TDRS 13

TDRS 13 (also identified by its pre-launch designation TDRS-M and catalogued under NORAD ID 42915 and international designator 2017-047A) is an American communications satellite operated by NASA. Launched on August 17, 2017, it serves as an orbital relay node within the Tracking and Data Relay Satellite System (TDRSS), a constellation of spacecraft that provides near-continuous communications links between ground controllers and assets operating in low Earth orbit. As the thirteenth member of the TDRSS fleet and the third and final spacecraft of the system's third generation, TDRS 13 represents the culmination of a decades-long program that has fundamentally shaped how NASA manages communications with crewed missions, science platforms, and robotic spacecraft.

Mission and Purpose

The Tracking and Data Relay Satellite System was developed to solve a persistent challenge in space operations: ground stations can only maintain line-of-sight contact with a low-orbiting spacecraft for a fraction of each orbit. By positioning relay satellites in high geostationary orbits, NASA created a set of communication bridges capable of providing coverage for the vast majority of any given orbital pass. TDRS 13 performs this relay function, receiving signals from user spacecraft in lower orbits and forwarding them to ground terminals, most notably the White Sands Complex in New Mexico, which serves as the primary ground node for the network.

The system supports an extraordinarily diverse range of users. The International Space Station depends heavily on TDRSS for its continuous voice, video, and data links. Scientific missions studying Earth's atmosphere, oceans, and land surfaces, as well as astrophysical observatories and space environment sensors, all route communications through the relay network. Historically, TDRSS also underpinned communications for crewed Space Shuttle missions. TDRS 13 and its sister satellites therefore occupy a role that is quietly indispensable to American human spaceflight and space science, even though the satellites themselves rarely attract the same public attention as the missions they support.

Before launch, TDRS 13 was referred to internally and in NASA planning documents as TDRS-M, following the alphabetical designation scheme used for satellites awaiting their orbital assignments. Upon successful on-orbit checkout and entry into service, it received the numerical designation TDRS 13. This naming transition is standard practice within the program and reflects the satellite's formal acceptance into the operational fleet.

Orbit and Tracking

TDRS 13 occupies a geostationary orbit, a regime approximately 35,786 kilometers above the equator where an object's orbital period naturally synchronizes with Earth's rotation, causing the satellite to appear nearly stationary when observed from the ground. According to current tracking data, the satellite's apogee stands at 35,856 km and its perigee at 35,733 km, indicating a very nearly circular orbit with only a modest difference between its highest and lowest points — a characteristic expected of a mature geostationary spacecraft that has completed its drift to an assigned slot. Its orbital inclination of 3.4 degrees represents a slight departure from a perfectly equatorial plane, a normal consequence of long-duration operations in geostationary orbit, where gravitational perturbations from the Moon and Sun gradually introduce a small inclination over time unless periodic north-south stationkeeping maneuvers are performed. The orbital period of approximately 1,436.2 minutes aligns closely with Earth's sidereal rotation period, confirming its geostationary character.

The satellite carries NORAD catalog ID 42915 and was assigned the COSPAR international designator 2017-047A, indicating it was the primary payload of the 47th orbital launch attempt of 2017. Tracking data maintained by the 18th Space Control Squadron and distributed through standard two-line element (TLE) sets allows the satellite's position to be monitored and its coverage footprint to be inferred. At its orbital altitude and inclination, TDRS 13 maintains a wide field of view over a substantial arc of Earth's surface, consistent with its role as a broadband relay in a system designed for near-hemispheric coverage.

The satellite remains in orbit as of the time of publication, with no decay or reentry event on record. Given its geostationary altitude, natural orbital decay is not a meaningful concern on any near-term timescale; spacecraft at this altitude remain in orbit for extremely long periods without active maintenance.

Design and Operator

TDRS 13 was built by the Boeing Satellite Development Center, a major American commercial satellite manufacturer with extensive experience producing large geosynchronous spacecraft for both government and commercial customers. The satellite has a launch mass of 3,770 kg, placing it in the category of large geostationary communications platforms. This mass is consistent with the size and capability expected of a third-generation TDRSS spacecraft, which are generally more capable and more massive than their predecessors in the program's first and second generations.

The TDRSS program is owned and operated by NASA, specifically managed through the agency's Space Communications and Navigation (SCaN) program office. NASA relies on the relay network to meet the communications requirements of its human spaceflight programs, Earth-observing science missions, and deep-space mission support where TDRSS coverage is applicable. The United States is listed as the owner country, consistent with TDRS 13's status as a government asset funded and operated through federal space appropriations.

Third-generation TDRSS spacecraft, of which TDRS 13 is the final example, incorporated design improvements over earlier generations to increase data throughput, extend service life, and provide enhanced flexibility in supporting a growing and evolving user community. TDRS 11 and TDRS 12 preceded TDRS 13 as the first and second third-generation spacecraft, with TDRS 12 having launched in 2014. TDRS 13's launch in 2017 completed the planned third-generation replenishment of the fleet and provided NASA with a measure of redundancy and longevity for the network going forward.

Significance and Current Status

The completion of the third-generation TDRSS constellation with the launch and commissioning of TDRS 13 marked the end of a long procurement and deployment arc that began when NASA first recognized the limitations of ground-only tracking networks. The TDRSS concept, which dates to planning efforts in the 1970s and whose first satellites entered service in the 1980s, has proven durable enough that it has been expanded and refreshed across three generations of spacecraft while remaining fundamentally committed to the same relay architecture. TDRS 13's arrival closed out the third generation and provided NASA with a fleet offering substantial operational overlap between older and newer satellites, an important hedge against the failure or degradation of any individual node.

The satellite's role in supporting the International Space Station is particularly significant from a programmatic perspective. The ISS requires enormous amounts of communications bandwidth to support science operations, crew communications, telemetry, and command uplinks. Without a robust relay network, maintaining that level of contact would require a far more extensive and geographically dispersed ground station network. TDRSS, and by extension TDRS 13, makes continuous high-data-rate contact feasible from a small number of ground facilities.

The specific details of TDRS 13's current operational assignment — including which orbital longitude slot it occupies and which users it actively serves at any given time — are managed by NASA's SCaN program and are subject to change as the agency adjusts its relay architecture in response to operational demands and fleet management considerations. These operational specifics are not always publicly catalogued in standard satellite databases.

Although the LowEarth catalog entry for TDRS 13 does not record a specific mission type or current mission status in its public metadata fields, this absence reflects the conventions of catalog data management rather than any ambiguity about the satellite's general purpose. TDRS 13 is a well-documented relay communications asset whose broad function is publicly established, even where fine-grained operational details are not published in open registries.

Looking ahead, NASA has been developing its next-generation space communications architecture under the Space Communications and Navigation program, which envisions transitioning some relay functions toward commercial service providers as the legacy TDRSS fleet ages. TDRS 13, as the youngest and most recently launched member of the TDRSS fleet, is positioned to remain a relevant operational asset for years to come, providing continuity as NASA's communications strategy evolves through the mid-2020s and beyond.