EOS-6 (OCEANSAT-3)

EOS-6, formally designated Oceansat-3 and catalogued under NORAD ID 54361 with the international designator 2022-158A, is an Indian Earth observation satellite operated by the Indian Space Research Organisation (ISRO). Launched in late November 2022 aboard a Polar Satellite Launch Vehicle (PSLV) from the Satish Dhawan Space Centre on India's southeastern coast, the spacecraft is the third member of ISRO's dedicated Oceansat lineage — a series that has, over more than two decades, built India's indigenous capacity to monitor the world's oceans from space. Flying in a nearly circular sun-synchronous orbit at altitudes approaching 740 kilometres, EOS-6 continues and expands upon a tradition of ocean-colour and sea-surface monitoring that its predecessors established.

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Mission and Purpose

The Oceansat programme was conceived to give India — and the broader international scientific community — consistent, space-based access to oceanographic data that would otherwise require extensive and expensive ship-based surveys. Ocean-colour imaging, sea-surface temperature mapping, and sea-surface wind measurement are among the core observational disciplines that satellites in this family are designed to support. These measurements underpin a wide range of applications: fisheries management, monsoon forecasting, coastal ecosystem monitoring, ship-routing, and contributions to global climate research. Each successive Oceansat mission has been designed with improved or expanded instrumentation relative to its forerunner, maintaining continuity of data records while increasing their resolution and coverage.

EOS-6 — the "EOS" prefix reflecting ISRO's broader Earth Observation Satellite naming convention adopted in recent years — carries on this mandate as the third generation in the series. Its principal scientific objective is to enhance remote sensing capabilities in the field of oceanography, building on datasets accumulated since the original Oceansat-1 launched in 1999. Continuity is a key word here: long-term ocean data records are scientifically valuable only when successive missions can be cross-calibrated and compared, so the design and objectives of EOS-6 were shaped with backward compatibility with earlier datasets very much in mind.

The mission sits within India's wider commitment to developing an independent, reliable capacity for Earth observation. Rather than depending on data purchased from foreign providers, ISRO's Earth observation programme — of which the Oceansat series is a flagship component — ensures that Indian government agencies, research institutions, and disaster-management bodies have direct and sovereign access to remotely sensed information about the country's extensive coastline, adjacent seas, and the broader Indian Ocean region.

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Orbit and Tracking

EOS-6 occupies a sun-synchronous orbit (SSO), one of the most widely used orbital regimes for Earth observation satellites. In a sun-synchronous orbit, the satellite's orbital plane precesses at a rate that keeps it aligned with the Earth-Sun direction throughout the year, meaning the spacecraft passes over any given point on Earth's surface at approximately the same local solar time on each successive visit. This consistency is scientifically important: by ensuring that lighting conditions are nearly identical from one overpass to the next, sun-synchronous orbits make it far easier to detect genuine changes on the surface rather than artefacts introduced by varying sun angles.

According to current tracking data, EOS-6 maintains an apogee of 741 km and a perigee of 738 km, making it an extremely circular orbit with a difference of only 3 km between its highest and lowest points. This near-perfect circularity is characteristic of a well-executed operational insertion and helps ensure uniform imaging geometry across the satellite's swath. The orbital inclination is 98.4°, consistent with a retrograde, sun-synchronous trajectory — slightly past 90° to achieve the necessary nodal precession. The satellite completes one full revolution of Earth approximately every 99.5 minutes, translating to roughly 14 to 15 orbits per day and providing frequent revisit opportunities over ocean and coastal regions.

At an orbital altitude of roughly 740 km, EOS-6 remains well within the thermosphere but comfortably above the denser atmospheric layers that cause rapid orbital decay for lower satellites. As of the time of writing, the spacecraft has not re-entered and continues to operate in orbit. Trackers and satellite observers can locate EOS-6 using its NORAD catalog number 54361 on standard tracking platforms. Passes are predictable and can be computed for any ground location using publicly available two-line element (TLE) data.

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Design and Operator

EOS-6 was built and launched under the authority of the Indian Space Research Organisation (ISRO), the government agency responsible for India's space programme. ISRO is headquartered in Bengaluru and operates a network of facilities including the Satish Dhawan Space Centre at Sriharikota, the spaceport from which the satellite was lofted. The agency has a long track record with the PSLV launch vehicle, which has become one of the most reliable medium-lift rockets in the world and the workhorse of India's Earth observation launch manifest.

The satellite was launched on 25 November 2022 (Eastern Standard Time), corresponding to 26 November 2022 at 06:26 UTC, reflecting the overnight launch window at Sriharikota that placed it into its sun-synchronous orbit efficiently. PSLV missions to sun-synchronous orbits are a routine but technically demanding operation, requiring precise injection to achieve the target inclination and altitude that define the orbit's repeating ground track.

Specific details regarding the satellite's mass and the identity of its primary hardware manufacturer are not recorded in the public catalog entry for this object. What is publicly known is that Oceansat-class satellites carry ocean-colour monitors, sea-surface temperature radiometers, and, in some configurations, scatterometers for wind-vector retrieval — instrument types that are standard for this class of oceanographic mission. The precise payload complement of EOS-6 reflects ISRO's engineering evolution over the two-plus decades since the first Oceansat mission.

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Significance and Context

The Oceansat series holds a particular place in the history of space-based oceanography. Oceansat-1, launched in 1999, was India's first dedicated ocean observation satellite and provided ocean-colour data that was used not only domestically but shared with international partners. Its successor continued and refined that work. EOS-6 represents the programme's maturation: three generations of operational satellites have now accumulated a data archive spanning more than two decades, a record long enough to begin examining decadal-scale changes in ocean biology, temperature patterns, and surface wind regimes.

From a geopolitical and scientific standpoint, India's ability to independently sustain this observation capability is significant. The Indian Ocean is among the most dynamically important ocean basins on Earth, influencing the monsoon system that delivers rainfall to more than a billion people across South and Southeast Asia. Sustained observation of sea-surface temperatures, chlorophyll concentrations, and wind fields in this basin contributes directly to seasonal forecasting systems that have real consequences for agricultural planning, disaster preparedness, and water resource management.

EOS-6 also fits within a broader pattern of international collaboration in Earth observation. Ocean-colour data from satellites in this lineage has historically been shared through frameworks that allow cross-calibration with instruments on satellites operated by NASA, ESA, and other agencies — extending the scientific value of any single mission well beyond the borders of its operating country.

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How to Spot It

EOS-6 orbits at approximately 740 km altitude in a sun-synchronous trajectory inclined at 98.4°, which means it passes over virtually every location on Earth between roughly 82° north and south latitude — essentially global coverage. At this altitude and with a typical spacecraft profile, it may be visible to the naked eye under favorable conditions, though it is not among the brightest satellites in low Earth orbit and lacks the conspicuous flare behaviour associated with some older commercial constellations.

The best opportunities for visual observation occur in the hour or so after local sunset or before local sunrise, when the observer on the ground is in darkness but the satellite is still illuminated by sunlight. During these windows, EOS-6 will appear as a slow-moving, non-flashing point of light crossing the sky over the course of two to four minutes, depending on the geometry of the pass. Passes that reach high elevation angles — above 60° or so — will appear brightest and longest.

To find upcoming passes for your location, enter NORAD ID 54361 into any standard satellite tracking tool or application. Pass predictions are updated continuously as new TLE data is published, and no special equipment is required for observation — a clear, dark sky and a few minutes of patience are sufficient.