Please make a donation to support Gunter's Space Page.
Thank you very much for visiting Gunter's Space Page. I hope that this site is useful and informative for you.
If you appreciate the information provided on this site, please consider supporting my work by making a simple and secure donation via PayPal. Please help to run the website and keep everything free of charge. Thank you very much.

T0TR 1, ..., 4 (Tracking Layer Tranche 0, BB)

The Tracking Layer is an experimental military satellite constellation developed by the SDA (Space Development Agency), which will provide global indications, warning, tracking, and targeting of advanced missile threats, including hypersonic missile systems.

SDA announced October 5 two contract awards for the first generation of the Tracking Layer. These awards represent the next major and highly visible steps toward developing the National Defense Space Architecture’s inaugural tranche (called Tranche 0). Once fully operational, the SDA Tracking Layer will consist of a proliferated heterogeneous constellation of Wide Field of View (WFOV) space vehicles (SVs) that provide persistent global coverage and custody capability combined with the Missile Defense Agency (MDA) Hypersonic and Ballistic Tracking Space Sensor (HBTSS) Medium Field of View (MFOV) SVs that provide precision global access capability. This set of contract awards will initiate the development of the first eight low-cost proliferated WFOV SVs. The capability demonstrated by the Tracking Layer Tranche 0 will provide missile warning and tracking information to national defense authorities, and tracking and cueing data for missile defense elements.

SDA’s Tracking Layer is exploring technical areas including, but not limited to:

  • Integrated, hybrid architectures including existing and planned missile warning / missile defense (MW/MD) capabilities,
  • Significant reductions in size, weight, power, and cost (SWaP-C) and/or significant performance improvements over traditional MW/MD hardware, software, algorithms, subsystem, component concepts or designs,
  • Identification and exploration of novel MW/MD sensing concepts or design, and
  • Enabling disciplines and technologies such as systems engineering, program security, cybersecurity, logistics, or mission and quality assurance.

Each satellite will have a “wide field of view” overhead persistent infrared (OPIR) sensor capable of detecting and tracking advanced missile threats from low Earth orbit. The satellites will also be equipped with optical crosslinks to pass data to the Transport Layer relay satellites.

In October 2020, SDA awarded contracts to SpaceX and L3Harris for each four Tranche 0 satellites. These are to be launched in 2022.

SpaceX’s missile-tracking satellite will be based on its Starlink bus with an OPIR sensor acquired from another supplier, Tournear said. He declined to name the payload provider and SpaceX has not disclosed subcontractors for the project.

Following Tranche 0, the SDA plans to continuously upgrade and add to its on orbit constellation in two year cycles, with Tranche 1 coming online in FY2024, Tranche 2 supplementing the system in FY2026.

Nation: USA
Type / Application: Early warning
Operator: SDA
Contractors: SpaceX (prime); Leidos (payload)
Configuration: Starshield bus ?
Propulsion: ?
Power: Solar arrays, batteries
Orbit: 950 km × 950 km, 80-89.5°
Satellite COSPAR Date LS Launch Vehicle Remarks
T0TR 1 (BB 1) 2023-050K 02.04.2023 Va SLC-4E Falcon-9 v1.2 (Block 5) with T0TL A-Cl. 1, ..., 5, T0TL B-Cl. 1, ..., 3, T0TR 1, 2
T0TR 2 (BB 2) 2023-050J 02.04.2023 Va SLC-4E Falcon-9 v1.2 (Block 5) with T0TL A-Cl. 1, ..., 5, T0TL B-Cl. 1, ..., 3, T0TR 1, 2
T0TR 3 (BB 3) 2023-133D 02.09.2023 Va SLC-4E Falcon-9 v1.2 (Block 5) with T0TL A-Cl. 7, ..., 13, T0TL B-Cl. 4, T0TL B-Cl. 5, ..., 7, T0TR 3, 4
T0TR 4 (BB 4) 2023-133B 02.09.2023 Va SLC-4E Falcon-9 v1.2 (Block 5) with T0TL A-Cl. 7, ..., 13, T0TL B-Cl. 4, T0TL B-Cl. 5, ..., 7, T0TR 3, 4
Further NDSA missions:

Tracking Layer Transport Layer Demonstration and Experimentation System
  • T1DES 1, ..., 12 [York]

Cite this page: