Despite being funded only through the end of 2015, there is widespread political support domestically and internationally to extend the ISS' operations through 2020 and beyond. However, the Space Shuttle fleet is due to be retired by the end of 2010, which would make unavailable large parts that are deliverable only by the Space Shuttle and its massive cargo bay.

In order to mitigate this problem, NASA has planned a series of flights that will deliver large-sized spare parts to the ISS, starting with yesterday's launch of the Space Shuttle Atlantis. There are nearly 30,000 pounds (13.6 tons) of parts and equipment that will be delivered during STS-129.

"In terms of being the flight that brings up all the spares for station, this is really full," said Bill Gerstenmaier, NASA's Director of Space Operations. "This flight, and a couple of the other shuttle flights that come later, really set us up very well for kind of the end of the shuttle servicing era."

Atlantis' payload bay is chock full of equipment and parts mounted on two cargo pallets, known as ExPRESS Logistics Carriers (ELCs).

ELC-1 contains an Ammonia Tank Assembly (ATA), a Battery Charge Discharge Unit (BCDU), a Space Station Remote Manipulator System (SSRMS) Latching End Effector (LEE) that will be used in the station's Canadarm2 robotic arm, a Control Moment Gyro (CMG), a Nitrogen Tank Assembly (NTA), a Pump Module (PM), a Plasma Contactor Unit (PCU), and two empty Passive Flight Releasable Attachment Mechanisms (PFRAMs) used for storage.

A box containing spare circuit breakers and a Canadian robot known as DEXTRE are mounted on the outside.

ELC-2 contains a High Pressure Gas Tank (HPGT), a Cargo Transport Container 1 (CTC-1) mounted to a Small Adapter Plate Assembly (SAPA), a Utility Transfer Assembly (UTA), an empty Payload PFRAM,and a Mobile Transporter/Trailing Umbilical System (MT/TUS) used in the Canadarm2. There is also an extra Control Moment Gyro, a Nitrogen Tank Assembly, and Pump Module. ELC-2 also contains flight equipment and MISSE-7.

The Materials International Space Station Experiment 7 (MISSE-7) is a test bed for
advanced materials and electronics that will be attached to the outside of the ISS. These
materials and electronics include solar cells, coatings, thermal protection, optics, sensors, and computing elements could be used in the next generation of satellites, space probes and launch systems.

There is also a spare S-band Antenna Support Assembly (SASA) that will be attached
to the sidewall inside the space shuttle payload bay. The SASA is an assembly that consists of the Assembly Contingency Radio Frequency Group, SASA Boom, and Avionics Wire Harness.  It is used to communicate with NASA's fleet of Tracking Data and Relay Satellites, which are used to ensure fast and reliable communications with Mission Control.

The two ELC pallets will be mounted on the left and right sides of the station's primary solar power truss. Connections will be made to the electrical grid of the ISS in order to power heaters and provide telemetry. The new oxygen tank will be attached to the station's airlock during one of the three spacewalks.

"It is establishing critical spares on board the International Space Station," commented  lead shuttle Flight Director Mike Sarafin. "We're going to warehouse parts that only the shuttle can deliver in large volume to the International Space Station for the pending retirement of the space shuttle, roughly a year from now".

There are five more Space Shuttle missions scheduled, the final three of which involve the delivery of more spare parts.