Landsat is 50 – Happy Birthday!
Fifty years ago on July 23, 1972, the US Landsat-1 satellite was launched from Vandenberg Air Force Base in California. This was the beginning of an ongoing satellite series and the start of the earth observation era. With its four channels in the visible spectrum and near-infrared as well as its then-revolutionary 60-metre resolution, scientists could for the first time continuously document changes in the land surface at high resolution. Starting in 1976 the German Remote Sensing Data Center DFD was selected to process and distribute Landsat data.
Landsat-1 was first designated as the Earth Resources Technology Satellite, (ERTS-1). Its remote sensing recording instrument, the Multi Spectral Scanner (MSS) turned out to be extremely useful. It made it possible to calculate for the first time the Normalized Difference Vegetation Index (NDVI), an indicator still in use today. NDVI allows conclusions to be drawn about the development and vitality of vegetation on Earth’s surface. The condition and dynamics of forests, agriculture and cities could be monitored with MSS data. This data gave geoscientists a new impetus and made geo-ecologic relationships evident.
For 50 years now, the Landsat programme has been the continuous responsibility of the United States Geological Survey (USGS), with technical management by NASA. The youngest satellite of the series, Landsat-9, was launched in 2021 and will continue to supply multispectral data with up to 15 meter resolution. One of its predecessors, Landsat 5, even managed a service life exceeding 29 years, which put it in the Guinness Book of World Records.
The programme also significantly influenced European earth observation. ESA, founded in 1975, collaborated from the beginning with USGS. On its behalf stations in Europe also acquire Landsat data, while at the same time processing and safeguarding them. That was the basis of ESA’s earth observation programme in 1976. The still existing Earthnet programme created the framework for Europe’s earth observation data exchange. So-called National Points of Contact (NPOC) in ESA member countries ensure the distribution of Landsat data to their national users. DFD was from the beginning one of these national contacts (NPOC) for earth observation data and thus a valued partner in Germany for the geographic institutes of many universities. Landsat data were sent from Oberpfaffenhofen on Computer Compatible Tapes (CCT) to German universities and companies.
In turn, students came to DFD to work toward their diploma and, later, doctoral theses. Its high-quality photochemically generated image products containing processed satellite scenes were a special attraction. They were produced up to the early 2000s in DFD’s customized photo lab.
Before the US government decided in 2008 to make all Landsat data available to the public free of charge, they were commercially marketed worldwide, in Europe by the Eurimage company, which was based in Rome. Also here, use was made of DFD‘s technical resources of that time to archive, and distribute the data and to generate high-quality large-format photos.
In the 1990s DFD initially began on behalf of ESA also to acquire Landsat data in Libreville, Gabon, and later also in Chetumal, Mexico, using the transportable station that it had already employed for ERS.
In 1999 a commission for Landsat-7 data acquisition in Neustrelitz was forthcoming. After the ESA contract expired, reception was continued in direct cooperation with USGS, and in 2013 the DFD ground station in Neustrelitz became an official “International Cooperator” in the Landsat station network. DFD’s reliability in data reception, plus the location of Neustrelitz in the heart of Europe, prompted USGS to designate Neustrelitz as one of the five key acquisition stations of the Landsat system. Currently, ca. 4000 Landsat passages are acquired every year, sent to USGS in Sioux Falls, South Dakota, and from there made available to international users, including Europe’s Copernicus system. This living principle of distributed cooperation among satellite operators and ground-segment suppliers like DFD also served as a model for the architecture of the European satellite programmes ERS, Envisat, and finally Copernicus.
With their higher spatial and temporal resolution the Sentinel-2 satellites of Europe‘s Copernicus programme now augment Landsat. But Landsat data continue to be important as a substantial component of the assessment routine. Especially the long timespan covered by the Landsat programme makes it possible to derive and quantify several decades of dynamics. For example, geoinformation products like the annual World Settlement Footprint and the Europe-wide derivation of snow lines are based on Landsat time series that extend back to the 1980s. Landsat acquisitions are also combined with Sentinel data for use in numerous research projects to achieve even higher temporal coverage, such as for the Germany-wide mapping of forest health and forest canopy loss
Landsat decisively influenced the evolution of DFD. Activities like station operation and data management increased and developed further because of Landsat acquisition. And data from the Landsat programme continue to be a sturdy research pillar for the creation of applications throughout EOC.
We are profoundly thankful for Landsat and heartily wish it:
Happy Birthday and much success for the next 50 years!