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| Orbiter Operations |
| Overview |
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Rendezvous and Docking The orbiter will rendezvous with the International Space Station (ISS) on Flight Day (FD) 3 at a time based on ISS-orbiter phasing. The orbiter will perform a minus R-bar approach to the ISS to protect communications with Russian ground sites and will dock with Pressurized Mating Adapter (PMA) 2 on the forward common berthing mechanism (CBM) of Node 1. If beta angles exceed 45 degrees, the ISS may need to perform a 90-degree roll to ensure adequate power production. If this occurs, the orbiter will have to perform a 90-degree yaw during the approach. The primary prerendezvous activities include checking out the orbiter's tobotic arm, the extravehicular maneuvering units (EMUs), the Ku-band antenna, the orbiter docking system (ODS), and the ground command system. It may be necessary to power down the station's systems to minimize battery discharge during solar array feathering. The power-down will be performed at 2:15 before the terminal phase initiation, or Ti, burn. Next the orbiter rendezvous radar will be activated, but it will not be used until after the normal course correction burn. The crew will then power the ODS and activate the docking lights at 1:15 before the Ti burn. The Ti burn will be performed when the ISS is ready for docking. If ISS power or thermal concerns arise, a Ti delay burn will be performed instead of the Ti burn. Zvezda and Zarya solar arrays will be feathered (or positioned) and locked when the orbiter is 150 feet from the station. Feathering is initiated by a command to reposition and hold each beta (and alpha) joint at a predetermined angle, which will limit the induced loads. The ISS will automatically switch to free drift at capture, and the orbiter will go to free drift to avoid imposing excessive loads on the orbiter docking system (ODS). Light-emitting diodes (LEDs) on PMA-2 will blink when the ISS is in free drift. The crew will be able to see the red indicators through the overhead window on the orbiter's aft flight deck and verify that the ISS is in the free-drift mode. The ODS will begin the automatic rigidization and retraction process, and its capture hooks will be closed. Then the ODS will be deactivated, Zvezda and Zarya solar arrays will resume sun tracking, and the orbiter-ISS stack will maneuver to the mated attitude. Docked Operations After the orbiter docks with the ISS, the crew will enter PMA-2, take an air sample from Node 1, and activate the Unity cabin fan to scrub the atmosphere. After a 2-hour scrub, the crew will take another air sample. On FD4, the crew will unberth the Z1 segment of the station's integrated truss structure from the orbiter payload bay and mate it with Unity's zenith CBM port. After the CBM operations have been completed, the crew will enter Inity and Zarya. Over the next four days, crew members will conduct four spacewalks to connect umbilicals and configure hardware for future operations. The crew will re-enter the ISS on FD9 to transfer EMU hardware and complete any remaining entry or transfer tasks. The orbiter will undock from the ISS on FD10. During mated operations, the orbiter will provide attitude control. Departure Before the orbiter departs on FD10, ground personnel will update the ISS vector and mass data. This data includes attitude departure maneuver data, attitude hold data, postdeparture mass properties, and postdeparture attitude maneuver data. A navigation platform alignment will be performed. Zvezda and Zarya solar arrays will be commanded to stop sun tracking and will be feathered to the edge-on position. The orbiter crew will configure orbiter hardware for departure. This involves enabling rendezvous navigation and performing an orbiter-to-target state vector transfer. Next, the crew will configure the ODS. The orbiter docking lights will be activated, and orbiter power will be applied to the ODS. The orbiter digital autopilot will be configured for proximity operations and commanded to free drift. Orbiter interface unit (OIU) operations will be terminated, and OIU interfaces will be powered off. The crew will undock the orbiter from PMA-2 and perform a series of separation burns with the primary RCS jets to move the orbiter away from the ISS. Zvezda's flight control system will be activated by a separation signal from the androgynous peripheral attachment system (APAS). This signal initiates a 250-second delay before Zvezda's attitude control system is activated. Separation must occur within Russian ground coverage because the APAS indicator is mechanically zero-fault tolerant and electrically single-fault tolerant. Russian ground personnel will activate the attitude control system if the APAS indicator fails. Zvezda will maneuver to its postdeparture attitude and return to the XPOP flight mode. Zvezda and Zarya solar arrays will resume sun tracking. Finally, Russian segment equipment needed only during mated and departure operations (docking system, lights, etc.) will be deactivated. |
Editorial/Technical Comments: ShuttlePresskit
