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Zarya (Russian: Заря́; lit. dawn), also known as the Functional Cargo Block or FGB (from the Russian "Функционально-грузовой блок", Funktsionalno-gruzovoy blok or ФГБ), was the first module of the International Space Station to be launched. The FGB provided electrical power, storage, propulsion, and guidance to the ISS during the initial stage of assembly. With the launch and assembly in orbit of other modules with more specialized functionality, Zarya is now primarily used for storage, both inside the pressurized section and in the externally mounted fuel tanks. The Zarya is a descendant of the TKS spacecraft designed for the Russian Salyut program. The name Zarya was given to the FGB because it signified the dawn of a new era of international cooperation in space. Although it was built by a Russian company, it is owned by the United States.


Construction

The FGB design was originally intended as a module for the Russian Mir space station, but was not flown as of the end of the Mir program. A FGB cargo block was incorporated as an upper stage engine into the Polyus spacecraft, flown (unsuccessfully) on the first Energia launch. With the end of the Mir program, the design was adapted to use for the International Space Station.

The research and development of similar design was paid for by Russia and the Soviet Union, the design of the module and all systems are Soviet/Russian. The United States funded Zarya through the U.S. prime contracts in the 1990s as the first module for ISS. Built from December 1994 to January 1998 in Russia at the Khrunichev State Research and Production Space Center (KhSC) in Moscow, its control system was developed by the Khartron Corp. (Kharkiv, Ukraine). The module was included as part of NASA's plan for the International Space Station (ISS) instead of Lockheed's "Bus-1" option because it was significantly cheaper (US$220 million vs. $450 million). As part of the contract Khrunichev constructed much of an identical module (referred to as "FGB-2") for contingency purposes. FGB-2 has been proposed for a variety of projects; it is now slated to be used to construct the Russian Multipurpose Laboratory Module Nauka.


Design

Zarya weighs 19,300 kilograms (43,000 lb), is 12.55 meters (41.2 ft) long and 4.1 meters (13 ft) wide at its widest point.

The module has three docking ports: one axially on the front end at the docking sphere, one on the earth-facing side (nadir) of the docking sphere and one axially on the aft end. Attached to the forward port is the Pressurized Mating Adapter PMA-1, which in turn is connected to the Unity Module – this is the connection between the Russian Orbital Segment (ROS) and the US Orbital Segment (USOS). Attached to the aft port is the Zvezda Service Module. The lower port (nadir) was initially used by visiting Soyuz spacecraft and Progress spacecraft to dock to the ROS; The Rassvet module is now docked semipermanently on the nadir port of Zarya, and visiting spacecraft use Rassvet's nadir docking port instead.

Zarya has two solar arrays measuring 10.67 by 3.35 meters (35.0 by 11.0 ft) and six nickel-cadmium batteries that can provide an average of 3 kilowatts of power – the solar arrays have been however retracted so the P1/S1 radiators of the Integrated Truss Structure could deploy. Zarya has 16 external fuel tanks that can hold over 5.4 metric tons of propellant. Zarya also has 24 large steering jets, 12 small steering jets, and two large engines that were used for reboost and major orbital changes; with the docking of Zvezda these are now permanently disabled. Since they are no longer needed for Zarya's engines, Zarya's propellant tanks are now used to store additional fuel for Zvezda.


Launch and flight

Zarya was launched on November 20, 1998 on a Russian Proton rocket from Baikonur Cosmodrome Site 81 in Kazakhstan to a 400 km (250 mi) high orbit with a designed lifetime of at least 15 years. After Zarya reached orbit, STS-88 launched on December 4, 1998 to attach the Unity Module.

Although only designed to fly autonomously for six to eight months, Zarya was required to do so for almost two years due to delays to the Russian Service Module, Zvezda. Zvezda was finally launched on July 12, 2000, docking with Zarya on July 26 using the Russian Kurs docking system.

Zarya initially had problems with battery charging circuits, but these were resolved.

Zarya passed the 50,000-orbit mark at 15:17 UTC on August 14, 2007 during the STS-118 mission to the International Space Station.