Satellite sensor requirements for monitoring essential biodiversity variables of coastal ecosystems
Authors: Muller‐Karger Frank E. , Hestir Erin , Ade Christiana , Turpie Kevin , Roberts Dar A. , Siegel David , Miller Robert J. , Humm David , Izenberg Noam , Keller Mary , Morgan Frank , Frouin Robert , Dekker Arnold G. , Gardner Royal , Goodman James , Schaeffer Blake , Franz Bryan A. , Pahlevan Nima , Mannino Antonio G. , Concha Javier A. , Ackleson Steven G. , Cavanaugh Kyle C. , Romanou Anastasia , Tzortziou Maria , Boss Emmanuel S. , Pavlick Ryan , Freeman Anthony , Rousseaux Cecile S. , Dunne John , Long Matthew C. , Klein Eduardo , McKinley Galen A. , Goes Joachim , Letelier Ricardo , Kavanaugh Maria , Roffer Mitchell , Bracher Astrid , Arrigo Kevin R. , Dierssen Heidi , Zhang Xiaodong , Davis Frank W. , Best Ben , Guralnick Robert , Moisan John , Sosik Heidi M. , Kudela Raphael , Mouw Colleen B. , Barnard Andrew H. , Palacios Sherry , Roesler Collin , Drakou Evangelia G. , Appeltans Ward , Jetz Walter 
Published: March 2018

The biodiversity and high productivity of coastal terrestrial and aquatic habitats are the foundation for important benefits to human societies around the world. These globally distributed habitats need frequent and broad systematic assessments, but field surveys only cover a small fraction of these areas. Satellite‐based sensors can repeatedly record the visible and near‐infrared reflectance spectra that contain the absorption, scattering, and fluorescence signatures of functional phytoplankton groups, colored dissolved matter, and particulate matter near the surface ocean, and of biologically structured habitats (floating and emergent vegetation, benthic habitats like coral, seagrass, and algae). These measures can be incorporated into Essential Biodiversity Variables (EBVs), including the distribution, abundance, and traits of groups of species populations, and used to evaluate habitat fragmentation. However, current and planned satellites are not designed to observe the EBVs that change rapidly with extreme tides, salinity, temperatures, storms, pollution, or physical habitat destruction over scales relevant to human activity. Making these observations requires a new generation of satellite sensors able to sample with these combined characteristics: (1) spatial resolution on the order of 30 to 100‐m pixels or smaller; (2) spectral resolution on the order of 5 nm in the visible and 10 nm in the short‐wave infrared spectrum (or at least two or more bands at 1,030, 1,240, 1,630, 2,125, and/or 2,260 nm) for atmospheric correction and aquatic and vegetation assessments; (3) radiometric quality with signal to noise ratios (SNR) above 800 (relative to signal levels typical of the open ocean), 14‐bit digitization, absolute radiometric calibration <2%, relative calibration of 0.2%, polarization sensitivity <1%, high radiometric stability and linearity, and operations designed to minimize sunglint; and (4) temporal resolution of hours to days. We refer to these combined specifications as H4 imaging. Enabling H4 imaging is vital for the conservation and management of global biodiversity and ecosystem services, including food provisioning and water security. An agile satellite in a 3‐d repeat low‐Earth orbit could sample 30‐km swath images of several hundred coastal habitats daily. Nine H4 satellites would provide weekly coverage of global coastal zones. Such satellite constellations are now feasible and are used in various applications.