Satellite imagery used to cost thousands of dollars a scene, but today the best sources are free: Landsat, Sentinel, and a growing list of open datasets cover the whole planet in multiple resolutions and wavelengths. The challenge is no longer access but choice, because each source suits a different job. This guide lists the free sources that matter in 2026 and how to choose between them.

Landsat: The Longest Record

Landsat is the longest-running Earth observation programme, with continuous imagery since 1972, and all of it is free from the USGS EarthExplorer. Landsat 8 and 9 provide 30-metre multispectral imagery every 16 days, which suits land cover change, agriculture, and long-term studies. The archive's depth is its superpower: no other source lets you compare a landscape in 1985 with the same place today. Download from EarthExplorer or access it through Google Earth Engine.

Sentinel: The European Workhorse

The European Space Agency's Sentinel satellites provide free, open imagery with better resolution and revisit times than Landsat: Sentinel-2 offers 10-metre multispectral imagery every five days, and Sentinel-1 provides radar imagery that sees through clouds and at night. Access them through the Copernicus Data Space Ecosystem, which offers a browser, an API, and cloud processing. Sentinel is the best choice for current monitoring, vegetation analysis, and any work that needs frequent revisits.

Google Earth Engine: The Cloud Platform

Google Earth Engine is not a satellite but a cloud platform that hosts Landsat, Sentinel, MODIS and hundreds of other datasets, with the computing power to analyse them without downloading anything. It is free for research, education and non-commercial use, and it turns a task that would take days of downloading into a few lines of code. The learning curve is real, but for large-area or time-series analysis, there is no better tool.

Other Free Sources Worth Knowing

NASA's Worldview shows near-real-time imagery from MODIS and VIIRS, useful for fires, floods and weather. The USGS also offers high-resolution aerial photography for the United States through the National Map. OpenAerialMap hosts crowdsourced drone imagery, and the European Space Agency's EO Browser provides a simple interface for browsing Sentinel data. Each source fills a niche, and together they cover almost every need.

Choosing the Right Source

Choose Landsat for long-term change detection, Sentinel-2 for current monitoring at 10 metres, Sentinel-1 for radar through clouds, and Earth Engine for large-area analysis without downloading. Check the resolution, the revisit time, and the spectral bands before you commit, because the wrong source wastes hours. Start with the Copernicus browser for a quick look, then move to Earth Engine when you need serious analysis.

Satellite Data and Climate Monitoring

Satellite imagery is the backbone of climate monitoring: the same data that you download for free is used by scientists to track deforestation, glacier retreat, and sea-level rise. The Landsat archive goes back to 1972, which means you can compare a landscape today with the same landscape fifty years ago, and the change is visible. The free data is not just a resource for professionals, it is a public good, and the more people who use it, the more value it creates. Download the data, explore it, and see the planet change.

Key Takeaways

- Landsat offers free 30-metre imagery back to 1972 - Sentinel-2 offers 10-metre imagery every five days - Google Earth Engine hosts the data with cloud computing for analysis - Choose by resolution, revisit time and spectral bands, not by brand

Frequently Asked Questions

Where can I download free satellite imagery? From the USGS EarthExplorer for Landsat, the Copernicus Data Space Ecosystem for Sentinel, and Google Earth Engine for cloud-based analysis of both.

The best satellite imagery is free. Landsat for history, Sentinel for the present, and Earth Engine when you need to analyse it all.