Goddard Engineering and Technology Directorate

Telemetry and Command (T&C) Systems

Artist's concept of Laser Communication Relay Demonstration (LCRD) in geosynchronous orbit transmitting. LCRD is one of the many missions ETD's Telemetry and Command Systems' capabilities have supported. Credit: NASA
Artist’s concept of Laser Communication Relay Demonstration (LCRD) in geosynchronous orbit transmitting. LCRD is one of the many missions ETD’s Telemetry and Command Systems’ capabilities have supported. Credit: NASA

Supporting Missions from Ground to Orbit

The Engineering and Technology Directorate (ETD) at Goddard Space Flight Center developed two flagship Telemetry and Command (T&C) systems:

  • Advanced Spacecraft Integration and System Test (ASIST)
  • Integrated Test and Operations System (ITOS)

ETD engineers designed these systems to meet the evolving needs of NASA’s diverse mission portfolio, leveraging decades of flight operations experience. Through continuous improvement cycles, ETD has enhanced these capabilities to incorporate modern software practices while still preserving their mission-proven core functionalities. These systems exemplify ETD’s role in bridging spacecraft integration and on-orbit operations phases, advancing NASA’s ground systems technology to support increasingly complex space missions.

Both ASIST and ITOS are robust, mature, configurable, and reliable real-time T&C systems capable of processing and encoding/decoding standard Consultative Committee for Space Data Systems (CCSDS) and framing protocols. Typically used across the earlier phases of pre-launch spacecraft design, as well as later during mission, science, and payload activities to generate raw or minimally processed data, they logged hundreds of thousands of hours in component and spacecraft development, integration, and operations.

For testing, ASIST and ITOS can simulate software, driven only by a database with Systems Test and Operations Language (STOL) procedures, or hardware, connected through MIL-STD-1553, SpaceWire, or synchronous serial cards. Both systems are managed by the Code 583 T&C Service Line, which provides extensive user support and training for developers, testers, and operators.

ASIST

ASIST pairs with the Front-End Data System (FEDS) ground subsystem to address space mission needs and requirements independently or in tandem. Together, they create a powerful interface capable of handling CCSDS communications as well as a rich ecosystem for packet handling, data extraction and distribution, as well as display and STOL interaction critical to the spacecraft environment.

ITOS

ITOS is capable of decoding most advanced frame formats and performing frame synchronization, Cyclic Redundancy Check, error correction, and pseudo randomization of data without a dedicated Front-End Processor that traditionally handles the initial processing of downlinked telemetry. ITOS can also run fully headless as a background service, attaching to a graphical user interface as necessary.

ASIST & ITOS are managed by ETD’s Software Engineering Division (SED). Contact SED for more information.