INTELSAT 21 (IS-21)

Intelsat 21 (IS-21) is a commercial geostationary communications satellite operated by Intelsat, one of the world's largest satellite services providers. Launched in August 2012, it has served as an orbital relay platform delivering telecommunications and broadcasting services across the Americas, particularly for operators and broadcasters relying on the 58° West longitude orbital slot in the geostationary arc. Catalogued by NORAD under identifier 38749 and internationally designated 2012-045A, the satellite continues to orbit the Earth at geostationary altitude as of this writing.

Mission and Purpose

IS-21 was placed at the 58° West longitude position in geostationary orbit, where it took over responsibilities from its predecessor, Intelsat 9, which had previously served that slot. The 58° West position sits above the Atlantic Ocean, offering a favorable line of sight to both South America and North America, making it well suited for delivering direct-to-home television, broadband connectivity, corporate networking, and other telecommunications services across the Western Hemisphere.

Communications satellites at this longitude are particularly valuable for Brazilian and broader South American markets, where demand for broadcast and data relay capacity has grown substantially over the decades. An orbital slot of this kind is a licensed resource governed by international coordination through the International Telecommunication Union, and the transition from Intelsat 9 to IS-21 represents a routine fleet-renewal strategy common among major satellite operators — retiring older hardware and replacing it with a higher-capacity platform to meet evolving commercial demand.

Intelsat is a Luxembourg-headquartered company with a long history of operating global satellite fleets, and the deployment of IS-21 was consistent with its strategy of maintaining continuous coverage across key orbital positions. The specific transponder configuration, frequency bands, and nominal payload capacity of IS-21 are not recorded in the public tracking catalog for this entry, but the satellite's role as a commercial relay payload is well established from its mission context.

Orbit and Tracking

IS-21 occupies a near-perfect geostationary orbit, as reflected in its tracked orbital parameters. Its apogee stands at 35,803 km and its perigee at 35,789 km, yielding an extremely low eccentricity that places the satellite in an essentially circular orbit approximately 35,790 km above the equator. The orbital inclination is recorded at 0.0°, confirming that the satellite's orbital plane is aligned with Earth's equatorial plane — a defining characteristic of true geostationary orbit, where the satellite's angular velocity matches the planet's rotation and the satellite appears stationary relative to ground-based observers.

The orbital period of IS-21 is 1,436.2 minutes, or just over 23 hours and 56 minutes, which closely matches the Earth's sidereal rotation period. This synchronization is what produces the satellite's apparent fixed position in the sky, an essential quality for the fixed-dish ground antennas used by the broadcasting and telecommunications customers it serves.

From a tracking perspective, geostationary satellites like IS-21 move so slowly relative to the ground that they appear essentially motionless to casual sky observers. Dedicated satellite-tracking tools can still resolve its precise sub-degree positional variations, which may shift slightly over time due to station-keeping maneuvers performed periodically to counteract gravitational perturbations from the Moon, Sun, and Earth's non-uniform gravitational field. IS-21 remains in orbit as of the most recent catalog update, with no decay or reentry date recorded.

The satellite is classified as a payload object — meaning it is the primary functional spacecraft rather than a spent rocket stage or mission-related debris — and carries NORAD catalog ID 38749 along with its international designator 2012-045A, the latter indicating it was the first catalogued object from the 45th orbital launch of 2012.

Design and Operator

IS-21 was built by Boeing Space Systems, also known as Boeing Satellite Systems (BSS), on the BSS-702MP satellite bus. The 702MP (Medium Power) is a well-established commercial platform that Boeing developed as a more flexible variant of its larger 702 series, designed to accommodate a wide range of payload configurations while remaining compatible with a broader selection of launch vehicles. The 702MP bus uses an all-electric or hybrid propulsion approach and incorporates high-efficiency solar arrays, though the specific power and propulsion configuration of IS-21 is not confirmed in the public catalog entry for this satellite.

The satellite was launched on 19 August 2012, at 06:54:59 UTC, by a Zenit-3SL rocket operating under the Sea Launch program. The Zenit-3SL was a Ukrainian-designed rocket adapted for launches from the Odyssey launch platform, a converted offshore oil-drilling vessel positioned on the equatorial Pacific Ocean for each mission. Launching from the equator provides a significant efficiency advantage for geostationary missions, as the rocket requires less energy to achieve the equatorial orbital inclination needed for geostationary transfer. Sea Launch was a joint commercial venture that operated a series of such missions in the 2000s and 2010s, and IS-21 was among its notable payloads.

The launch date recorded in the tracking catalog is 18 August 2012 in Eastern Daylight Time (20:00 EDT), which corresponds to the UTC launch date of 19 August 2012 given the time zone offset — a common source of minor discrepancy in catalog records that reference different time zones. The satellite's mass is not publicly recorded in the available catalog data.

Intelsat, the satellite's operator and owner, is one of the oldest and most extensive commercial satellite fleet operators in the world, tracing its origins to the International Telecommunications Satellite Consortium established in the 1960s. Today it operates a large fleet of geostationary satellites covering the globe, with IS-21 forming one node in that network above the Americas.

Current Status and Significance

IS-21 remains in active geostationary orbit, having now been on station for over a decade since its 2012 launch. Its sustained presence in orbit reflects the typical operational design lifetimes of commercial geostationary spacecraft, which are generally engineered for 15 years or more of service, contingent on propellant reserves for station-keeping and the health of onboard systems.

The satellite's positioning at 58° West has historically made it a key platform for South American telecommunications infrastructure. Brazil, in particular, represents one of the largest and fastest-growing satellite services markets in Latin America, and orbital slots at 58° West have strategic importance for reaching that market as well as neighboring countries across the continent.

As a replacement for Intelsat 9 at that slot, IS-21 continued a lineage of Intelsat presence at 58° West that predates its own launch, ensuring continuity of service for customers who had antenna infrastructure pointed at that fixed orbital position. This kind of slot continuity is an important commercial and logistical consideration: ground station operators generally prefer to avoid repointing fixed dish antennas, so a successor satellite placed precisely at the same orbital longitude minimizes disruption to existing customers.

The Boeing 702MP bus on which IS-21 is based has a strong operational heritage, with multiple satellites built on the same platform serving various operators worldwide. Its selection by Intelsat for this mission reflects the platform's reputation for reliability and its ability to carry competitive commercial payloads.

Because IS-21's specific mission status and current operational health are not recorded in the public tracking catalog, it is not possible to confirm from catalog data alone whether the satellite is actively serving customers, has been moved to a graveyard orbit, or is in a transitional operational state. No reentry or decay date is recorded, confirming that it has not reentered Earth's atmosphere. Satellites at geostationary altitude do not naturally decay within any human-relevant timeframe without deliberate maneuvers; the altitude is simply too high for atmospheric drag to play a meaningful role. End-of-life disposal for geostationary satellites typically involves raising the spacecraft into a slightly higher "graveyard orbit" several hundred kilometers above the geostationary belt, a practice encouraged by international guidelines to protect the operationally valuable geostationary arc from long-term debris accumulation.

Observability

IS-21 is a geostationary satellite and as such is not typically visible to the naked eye under normal conditions. Unlike low Earth orbit objects that streak visibly across the night sky, geostationary satellites remain fixed relative to the ground and are located at extreme altitude — roughly 35,800 km above the surface. At that distance, even sizable spacecraft do not generate sufficient reflected sunlight to be easily visible without optical aids.

Observers with binoculars or small telescopes and knowledge of where to look along the geostationary arc can sometimes detect such satellites as faint, stationary points of light amid the background stars. Because IS-21 sits at 0.0° inclination, it lies precisely on the celestial equator as seen from Earth, making it part of the continuous band of geostationary satellites that experienced observers can trace across that line of the sky. Dedicated satellite-tracking software fed with current two-line element (TLE) data can calculate the precise azimuth and elevation to IS-21 from any ground location, though visual detection without optical assistance remains unlikely for most observers.