EWS-G2 (GOES 15)

EWS-G2, catalogued under NORAD ID 36411 and international designator 2010-008A, is a geostationary weather satellite currently operated by the United States Space Force. Originally launched as GOES-15 in March 2010 under the stewardship of the National Oceanic and Atmospheric Administration (NOAA), the spacecraft has since transitioned roles and designations while remaining in orbit. Built by Boeing on the proven BSS-601 satellite bus, it represents the final member of a trio of GOES satellites sharing that platform. As of the time of writing, the spacecraft remains in orbit, continuing its decades-long story as one of the longer-serving members of the American geostationary environmental monitoring fleet.

Mission and Purpose

The Geostationary Operational Environmental Satellite (GOES) program has been a cornerstone of American meteorological infrastructure for decades, providing continuous imaging and atmospheric sounding data across the Western Hemisphere. GOES-15, now redesignated EWS-G2, was designed to fulfill the standard mission profile of the GOES series: near-continuous observation of cloud cover, storm systems, sea surface temperatures, and a range of atmospheric phenomena from a fixed vantage point above the equator.

During its years of active NOAA operations, GOES-15 served primarily as a backup and operational asset for the western United States and the Pacific basin, a region where reliable meteorological surveillance is critical for tracking Pacific storms, monitoring wildfire smoke, and supporting aviation weather services. The satellite's imager and sounder instruments were capable of capturing visible, infrared, and water vapor imagery at regular intervals, feeding data into forecast models relied upon by federal agencies, emergency managers, and commercial weather services alike.

The transition to the EWS-G2 designation reflects a handover to the U.S. Space Force, which took on responsibility for the spacecraft as part of the Environmental Weather Satellite (EWS) program — an effort to repurpose aging GOES assets for national security-oriented weather monitoring. Under this arrangement, the satellite's operational mission and specific tasking are not publicly detailed in standard catalog records, and the current mission type and status are not definitively confirmed in open sources. What is clear is that the hardware and its geostationary position continue to offer value to operators beyond its original civilian meteorological mandate.

Orbit and Tracking

EWS-G2 occupies a near-circular geostationary orbit, consistent with its role as a continuously positioned Earth observation platform. The spacecraft's apogee is recorded at 35,816 km and its perigee at 35,771 km, placing it in a remarkably tight, stable band characteristic of well-maintained geostationary satellites. The slight difference between these two figures reflects a marginally elliptical orbit rather than a perfectly circular one, though the deviation is minor and typical of operational geostationary platforms after years of station-keeping maneuvers.

The orbital inclination is 1.2°, a small but nonzero figure indicating that the satellite's orbital plane is very slightly tilted relative to the equatorial plane. A perfectly geostationary satellite would ideally have an inclination of 0°, keeping it fixed above a single point on the equator. An inclination of 1.2° introduces a slow, predictable north-south oscillation — a figure-eight pattern in the sky known as an analemma — as seen from a fixed ground point. This is common in satellites that have aged past their active station-keeping phase or are operating with reduced propellant reserves.

The orbital period of 1,436.1 minutes — very close to 24 hours — confirms the satellite's membership in the geostationary belt, where objects orbit at the same angular rate as Earth's rotation. Tracking EWS-G2 is largely a matter of maintaining a fixed or near-fixed pointing angle for ground antennas, rather than actively tracking a moving target as would be necessary for low Earth orbit objects. Its NORAD catalog entry (36411) allows observers and tracking systems worldwide to monitor its position and any gradual drift that may occur over time.

Design and Operator

EWS-G2 was manufactured by Boeing and is based on the BSS-601 satellite bus, a platform with a long heritage in commercial and government satellite programs. The BSS-601 (sometimes referred to as HS-601 in older documentation) was a widely used medium-to-large class geostationary bus capable of supporting substantial payloads and offering multi-year operational lifespans. Within the GOES series, three satellites shared this platform: GOES-13, GOES-14, and GOES-15. The latter — now EWS-G2 — was the last of the three to be launched, and the platform's use in the GOES program concluded with it.

GOES-13 and GOES-14 preceded EWS-G2's original launch by several years, with the three spacecraft forming a generational cohort within the broader GOES program. EWS-G2 was the sixteenth GOES satellite launched overall, a milestone that underscores the program's long operational continuity.

The spacecraft has a mass of 1,800 kg, placing it in the medium-to-large category among geostationary satellites. This mass reflects the combined weight of the bus structure, propellant, and scientific instrument complement. Primary operational responsibility now rests with the U.S. Space Force rather than NOAA, though the spacecraft's country of ownership remains the United States. The specific configuration of its current operational payload and instruments in its EWS-G2 role is not publicly detailed in catalog records.

Significance and Current Status

EWS-G2's trajectory from a civilian weather satellite to a military-affiliated asset illustrates a broader trend in American space policy: the deliberate extension of useful satellite lifespans beyond their original mission profiles, particularly when repositioning or repurposing can serve national security needs at a fraction of the cost of launching new hardware. The Environmental Weather Satellite program represents an acknowledgment that geostationary weather observation has strategic as well as scientific value, and that older but functional spacecraft can fill coverage gaps in areas of interest to defense operators.

GOES-15's original operational period under NOAA was notable for its contributions to Pacific weather monitoring. It served as the primary GOES-West satellite during portions of its NOAA service life and provided critical backup coverage during various periods when other assets underwent maintenance or experienced anomalies. Its longevity reflects the quality of the BSS-601 platform and the disciplined management of propellant and power resources by ground controllers over many years.

As of the most recent catalog data, EWS-G2 remains in orbit and has not undergone reentry. Its near-geostationary orbital parameters indicate ongoing or recent station-keeping activity, or at least that no major orbital decay has occurred. Geostationary satellites at end of life are typically raised into a graveyard orbit several hundred kilometers above the geostationary belt to prevent long-term debris clutter in the operationally valuable GEO zone. Whether EWS-G2 has reached that phase or continues in an operational or standby capacity is not confirmed in publicly available catalog records.

The satellite's long life in orbit — spanning from its 2010 launch to the present — positions it among a select group of American geostationary spacecraft that have remained relevant across multiple operational eras. From its origins as part of NOAA's civilian environmental monitoring mandate to its current designation under Space Force stewardship, EWS-G2 reflects the evolving complexity of how the United States manages and assigns its space-based assets over time.

How to Spot It

EWS-G2 is a geostationary satellite, which means it does not move across the sky in the way that low Earth orbit objects do. From any fixed location, it appears as a stationary point relative to the background stars, hovering above a fixed point near the equator. Because of this, it cannot be observed as a moving track in the manner of the International Space Station or polar-orbiting Earth observation satellites.

At an altitude of approximately 35,800 km, EWS-G2 is far fainter than naked-eye visibility thresholds for most observers. Spotting geostationary satellites typically requires at least a moderate-aperture telescope and knowledge of precise pointing coordinates. The satellite's slight inclination of 1.2° means it traces a very slow, shallow figure-eight pattern over the course of a sidereal day rather than remaining perfectly locked over a single equatorial longitude, but this motion is far too gradual to be perceptible in short observation sessions.

Dedicated amateur astronomers who specialize in geostationary satellite observation can use the NORAD catalog ID 36411 and current two-line element sets to calculate the satellite's precise sky coordinates and confirm its position using long-exposure photography or video astronomy equipment.