CARTOSAT-2D

CARTOSAT-2D is an Indian Earth observation satellite operated by the Indian Space Research Organisation (ISRO) and catalogued under NORAD ID 41948. Launched on February 15, 2017 (UTC), it occupies a near-circular Sun-synchronous orbit at an altitude of roughly 510–515 kilometres above Earth's surface. As the fifth member of ISRO's long-running Cartosat series, it continues a lineage of remote-sensing spacecraft that have provided India and the broader international community with high-resolution imagery for cartographic, developmental, and land-management applications. The satellite carries the international designator 2017-008A, indicating it was the primary payload of the eighth launch of 2017.

Mission and Purpose

The Cartosat programme represents one of ISRO's most sustained commitments to civilian Earth observation. Since the series began, successive Cartosat satellites have been designed to capture detailed optical imagery of Earth's surface, supporting applications that range from urban planning and agricultural monitoring to disaster response and infrastructure mapping. CARTOSAT-2D fits squarely within this tradition, serving as a continuation and incremental refinement of the capabilities established by its predecessors.

Earth observation satellites in this class typically carry panchromatic and multispectral cameras capable of resolving features on the ground at sub-metre scales, enabling analysts to generate accurate cartographic products, monitor changes in land use over time, and assess the condition of terrain following natural disasters or other significant events. Such data has practical value for government agencies, urban planners, environmental scientists, and defence establishments. ISRO makes Cartosat imagery available through the National Remote Sensing Centre (NRSC) and has historically shared data internationally, reinforcing India's standing as a provider of public-benefit geospatial information.

The satellite's mission type is not formally specified in the public tracking catalog, and details of its specific sensor complement and operational tasking remain outside what is officially disclosed in open registries. What is established is that CARTOSAT-2D belongs to a workhorse class of Indian remote-sensing spacecraft that has been central to ISRO's strategy of building indigenous capability in satellite-based Earth observation.

The launch of CARTOSAT-2D aboard a Polar Satellite Launch Vehicle (PSLV) was notable not only for the satellite itself but for the record-setting nature of the mission. The PSLV-C37 mission, of which CARTOSAT-2D was the primary payload (as indicated by the 2017-008A designator), deployed an extraordinary number of co-passenger satellites in a single flight — a demonstration of India's growing capacity to offer affordable, reliable rideshare launch services to international customers.

Orbit and Tracking

CARTOSAT-2D operates in a Sun-synchronous orbit (SSO), a specific type of near-polar orbit in which the satellite's orbital plane maintains a nearly constant angle relative to the Sun throughout the year. This geometry ensures that the spacecraft passes over any given point on Earth's surface at approximately the same local solar time on each revisit, providing consistent lighting conditions for optical imaging. Consistency in illumination is a significant practical advantage for Earth observation missions, because it makes it possible to compare images taken on different dates without the complicating factor of dramatically different shadow lengths or lighting angles.

The orbit is very nearly circular, with an apogee of 515 kilometres and a perigee of 510 kilometres, giving an eccentricity close to zero. The orbital inclination is 97.4 degrees, which is the slightly retrograde tilt characteristic of Sun-synchronous orbits at this altitude — the small excess beyond 90 degrees provides the westward precession of the orbital plane that keeps it aligned with the Sun as Earth moves around it over the course of a year. At this inclination and altitude, CARTOSAT-2D completes one orbit approximately every 94.7 minutes, meaning it circles the globe roughly 15 times per day.

From a tracking perspective, the satellite is monitored continuously by the global network of sensors that feed into the US Space Surveillance Network, and its orbital elements are publicly available through space-track.org and aggregated on tracking platforms such as LowEarth. The NORAD catalog ID 41948 serves as the definitive numerical identifier for the object across all tracking databases. As of the time of writing, CARTOSAT-2D remains in orbit and has not undergone atmospheric reentry.

The relatively low altitude of the orbit — just over 500 kilometres — means that the satellite is subject to a measurable, if slow, atmospheric drag that will gradually cause orbital decay over time. However, operational Earth observation satellites at this altitude are typically equipped with propulsion systems for station-keeping and orbit maintenance, which can extend their operational lives considerably.

Design and Operator

CARTOSAT-2D was built and is operated by the Indian Space Research Organisation, India's national space agency, headquartered in Bengaluru. ISRO has been developing and launching remote-sensing satellites since the 1980s and has built substantial in-house expertise in satellite design, manufacturing, launch vehicle development, and ground-segment operations. The Cartosat series in particular has been a flagship programme demonstrating ISRO's ability to produce high-performance Earth observation platforms using predominantly domestic technology and infrastructure.

The satellite has a mass of approximately 714 kilograms, placing it in the medium-mass category for Earth observation spacecraft. This mass is consistent with the broader Cartosat-2 sub-series, which has used a standardised bus design to carry imaging payloads while allowing incremental improvements in sensor and onboard system performance across successive missions. The specific manufacturer of individual subsystems is not detailed in the public catalog record.

The spacecraft was launched from the Satish Dhawan Space Centre (SDSC), located at Sriharikota on India's southeastern coast, which serves as ISRO's primary launch facility. The PSLV, which carried CARTOSAT-2D, is one of the world's most reliable small-to-medium launch vehicles and has been the backbone of India's satellite deployment capability for decades. Its four-stage design, alternating solid and liquid propulsion stages, provides the flexibility to insert payloads into a wide range of orbits, including the Sun-synchronous orbits favoured by Earth observation missions.

ISRO manages the satellite's operations through its network of ground stations, processing and distributing the data it collects through established channels to domestic and international users. The agency has a long-standing practice of maintaining operational continuity in the Cartosat programme by launching successive satellites before their predecessors degrade, ensuring uninterrupted coverage and data availability.

Significance and Current Status

Within the context of India's space programme, CARTOSAT-2D occupies a meaningful position as one of a series of satellites that have collectively made India a significant force in civil remote sensing. The Cartosat-2 sub-series, of which this satellite is a member, advanced the resolution and revisit capabilities available to Indian users and demonstrated ISRO's ability to rapidly iterate on a proven design. Each successive satellite in the series has represented a modest but cumulative improvement in capability, reflecting a design philosophy that values incremental progress and operational reliability over radical innovation.

The record co-manifesting of satellites on the PSLV-C37 mission that carried CARTOSAT-2D into orbit attracted widespread international attention and cemented ISRO's reputation as a cost-effective provider of launch services. While the attention inevitably focused on the sheer number of satellites deployed, the primary mission — delivering CARTOSAT-2D to its operational orbit — was completed successfully, and the satellite began its imaging operations on schedule.

CARTOSAT-2D continues to be tracked as an active on-orbit object. Its current orbital parameters — an apogee of 515 kilometres, a perigee of 510 kilometres, an inclination of 97.4 degrees, and a period of 94.7 minutes — indicate a stable, well-maintained orbit consistent with an operational satellite. Whether it remains in active imaging service, has entered a reduced-operations phase, or is maintained purely as a tracked object is not specified in the public catalog record. What is confirmed is that it has not decayed from orbit and continues to be catalogued among the active and tracked population of Earth-orbiting objects.

For the broader story of Indian Earth observation, CARTOSAT-2D represents a reliable building block in a programme that has grown steadily in ambition and international relevance. As ISRO continues to develop and launch next-generation observation platforms, earlier members of the Cartosat family remain part of the operational record that informs how future missions are designed, procured, and deployed.

How to Spot It

CARTOSAT-2D is potentially observable with the naked eye or binoculars under the right conditions, as satellites in low Earth orbit at approximately 500 kilometres altitude can reach naked-eye visibility when they pass through sunlight against a dark sky. The best opportunities occur during the hour or two after sunset or before sunrise at the observer's location, when the satellite is still illuminated by the Sun while the observer is in Earth's shadow. During these windows, CARTOSAT-2D will appear as a steadily moving point of light tracking smoothly across the sky, distinguishable from aircraft by the absence of blinking lights and from stars by its apparent motion.

Precise pass predictions depend on the observer's geographic location and the current orbital elements, which are updated regularly as tracking data is refined. LowEarth's built-in pass predictor, using the NORAD ID 41948, can generate accurate overpass times, approach directions, and peak elevation angles for any location on Earth. Passes at higher elevation angles — closer to directly overhead — will generally appear brighter and last longer than low-horizon passes.