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IRS-1A
NamesIndian Remote Sensing satellite-1A
Mission typeEarth observation
OperatorISRO
COSPAR ID1988-021A Edit this at Wikidata
SATCAT no.18960
Websitehttps://www.isro.gov.in/
Mission duration3 years (planned)
4 years (achieved)
Spacecraft properties
SpacecraftIRS-1A
BusIRS-1
ManufacturerIndian Space Research Organization
Launch mass975 kg (2,150 lb)
Dry mass895 kg (1,973 lb)
Dimensions1.56 m x 1.66 m x 1.10 m
Power600 watts
Start of mission
Launch date17 March 1988, 06:43:00 UTC
RocketVostok-2M s/n L15000-79
Launch siteBaikonur Cosmodrome, Site 31
ContractorOKB-1
Entered serviceJune 1988 [1]
End of mission
Deactivated1 July 1992 [1]
Orbital parameters
Reference systemGeocentric orbit[2]
RegimeSun-synchronous orbit
Perigee altitude863 km (536 mi)
Apogee altitude917 km (570 mi)
Inclination99.01°
Period102.7 minutes
Instruments
Linear Imaging Self-Scanning Sensor-1 (LISS-1)
Linear Imaging Self-Scanning Sensor-2 (LISS-2)
IRS-1B →

IRS-1A, Indian Remote Sensing satellite-1A, the first of the series of indigenous state-of-art remote sensing satellites, was successfully launched into a polar Sun-synchronous orbit on 17 March 1988 from the Soviet Cosmodrome at Baikonur. IRS-1A carries two sensors, LISS-1 and LISS-2, with resolutions of 72 m (236 ft) and 36 m (118 ft) respectively with a swath width of about 140 km (87 mi) during each pass over the country. Undertaken by the Indian Space Research Organisation (ISRO). It was a part-operational, part-experimental mission to develop Indian expertise in satellite imagery.

History

[edit]

The availability of Landsat imagery created a lot of interest in the science community. The Hyderabad ground station started receiving Landsat data on a regular basis in 1978. The Landsat program with its design and potentials was certainly a great model and yardstick for the IRS programme. IRS-1A was the first remote sensing mission to provide imagery for various land-based applications, such as agriculture, forestry, geology, and hydrology.[3] The mission's long-term objective was to develop indigenous remote sensing capability.[4]

Satellite description

[edit]

The satellite bus, measuring 1.56 m x 1.66 m x 1.10 metres, had the payload module attached on the top and a deployable solar panels stowed on either side. Attitude control was provided by four-momentum wheels, two magnetic torques, and a thruster system. Together, they gave an estimated accuracy of better than ± 0.10° in all three axes.[3]

Instruments

[edit]

IRS-1A carried two "Linear Imaging Self-Scanning Sensor", LISS-1 and LISS-2, with a spatial resolution of 72 m (236 ft) and 36 m (118 ft) respectively.[5] The three-axis-stabilised Sun-synchronous satellite carried LISS sensors which performed "push-broom" scanning in visible and near-infrared bands to acquire images of the Earth. Local equatorial crossing time (ECT) was fixed at around 10:30 of the morning.[3]

Launch

[edit]

IRS-1A was launched on 17 March 1988, at 06:43:00 UTC. It had a perigee of 863 km (536 mi), an apogee of 917 km (570 mi), an inclination of 99.01°, and an orbital period of 102.7 minutes.[2]

Mission

[edit]

IRS-1A was operated in a Sun-synchronous orbit. IRS-1A successfully completed its mission on 1 July 1992 after operating for 4 years.[1]

See also

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

IRS-1A

View on Grokipedia
from Grokipedia
IRS-1A was the inaugural satellite in India's Indian Remote Sensing (IRS) program, developed and operated by the Indian Space Research Organisation (ISRO) for Earth observation purposes.[1] Launched on March 17, 1988, from the Baikonur Cosmodrome in Kazakhstan aboard a Soviet Vostok-2M rocket, it weighed 975 kg at launch and was placed into a sun-synchronous polar orbit at an altitude of approximately 904 km with an inclination of 99.08°.[2][3] The satellite carried two primary sensors: the Linear Imaging Self-Scanning Sensor I (LISS-I) with a spatial resolution of 73 meters and the LISS-II with 36 meters, both providing a swath width of about 140 km for multispectral imaging in the visible and near-infrared bands.[1][4] Designed primarily for resource monitoring and management, IRS-1A supported applications in agriculture, forestry, land use mapping, water resources assessment, regional geology, and vegetation studies, marking India's entry into operational remote sensing capabilities.[5] It operated successfully until July 1996, exceeding its planned three-year design life, and provided data that enabled the creation of national atlases for renewable resources and disaster management.[3][1] The mission's success paved the way for subsequent IRS satellites, establishing a robust indigenous remote sensing infrastructure that continues to evolve.[6]

Background and Development

Historical Context

The development of India's remote sensing capabilities began in the 1970s, when the country started receiving and processing Landsat satellite data from NASA's program to support applications in agriculture, forestry, and land use monitoring. In 1974, the Department of Science and Technology established the National Remote Sensing Agency (NRSA) in Hyderabad to acquire and analyze this data, marking the initial step toward building indigenous expertise in Earth observation. A 1978 memorandum of understanding facilitated the setup of a dedicated ground station there. This infrastructure laid the foundation for India's transition from data user to satellite developer, driven by the need for timely and cost-effective remote sensing solutions tailored to national priorities. NRSA was transferred to the Department of Space in 1982 and fully integrated into ISRO, renaming to the National Remote Sensing Centre (NRSC) in 2008.[7][8] Inspired by the success of NASA's Landsat program, which demonstrated the value of multispectral imaging for civilian applications, Indian scientists recognized the limitations of relying on foreign satellites, including delays in data access and dependency on international policies. The push for indigenous satellites gained momentum in the late 1970s, focusing on land-based applications such as crop assessment, hydrology, and environmental monitoring to address India's agricultural and resource management challenges. This vision aligned with broader goals of self-reliance in space technology, prompting the Indian Space Research Organisation (ISRO) to prioritize remote sensing as a key area. Key milestones in the early 1980s included the formal establishment of ISRO's remote sensing program, which integrated efforts from the Space Applications Centre in Ahmedabad and the NRSC. By 1983, ISRO had approved the development of the Indian Remote Sensing (IRS) satellite series, with IRS-1A designated as the first operational mission to provide indigenous, high-resolution imagery for sustainable development. International collaborations played a crucial role, notably with the Soviet Union providing technical assistance and launch support through the Vostok rocket, enabling India to overcome limitations in domestic launch capabilities at the time.

Objectives and Design Goals

The primary objectives of IRS-1A centered on operational Earth observation to support India's natural resource management, including applications in land use mapping, agriculture, forestry, geology, hydrology, and vegetation studies for national-scale monitoring and assessment.[9] These goals extended to disaster management, soil classification, and water resource evaluation, aiming to evolve methodologies for data reception, processing, and analysis to aid decision-making in resource sectors.[6][10] Key design goals focused on deploying a three-axis stabilized satellite in a sun-synchronous polar orbit at approximately 904 km altitude to provide consistent imaging conditions across multiple passes, with a 22-day repeat cycle for temporal coverage.[6] The system incorporated multi-spectral pushbroom scanners operating in visible (0.45–0.68 µm) and near-infrared (0.77–0.86 µm) bands to capture detailed surface features, while ensuring seamless integration with indigenous ground stations for real-time data acquisition, quick-look processing, and application-specific dissemination.[9][10] The mission was designed for a nominal operational life of three years, emphasizing the development of fully indigenous technologies—including spacecraft bus, sensors, and attitude control systems—to build self-reliant remote sensing capabilities and diminish dependence on international satellites like Landsat for Earth observation data.[6][9] To meet application demands, the design targeted spatial resolutions of 72 m for broader contextual imaging and 36 m for finer detail in resource surveys, paired with a 140 km swath width to facilitate efficient regional-scale coverage without excessive gaps.[6][9]

Spacecraft Design

Configuration and Subsystems

IRS-1A featured a compact, box-like configuration measuring 1.56 m in height, 1.66 m in width, and 1.10 m in depth, constructed primarily from aluminum honeycomb panels surrounding a central load-bearing aluminum cylinder to provide structural integrity during launch and in-orbit operations.[11] The spacecraft's launch mass was 975 kg, including 80 kg of hydrazine propellant, while its dry mass stood at 895 kg.[4] This design was based on an indigenous Indian satellite bus developed by the Indian Space Research Organisation (ISRO), emphasizing self-reliance in key technologies for remote sensing missions.[12] The spacecraft bus incorporated essential non-payload subsystems tailored for a sun-synchronous orbit, including a passive thermal control system utilizing optical solar reflectors, multi-layer insulation blankets, and surface treatments to maintain component temperatures within operational limits, such as 0–40°C for electronics.[13] Propulsion was minimal, relying on a monopropellant hydrazine system with sixteen 1-newton thrusters for attitude control, momentum dumping, and minor orbit maintenance maneuvers.[6] The communication subsystem supported reliable data handling through an S-band transponder for telemetry, tracking, and command (TT&C) operations at rates up to 4 kbps, alongside VHF for commanding; payload data transmission occurred via S-band at 5.4 Mbit/s for LISS-I and X-band at 10.4 Mbit/s per channel for LISS-II.[12][6] Power generation was provided by deployable solar panels, contributing to the overall bus architecture.[6] Attitude and orbit control was achieved through a three-axis stabilization system with zero angular momentum, employing four reaction wheels for primary control, supplemented by magnetic torquers for desaturation and fine adjustments, enabling attitude determination accuracy of ±0.10° in pitch, roll, and yaw for nadir pointing of 0.3° in pitch and roll, and 0.5° in yaw.[12][6] Sensors including sun sensors, earth horizon sensors, star sensors, and dynamically tuned gyros facilitated precise attitude determination to support imaging requirements.[13]

Power and Control Systems

The power subsystem of IRS-1A was designed to generate and store electrical energy sufficient for the satellite's three-year mission life, utilizing deployable solar panels and rechargeable batteries. The system produced 600 W of power at the beginning of life from two deployable solar panels with a total area of 8.6 m², providing the necessary energy for onboard subsystems and payloads during sunlight periods.[12][6] Two 40 Ah nickel-cadmium (Ni-Cd) batteries stored energy to support operations during eclipse phases, ensuring uninterrupted power supply with redundant charging and distribution electronics for fault tolerance.[13][14] The attitude and orbit control system (AOCS) maintained three-axis stabilization using a zero-momentum configuration to achieve nadir pointing accuracy of 0.3° in pitch and roll, and 0.5° in yaw, essential for precise Earth observation in the sun-synchronous orbit. Four reaction wheels served as primary actuators for momentum storage and fine attitude adjustments during nominal operations.[6] Sixteen 1 N hydrazine thrusters, supported by 80 kg of propellant, were employed solely for initial attitude acquisition post-launch and occasional momentum dumping, with no ongoing propulsion for station-keeping.[6] Attitude determination relied on a suite of sensors, including Earth horizon scanners, coarse and fine sun sensors, a star tracker for yaw estimation, and dynamically tuned gyros for rate measurement.[6][9] Control algorithms processed sensor data to command actuators, ensuring orbit stability and precise imaging orientation while compensating for environmental disturbances. Magnetic torquers facilitated periodic unloading of reaction wheel momentum by interacting with Earth's magnetic field, producing torque according to the formula
τ=m×B×sin⁡θ,\tau = m \times B \times \sin \theta,
 where τ\tau is the torque, mm the dipole magnetic moment, BB the local magnetic field strength, and θ\theta the angle between the magnetic moment vector and the field.[6] The AOCS incorporated redundant electronics and fault-tolerant software to enhance reliability, enabling the satellite to exceed its design life by operating successfully for over eight years until July 1996.[6][15]

Instruments

LISS-I Sensor

The Linear Imaging Self-Scanning Sensor-I (LISS-I) was the primary instrument on IRS-1A for acquiring multispectral imagery at coarser spatial resolution, enabling broad-area monitoring of Earth's surface.[6] It operated as a push-broom scanner, utilizing linear charge-coupled device (CCD) arrays to capture along-track lines of data simultaneously across four spectral bands in the visible and near-infrared regions.[6][16] The sensor achieved a spatial resolution of 72.5 meters, suitable for applications such as regional land use classification and vegetation assessment over large areas.[6][17] LISS-I featured four spectral bands: blue (0.45–0.52 μm), green (0.52–0.59 μm), red (0.62–0.68 μm), and near-infrared (0.77–0.86 μm), spanning the overall range of 0.45–0.86 μm.[6][17] Each band employed a linear CCD array with 2,048 pixels, providing a swath width of 148 km and supporting a 22-day repeat cycle for global coverage in daylight conditions.[16][17] The optical system utilized refractive optics with a focal length of 162.2 mm and a field of view of 9.4 degrees, ensuring efficient collection of radiance data at a downlink rate of 5.2 Mbit/s via S-band.[6][16][9] For radiometric stability, LISS-I incorporated onboard calibration using two light-emitting diodes (LEDs) per spectral band to perform in-flight absolute calibration during non-imaging periods.[6][18] This was complemented by vicarious calibration techniques, which relied on well-characterized ground targets to verify and adjust sensor response post-launch, ensuring long-term accuracy in radiance measurements.[9] The sensor's design emphasized reliability for operational remote sensing, with a mass of 38.5 kg and power consumption of 34 W, while providing 128 grey levels of radiometric resolution.[16] In conjunction with the higher-resolution LISS-II, it facilitated complementary wide-area observations.[6]

LISS-II Sensor

The Linear Imaging Self-Scanning Sensor-II (LISS-II) was a key payload on the IRS-1A satellite, providing medium-resolution multispectral imagery optimized for detailed terrestrial feature analysis. Comprising two identical pushbroom cameras, LISS-IIA and LISS-IIB, it achieved a spatial resolution of 36.25 meters—half that of the co-boresighted LISS-I sensor—enabling applications such as crop type discrimination, soil boundary mapping, and vegetation health assessment.[17][6][19] Each LISS-II camera imaged a 74 km swath width, with the units offset by approximately 70 km to yield a combined coverage of about 140–148 km, complementing the wider but coarser LISS-I for comprehensive scene acquisition during orbital passes. The sensor operated in four spectral bands identical to those of LISS-I: band 1 (blue, 0.45–0.52 μm), band 2 (green, 0.52–0.59 μm), band 3 (red, 0.62–0.68 μm), and band 4 (near-infrared, 0.77–0.86 μm), capturing reflected solar radiation for multispectral analysis.[17][6][16] LISS-II utilized solid-state linear charge-coupled device (CCD) arrays for scanning, with each camera employing eight 2048-element detector arrays (two per spectral band) to generate 8192 pixels per scan line at the focal plane, supporting the finer resolution through adjusted integration times relative to LISS-I. Data from each camera were downlinked at 10.4 Mbps in X-band, doubling to 20.8 Mbps for the pair, with 7-bit radiometric quantization to balance dynamic range and noise for land cover interpretations.[6][16][19] The optical subsystem featured refractive telescope optics focused onto the CCD arrays, ensuring compatibility with the satellite's nadir-pointing configuration for stable along-track imaging. This design prioritized sharp edge response and low distortion for medium-scale mapping, with the higher pixel density facilitating enhanced discrimination of agricultural and hydrological features compared to broader-coverage sensors.[6][2]

Launch

Launch Vehicle and Site

The IRS-1A satellite was launched aboard a Vostok-2M rocket, an expendable carrier rocket developed by the Soviet Union under the GRAU index 8A92M, as part of cooperative efforts between the Indian Space Research Organisation (ISRO) and Soviet space authorities.[2] The Vostok-2M featured a three-stage configuration derived from the R-7 family, including four strap-on boosters for the first stage, a central core as the second stage, and a Block-E upper stage for orbital insertion, with a payload fairing diameter of 2.58 meters designed to enclose satellites like IRS-1A.[20] The launch occurred from Baikonur Cosmodrome in present-day Kazakhstan (then part of the USSR), utilizing Launch Complex 31 (Pad 31/6), a facility dedicated to Vostok-series vehicles and equipped with integration halls, fueling systems, and support infrastructure for payload mating and pre-launch processing.[2][21] This site was selected for its latitude, enabling efficient access to polar sun-synchronous orbits. Cooperation between ISRO and the Soviet Union was formalized through an agreement signed on May 10, 1972, with the USSR Academy of Sciences, which provided for launch services from Soviet cosmodromes and marked an early milestone in India's international space partnerships.[15] Preparations included satellite assembly and initial testing in India before shipment to Baikonur for final integration with the Vostok-2M, ensuring compatibility for deployment into the planned 904 km polar sun-synchronous orbit.[2][1]

Mission Timeline and Orbit

IRS-1A was launched on 17 March 1988 at 06:43:00 UTC from the Baikonur Cosmodrome in Kazakhstan aboard a Vostok-2M rocket. The ascent profile followed the standard Vostok sequence, with liftoff initiating the powered flight, first stage burnout and separation occurring at approximately T+120 seconds, second stage separation at T+300 seconds, and third stage burnout leading to payload deployment at around T+600 seconds.[22][23] Upon separation, IRS-1A was inserted into an initial sun-synchronous orbit with a perigee of 863 km, an apogee of 917 km, an inclination of 99.01°, and a nodal period of 102.7 minutes. The orbit was designed for a local equator crossing time of 10:30 AM on the descending node to optimize imaging conditions.[24][12] Post-deployment, the first telemetry, tracking, and command (TT&C) contact was established shortly after separation, confirming satellite health. Initial maneuvers using the onboard hydrazine propulsion system circularized the orbit to an altitude of 904 km, achieving the operational sun-synchronous configuration.[6][25] Mission success was verified through deployment confirmation and initial attitude acquisition within 24 hours of launch, enabling the satellite to commence preparations for nominal operations.[12]

Operations

In-Orbit Operations

Following its launch on March 17, 1988, IRS-1A underwent a commissioning phase during the first month in orbit, involving subsystem checkouts, orbit stabilization, and payload activation to verify functionality.[15] By April 1988, the satellite was fully commissioned and transitioned to routine operations, conducting Earth imaging during its 14 daily orbits, each lasting approximately 103 minutes. These operations focused on systematic data acquisition for remote sensing applications, with the satellite maintaining a sun-synchronous orbit at 904 km altitude.[6] Orbit maintenance was achieved through the satellite's three-axis stabilization system, which utilized four reaction wheels for attitude control and magnetic torquers for periodic momentum dumping to counteract accumulated angular momentum from environmental disturbances.[9] Altitude decay due to atmospheric drag was managed via onboard hydrazine thrusters, ensuring the equator crossing time remained near 10:30 a.m. on the descending node throughout the mission to preserve imaging consistency.[6] Minor anomalies, such as occasional attitude perturbations, were addressed through ground-commanded adjustments to restore nominal performance without significant disruptions.[15] Payload operations involved selective activation of the Linear Imaging Self-Scanning Sensors (LISS-I and LISS-II) during orbital passes over target areas, operating in push-broom mode across four spectral bands in the visible and near-infrared regions.[6] Imaging was scheduled to prioritize high-value regions like India, with real-time data downlinked at rates of 5.2 Mbit/s for LISS-I (S-band) and 10.4 Mbit/s per camera for LISS-II (X-band), enabling continuous acquisition without onboard storage.[6] Over its lifetime, the sensors captured more than 60,000 scenes in the first three years alone, supporting applications in agriculture and resource monitoring.[26] Designed for a three-year lifespan, IRS-1A demonstrated robust resource management, extending operations through efficient power and propulsion usage until mission completion in July 1996, achieving 8 years and 4 months of service.[12] Deactivation followed the exhaustion of onboard propellant and gradual performance degradation, marking the end of its in-orbit phase.[12]

Ground Segment and Data Processing

The ground segment for IRS-1A was primarily managed by the National Remote Sensing Agency (NRSA, now NRSC) at its facility in Shadnagar near Hyderabad, India, which served as the main reception station equipped with S-band and X-band antennas for capturing downlink signals from the satellite's Linear Imaging Self-Scanning Sensors (LISS-I and LISS-II).[6][27][7] This station handled the initial acquisition of imagery data, enabling real-time monitoring and operational control during the mission. While the primary infrastructure was domestic, IRS-1A's data compatibility with international systems like those for Landsat and SPOT allowed reception at select foreign ground stations for enhanced global coverage, though formal international agreements for direct IRS data access, such as with INPE in Brazil, were established later in the IRS series.[6][28] Data flow from IRS-1A involved real-time downlink transmission at rates of 5.2 Mbps for LISS-I via S-band and 10.4 Mbps each for the two LISS-II cameras via X-band, totaling up to 20.8 Mbps during simultaneous operations.[6] Upon reception at Shadnagar, quick-look processing was performed to generate preliminary images for immediate orbit assessment and mission health checks, facilitating rapid evaluation of data quality and coverage.[27] Acquired raw data was then archived at the NRSC facility, where it underwent systematic storage for long-term preservation and future access.[29] The processing pipeline at NRSC focused on transforming raw telemetry into usable products through radiometric correction, which adjusted for sensor calibration data from LISS instruments to ensure consistent brightness values across scenes, and geometric rectification, aligning imagery to standard map projections like Universal Transverse Mercator (UTM) using orbital ephemeris.[13][30] These steps produced level-1 products (radiometrically corrected but geometrically uncorrected) and level-2 products (fully geometrically corrected and georeferenced), enabling reliable analysis for applications in resource management.[13] User access to IRS-1A data was facilitated through NRSC's dissemination mechanisms, including distribution on physical media such as magnetic tapes and later CD-ROMs, alongside early digital networks for priority users like government agencies involved in agriculture and hydrology monitoring.[6] In the first three years, more than 60,000 scenes were processed and made available, marking a significant expansion in India's remote sensing data repository.[3]

Mission Results and Legacy

Performance and Achievements

IRS-1A was designed for a nominal mission life of three years but far exceeded this, operating successfully for 8 years and 4 months until its deactivation in July 1996. This extension was enabled by minimal degradation of key subsystems, including the solar arrays, which exhibited no appreciable power loss throughout the mission.[6][18][2] A major technical achievement was the implementation of push-broom imaging technology via solid-state CCD linear array cameras on an Indian satellite, marking the first such use in the nation's remote sensing program. These LISS-I and LISS-II sensors delivered high-quality multispectral data, with the satellite acquiring over 60,000 scenes in its initial three years of operation. Orbit stability was maintained in a sun-synchronous configuration at a nominal altitude of 904 km, supporting consistent imaging passes.[3][6][15] Early operational challenges included the absence of onboard data storage, necessitating real-time direct downlink of imagery, which was effectively managed through ground station coordination without onboard tape recorders. The mission's 22-day repeat cycle provided systematic coverage of India and neighboring regions, facilitating multi-temporal analysis for resource monitoring.[6]

Impact on Remote Sensing in India

The launch of IRS-1A marked a pivotal advancement in India's remote sensing capabilities, enabling comprehensive applications in resource management. Its data facilitated national-scale land use and land cover mapping at 1:250,000 scale across the country, supporting district-level planning for agriculture, urban development, and environmental monitoring. In agriculture, IRS-1A imagery was instrumental in crop yield estimation, particularly for wheat and rice, by providing multispectral data that improved pre-harvest production forecasts and enhanced food security planning in regions like Punjab and Orissa. Forestry inventories also benefited, with the satellite's sensors used to assess forest cover extent, density classification, and resource depletion, aiding conservation efforts in diverse ecosystems.[31][32][9] Technologically, IRS-1A laid the foundation for the evolution of India's remote sensing program, directly paving the way for IRS-1B in 1991 and the broader IRS series, while promoting indigenous development of payloads like the Linear Imaging Self-Scanning Sensors (LISS) and upgrades to ground receiving stations for real-time data processing. This self-reliance reduced dependence on foreign satellites, such as Landsat, and boosted national expertise in Earth observation infrastructure. Scientifically, the satellite's data contributed to numerous studies on vegetation health, including calculations of the Normalized Difference Vegetation Index (NDVI) using LISS-I and LISS-II bands to monitor crop stress and land degradation. For instance, NDVI analyses from IRS-1A supported assessments in watershed management and post-disaster vegetation recovery, with applications in events like the 1990 Andhra Pradesh cyclone for damage evaluation and relief planning.[6][33][34][35] On the policy front, IRS-1A's success integrated remote sensing into India's National Natural Resources Management System (NNRMS), strengthening the role of the National Remote Sensing Centre (formerly NRSA) in data dissemination and application development. This fostered policy frameworks for sustainable resource use, disaster mitigation, and economic planning, emphasizing indigenous technology to achieve self-sufficiency in Earth observation and influencing subsequent national space policies.[6][33]

References

  1. IRS-1A - ISRO
  2. IRS 1A, 1B - Gunter's Space Page
  3. Three Years of mission performance - IRS-1A - NASA ADS
  4. Satellite: IRS-1A - WMO OSCAR
  5. IRS-1A Satellite Mission Summary | CEOS Database
  6. IRS (Indian Remote Sensing Satellites) - eoPortal
  7. [PDF] Indian Remote Sensing Missions & Payloads- A Glance - URSC
  8. IRS (Satellite) - an overview | ScienceDirect Topics
  9. [PDF] The Indian remote sensing satellite: a programme overview
  10. IRS-1A
  11. [PDF] indian remote sensing missions & payloads a glance - URSC
  12. On orbit performance of IRS1A 40 Ah nickel cadmium batteries - ADS
  13. Indian Remote Sensing Satellite, IRS-1A - ISRO
  14. IRS-1A, 1988 - csre.iitb.ac.
  15. None
  16. [PDF] irs mission - Publications of the IAS Fellows
  17. Details for Instrument LISS-2 - WMO OSCAR
  18. Vostok-2 | OKB-1 - Next Spaceflight
  19. IRS-1B | Vostok-2M - Next Spaceflight
  20. IRS
  21. The launch of Vostok spacecraft - RussianSpaceWeb.com
  22. [PDF] JPRS Report Science and Technology USSR: Space. - DTIC
  23. [PDF] JPRS Report, Science & Technology, USSR: Space. - DTIC
  24. https://ui.adsabs.harvard.edu/abs/1991JSpT....1...57K/abstract
  25. 25 years of IRS: Touching the skies - Geospatial World
  26. National Remote Sensing Centre (NRSC) - ISRO
  27. [PDF] 25 Years of Indian Remote Sensing Satellite (IRS) Series - UNOOSA
  28. NRSC | NRSC Website
  29. [PDF] INDIAN REMOTE SENSING SATELLITES
  30. IRS-1A Application for Land Use/Land Cover Mapping in India on ...
  31. Pre-harvest wheat yield and production estimation for the Punjab ...
  32. None
  33. Integrated remote sensing and GIS based spatial modelling through ...
  34. (PDF) India's EO infrastructure for disaster reduction - ResearchGate
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