Article 5. Gateway Elements
5.5 The Gateway is comprised of the following elements, although the Parties recognize these are subject to change in the course of the detailed design, development, and operation of the Gateway. The Parties intend for an up-to-date listing of all of the Gateway's elements to be maintained in accordance with Article 8 (Management).
(a) NASA:
1. Power and Propulsion
2. Habitation Capability
3. Avionics and Communications Infrastructure
4. Logistics Resupply
5. Crew Transportation
6. Extravehicular Activity (EVA) System
(b) CSA:
1. External Robotic Capability
2. External Robotics Interfaces
3. End-to-End External Robotic Operations
(c) ESA:
1. Habitation Capability (I-Hab)
2. Enhanced Lunar Communications
3. Refueling and Viewing Capability
4. European Service Modules in support of Orion missions
(d) The GOJ [Japan]:
1. Habitation Capability Infrastructure Functions
2. Logistics Resupply
(e) ROSCOSMOS:
1. Crew Airlock
Article 6. Major Program Milestones
6.1 Major target milestones are as follows:
(a) 2023 — Delivery of the first Gateway element, power and propulsion, to lunar orbit
(b) 2023 — Delivery of the initial habitation capability with enhanced lunar communications to the Gateway
(c) 2024 — Gateway ready for the first crewed mission
(d) 2025 — Delivery of additional habitation capability to the Gateway (I-Hab)
(e) 2026 — Delivery of external robotic capability to the Gateway
(f) 2027 — Delivery of refueling and viewing element to the Gateway
(g) 2028 — Delivery of the crew airlock to the Gateway
https://assets.documentcloud.org/documents/20417948/memorandum-of-understanding-between-the-nallonal-aeronautics-and-space-administration-of-tiie-united-states-of-america-and-the-european-space-agency-concerning-cooperation-on-the-civil-lunar-gateway.pdf 
