External Stowage Platform

External stowage platforms (ESPs) are key components of the International Space Station (ISS). Each platform is an external pallet that can hold spare parts, also known as Orbital Replacement Units (ORUs), for the space station. As a platform it is not pressurized, but does require electricity to power the heaters of some of the stored equipment. ORUs are attached to the ESP via Flight Releasable Attachment Mechanisms (FRAMs), matching witness plates that mate the ORU to the platform.

While ESP-1 is unique in shape, ESP-2 and ESP-3 were based on the deployable version of the Integrated Cargo Carriers (ICC), which were designed to transport unpressurized cargo inside the Space Shuttle's cargo bay. ESP-1 was transported to the International Space Station on STS-102, ESP-2 flew on mission STS-114 'Return to Flight' and ESP-3 on mission STS-118.

The first of the external stowage platforms, called ESP-1, was installed on the port side trunnion pin on the outer hull of the Destiny Laboratory Module on March 13, 2001 during the second EVA of the STS-102 Space Shuttle mission. It is powered by the Unity Module and has two attach points to store ORUs.

ESP-1 was carried into orbit on the underside of an Integrated Cargo Carrier. It is smaller than the other ESPs and ELCs, with dimensions approximately 0.46 m wide by 2.4 m long, and is differently shaped.

ESP-1 holds the following ORUs:

ESP-1 and hardware installation locations on the Destiny during STS-102

ESP-1 attached to the Destiny portside trunnion pin, PFCS on the left

Another view of ESP-1

ESP-1 attached to the Destiny portside trunnion pin on the right

...
Wikipedia