews and compares the reported status to expected values.
The crew receives the current overall CBM command status, subsystem identification (latch/bolt controller), time, status of the motor current, motor speed, bolt load, and shaft position. This operation also sets all powered bolt and latch controller positions. Because the system has been initialized, these positions should have a reading of zero. If controller channel faults are present, fault detection, isolation, and recovery (FDIR) activities are initiated. If no faults are detected, the crew continues with the ACBM checkout.
The crew members test the bolts by turning them two turns out and three turns in before berthing to ensure that they are operable. The capture latch actuators fully deploy the four capture latches to ensure that they are operable before element berthing begins.
The capture latches are then moved from the deploy position to the capture position as part of the preberthing latch operation testing. The capture latches must then be redeployed before Z1 is positioned in Unity's zenith ACBM capture envelope. The crew uses the same procedure to perform a capture latch deploy test.
After the ACBM has been checked out successfully and the capture latches are extended, the robotic arm is maneuvered to the grapple position. Z1 is grappled, and the crew unlatches the payload retention latch assemblies (PRLAs) and the active keel assembly (AKA) holding Z1. The orbiter is taken to free drift, and the arm unberths and maneuvers Z1 to a low hover position. After some orbiter attitude cleanup, the orbiter is taken to free drift again, and Z1 is maneuvered to the premate position. After more attitude cleanup, the orbiter is taken back to free drift, and Z1 is maneuvered to the capture position. The orbiter must remain in free drift until initial bolt loading (ABOLT) occurs.
When the bolts are ready, they are taken to the final preload bolt (FBOLT) values by tightening the bolts, four at a time. An adequate pressure seal can be achieved if 15 of the 16 bolts or 14 of 16 (nonadjacent) bolts are at the FBOLT load. After FBOLT has been achieved, the capture latches are commanded from the capture position to the close position. Power is then removed from Unity's zenith ACBM.
PMA-3 Installation
Before PMA-3 is mated with Unity, the nadir ACBM is activated and checked out. This is initiated by applying power to the controllers that control the Node 1 nadir ACBM. After power has been applied, the 20 individual controller channels begin a POST. The test results are relayed after a master motor controller has been designated during the initialization.
The master controller controls all ACBM functions and reports statuses that it gathers from the slave controllers. The EPCS reports the status of the power-up and RPCM switches, and the crew reviews and compares the status to expected values. The crew receives the current overall CBM command status, subsystem identification (latch/bolt controller), time, status of the motor current, motor speed, bolt load, and shaft position. This operation also sets all powered bolt and latch controller positions.
Before berthing begins, the crew members test the bolts to ensure that they are operable, and the capture latch actuators fully deploy the four capture latches to ensure that they are operable. The capture latches are moved from the deploy position to the capture position as part of the preberthing latch operation testing. The capture latches must then be redeployed before Z1 is positioned in Unity's zenith ACBM capture envelope. The crew uses the same procedure to perform a capture latch deploy test. After the activation and checkout of the ACBM, the crew must visually verify that there is no debris or contamination that would prevent mating with the PCBM or cause degradation of the CBM seals.
After the ACBM has been checked out and the capture latches are extended, the EVA crew manually releases PMA-3 from the Spacelab pallet (SLP). The arm grapples PMA-3, and PMA-3 is released from the SLP. Due to the extremely tight clearances (6 inches) between the PMA-3 and the SLP, an EVA crew member monitors the unberthing.
When PMA-3 is clear of structure, it is maneuvered to the capture position. The orbiter must remain in free drift until ABOLT occurs.
After capture is complete, the arm releases PMA-3. Then spacewalkers
At this point, the EVA crew connects two sets of umbilicals to PMA-3 and Node 1. An operational hold is required to prevent CBM seal scrubbing because of an excessive temperature delta between the ACBM and PCBM.
At the beginning of the next flight day, the powered bolts are taken to IBOLT values by tightening the bolts, four at a time. In order to achieve an acceptable seal between the PCBM and the ACBM, 15 of the 16 powered berthing bolts or 14 of 16 (nonadjacent) bolts must be engaged. Once the bolts have reached IBOLT status, they are taken to the FBOLT values by furhter tightening the bolts. After the final preload status has been achieved, the capture latches are commanded from the CAPTURE position to the CLOSE position.
DDCU Heat Pipe (HP) Aliveness Test
During EVA3, Mission Control Center, Houston (MCC-H) will perform a DDCU-HP aliveness test to verify that the DDCU-HP blind-mate connections mated. There is no visible indication of proper connector mating, so this test mitigates the effect of a DDCU failure on follow-on flights. The orbiter crew can perform the procedure, but MCC-H will have the primary responsibility.
EVA Operations
Relocation of S-Band Antenna Subassembly (SASA)
Leroy Chiao (EV1) and Bill McArthur (EV2) remove eight bolts on various parts of the SASA using the pistol grip tool (PGT). Using handrails on the SASA, McArthur pulls the unit away from Z1, ensuring it does not contact any structure. (The SASA can survive for only 1 hour if it is not attached to a structure.) The SRMS guides McArthur through the unstow path as Chiao monitors progress and provides other assistance to McArthur. Chiao rotates SASA 180 degrees so that the high-gain antenna (HGA) is pointing in the nadir direction and then aligns the mast fasteners with a stowage bracket. Chiao then secures the mast to the stowage bracket. McArthur releases a bracket from the SASA and stows it in the Z1 stowage bin. Chiao connects cables W34-P4 and W07S-P3 to the SASA. The receptacle covers for J3 and J4 are then stowed on Z1 dummy receptacles. The ground applies heater power soon after the connectors have been mated.
This task must occur before the DDCU is installed because the SASA is launched in the DDCU installation locations.
Connection of Z1-to-Unity Umbilicals
The immediate purpose of this task is to connect the umbilicals that provide keep-alive power to critical on-orbit replaceable units (ORUs) on Z1. Several Unity umbilicals provide APCU power to the CBMs, and these are not disconnected until CBM operations are completed later in the flight. With the exception of Russian-American conversion unit (RACU) commanding, all power-down and activation commands are sent via the portable computer system (PCS) on board the orbiter.
Installation of Space-to-Ground Antenna (SGANT)
Before the SGANT dish can be removed from its launch location, RPCM Z14B-B mut be verified to be operational. Once the antenna is removed from the structure, the dish cools quickly, and the antenna cannot be reinstalled in the launch location. After the orbiter docks with the ISS, the SGANT will violate lower thermal limits within 20 hours, according to preflight thermal analysis.
To install the SGANT, Chiao positions himself in an APFR on the Z1 zenith bulkhead, and McArthur moves on the SRMS near the SGANT. McArthur unfastens two launch restraints on the antenna while Chiao holds it. Chiao slides the SGANT to the hard stop on Z1 and raises it using the upper deployment handles. The SRMS positions McArthur near the boom attachment interface while Chiao removes the APFR and installs and enters the APFR near the boom attachment interface.
Using the upper deployment handles and handles on the antenna group interface tube (AGIT), McArthur positions the AGIT near the boom. Chiao grasps the AGIT handles and aligns the AGIT coarse guide pins with the boom interface holes until the AGIT fine-guide pins are aligned and the SGANT dish is secured to the boom with four bolts. McArthur then connects the J1 and J2 connectors. The intravehicular (IV) crew member verifies that the RPCs feeding connector J1 are open and that closure is inhibited before mating.
Deployment of SGANT Boom
Before deploying the boom, the crew verifies that the SGANT and transmit/receive control (TRC) heaters are active. Preflight thermal analysis shows that the SGANT will violate lower thermal limits within 30 minutes after the boom is deployed.
The spacewalker on tne arm removes a pip pin from the launch restraint bolt and then unfastens the bolt. The SGANT with boom is unstowed by both spacewalkers. McArthur attaches the antenna to Z1 by fastening two captive EVA bolts on the boom to the Z1 zenith bulkhead using the PGT.
Installation of DDCU-HP
Two DDCU-HPs are being flown on STS-92. DDCU Z1-3B is on the starboard sidewall of the payload bay, and DDCU Z1-4B is on the port sidewall. The installation procedures for the two units are similar.
After the DDCU is released, the heat pipe radiator causes heat to leak from the DDCU. The DDCU will reach its survival thermal limit in one hour.
McArthur aligns the DDCU-HP on Z1, using the alignment marks on the DDCU-HP with marks on Z1, and guides the box onto the aft tie-down nuts until the box is seated. When the DDCU-HP front screw is fastened to a hard stop, the front status indicator changes from UNLOCK to LOCK and the rear status indicator goes from LOCK to UNLOCK. After the rear screw is fastened to a hard stop, the rear status indicator goes from UNLOCK to LOCK. The ORU is installed.
The DDCU will continue to cool down until heater power is applied, which should occur within 1 hour of the installation on the Z1 structure.
Release of PMA-3 From SLP
Once the Unity nadir ACBM has been activated and checked out and the ACBM capture latches are all extended, EVA crew members Jeff Wisoff and Michael Lopez-Alegria can remove PMA-3 from the Spacelab pallet (SLP).
With the robotic arm attached to PMA-3, the two spacewalkers loosen the berthing bolts while deploying the capture latches. This series of maneuvers prevents asymmetrical loading on the PMA-3 from the MBM.
PMA-3 must be unberthed from the SLP in daylight because cameras must be used during the procedure. Because of the tight clearances, camera views are necessary to assist the SRMS crew member.
One spacewalker must open and close the capture latches to ensure that they are operational.
With the latches closed, the spacewalkers first loosen all bolts one-half turn to relieve pressure on the PCBM seal. This is done so that unloading occurs symmetrically; however, it does not have to be performed by the two crew members simultaneously. Because of the loading conditions, the crew members fully loosen and release all but the four bolts next to the MBM capture latches. The EVA astronauts fully unbolt the remaining berthing bolts simultaneously while working opposite from each other. PMA-3 is now free of all berthing bolts on the MBM ring.
The remaining restraints are the four capture latches. An EVA crew member takes up a position at the capture latch drive assembly and drives the latches at a low torque setting until they are one turn from being fully deployed. Then the latches are fully opened at a higher torque setting. After PMA-3 has been moved from the envelope of the MBM, an EVA astronaut drives the capture latches back to their closed position for entry, first within one turn of being fully deployed at a higher torque and then to the final position at a lower torque.
Monitoring PMA-3 Unberthing
Because of the 6-inch clearance between the PMA-3 docking light assembly and the SLP, an EVA crew member must monitor the unberthing. The orbiter-ISS stack must be in free drift; once the PMA-3 is clear of the SLP, the orbiter's vernier reaction control system (VRCS) is used for attitude control.
Connection of PMA-3 Umbilicals
Once PMA-3 has been successfully berthed and latched to Node 1, an EVA crew member can support the primary umbilical release. Lopez-Alegria releases launch restraints and clamps so that he can release the zero-gravity connectors and slide the thermal covers off the zero-g connectors. Lopez-Alegria then releases one PMA-3 primary umbilical launch fitting and disconnects the primary umbilicals from the dummy panel. The PMA-3 primary umbilical bunch is free of the PMA when the stanchion fitting is released. (A minimum of 20 pounds is required to release the stanchion after the EVA bolt is free.)
Lopez-Alegria moves to the node after releasing EVA clamp C4 and is ready to help guide the umbilical around the grapple fixture. The remaining clamps are released, and the primary umbilical is controlled to ensure that the lower part of the umbilical does not float into the path of the Wisoff or the SRMS. Wisoff carries the PMA-3 primary umbilical on the SRMS around the starboard side (orbiter port) of PMA-3 to the Node 1 end cone handrail, where it is temporarily secured. Wisoff holds the PMA-3 primary umbilical stanchion and controls the umbilical while moving to the Node 1 end cone on the SRMS. Lopez-Alegria must help guide the umbilical around the grapple fixture and ensure that it does not become entangled. The RPCs for the PMA shell heaters are opened to provide adequate safety inhibits before connectors are mated.
The primary PMA-3 umbilicals will be connected to Unity's forward nadir end cone connector panel. After a heater is used overnight to equalize the temperature of the two elements, the mating of PMA-3 with Node 1 will be completed at the start of FD7. After the two elements have been mated, the redundant cable bundle is connected at the beginning of EVA3 on FD7.
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