Section 1.4 Remote Sensing

Remote sensing deals with the monitoring of Earth surface variables and processes from a range of spatial and temporal scales using in-situ, airborne and spaceborne instruments. Within the Research Field Earth and Environment of the Helmholtz-Association, we focus on the development and use of remote sensing techniques for the monitoring of land surfaces.

In particular, research lines in our section comprise (i) methodological developments for remote sensing data analysis and definition of future satellite missions, and (ii) application-oriented research for the monitoring of bio- and geophysical parameters of interest to a wide range of scientific disciplines, including soil and land degradation studies, geological exploration, precision agriculture and global vegetation functioning, natural and man-made hazards, and land-atmosphere interactions.

Data and methods

We use diverse remote sensing techniques for our application-oriented research. First, much information for the monitoring of bio- and geophysical parameters is based on airborne and spaceborne hyperspectral remote sensing, also known as imaging spectroscopy. This technique relies on remote measurements of the solar radiation reflected by the Earth's atmosphere and surface in a high number of spectral channels distributed along the visible, near- and shortwave infrared parts of the electromagnetic spectrum. Characteristic absorption features present in the resulting spectra enable the identification and quantification of surface materials such as minerals, plant pigments or water constituents.

We also use satellite data from optical multispectral sensors such as RapidEye, Sentinel-2 and Landsat for applications requiring observations with a high spatial and temporal resolution, like for instance the monitoring of landslides and the characterisation of phenological changes in crops. Multispectral instruments work on a similar basis as hyperspectral instruments, but typically provide a higher spatial and temporal coverage at the expense of a reduced spectral information. 

In addition, active satellite sensors such as synthetic aperture radar (SAR) and interferometry techniques are used to detect and analyze subtle geometric-morphologic changes at the Earth’s surface. This provides key information for studies dealing with e.g. hazards such as earthquakes, landslides, and urban surface deformations, or geophysical processes such as glacier dynamics. 

Apart from the exploitation of remote sensing data sets to infer information on the Earth surface, we also deploy field campaigns for both validation of satellite-based measurements and detailed investigation of processes at local scales. Measurements from ground-, tower- and aircraft-based sensors are part of these campaigns. Many of our retrieval algorithms also benefit from basic research performed in our lab, which comprises a number of optical and thermal spectrometers.

Overarching projects

We hold the role of principal investigator of the upcoming EnMAP (Environmental Mapping and Analysis Program) spaceborne imaging spectroscopy mission funded by the German Federal Ministry for Economic Affairs and Energy (BMWi in the German acronym). In EnMAP, we are responsible for the coordination of the mission's scientific programme, the support of industrial activities towards system construction, and interactions with the user community and outreach.  

Part of our applied remote sensing research supports the development of the GFZ’s Earth System Observatories. For example, our work on remote sensing based analysis of landslide hazard in Southern Kyrgystzan is embedded in the Global Change Observatory Central Asia. We also contribute to the data set being collected by the TERENO German Northeastern Lowlands Observatory initiative with in-situ and remote sensing measurements acquired over the DEMMIN study site. DEMMIN is also a key site for some of our research activities on the monitoring of agricultural areas, and is widely used for the development of algorithms for the retrieval of soil and vegetation parameters from EnMAP.  

Our section hosts two so-called Young Investigator groups: the GlobFluo group , funded by the German Research Foundation (DFG in the German acronym), is focused on the global monitoring of terrestrial photosynthesis through the remote sensing of the chlorophyll fluorescence signal. The TEAM group, funded by the Helmholtz Association, studies Earth-atmosphere interactions such as the exchange of sensible and latent heat (evapotranspiration), carbon dioxide, and methane on multiple spatial scales.