Small satellite mission targets maritime activity monitoring from orbit

by Robert Schreiber
Berlin, Germany (SPX) Dec 03, 2025

The OTTER Optical Traffic Tracking Experiment for Responsive Space satellite has entered service in orbit to support maritime monitoring following its launch on 28 November 2025 into an orbit at about 500 kilometres altitude. The nanosatellite has a mass of roughly six kilograms, is comparable in size to a shoebox and deployed its solar panels and instruments after separation from the launcher. The German Aerospace Center DLR leads the OTTER mission with industry partners as an experimental effort to determine how small satellites can help deliver space based capabilities more quickly and supplement existing maritime reconnaissance systems.

OTTER uses one antenna to receive position signals from ships while its onboard camera acquires images to verify the reported locations. Additional antennas, receivers and reflectors enable detection of illegal fishing, ships in distress, oil pollution and suspected manipulation of signals on the high seas. The mission will operate for about two years in low Earth orbit before the satellite re enters Earths atmosphere, with an electric propulsion system available to hasten its controlled destructive re entry.

Satellites in orbit can build situational pictures of maritime activity across ocean regions that are not limited by national borders, which differentiates them from land or sea based systems. Alongside large dedicated satellites, operators now employ growing numbers of commercial small satellites to extend coverage and improve resilience because multiple smaller spacecraft can be replaced more easily if a unit fails.

DLRs Responsive Space Cluster Competence Center RSC3 in Trauen, Lower Saxony, manages the OTTER mission and conducts research on responsive space concepts for maritime applications. Responsive space in this context refers to the ability to provide satellite services at short notice, such as expanding infrastructure, replacing failed satellites or deploying new capabilities. The RSC3, founded five years ago with support from Germanys Federal Ministry of Defence, coordinates research, users and industry to develop these capabilities.

The OTTER spacecraft is a three unit 3U CubeSat that SpaceX launched from the United States. Over its planned two year mission, it will downlink data from ships Automatic Identification System AIS together with camera imagery to a ground station, where teams process and evaluate the information. Through the same ground segment, controllers upload new instructions and observation schedules to adjust operations as needs change.

Spacecraft with masses below 500 kilograms are classified as small satellites or SmallSats. At about six kilograms, OTTER falls into the nanosatellite class, defined for satellites up to ten kilograms, and serves as a testbed for methods to design, build and operate such systems for monitoring marine activities from orbit.