The Resourcesat Satellites Explained

Resourcesat is a series of Indian multispectral earth-observation satellites in the Indian Remote Sensing (IRS) family, designed by the Indian Space Research Organisation (ISRO) to monitor agriculture, forests, water and land use using three cameras called LISS-3, LISS-4 and AWiFS. The series comprises Resourcesat-1 (also called IRS-P6), Resourcesat-2 and Resourcesat-2A, all launched on the Polar Satellite Launch Vehicle (PSLV) into a sun-synchronous polar orbit.

Together, the Resourcesat satellites give India a continuous stream of imagery at three different scales, from village-level detail to whole-state coverage. This article explains what the Resourcesat satellites are, how their cameras differ, how the orbit works and what the data is used for.

Key Takeaways

• Resourcesat is an ISRO series of three multispectral earth-observation satellites: Resourcesat-1, Resourcesat-2 and Resourcesat-2A.
• Each Resourcesat satellite carries three optical cameras, LISS-4, LISS-3 and AWiFS, which image the same land at fine, medium and coarse resolution.
• The Resourcesat satellites fly in a sun-synchronous polar orbit, so they pass over any given place at nearly the same local solar time on every visit.
• Resourcesat imagery supports crop area estimation, land-use and land-cover mapping, water-body monitoring, forestry assessment and flood and drought mapping across India.
• All Resourcesat satellites were launched by ISRO’s PSLV from the Satish Dhawan Space Centre at Sriharikota.
• Resourcesat data is archived and supplied by the National Remote Sensing Centre (NRSC) in Hyderabad, and much of it is accessible through ISRO’s Bhuvan geoportal.

What Is Resourcesat?

Resourcesat is ISRO’s flagship series of resource-monitoring satellites, built to map natural resources on land such as crops, forests, soils and water. The series continues the work of the earlier IRS satellites, which began with IRS-1A in the late 1980s and made India one of the world’s major providers of civilian remote-sensing data.

The word “Resourcesat” is a short form of “resources satellite”. The first satellite of the series, Resourcesat-1, was also called IRS-P6 because it belonged to the “P” line of IRS satellites designed for launch on the PSLV. Resourcesat-2 and Resourcesat-2A were later built as follow-on missions to keep the same observing capability alive and to improve it.

Remote sensing means gathering information about the Earth’s surface from a distance, here by recording sunlight reflected from the ground in several colour bands. Resourcesat is a passive system: it does not send out a signal of its own but records the sunlight reflected by fields, forests, rivers and cities.

Which Satellites Make Up the Resourcesat Series?

The Resourcesat series consists of three satellites: Resourcesat-1, Resourcesat-2 and Resourcesat-2A, launched in 2003, 2011 and 2016 respectively. Each was launched on a PSLV rocket and placed in a polar orbit, with each newer satellite improving on the sensors of its predecessor.

The gap between satellites is deliberate. ISRO plans follow-on launches while an older satellite is still working, so that users in agriculture and planning departments do not face a break in their data. A further generation of resource-monitoring satellites has been planned under ISRO’s earth-observation roadmap.

What Cameras Does Resourcesat Carry?

Each Resourcesat satellite carries three optical cameras: LISS-4, LISS-3 and AWiFS, which differ mainly in how sharp the image is and how wide a strip of ground they cover. Together they form a “multi-scale” system in which one satellite can serve both a village-level survey and a country-wide crop assessment.

LISS-4 (Linear Imaging Self-Scanning Sensor-4)

LISS-4 is the high-resolution camera of Resourcesat, giving a ground pixel of a little under six metres. It has three spectral bands (green, red and near-infrared) and can also operate in a single-band panchromatic mode over a wider swath. Its pointing can be steered across the track, which lets users request images of a specific place more often than the normal repeat cycle would allow. LISS-4 is used for detailed work such as urban land use, small-farm mapping and infrastructure studies.

LISS-3 (Linear Imaging Self-Scanning Sensor-3)

LISS-3 is the medium-resolution camera of Resourcesat, with a ground pixel of roughly 23.5 metres and a swath of about 140 km. It records four bands: green, red, near-infrared and shortwave-infrared. The shortwave-infrared band is especially useful for distinguishing moisture in vegetation and soil. LISS-3 is the workhorse for regional land-cover and forest mapping.

AWiFS (Advanced Wide Field Sensor)

AWiFS is the wide-view camera of Resourcesat, covering a swath of roughly 740 km with a pixel of about 56 metres. It records the same four bands as LISS-3, but because it sweeps such a broad strip it revisits the same area every few days. This frequent coverage makes AWiFS ideal for tracking the progress of crop seasons, floods and snow cover over large regions.

What Orbit Do the Resourcesat Satellites Use?

The Resourcesat satellites use a near-polar, sun-synchronous orbit at an altitude of roughly 800 km, which means each satellite crosses the equator at nearly the same local solar time on every pass. The orbit is tilted by a little under 100 degrees to the equator, so the satellite travels almost from pole to pole while the Earth rotates beneath it.

Sun-synchronous orbits are valuable for earth observation because consistent lighting makes images taken on different dates directly comparable. If an image of a wheat field is captured at the same local time every few weeks, changes in colour reflect changes in the crop and not changes in the angle of the sun. Resourcesat is designed to cross the equator in the late morning, when sunlight is strong and cloud cover over many tropical regions is still limited.

The satellite completes about fourteen orbits a day. Because the cameras scan the ground in a narrow strip, successive orbits fall slightly west of each other, and after a fixed repeat cycle the satellite returns to image exactly the same ground track. The different swath widths of the three cameras mean that the repeat interval for the same place differs sharply between AWiFS and LISS-3.

How Does Resourcesat Collect and Deliver Its Data?

Resourcesat collects data by scanning the Earth’s surface in a push-broom fashion, with lines of detectors recording reflected sunlight as the satellite moves along its track. The signals are digitised, stored on board and then sent to ground stations as the satellite passes within range.

The main reception facility is the Shadnagar ground station of the National Remote Sensing Centre (NRSC), near Hyderabad. NRSC processes the raw data into products corrected for geometric and radiometric errors, catalogues them and supplies them to users. Many users receive data through NRSC’s Bhuvan geoportal, ISRO’s online platform for satellite imagery and map services.

Processing typically includes several steps:

• Radiometric correction, which removes sensor-related variations in brightness.
• Geometric correction, which aligns the image to map coordinates.
• Ortho-rectification, in which terrain relief distortion is removed where required.
• Band compositing, in which three bands are combined into false-colour views that make vegetation easier to see.

How Is Resourcesat Used in Agriculture?

Resourcesat is used in agriculture to estimate how much land is under each crop, to monitor crop condition through the growing season and to support yield forecasts. Healthy vegetation reflects strongly in the near-infrared band and absorbs red light, so combining the two bands produces vegetation indices that track crop vigour.

The wide AWiFS swath gives frequent coverage during a season, while LISS-3 and LISS-4 help verify results at finer scales. ISRO uses such data in national programmes for forecasting crop acreage and production, working with the Ministry of Agriculture and Farmers Welfare and with state agencies. Common agricultural applications include:

• Crop acreage estimation for major crops such as wheat, rice, cotton and sugarcane.
• Crop condition and stress monitoring during drought or unseasonal weather.
• Cropping pattern and crop rotation analysis.
• Identification of fallow land and irrigated area.
• Support for crop insurance by providing independent records of crop area and damage.

How Does Resourcesat Help with Land Use and Land Cover Mapping?

Resourcesat helps map land use and land cover by classifying satellite pixels into categories such as cropland, forest, built-up area, wetland, water and wasteland. Land use describes how people use land, while land cover describes what physically covers it, and both can be derived by comparing colour and brightness patterns across several bands.

ISRO’s national land-use and land-cover programme has repeated this classification over successive years using multi-temporal AWiFS and LISS-3 imagery. Comparing maps over time shows where forests have shrunk, where cities have expanded and where farmland has been converted to other uses. Similar methods have been used to prepare a national wasteland atlas, which identifies degraded land that could potentially be reclaimed for productive use.

These maps are used by town planners, watershed development programmes, forest departments and researchers studying changes in the Indian landscape.

What Role Does Resourcesat Play in Water, Forestry and Disaster Management?

Resourcesat plays a role in water, forestry and disaster management by providing frequent, wide-area images in which water, vegetation and damage are easy to distinguish. The near-infrared and shortwave-infrared bands make water bodies look dark and sharply defined against land.

Water resources

Resourcesat imagery is used to map surface water such as reservoirs, lakes, ponds and rivers, and to measure how their extent changes between seasons. This helps agencies track the filling and drawdown of reservoirs and identify irrigated areas.

Forestry

Forest departments use Resourcesat images to map forest cover types, monitor degradation and detect forest fire scars. Repeat imagery shows where canopy has been cleared and where plantation work has restored cover.

Floods, drought and other disasters

During the monsoon, AWiFS data is used to map the extent of inundated land in river basins such as the Ganga, Brahmaputra and Kosi. In dry years, falling vegetation indices flag agricultural drought. Images taken before and after cyclones, landslides or forest fires help assess damage and plan relief. Resourcesat works together with other ISRO satellites, including radar satellites that can see through cloud, for disaster response.

Why Is the Resourcesat Series Important for India?

The Resourcesat series is important because it gives India a self-reliant, long-running source of multispectral imagery for managing food, water and land resources. India has a large agrarian population, diverse climate zones and frequent weather extremes, so up-to-date information on land and crops has direct practical value.

Several points explain its significance:

• Continuity: Successive satellites have preserved a consistent data record covering many years, which is essential for detecting long-term trends.
• Multi-scale design: Having three cameras on one platform lets analysts move from national statistics to individual fields without switching data sources.
• Self-reliance: Indian agencies do not depend on foreign satellites for routine national surveys.
• Open access: A large share of the data is made available to government departments, researchers and the public through NRSC and Bhuvan.
• Applications ecosystem: The satellites support many ministry programmes in agriculture, water, rural development and urban planning.

How Does Resourcesat Compare with Other Indian Earth-Observation Satellites?

Resourcesat differs from other Indian earth-observation satellites mainly in its focus on moderate-resolution multispectral coverage of land. Other series serve different needs, such as very sharp mapping, radar imaging, ocean colour or weather monitoring.

Because their roles overlap in useful ways, scientists often combine Resourcesat optical images with radar data to follow floods and crops during cloudy monsoon months.

What Are the Limits of Resourcesat?

The main limit of Resourcesat is that, being an optical system, it cannot see through clouds or at night. During the Indian monsoon, heavy cloud can block many scenes, which is one reason ISRO also operates radar satellites.

Other limits include a coarser resolution than commercial very-high-resolution satellites, which can resolve objects below one metre, and a fixed revisit schedule for the finer cameras. AWiFS revisits often but at lower detail, while LISS-4 gives sharp detail but covers a narrow strip. Analysts therefore choose the camera that matches the question: AWiFS for large and fast-changing patterns, LISS-3 for regional maps and LISS-4 for local detail.

Bottom Line

Resourcesat is ISRO’s long-running series of multispectral earth-observation satellites, built around the LISS-4, LISS-3 and AWiFS cameras and flown in a sun-synchronous orbit by PSLV. Its imagery underpins India’s work on crop monitoring, land-use mapping, water resources, forestry and disaster response, and it remains a reference example of Indian space technology applied to everyday governance.

Frequently Asked Questions

What is Resourcesat?

Resourcesat is a series of Indian multispectral earth-observation satellites built by ISRO to monitor land resources such as crops, forests, water and land use. The series includes Resourcesat-1, Resourcesat-2 and Resourcesat-2A, and each carries the LISS-3, LISS-4 and AWiFS cameras.

How many Resourcesat satellites has India launched?

India has launched three Resourcesat satellites: Resourcesat-1 in 2003, Resourcesat-2 in 2011 and Resourcesat-2A in 2016. All three were launched on ISRO’s Polar Satellite Launch Vehicle (PSLV) from Sriharikota. Each newer satellite continued and improved the observing capability of the previous one.

What is the difference between LISS-3, LISS-4 and AWiFS?

The three cameras differ in resolution and swath width. LISS-4 gives the sharpest images, with a pixel of about six metres over a narrow strip. LISS-3 offers about 23.5 metres over roughly 140 km, and AWiFS offers about 56 metres over a very wide swath of roughly 740 km, so it revisits the same area more often.

What is the Resourcesat satellite used for?

Resourcesat is used for crop area estimation, crop condition monitoring, land-use and land-cover mapping, water-body and forest monitoring, wasteland mapping and flood and drought assessment. Government departments, researchers and planners use the data for resource management and policy decisions.

Which orbit does Resourcesat use?

Resourcesat uses a near-polar, sun-synchronous orbit at roughly 800 km altitude. This means the satellite passes over any location at nearly the same local solar time on each visit, which keeps lighting conditions consistent and makes images from different dates easy to compare.

Where can Resourcesat data be obtained?

Resourcesat data is archived and supplied by the National Remote Sensing Centre (NRSC) in Hyderabad, which is part of ISRO. Much of the imagery and derived map services can be viewed or requested through ISRO’s Bhuvan geoportal, subject to ISRO’s data policy.

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