Spaceflight mission report: STS-116 (original) (raw)

Launch from Cape Canaveral (KSC) and landing at Cape Canaveral (KSC), Runway 15.

Liftoff was originally scheduled for December 07, 2006, but that attempt was canceled due to a low cloud ceiling.

The main goals of the missionSTS-116 (ISS-20-12A.1SH-LSM ITS-P5) were delivery and attachment of the International Space Station's P5 truss segment, a major rewiring of the station's power system. The shuttle also carried a Spacehab Logistics Module to resupply theISS, and an Integrated Cargo Carrier with four sub-satellites, which were deployed after undocking from theISS: the ANDE technology demonstrator, developed by the Naval Research Laboratory, and three CubeSats (RAFT-1 and MARScom for the United States Naval Academy, and MEPSI 2A/2B for DARPA). It was the first Shuttle mission to deploy satellites since STS-113 in 2002.
As one of the main goals ofSTS-116 was to exchangeISS Expedition 14 crew members, the crew ofSTS-116 changed mid-flight.ISS Flight Engineer Sunita "Suni"Williams was part of theSTS-116 crew for the first portion of the mission. She then replacedISS Flight Engineer ThomasReiter on theExpedition 14 crew and ThomasReiter joined theSTS-116 crew for the return to Earth.
ESA astronaut ChristerFuglesang performed a scientific program as part of the mission Celsius.

The primary assembly hardware Discovery will deliver to the space station is the $11-million Integrated Truss SegmentP5, which measures 11 feet long by 15 feet wide by 14 feet high (3.3 x 4.5 x 3.2 meters). It will serve as a spacer and be mated to theP4 truss that was attached in September during theSTS-115 mission of Atlantis.
Attachment of the 4,000-pound (1,800-kilogram)P5 sets the stage for the relocation to its final assembly position of theP6 truss and the pair of solar arrays that have been located temporarily atop the station'sUnity module for six years.
P5 is part of the 11-segment integrated truss structure and the sixth truss element to be delivered. The truss structure forms the backbone of the International Space Station with mountings for unpressurized logistics carriers, radiators, solar arrays, other hardware and the various elements.
P5 is used primarily to connect power and cooling lines and serve as a spacer between theP4 photovoltaic module (PVM), or solar battery, andP6 PVM, which will be joined during a later assembly mission.P5 is very similar in construction to the long spacer located onP6. Without theP5 short spacer, theP4 andP6 solar arrays would not be able to connect due to the way the photovoltaic arrays (PVA) are deployed on orbit.
The girder-like structure is made of mostly aluminum and provides several extravehicular aids, robotic interfaces, ammonia servicing hardware (as part of the station's External Active Thermal Control System that allows ammonia fluid to transfer fromP4 toP6) and can also accommodate an external storage platform. The Enhanced Universal Trunnion Attachment System (EUTAS) allows platforms to be attached toP5 for the storage of additional science payloads or spare Orbital Replacement Units.P5 also has white thermal blankets on the structure, which help shade theP4 Solar Array AssemblyORUs.

The International Space Station (ISS) electrical power system consists of power generation, energy storage, power management, and distribution (PMAD) equipment. Electricity is generated in a system of solar arrays. Besides the solar arrays on the Russian element, the station currently has two photovoltaic modules, a term that refers to a set of solar arrays, batteries and the associated electronics, on orbit, with two more scheduled for delivery.
The Electric Power System (EPS) provides all user loads and housekeeping electrical power and is capable of expansion as the station is assembled and grows. Eight independent power channels for high overall reliability supply the electric power.
A photovoltaic (PV) electric power generation subsystem was selected for the space station. A PV system uses solar arrays for power generation and chemical energy storage (Nickel-hydrogen) batteries to store excess solar array energy during periods of sunlight and provide power during periods when the station is in Earth's shadow (eclipse). The station orbits the earth every 90 minutes and for about 35 minutes, the station must run on batteries while the station is in eclipse.
Flexible, deployable solar array wings that are covered with solar cells provide power for theISS. Each PV module contains two wings, and each wing consists of two blanket assemblies. The solar array wings are tightly folded inside a blanket for launch. They are deployed in orbit and supported by an extendable mast.
Nominal electrical output of each power channel is about 11 kilowatts (kW), or 20.9 kW per PV module. Four PV modules will supply approximately 83.6 kW.
The primary purpose of the Energy Storage Subsystem (ESS) is to provide electrical power during periods when power from the solar arrays is not enough to support channel loads. The ESS stores energy during periods when solar arrays can generate more power than necessary to support loads. The system consists of three nickel-hydrogen (Ni-H2) batteries per power channel and each battery consists of two battery Orbital Replacement Units (ORUs). Each battery also has a charge/discharge unit (BCDU). The Ni/H2 battery design was chosen because of its high energy density light weight and proven heritage in space applications since the late 1970s to early 1980s.
The entire EPS may be divided into two power subsystems. The primary power subsystem operates at a voltage range of 137 to 173 volts direct current (Vdc) and consists of power generation, storage and primary power distribution. The secondary power subsystem operates at a voltage range of 123 to 126 Vdc and is used to supply power to user loads. Direct Current-to-Direct Current Converter Units (DDCUs) are used to convert primary power to secondary power.
The U.S. power system is also integrated with Russian power sources, so that power from the American power bus can be transferred to the Russian power bus and vice versa. The Russian power system operates at a nominal voltage of 28 Vdc. American to Russian Converter Units (ARCUs) and Russian to American Converter Units (RACUs) are used to convert power from the American secondary power bus to the Russian power bus and vice versa.
The most powerful solar arrays ever to orbit Earth capture solar energy to convert it into electric power for theISS.
Eight solar array wings supply power at an unprecedented voltage level of 137 to 173 Vdc that is converted to a nominal 124 Vdc to operate equipment on theISS. The Space Shuttle and most other spacecraft operate at nominal 28 Vdc, as does the RussianISS segment.
The higher voltage meets the higher overallISS power requirements while permitting use of lighter-weight power lines. The higher voltage reduces ohmic power losses through the wires. Some eight miles of wire distribute power throughout the station.
Each PV module contains two solar array wings. An individual wing is 110-feet (33.5 meters) long by 38-feet (11.6 meters) wide. Each wing consists of two array blankets that are covered with solar cells. The blankets can be extended or retracted by a telescopic mast which is located between the two blankets. Each solar array wing is connected to theISS's 310-foot (94.5 meters) long truss and extend outward at right angles to it (P4 andP6 are currently on orbit). A series of 400 solar cells, called a string, generates electricity at high primary voltage levels while 82 strings are connected in parallel to generate adequate power to meet the power requirement for each power channel. There are a total of 32,800 cells per power channel or 65,600 solar cells on each PV module.
A solar cell assembly is about three inches square. The cells are made of silicon and have a nominal 14.5 percent efficiency for sunlight-to-electricity conversion. Cells are welded on to a flexible printed circuit laminate that connects cells electrically. The sun-facing surface of the cell is protected by a thin cover glass. Each group of eight cells, connected in series, is protected by a bypass diode to minimize performance impact of fractured or open cells on a string. Solar arrays are designed for an operating life of 15 years.
Two mutually perpendicular axes of rotation are used to point solar arrays towards the Sun. Each solar array wing is connected to one Beta Gimbal Assembly (BGA), located on each PV module, that is used to rotate that solar array wing. Another rotary joint, called Solar Alpha Rotary Joint (SARJ), is mounted on the truss and rotates the four solar array wings together. When the station is complete, there will be eight BGAs and twoSARJs. These rotary joints are computer controlled and ensure full sun-tracking capability as theISS goes around the earth under a wide range of orbits andISS orientations.

Flight day 2 began for the astronauts at 15:47UTC. The first order of business for the day was a thorough inspection of the Shuttle. Using sensors and cameras attached to a fifty-foot (15 meters) boom, which was in turn connected to a fifty-foot robotic arm, NicholasPatrick inspected the leading edge of the wings and the nose cap. The process, which took five and a half hours, suffered a minor glitch that required NicholasPatrick to order the arm to manually grab the boom. During this time, the crew also inspected the upper surface of the orbiter. Astronauts also completed a check of the spacesuits to be used during the mission, along with preparation for docking with the International Space Station.

Discovery's final approach to the International Space Station during theSTS-116 rendezvous and docking process included the now-standard back flip pirouette maneuver to allow station crewmembers to take digital images of the shuttle's heat shield.
With shuttle Commander MarkPolansky at the controls, the shuttle performed the circular pitch-around from a distance of about 600 feet (182.9 meters) below the station. The 9-minute flip offersExpedition 14 Commander MichaelLopez-Alegria andFlight Engineer MikhailTyurin time to document through digital still photography the required imagery of Discovery's thermal protection system.
The photos then were transmitted to imagery experts in the Mission Evaluation Room at Mission Control, Houston, via the station's Ku-band communications system.
The photography was performed out of windows 6 and 8 in theZvezda Service Module with Kodak DCS 760 digital cameras and 400 mm and 800 mm lenses. The Rendezvous Pitch Maneuver (RPM) or R-bar Pitch Maneuver (RPM) was one of several inspection procedures designed to verify the integrity of the shuttle's protective tiles and reinforced carbon-carbon wing leading edge panels.
The sequence of events that brought Discovery to its docking with the station began with the precisely timed launch of the shuttle, placing the orbiter on the correct trajectory and course.
The sequence of events that culminate with Discovery's docking to the station actually began with the precisely timed launch that places the orbiter on course for its two-day chase to arrive at the station. The 43-hour rendezvous included periodic thruster firings that ultimately placed Discovery about 9 statute miles (15 km) behind the station, the starting point for final approach.
About 2.5 hours before the scheduled docking time on flight day 3, Discovery reached a point about 50,000 feet (15,240 meters) behind the station. Discovery's jets were fired in what is called the Terminal Initiation (TI) burn to begin the final phase of the rendezvous. Discovery closed the final miles to the station during the next orbit.
As Discovery moved closer to the station, the shuttle's rendezvous radar system and trajectory control sensor (TCS) began tracking the complex, and providing range and closing rate information to the crew. During the final approach, Discovery executed four small mid-course corrections with its steering jets to position the shuttle about 1,000 feet (304.8 meters) directly below the station. From this point, MarkPolansky took over the manual flying of the shuttle up an imaginary line drawn between the station and the Earth known as the R-Bar - or radial vector.
He slowed Discovery's approach at about 600 feet (182.9 meters) and waited for proper lighting conditions to optimize inspection imagery gathering as well as crew visibility for the final rendezvous to docking.
On verbal confirmation by Pilot WilliamOefelein to alert the station crew, MarkPolansky commanded Discovery to begin a nose forward, three-quarters of a degree per second rotational back flip. AtR-bar Pitch Maneuver (RPM) start, the station crew began a series of precisely-timed photography for inspection. The sequence of mapping optimizes the lighting conditions.
Both the 400 mm and 800 mm digital camera lenses were used to capture imagery of the required surfaces of the orbiter. The 400 mm lens provided up to 3-inch (7.6 centimeters) resolution and the 800 mm lens could provide up to 1-inch (2.5 centimeters) resolution and detect any gap filler protrusions greater than ¼ inch (6.4 mm). The imagery included the upper surfaces of the shuttle as well as Discovery's underside, nose cap, landing gear door seals and the elevon cove areas with 1-inch (2.5 centimeters) analytical resolution. The photography included detection of any gap filler protrusions when the orbiter is at 145 and 230-degree angles during the flip. The maneuver and lighting typically offered enough time for two sets of pictures.
When Discovery completed its rotation, it returned to an orientation with its payload bay facing the station. MarkPolansky then moved Discovery to a position about 400 feet (121.9 meters) in front of the station along the V-Bar, or the velocity vector - the direction of travel for both spacecraft. WilliamOefelein provided navigation information to MarkPolansky as the shuttle inched toward the docking port at the forward end of the station'sDestiny Laboratory.
WilliamOefelein joined Mission Specialists NicholasPatrick and JoanHigginbotham in playing key roles in the rendezvous. They operated laptop computers processing the navigational data, the laser range systems and Discovery's docking mechanism.
Using a camera view from center of Discovery's docking mechanism as a key alignment aid, MarkPolansky precisely matched the docking ports of the two spacecraft and flew to a point 30 feet (9.14 meters) from the station before pausing to verify the alignment.
For Discovery's docking on December 11, 2006, MarkPolansky closed the final 30 feet (9.14 meters) at a relative speed of about one-tenth of a foot per second (3 centimeters per second) (while both spacecraft were traveling 17,500 mph = 28,163 km/h), and kept the docking mechanisms aligned within a tolerance of three inches (7.6 centimeters).
At contact, preliminary latches automatically attached the two spacecraft. Immediately after Discovery docked, the shuttle's steering jets were deactivated to eliminate forces acting at the docking interface. Shock absorber-like springs in the docking mechanism dampened any relative motion between the shuttle and the station.
Once motion between the two spacecraft had stopped, Mission Specialists RobertCurbeam and ChristerFuglesang secured the docking mechanism, sending commands for Discovery's docking ring to retract and to close a final set of latches between the two vehicles.

The docking set the stage for the opening of the hatches and the start of joint operations, including the transition of SunitaWilliams to theExpedition 14.
After docking, the first priority was to transfer form-fitting seat liners in theSoyuz spacecraft making SunitaWilliams an official member of theExpedition 14 crew along with Commander MichaelLopez-Alegria andFlight Engineer MikhailTyurin. ThomasReiter then became a member of the shuttle crew with which he returned home after a six-month stay on the station.

On flight day 3, NicholasPatrick carefully lifted theP5 spacer with the shuttleRMS and handed it to the waiting station arm. JoanHigginbotham and SunitaWilliams controlled the station arm at the station's robotic work station in theDestiny Laboratory. The spacer remained on the station's arm overnight in preparation for installation the next day during the first of three planned spacewalks.

The firstEVA by RobertCurbeam and ChristerFuglesang occurred on December 12, 2006 (6h 36m) to align and connect theP5 truss segment toP4. They also replaced a faulty video camera attached to theS1 truss. Since they worked ahead of the time-line, the two astronauts were also able to complete some get-ahead tasks.
On flight day 4, the station's arm - the Space Station Remote Manipulator System orSSRMS - was used to move theP5 spacer to a pre-installation position on the left, or port, side ofP4. Once theP5 is in position, RobertCurbeam and ChristerFuglesang removed the locks that secured the spacer's hardware during its launch on the shuttle. RobertCurbeam removed theP5 launch locks from corners 3 and 1. ChristerFuglesang removed locks from corners 2 and 4.
Once the locks were removed, the two provided verbally guide SunitaWilliams as she maneuvered the station arm to alignP5 toP4. The installation was completed by mating six utility cables.
Before theP5 was locked in place, Mission Control had to take several measures to ensure nothing disturbs the operation. The station's thrusters were turned off and the control moment gyroscopes were in a mode that creates as little disturbance as possible until the crew had tightened three of the four Modified Rocketdyne Truss Attachment System (MRTAS) bolts. Mission Control configured the Solar Alpha Rotary Joint and Beta Gimbal Assemblies - used to swivel the solar arrays to allow them to track the sun - into the proper positions forP5 installation. All of the joints were locked to ensure there is no unexpected motion.
After theP5 launch locks were removed, the station robotic arm guidedP5 into the soft capture position, with RobertCurbeam and ChristerFuglesang assisting by monitoring structural clearances. Once theP5 coarse alignment cone had captured theP4 soft capture pin, the spacewalkers used a pistol grip tool - similar to a portable hand drill - to tighten the attachment bolts. First the bolts on corner 1 (forward/zenith) and 2 (forward/nadir) were tightened, in that order, to an initial torque. Next, bolts on corners 3 (aft/zenith) and 4 (aft/nadir) were driven to final torque. Finally, bolts 1 and 2 were tightened to their final torque. After the bolts were driven, the crew attached grounding straps on each corner and removed the soft capture pins.
Next, the crew moved the Photovoltaic Radiator Grapple Fixture (PVRGF) from theP5 to a place on the station's Mobile Base System. The grapple fixture was temporarily stored there until it could be moved to theP6 aft radiator on a later spacewalk. The PVRGF is a handle that was installed on the top, or zenith, side of theP5 spacer and used by the shuttle and station arms to move the truss. It is being removed to provide enough clearance for the solar arrays to rotate and track the sun.
To accomplish this, RobertCurbeam and ChristerFuglesang moved to the grapple fixture, where RobertCurbeam used the pistol grip tool to begin removing fasteners. Meanwhile, ChristerFuglesang moved a foot restraint to a new worksite interface. Once the foot restraint was in place, ChristerFuglesang began removing grapple fixture fasteners. Once all the fasteners were removed, ChristerFuglesang and RobertCurbeam performed an almost acrobatic transfer of the tethered grapple fixture from one to the other as they moved to the station's keel.
The final task for this spacewalk was the removal and replacement of a camera located at port 3 of the station's starboard 1 (S1) truss. The camera is needed to view clearances during future installations and deployments. RobertCurbeam set up the worksite while ChristerFuglesang retrieved the replacement camera from the airlock. Both worked to remove the failed camera and installed the new one.

On December 13, 2006, the crew attempted retraction of theP6 port-side solar array. Problems with the array folding due to 'kinks' and 'billows' led the controllers to redeploy the array (from about 40% retracted). There then followed a series of more than 40 commands to furl and unfurl the arrays in an effort to get them properly aligned and folded. The retraction efforts were abandoned for the day.

The secondEVA was performed by RobertCurbeam and ChristerFuglesang on December 14, 2006 (5h 00m) to reconfigure power on channels 2 and 3 of the station's electrical system.
First, RobertCurbeam and ChristerFuglesang reconfigured power on the Channel 2/3 side of the station's Electrical Power System to route it through the Main Bus Switching Units. The power reconfiguration required that all power was shut down from Channel 2/3. To accomplish this, a lengthy set of power down procedures were executed from the ground while the crew prepared for the spacewalk.
During the spacewalk, primary power from channels 2A and 2B were connected to the main bus switching unit 2. The work was done at the Starboard 0 (S0) truss segment near the forwardS0-Lab struts. RobertCurbeam translated to theS0 to disconnect the lab's secondary power, installed a cable to route power from theS0 truss to theP1 truss, and reconfigured theS0-2B dc converter unit, the bypass jumper on the main bus switching, and theP1-3A dc converter.
TheS0 truss segment sits in the middle position on the truss structure on top of the U.S.Destiny Laboratory, flanked by theS1 andP1 truss elements. That truss, along with theS1 andP1 trusses, contain the major electrical components of the permanent electrical system, including the main bus switching units and the DC-to-DC converter units.
The power produced by the station's solar arrays is routed to batteries for storage and then to the main bus switching units. The main buses route power to DC-to-DC converter units (DDCUs) which then adjust the primary, 160-volt dc electricity it receives from the main buses to about 125 volts of power. The dc converters feed the station through the Remote Power Controller Modules (RPCMs). A simplified comparison is that the main buses are similar to a power substation, the dc converters are like transformers, and the controller modules are like the electrical switches inside a home.
While RobertCurbeam was configuring power to the Unit 2 main bus, ChristerFuglesang were removing Circuit Interrupt Devices (CIDS) 3, 4, and 5. Once the main bus is operating, the circuit interrupt devices won't be needed. The circuit interrupts served as early "circuit breakers" for the crew. They were returned to Earth. All three circuit interrupters are located at the lab's aft end cone panel, in an area known as "the rat's nest".
Because the main bus switching unit generates heat once it is activated, a pump module must also be activated to enable ammonia to flow through large cold plate loops that cool the bus. Prior to both the second and the third spacewalks, the station's External Thermal Control System (ETCS) ammonia loops were filled so they are ready when the buses are activated.
Once theEVA crewmembers had finished the Channel 2/3 power reconfiguration, they began other tasks while Mission Control powered up the station. RobertCurbeam and ChristerFuglesang relocated two crew and equipment translation aid (CETA) carts from their current locations on theS1 truss to theS0 truss to clear the way for Atlantis' astronauts to install theS3 andS4 truss segments on the STS-117 mission.
The crew also installed a thermal cover on the force moment sensors on the latching end effector on the station's robotic arm and reconfigured power to theZ1 truss electrical patch panel 6, which provides power to theZ1 truss as well as the Russian segment.
The electrical panel task must be conducted separately from the main power down because the S-band communication antennas powered by Channel 2/3 are sensitive to cold and should not be shut down for a protracted period of time.
While RobertCurbeam was busy with this reconfiguration, ChristerFuglesang retrieved the starboard and port quick disconnect bags - stowage bags filled with maintenance hardware and tools - from the airlock and installed the bags on top, or the zenith side, of the airlock.

The thirdEVA by RobertCurbeam and SunitaWilliams was conducted on December 16, 2006 (7h 31m) to reconfigure power on channels 1 and 4 of the station's electrical system.
The third spacewalk on flight day 8 was basically a repeat of the flight day 6 power reconfiguration activities. DuringEVA 3, the Channel 1/4 side of the station's Electrical Power System was reconfigured to route primary power through the Main Bus Switching Units. As on flight day 6, this spacewalk required that all power be shut down - this time from Channel 1/4. Again, a lengthy set of power down procedures were executed from the ground while the crew prepared for the walk.
The work again was at the Starboard 0 (S0) truss segment. RobertCurbeam reconfigured the S0 forward starboard avionics and theS1-4B andS0-1A dc converters, disconnected the secondary power Lab 4A dc converters, routed theS0/N1 power cable, and reconfigured the bus bypass jumper.
While he was disconnecting and connecting cables, SunitaWilliams removed the 1 and 2 circuit interrupt devices and reconfigured the other half of theZ1 truss electrical patch panel 5. The circuit interrupters were returned on the shuttle. Also, during theZ1 patch panel task, the crew ventured out to the Russian segment interface atNode 1 and reconfigured the Russian power feeds from the U.S. segment. This reconfiguration allowed the Russians to draw additional power from the U.S. segment by moving some of their power feeds to larger switches, capable of transferring more current, should that be needed.
As RobertCurbeam and SunitaWilliams reconfigured external power connectors, the crew inside reconfigured an electrical patch panel in the Destiny lab. This new configuration will provide twice as much power for payload use.
Once power was reconfigured for Channel 1/4, RobertCurbeam and SunitaWilliams moved to the shuttle's payload bay to attach three Service Module Debris Panel bundles (SMDPs) on to an adapter. The three bundles and adapter were launched on the Integrated Cargo Carrier (ICC), a pallet located at the rear of the payload bay. Once the bundles were attached to the adapter, the assembly is referred to as "the Christmas tree".
SunitaWilliams worked from the shuttle arm to move the "Christmas tree" to stow it on the grapple fixture located on the aft side of thePressurized Mating Adapter 3. The bundles are composed of individual panels that were installed on the Service Module to provide additional micrometeroid debris protection.
While SunitaWilliams completed clean-up of the task, RobertCurbeam moved to reconfigure power to theZ1 truss electrical patch panel 1.
During the third spacewalk, RobertCurbeam and SunitaWilliams also transferred the Adjustable Grapple Bar (AGB) - a portable handle that can be installed on objects to make it easier for the crew to move them around during spacewalks - to the Flex Hose Rotary Coupler (FHRC) on the airlock's External Stowage Platform-2, where it was stowed for future use.
As an "add-on task" to theEVA, astronauts RobertCurbeam and SunitaWilliams also continued work on the retraction of a sticking solar array, enabling the retraction of another six sections of theP6 array. At the end of theEVA there were another 11 "bays", or 35% left to retract.

The fourth and unplanned EVA by RobertCurbeam and ChristerFuglesang was performed on December 18, 2006 (6h 38m) to try to fully close the last eleven bays of the balkyP6-port Solar Array Wing. The rapidly plannedEVA was successfully completed.

With additional inspections of Discovery's heat shield after undocking, the orbiter departed the station with the shuttle robotic arm and Orbiter Boom Sensor System (OBSS) in their stowed configuration. TheOBSS was unstowed to accommodate the inspections.
Once Discovery was ready to undock, ChristerFuglesang sent a command to release the docking mechanism. At initial separation of the spacecraft, springs in the docking mechanism pushed the shuttle away from the station. Discovery's steering jets were shut off to avoid any inadvertent firings during the initial separation.
Once Discovery was about two feet (61 centimeters) from the station, with the docking devices clear of one another, WilliamOefelein activated the steering jets to very slowly move away. From the aft flight deck, WilliamOefelein manually controlled Discovery within a tight corridor as it separated from the station - essentially the reverse of the task performed by MarkPolansky during rendezvous.
Discovery continued away to a distance of about 450 feet (137.2 meters), where WilliamOefelein guided the shuttle in a circular flyaround of the station. Once Discovery completed 1.5 revolutions of the complex, WilliamOefelein fired Discovery's jets to depart the station's vicinity for the final time.
Discovery separated to a distance of about 40 nautical miles (74 km) and remained there to protect for a return to the complex in the unlikely event the late inspection reveals any damage to the shuttle's thermal heat shield.

Flight day 12 began for the astronauts at 12:48UTC. They spent the day verifying the integrity of Discovery's heat shield and preparing for deorbit and landing on December 22, 2006 (Flight day 14). Because of the extended spaceflight, the shuttle was required to make a landing attempt on flight day 14 unless all three landing sites were "no-go". Two satellites were also launched: MEPSI (Microelectromechanical System-Based PICOSAT Inspector) resembles a pair of tethered coffee-cups, and is being tested as a reconnaissance option for disabled satellites; RAFT (Radar Fence Transponder) is a pair of 5" (12.7 centimeters) cubes built by the U.S. Naval Academy which will test space radar systems and also act as data relays for mobile ground communications.

On flight day 13 Discovery's crew launched the ANDE (Atmospheric Neutral Density Experiment) microsats for the Naval Research Laboratory, which were designed to measure the density and composition of the low Earth orbit atmosphere in order to help better predict the movements of objects in orbit, but one of the satellites failed to emerge from its launch canister. ANDE is currently transmitting data, and emerged from the canister approximately 30 minutes after its launch according to satellite tracking data.

High cross-winds precluded a landing at Edwards Air Force Base while clouds and showers were an issue at Kennedy Space Center Shuttle Landing Facility on the first orbit. That combination raised the possibility of the first landing at White Sands Space Harbor sinceSTS-3 in 1982. Had landing taken place at White Sands, it could have taken as long as 60 days to return the orbiter to Kennedy Space Center. The first landing opportunity at Kennedy Space Center was abandoned due to unfavorable weather conditions. However, at 21:00UTC coordinates were sent to the shuttle to re-attempt a landing at Kennedy along runway 15, as the first contingency landing attempt at Edwards had been scrubbed due to high cross winds.