IRS and Landsat: Earth Observation Satellites

The Indian Remote Sensing (IRS) satellites and the Landsat series are two of the most prominent Earth observation satellite systems. Earth observation satellites have revolutionized our understanding of global environmental processes, land use changes, and natural resource management.

Indian Remote Sensing (IRS) Program

History:

The Indian Remote Sensing program was initiated by the Indian Space Research Organisation (ISRO) with the launch of IRS-1A on March 17, 1988 from the Soviet Cosmodrome at Baikonur. This was part of India’s strategy to develop indigenous satellite imagery for resource management and environmental monitoring. Over the years, ISRO has launched several IRS satellites, each enhancing capabilities in resolution, spectral bands, and coverage.

• Key Missions:
  • IRS-1A: Carried sensors like LISS-I and LISS-II, providing 72m and 36m resolution imagery respectively.
  • IRS-1B: Launched in 1991, similar to IRS-1A but phased differently in orbit for better coverage.
  • IRS-P2, IRS-1C, IRS-1D: Subsequent launches improved resolutions and added new sensors like LISS-III for enhanced spectral capabilities.
  • Cartosat Series (2005–present): The Cartosat satellites are part of the IRS series, focusing on high-resolution imagery for cartographic and urban planning applications.
  • ResourceSat and OceanSat Series: These satellites target resource management and oceanographic studies.

Landsat Program

The Landsat program, managed jointly by NASA and the U.S. Geological Survey (USGS), is one of the longest-running satellite programs in the world, providing continuous multispectral images of Earth since 1972. The Landsat program began with the launch of the Earth Resources Technology Satellite (ERTS-1) on July 23, 1972, later renamed Landsat 1. This initiative was the first of its kind to focus specifically on monitoring Earth’s land surfaces.

Evolution:

• Landsat 1 to 5: Utilized Multispectral Scanner System (MSS) and later Thematic Mapper (TM) instruments, significantly advancing remote sensing technology.
• Landsat 7: Launched in 1999 with the Enhanced Thematic Mapper Plus (ETM+), which included a panchromatic band for higher resolution.
• Landsat 8: Launched in 2013, introduced the Operational Land Imager (OLI) and Thermal Infrared Sensor (TIRS), offering improved data quality and additional spectral bands.
• Landsat 9: Launched on September 27, 2021, continues the mission with enhanced versions of Landsat 8’s instruments.

Spectral Bands and Their Applications

• IRS Satellites:
  • LISS-I/II: Four bands in the visible and near-infrared spectrum, useful for land use/cover, agriculture, and water resources.
  • LISS-III: Additional SWIR band for better differentiation of soil and vegetation types.
  • IRS satellites are equipped with sensors operating in multiple spectral bands:
  • Visible Bands (Blue, Green, Red): Useful for vegetation studies, water bodies, and soil mapping.
  • Near-Infrared (NIR): Effective for vegetation health monitoring and biomass estimation.
  • Shortwave Infrared (SWIR): Used for soil moisture content analysis and mineral exploration.
  • Thermal Infrared (TIR): Applied in surface temperature mapping and water stress assessment.

• Landsat Satellites:
  • MSS: Four bands in visible and NIR, foundational for early remote sensing applications.
  • TM/ETM+: Seven bands including thermal, used extensively for geological studies, vegetation monitoring, and urban planning.
  • OLI/TIRS (Landsat 8/9): Eleven bands, with two new bands for cirrus cloud detection and coastal/aerosol studies. This allows for more nuanced environmental mapping, including water quality assessments and cloud-free data collection.
  • Coastal/Aerosol Band (Landsat 8/9): Enhances coastal and aerosol studies.
  • Blue, Green, Red Bands: Primarily for vegetation and water body studies.
  • NIR Band: Vital for vegetation vigor and water content analysis.
  • SWIR Bands: Critical for assessing soil and vegetation moisture.
  • Thermal Infrared Bands: Useful for monitoring urban heat islands and geothermal activities.
  • Panchromatic Band: Provides high-resolution imagery for detailed analysis.

Spatial, Spectral, and Temporal Resolutions

IRS Satellites

• Spatial Resolution: Ranges from 2.5 meters (Cartosat) to 56 meters (ResourceSat) depending on the satellite.
• Spectral Resolution: Covers broad spectral bands, including visible, NIR, SWIR, and TIR.
• Temporal Resolution: Typically 5–22 days, depending on the satellite’s revisit capability.

Landsat Satellites

• Spatial Resolution: Landsat 8 and 9 offer a resolution of 15 meters (panchromatic) and 30 meters (multispectral).
• Spectral Resolution: Landsat covers up to 11 spectral bands, including thermal bands.
• Temporal Resolution: 16 days, ensuring regular data for change detection.

Recent Developments and Launches

IRS Satellites

• EOS-06 (2022): Part of the OceanSat series, focusing on oceanographic studies and atmospheric data collection.
• Cartosat-3 (2019): Provides very high-resolution imagery (up to 25 cm), making it one of the most advanced Earth observation satellites launched by ISRO.
• Upcoming launches include EOS-07, which aims to enhance capabilities in environmental and weather monitoring.

Landsat Satellites

• Landsat 9 (2021): Launched on September 27, 2021, it continues the legacy of Landsat 8, offering high-quality imagery for a wide range of applications.
• Future of Landsat: NASA and USGS are working on the Landsat Next program, aiming for higher spectral resolution and increased data availability.
• Landsat Next: Planned for late 2030/early 2031, this mission will feature 26 spectral bands, significantly enhancing spectral resolution and data application potential.