SARAL

SARAL (Satellite with ARgos and ALtiKa) is an Earth-observing satellite operated by the Indian Space Research Organisation (ISRO) and developed in partnership with the French space agency, the Centre National d'Études Spatiales (CNES). Launched on February 24, 2013, SARAL represents a significant cooperative venture between India and France in the domain of oceanographic remote sensing. The satellite carries altimetry instrumentation designed to make precise measurements of sea surface height, contributing to the ongoing international effort to monitor ocean circulation patterns, sea level changes, and related geophysical phenomena. As of the time of writing, SARAL remains in orbit and continues to be catalogued by the United States Space Surveillance Network under NORAD identifier 39086 and international designator 2013-009A.

Mission and Purpose

SARAL was conceived as a joint technology demonstration and scientific mission, with both ISRO and CNES contributing to its development and operations. The central purpose of the mission is oceanographic: the satellite is equipped to perform radar altimetry, a technique that uses precisely timed microwave pulses reflected off the ocean surface to determine the distance between the satellite and the sea below. When combined with accurate knowledge of the satellite's own orbital position, this allows scientists to derive sea surface elevation with remarkable precision — measurements that are foundational to understanding large-scale ocean dynamics.

The kind of data SARAL collects has broad scientific relevance. Sea surface height variations are closely linked to ocean circulation features such as gyres, currents, and eddies, all of which play important roles in distributing heat around the planet and influencing regional climates. Long-term records of sea surface elevation also provide direct evidence of sea level rise trends, which is among the most closely watched indicators of ongoing global climate change. By contributing a continuous stream of altimetric measurements, SARAL adds to a multi-decadal archive of ocean observations built up by successive generations of altimetry satellites operated by international partners.

SARAL's altimetry payload operates in the Ka band of the radio frequency spectrum, a higher frequency than the Ku band used by many earlier altimetry missions. This distinction is technically meaningful: Ka-band altimetry offers improved resolution and reduced signal contamination from rain, and is better suited to observing coastal zones and inland water bodies where conventional altimeters have historically struggled to perform accurately. In this respect, SARAL was positioned not just as a continuation of existing ocean monitoring capability but as an incremental technological step forward in the field of satellite altimetry.

The CNES contribution to the mission reflects France's long-standing leadership in spaceborne altimetry, a tradition that traces back to the TOPEX/Poseidon mission in the 1990s and continued through the Jason series of satellites. For ISRO, SARAL represented an opportunity to deepen technical expertise in precision Earth observation and to establish India as a participant in the global oceanographic monitoring community. The cooperative structure of the mission — with each agency contributing hardware, expertise, and ground infrastructure — is characteristic of the international partnerships that have come to define civilian space science.

Orbit and Tracking

SARAL occupies a sun-synchronous orbit (SSO), a type of near-polar orbit specifically engineered so that the satellite passes over any given point on Earth's surface at approximately the same local solar time on each revisit. For an Earth-observing satellite, this is a practical advantage: consistent illumination geometry makes it easier to compare images and measurements taken on different dates without having to account for dramatic changes in solar angle. Sun-synchronous orbits are achieved by carefully selecting the orbital inclination relative to the Earth's equatorial plane so that the gravitational influence of the Earth's equatorial bulge causes the orbital plane to precess at a rate that matches the Earth's annual journey around the Sun.

SARAL's orbit is nearly circular, with an apogee of 787 km and a perigee of 786 km, giving a height variation of just one kilometre between its highest and lowest points. This near-perfect circularity is important for altimetry missions, since any significant variation in altitude would complicate the relationship between the satellite's measured distance to the ocean surface and the absolute sea surface height. The orbital inclination is 98.6°, placing it in the retrograde inclination range characteristic of sun-synchronous orbits. At this altitude and inclination, SARAL completes one full orbit of the Earth approximately every 100.4 minutes, meaning it circles the globe roughly 14 times each day and achieves global coverage over successive days.

For observers and tracking systems, SARAL is catalogued under NORAD ID 39086. Its orbital elements are routinely updated by the Space Surveillance Network and distributed through public databases, allowing ground stations, researchers, and enthusiasts to compute the satellite's real-time position. The satellite was assigned the COSPAR international designator 2013-009A, indicating it was the primary payload of the ninth launch to reach orbit in 2013. This designation is the standard international identifier used in scientific literature and orbital catalogues to refer unambiguously to the object.

Design and Operators

SARAL was built as a cooperative payload, with ISRO serving as the primary satellite operator and owner. The spacecraft's precise mass is not recorded in public catalogs reviewed here. The satellite bus and integration were handled under the bilateral agreement between ISRO and CNES, with each organization responsible for specific components of the overall system. CNES, drawing on its extensive experience with altimetry instruments developed for earlier ocean-monitoring missions, played a leading role in providing the AltiKa altimeter payload — the Ka-band radar altimeter from which part of the satellite's name is drawn. ISRO provided the satellite bus and managed the launch, as well as contributing to operations and data reception through its ground infrastructure.

The Argos component of the satellite's name refers to the Argos data collection system, an international service originally developed by CNES and NOAA that relays signals from environmental monitoring platforms such as ocean buoys and animal-tracking transmitters. SARAL carries Argos instrumentation as part of its payload complement, continuing the long history of Argos system carriage on successive generations of Earth-observing satellites. This secondary mission capability allows SARAL to serve as a relay node for a global network of in-situ environmental sensors even while its primary altimetry work proceeds.

ISRO, headquartered in Bengaluru, India, is the national space agency responsible for India's civilian space programme. Established in 1969, the agency has developed a broad portfolio of launch vehicles, satellites, and space exploration missions. SARAL represents one facet of ISRO's Earth observation programme, which encompasses a wide range of satellites dedicated to resource monitoring, disaster management, meteorology, and scientific research.

Significance and Current Status

SARAL occupies a meaningful place in the timeline of satellite altimetry. By flying a Ka-band altimeter at operational scale, it helped validate the performance characteristics of this technology in a real-mission environment, generating data that informed the design of subsequent altimetry missions and demonstrated the advantages of higher-frequency operation for specific applications. The satellite's coastal and inland water altimetry data has been used in scientific studies examining river dynamics, lake level fluctuations, and near-shore oceanographic processes — applications that were difficult or impossible with earlier instruments.

The satellite's contribution to the international ocean observation record fits within a coordinated framework of altimetry missions that includes European, American, and now Indian assets. Data from SARAL is distributed to the scientific community through channels established by both ISRO and CNES, making it accessible for research purposes globally.

As of the date this article was compiled, SARAL remains in orbit. Its operational status and whether it continues to return useful scientific data in the current period are not definitively confirmed in the catalog records reviewed here. The satellite's orbital parameters — a near-circular orbit at approximately 786–787 km altitude with an inclination of 98.6° — remain consistent with its designed mission profile, and no reentry or decay has been recorded.

How to Spot It

SARAL orbits at roughly 787 km altitude in a sun-synchronous, near-polar orbit, which means it passes over virtually all latitudes on Earth, including most populated regions, during its daily cycle of approximately 14 orbits. Like most satellites at this altitude, it is potentially visible to the naked eye as a steadily moving point of light during the hours shortly after sunset or before sunrise, when the observer on the ground is in darkness but the satellite in its high orbit is still illuminated by sunlight. Its visibility on any given pass will depend on the geometry of the pass relative to the observer's location, the degree to which the satellite is sunlit, and local sky conditions. Predicted pass times and sky positions for SARAL can be calculated using the orbital elements associated with NORAD ID 39086, which are available through this site and other public tracking resources.