The Landsat program launched in the early 1970s and has had 8 different satellites (although the rocket carrying landsat 6 failed on launch) and 5 different sensors:
- RBV & MSS – multispectral scanner (early), visible to SWIR
- TM – 7 bands 3 visible, 1 thermal IR, 3 reflected IR
- TM+ – added panchromatic (15 m) band
(aboard landsat 7 but Scan Line Corrector (SLC) failure in 2003 when it started collecting data in stripes instead of whole scenes) - OLI & TIRS- Landsat 8, launched early in 2013,
– adds new IR bands, one for cirrus clouds, and a shorter-than blue coastal scanner (see image below)
– calibrated using the moon!
The Landsat 7 satellite looks like this and used a rotating mirror (that’s what failed; Landsat 8 uses a “pushbroom” approach)
for the optic path collecting radiation from earth.
Raw data below (note packages of undistorted scan lines) and then geometrically corrected (on right)
Landsat 7 failed in 2003.
Landsat data is ordered by ROW and PATH and date. Cloud cover and season are important considerations. Archived and very recent Landsat TM, ETM+, and OLI/TIRS images for anywhere in the world can be browsed and then downloaded from Landsat Look or the USGS Earth Explorer (my choice).
Google has seamed together cloudfree images for the entire world for the history of the landsat program (1984 to present)
https://earthengine.google.com/timelapse/
I recommend going to the rivers of Peru in the Amazon basin. Amazing.