The Landsat Program: A Complete Guide to 50+ Years of Earth Observation

Why Landsat Still Matters After 50 Years

Most satellites you read about are a few years old. Landsat is different: it is the longest space-based record of Earth's land surface, beginning with Landsat 1 (launched as ERTS-1 on 23 July 1972) and collecting imagery without interruption since (USGS).

That continuity is the whole point. If you want to know how a city, forest, glacier, or coastline has actually changed over decades — not modeled, but observed — Landsat is usually the only dataset that reaches that far back at 30m resolution. A 1985 Landsat scene and a 2025 Landsat scene can be compared directly, which makes the archive irreplaceable for climate and land-change science.

And since 2008, the Landsat products in the USGS EROS archive have been available for download at no cost (USGS). That single decision turned Landsat from an expensive niche product into the backbone of global Earth observation.

The Current Satellites: Landsat 8 and Landsat 9

Two satellites are operational today, working together on offset orbits (USGS Landsat 8, USGS Landsat 9):

	Landsat 8	Landsat 9
Launched	February 2013	September 2021
Imager	OLI	OLI (improved copy)
Thermal	TIRS	TIRS (improved copy)
Revisit (each)	16 days	16 days
Combined revisit	~8 days	~8 days
Orbit	705 km, sun-synchronous	705 km, sun-synchronous

Because Landsat 8 and 9 are offset by 8 days, together they image any given location roughly every 8 days. The earlier Landsat 7, whose scan line corrector failed permanently on 31 May 2003, is no longer imaging: its science imaging ended on 19 January 2024 and the satellite was decommissioned on 4 June 2025 (USGS). NASA still lists Landsat 8 as an active mission (NASA).

What the Sensors Measure

Each satellite carries two instruments:

OLI (Operational Land Imager) — captures 9 spectral bands in the visible, near-infrared, and shortwave infrared (wavelengths as listed by USGS):

Band	Wavelength	Primary use
1 — Coastal/Aerosol	0.43–0.45 µm	Water clarity, aerosols
2 — Blue	0.45–0.51 µm	Bathymetry, soil/vegetation
3 — Green	0.53–0.59 µm	Vegetation vigor
4 — Red	0.64–0.67 µm	Chlorophyll absorption
5 — NIR	0.85–0.88 µm	Vegetation structure, NDVI
6 — SWIR-1	1.57–1.65 µm	Moisture, burn mapping
7 — SWIR-2	2.11–2.29 µm	Geology, fire scars
8 — Panchromatic	0.50–0.68 µm	15m sharpening
9 — Cirrus	1.36–1.38 µm	Thin-cloud detection

TIRS (Thermal Infrared Sensor) — adds two thermal bands (Band 10: 10.6–11.19 µm; Band 11: 11.5–12.51 µm) at 100m resolution, used to derive land surface temperature for urban heat islands, evapotranspiration, and volcanic and wildfire monitoring. This thermal capability is something Sentinel-2 lacks entirely.

Most bands are 30m, the panchromatic band is 15m, and the thermal bands are collected at 100m and resampled to 30m (NASA).

What 30m Over 50 Years Lets You Do

Landsat's resolution is moderate, but its consistency is unmatched. That combination makes it the default choice for long-baseline change studies:

Application	Why Landsat fits
Deforestation & forest loss	The University of Maryland's annual global forest loss maps (from 2001, built from Landsat time series in partnership with Global Forest Watch) rest on the archive (UMD GLAD). See Deforestation Monitoring.
Urban expansion	Decades of consistent imagery reveal how cities sprawl. See Tracking Urban Sprawl with Satellite Time Series.
Glacier & ice retreat	Multi-decade baselines quantify long-term loss. See Glacier Retreat Monitoring.
Land surface temperature	TIRS thermal bands map heat directly. See Land Surface Temperature.
Burn severity	SWIR bands and NBR map fire scars. See Mapping Burn Severity After Wildfires.

Landsat vs Sentinel-2: Complementary, Not Competing

These two optical workhorses are often compared, but they are best understood as complementary:

	Landsat 8/9	Sentinel-2
Resolution	30m (15m pan)	10m / 20m / 60m
Revisit (combined)	~8 days	5 days at the Equator
Thermal bands	Yes (TIRS)	No
Red-edge bands	No	Yes (narrow 20m bands B5–B7, plus narrow NIR B8a)
Archive depth	Since 1972	Since 2015

Sentinel-2 figures are from ESA's Sentinel-2 mission page; its operational satellites are now Sentinel-2B and Sentinel-2C, with Sentinel-2A in an extension campaign. | Operator | USGS / NASA (USA) | ESA / EU (Copernicus) |

Use Landsat when you need the long historical baseline or thermal data; use Sentinel-2 when you need finer spatial detail or more frequent observations. For a fuller breakdown, see Sentinel-2 vs Landsat 9.

The best part: you often don't have to choose. NASA's Harmonized Landsat Sentinel-2 (HLS) product reconciles Landsat 8/9 and Sentinel-2A/B/C into a single 30m time series with an observation on average every 1.6 days (NASA Earthdata) — read Harmonized Landsat Sentinel (HLS) to see how that works.

What's Next: Landsat 10

The next mission in the joint USGS–NASA program is Landsat 10, expected to launch in 2031 under the Sustainable Land Imaging program. USGS lists 26 spectral bands (21 visible-to-shortwave-infrared and 5 thermal), 10–20m resolution for the visible, near-infrared and shortwave-infrared observations, 60m for the thermal and atmospheric bands, and an 18-day revisit (USGS). The goal, as always, is continuity — extending the record another generation while adding spectral detail.

Key Takeaways

• Landsat is the longest space-based Earth-surface record — continuous since 1972, free to download since 2008.
• Landsat 8 and 9 together provide an ~8-day revisit at 30m, with 15m panchromatic sharpening.
• The OLI imager covers visible-to-SWIR bands; the TIRS thermal sensor adds land surface temperature — a capability Sentinel-2 lacks.
• Landsat's edge is multi-decadal consistency and thermal data; Sentinel-2's edge is finer resolution and faster revisit.
• Combine both via HLS when you want dense, harmonized optical time series.
• Landsat 10 (expected 2031) is the next mission; Landsat 7 was decommissioned in 2025.

Landsat is operated jointly by the USGS and NASA. Landsat data from the USGS archive is available at no cost.