CARTOSAT-3

Cartosat-3 (NORAD catalog ID 44804, international designator 2019-081A) is an Indian Earth observation satellite developed and operated by the Indian Space Research Organisation (ISRO). Launched on November 27, 2019 (UTC), it represents a significant generational leap in India's indigenous remote sensing capabilities, succeeding the long-running Indian Remote Sensing (IRS) satellite series with substantially improved imaging resolution. The spacecraft occupies a sun-synchronous low Earth orbit at approximately 504–520 km altitude, where it continues to circle the globe on a regular cadence useful for systematic land observation.

Mission and Purpose

Cartosat-3 was designed to serve as a high-resolution Earth imaging platform capable of supporting a wide range of civilian and governmental applications. These typically include urban and rural land-use mapping, infrastructure planning, agricultural monitoring, disaster assessment, coastal zone management, and national cartographic programs. The satellite's panchromatic imaging capability, with a ground resolution of 0.25 metres, placed it among the most capable civilian Earth observation instruments in the world at the time of its launch—a resolution fine enough to distinguish individual vehicles, structures, and other surface features with considerable clarity. Its multispectral (MX) imaging capability offers a resolution of 1 metre, providing color and spectral information useful for vegetation analysis, land classification, and environmental monitoring.

The Cartosat series has been a cornerstone of India's civil remote sensing infrastructure for many years, and Cartosat-3 was conceived as a step-change replacement rather than a simple incremental upgrade. Where earlier members of the family delivered imagery measured in meters of resolution, Cartosat-3 moved into the sub-meter and deep sub-meter range, bringing Indian national capability into line with the most capable commercial and governmental imaging satellites operated elsewhere in the world. This level of resolution is particularly valuable for detailed cadastral mapping, city planning, and monitoring of construction or land change at fine spatial scales.

ISRO manages the satellite on behalf of India, with the data it collects feeding into domestic government programs as well as being made available through the National Remote Sensing Centre (NRSC) for various authorized civilian uses. Like many satellites in the Cartosat lineage, Cartosat-3 operates under a framework that balances open scientific and developmental uses with security-sensitive considerations inherent to very high resolution imaging.

Orbit and Tracking

Cartosat-3 operates in a sun-synchronous orbit (SSO), a near-polar orbital configuration in which the satellite's orbital plane maintains a roughly constant angle relative to the Sun throughout the year. This geometry ensures that the satellite passes over any given location on Earth at approximately the same local solar time on each revisit, which is critical for Earth observation because it means illumination conditions remain consistent between successive images of the same area. Consistent lighting makes change detection—identifying differences between images taken weeks or months apart—far more reliable and scientifically meaningful.

The satellite's current orbital parameters place its apogee at approximately 520 km and its perigee at approximately 504 km above Earth's surface, indicating a nearly circular orbit with very little eccentricity. This kind of tight, circular orbit is typical for Earth imaging satellites, as it keeps the spacecraft at a stable, predictable altitude that simplifies both image geometry and ground station contact scheduling. The orbital inclination is 97.4°, which is the slight retrograde tilt characteristic of sun-synchronous orbits; at this inclination, the slow drift of the orbital plane caused by Earth's equatorial bulge precisely cancels out over time to maintain the fixed relationship with the Sun.

With an orbital period of approximately 94.7 minutes, Cartosat-3 completes roughly fifteen to sixteen full orbits of the Earth each day. Over multiple days, this ground track pattern shifts slightly with each successive pass, ultimately building up coverage of the entire globe. The satellite's repeat cycle—the number of days required for the ground track to return exactly to a previous position—governs how frequently any given location on Earth can be imaged, and is a key operational parameter for scheduling imaging requests and tasking the satellite from the ground.

Tracking data for Cartosat-3 is maintained in the public catalog under NORAD ID 44804. Observers and researchers can use two-line element (TLE) sets derived from routine radar tracking to compute the satellite's current and predicted position at any time. Because the satellite operates at relatively low altitude, atmospheric drag will cause a slow, gradual decay of its orbit over time, though as of the current catalog data it remains in orbit and operational.

Design and Operator

Cartosat-3 was built and operated by ISRO, India's national space agency, which has been responsible for all satellites in the Cartosat series. The spacecraft's mass is not recorded in the public satellite catalog, and specific details of its bus design and subsystem architecture are not publicly available in verified form. What is established is that it carries an advanced optical payload capable of 0.25-metre panchromatic resolution and 1-metre multispectral resolution—a combination that reflects sophisticated optical design, precise attitude control, and high-bandwidth data downlink capability, all of which are prerequisites for sub-meter imaging from orbit.

Achieving 0.25-metre resolution from an altitude of roughly 500 km requires an exceptionally large aperture telescope by the standards of Earth observation satellites. The optics must collect sufficient light to form sharp images despite the satellite's rapid motion across the ground—at orbital velocities, the spacecraft covers several kilometres per second relative to the surface below, demanding either very fast exposure times or sophisticated image motion compensation to avoid smearing.

ISRO launched Cartosat-3 aboard its Polar Satellite Launch Vehicle (PSLV), the agency's workhorse rocket that has been used for the vast majority of Indian Earth observation satellite deployments. The launch took place on November 27, 2019 (UTC), from the Satish Dhawan Space Centre at Sriharikota on India's southeastern coast. The mission also carried a number of co-passenger small satellites, a common practice on PSLV missions that allows commercial or international rideshare payloads to reach orbit alongside the primary satellite.

Significance and Current Status

At the time of its launch, Cartosat-3's 0.25-metre panchromatic resolution made it one of the highest-resolution Earth observation satellites operating anywhere in the world. This placed India in a select group of nations with indigenous very-high-resolution imaging capability—a technically demanding achievement that reflects the maturity ISRO has developed over decades of building and operating the IRS and Cartosat satellite families.

The satellite's capabilities have direct implications for India's self-reliance in geospatial intelligence and national mapping. Before satellites of this resolution class became available domestically, detailed imagery of Indian territory at sub-meter resolution would have required procurement from foreign commercial providers, with associated dependencies and constraints. Cartosat-3 substantially reduces that dependency for civilian governmental purposes.

From a broader perspective, the Cartosat-3 program also demonstrates India's growing competitiveness in the Earth observation technology domain. The progression from the multi-meter resolutions of early IRS satellites through the Cartosat series to the sub-quarter-meter capability of Cartosat-3 represents a sustained, multi-decade investment in optical remote sensing technology that has compounded into a world-class national asset.

As of the current orbital data, Cartosat-3 remains in orbit, with no decay or reentry date recorded in the catalog. It continues to operate in its sun-synchronous orbit at approximately 504–520 km altitude, maintaining the orbital parameters under which it was originally placed. Any future changes in its operational status or orbital lifetime will depend on factors including fuel reserves, instrument health, and mission policy decisions by ISRO.

How to Spot It

Cartosat-3 is not among the satellites typically considered prime targets for naked-eye observation. At an orbital altitude of roughly 504–520 km, it is within the altitude range of observable low Earth orbit objects, but its visibility on any given pass depends on its size, surface reflectivity, and the geometry of the pass relative to the observer's location and the Sun's position. The satellite does not carry large reflective structures such as solar array wings as prominent as those on crewed stations or communications satellites, so it is likely to appear as a faint, steadily moving point of light rather than a bright, easily noticed object.

Observers who wish to attempt a sighting should use current TLE data from the LowEarth tracking tools to generate accurate pass predictions for their specific location. Passes occurring shortly after dusk or before dawn—when the observer is in darkness but the satellite is still illuminated by sunlight—offer the best chance of visibility. The satellite will move at a pace consistent with its roughly 95-minute orbital period, crossing the sky in a matter of minutes. Binoculars may improve the chances of detection on marginal passes.