Landsat 8 and Landsat 7 comparison, First Look

The Landsat Data Continuity Mission (LDCM), also known as Landsat 8, was one of the most anticipated satellite launches in recent history. Its arrival was particularly crucial following the failure of the Scan Line Corrector (SLC) onboard the Landsat 7 ETM+ sensor in 2003—just four years after its launch. The malfunction caused nearly 22% data loss in each scene, posing a significant challenge for climate change monitoring and various environmental studies.

During this gap, NASA had to rely on other satellites as interim solutions. Interestingly, the original LDCM concept was intended as a commercial data provision system, with NASA inviting proposals from private imaging companies. However, in September 2003, this plan was cancelled.

By August 2004, the White House Office of Science and Technology Policy (OSTP) directed that Landsat-type sensors be integrated into the National Polar-orbiting Operational Environmental Satellite System (NPOESS). Later, in December 2005, the OSTP officially instructed NASA to implement the LDCM as a free-flyer spacecraft carrying the Operational Land Imager (OLI).

In December 2009, the mission was further enhanced with the decision to add a Thermal Infrared Sensor (TIRS). Together, these instruments gave Landsat 8 its advanced imaging capabilities.

Landsat 8 Sensor Overview

Landsat 8 carries two key instruments:

• Operational Land Imager (OLI)

• Thermal Infrared Sensor (TIRS)

Both are push-broom sensors, capable of acquiring 12-bit data with an excellent signal-to-noise ratio (SNR).

Landsat 8 Bands

Here is the list of Landsat 8 bands provided by NASA’s pre-commissioning sample data:

Key Improvements over Landsat 7

Six of Landsat 8’s bands are equivalent to those on Landsat 7 ETM+, but there are important enhancements:

• Two new bands:

  • Ultra-blue (443 nm) for coastal/aerosol studies

  • Cirrus (1375 nm) for cloud detection

• Improved Panchromatic band (Band 8): Though still at 15 m resolution, it offers sharper images with better contrast.

• Narrower Near-Infrared (Band 5): Reduces atmospheric sensitivity, improving land cover classification.

• Thermal Imaging (Bands 10 & 11): Added through TIRS for advanced thermal mapping.

Landsat 8 vs. Landsat 7: A Visual Comparison

The Panchromatic band of Landsat 8 clearly demonstrates the technological leap. The image quality is visibly sharper, with finer details and reduced noise compared to Landsat 7.

• Landsat 8 Panchromatic Image:
  Excellent resolution with smooth radiometric details.

• Landsat 7 ETM+ Panchromatic Image:
  Grainier and noisier, reflecting both the SLC malfunction and older sensor technology.

Even though both sensors capture data at 15m resolution, the higher SNR of Landsat 8 results in images that appear more spatially refined.

Why Landsat 8 is a Game-Changer

1. Higher Radiometric Resolution:
   Landsat 8 records 12-bit data, allowing detection of subtle surface variations.

2. Push-Broom Technology:
   Reduces mechanical errors (compared to whisk-broom scanners) and improves SNR.

3. Spectral Refinement:
   Narrower bands minimize atmospheric effects, improving accuracy in land cover, vegetation, and water studies.

4. Thermal Imaging Capability:
   With TIRS, Landsat 8 supports urban heat mapping, water resource monitoring, and climate studies.

Conclusion

The launch of Landsat 8 marked a significant milestone in the Landsat program. By combining advanced spectral bands, higher radiometric quality, and thermal imaging capabilities, Landsat 8 provides researchers with a reliable, continuous, and improved dataset for environmental monitoring, climate studies, and land use analysis.

Its improvements over Landsat 7 ensure continuity while advancing the potential for more accurate Earth observation—making it a cornerstone of modern remote sensing.