DESIS Hyperspectral Applications: Tracking Ocean Garbage from Space

Teledyne and The German Aerospace Center are working together to make a difference in the clean-up of the world’s oceans. One of the most significant threats impacting oceans is marine plastic debris. Marine plastics can come from derelict fishing gear, ghost nets, trash that flows from rivers into the oceans, and numerous other sources. Marine life can become entangled in and, in some cases, ingest plastic refuse. This debris can prevent sunlight penetration into the ocean and impact plant and algae life-cycles. Large aggregate points for trash and pollution form around natural circulation points in the ocean currents called “gyres”. There are five major oceanic gyres and numerous smaller gyres that accumulate pollution. The major river systems, like the Ganges, Amazon, and Citarum, also contribute to the marine debris crisis.

These fields of debris, consisting largely of plastics, have become the focus of many organizations concerned with the health of the oceans. Yet, studying marine plastics with satellite and airborne imagery is a challenge due to the remoteness of these sites.

The ocean is a highly dynamicenvironment, which means thefloating debris fields are constantlymoving, and the sensitivity oftraditional satellite sensors are not designed to distinguish these materials. It is now possible to collect imagery that reveals the composition and density of these debris fields. With the use of the DLR Earth Sensing Imaging Spectrometer (DESIS) sensor aboard the Teledyne Multi-User System for Earth Sensing (MUSES) pointing platform on the International Space Station (ISS), coupled with the ocean current model General NOAA Operational Modeling Environment (GNOME), investigators will be able to both predict the location of and characterize these collection points. This will allow us to study the extent, monitor changes, and plan mitigation actions for the accumulated debris in these areas.

The DESIS sensor is a hyperspectral instrument, collecting reflected light in very narrow bands (~2.55nm). These narrow bands can be more sensitive to plastic debris signatures. Plastic is made of hydrocarbons, and even very small plastic particles can have an impact on the spectral signature from a 30x30-meter patch of water. Initial efforts to collect DESIS data over the center of the Eastern Pacific Garbage patch revealed distinctly different signatures from the water and clouds, which were determined to be rafts of plastic debris. Teledyne is collaborating with NOAA for their clean-up missions scheduled in 2020 to collect additional data from DESIS to support NOAA’s mitigation efforts.

The orbit of the ISS provides more opportunities to collect imagery over equatorial zones as opposed to satellites that orbit around the earth’s poles. Not only is the DESIS sensor well suited to detect debris, but it also has the capability to capture images of the ocean in areas that are notoriously cloudy. Plastic debris is an imminent threat, silently invading our oceans and, ultimately, impacting the food sources provided by our oceans.

Because the debris is so widespread, understanding the extent, amount, and impact must be evaluated from space. DESIS aboard the MUSES platform on the ISS provides a beachhead to design studies to assess this enormous problem.