ICARUS flies

ICARUS flies

Animal tracking from space

The ISS based project for researching the migration behavior of a variety of animal species has commenced operations. Radio technology from Rohde & Schwarz is used for data transfer.

The project participants had to overcome many hardships before they could celebrate the start of regular ICARUS operations. As Director at the Max Planck Institute of Animal Behavior in Radolfzell, Germany, Professor Martin Wikelski is the initiator and mastermind behind this project. The idea of observing animals from space came to him some 20 years ago. He has worked diligently since that time to bring the concept to fruition. Frequent setbacks tested his tolerance for frustration. Even the project name is testimony to Wikelski’s grim humor: The uninterested NASA predicted the project would never fly – just as the mythological Icarus was doomed by his highflying ambitions. The European ESA also declined to support the project. However, thanks to the Russian space agency Roskosmos (one of the main ISS operators) and the German Aerospace Center (DLR), this modern ICARUS was finally able to take to the skies. The name was transformed into an acronym that fits this serious project: International Cooperation for Animal Research Using Space.

From utopia to reality

Of course, the original idea was both daring and – from our current perspective – unfeasible using technology from the early 2000s. It was something to make a science fiction author proud: The notion that thousands of tiny solar-powered computers, loaded with sensors and radio modules, could autonomously communicate with a satellite in space from everywhere on earth and form an “internet of animals”.

However, rapid advances in the miniaturization of electronics and sensors as well as in batteries and solar cells were enough to turn this utopia into reality in recent years. INRADIOS, a small startup specializing in satellite communications that had just been founded by postdoctoral researchers in Dresden was given the challenging task of designing the radios for the project. They were supported by experts in the field of space technology from the company SpaceTech and the DLR. Now a member of the Rohde & Schwarz group, INRADIOS is working to further develop the ICARUS technology in close cooperation with the Max Planck Institute (MPIAB). Rohde & Schwarz is responsible for manufacturing the radios.

The ICARUS tag is hardly bigger than a euro cent coin. A special handheld radio is needed to fully read out the data memory. This radio can be used to command tags within a radius of a few kilometers to transmit their data. The radio forwards the data via WLAN to a smartphone or tablet which is used for actual operation.

Keeping a close eye on the animals

The most important condition for a viable animal transmitter (tag) is that the species under study must tolerate wearing the tag. As recommended by ethics committees, the tag should not exceed 3 % of the animal’s body weight in order to avoid influencing the animal’s behavior or even endangering it. Since it was also planned to equip small animals with the tags, the upper limits for the size and weight were very difficult to meet. The trackers based on mobile or analog radio that were conventional at that time were ruled out for animals under 1 kg, meaning that 75 % of all bird and mammal species could not be studied. The blackbird was chosen by the MPIAB as a reference animal due to the long-term focus on this songbird within the observation program. Prototypes of the ICARUS tag were tested preferably on these seemingly familiar birds – but whose migration behavior still brings up questions that could only be answered by means of continuous monitoring. Weighing in at 4.5 g, the lightest version of the tag is just light enough for the blackbird, assuming its use is limited to adult male specimens. For all other species to be fitted with a transmitter according to current ICARUS planning, the recommendation is easily fulfilled.

Small scale or large scale: Animal migrations can be tracked over any route – as seen in this example from Polynesia.

Small scale or large scale: Animal migrations can be tracked over any route – as seen in this example from Polynesia.

Along with the radio and location technology, the tags contain multiple sensors as well as enough memory to store the movement and environmental data for a single animal during its entire life (see box on next page). Up to 20 sets of position data are transmitted to ISS during each overhead pass, which generally occurs daily but can take place every three days at higher latitudes. The limited amount of data is due to the brief contact window of only 15 seconds (of which 3 seconds are used for transmission and the low bandwidth of the radio link. The fact that a miniature radio with only six milliwatts of transmit power can communicate with a satellite is extraordinary in itself. This is made possible by the large, high-performance ISS antennas as well as the sophisticated radio technology.

The tags use the regularly transmitted ISS ephemeris data along with their own position to calculate the next time of contact. They prepare to receive and transmit during the calculated time window, but mostly remain in stand-by mode to save power. Based on the regularly transmitted tracking data that is compiled in the database at movebank.org, researchers have already gained valuable insights (Figs. 2 and 3). However, another component is needed to access the entire data trove accumulated by the tags, including the environmental data. Migratory birds do not move constantly. Instead, they remain for longer periods of time in their winter and summer habitats. For most other species, the radius of movement is clear. This allows biologists to visit them in their habitats and make contact using an ICARUS handheld radio. A stable and much faster radio link can be set up on the ground that covers a distance of up to a few kilometers, allowing convenient readout of the tag memory without time pressure.

There are only about 50,000 specimens of the Hudsonian godwit left worldwide. This bird flies nonstop from Chile to North America over a period of one week before traveling onwards to Canada. ICARUS is providing detailed data about its migration routes and resting areas. The project is supported by Chilean biologists.

There are only about 50,000 specimens of the Hudsonian godwit left worldwide. This bird flies nonstop from Chile to North America over a period of one week before traveling onwards to Canada. ICARUS is providing detailed data about its migration routes and resting areas. The project is supported by Chilean biologists.

By combining various types of sensor data with precise position information, researchers are gaining entirely new insights into the living conditions and behavior of animals – especially if external weather and environmental data can be included. Once a few thousand "ICARUS birds" are flying, they could be used as meteorological drones to feed data to a global weather monitoring system. However, this would require an update to the transmission technology along with additional satellites in orbit. Nevertheless, this is the vision that Wikelski is targeting. Operation of ISS is only ensured until 2025. If the countries responsible for its operation cannot agree on its continuation, it might be possible for autonomous ICARUS satellites to take the place of ISS. Although the financing is obviously a challenge, MPIAB is refusing to be discouraged – especially in view of the other hurdles this project has already overcome.

Balancing the different interests

The tags are designed for a long life since they are expected to function during the animal’s entire lifespan and even allow reuse. In principle, this is a desirable feature. However, it can become a problem if the tag remains in the wilderness after the animal dies. Electronic components do not decay. Mechanisms were thus implemented to make it easier to find and collect the used tags. Once a tag is no longer moving, its GPS position becomes stable. The handheld radio can be used to switch the tag to ping mode so that it functions as a beacon transmitter. Then, the tag can be roughly localized with the radio. In addition, the tag calls attention to itself with a flashing LED. In case a third party finds the tag first, a contact address is provided on the rear of the tag. It is hoped that on the basis of these measures, the vast majority of the used tags will find their way back to MPIAB. The institute is paying close attention to this issue. Its scientists believe in protecting the world’s ecosystems and it is also our professional obligation. If the ICARUS project grows by another order of magnitude, it will be essential to reevaluate the project in light of sustainability issues. Organic electronic components are still far from commercial maturity. However, the developers might come up with some other ideas. Now that ICARUS has taken to the skies, it is a matter of ramping up the system and using it to full advantage for the intended purpose.

Animal transmitter (tag)

  • Weight: < 5 g, depending on battery size
  • Antenna length: 20 cm (radio) and 7.5 cm (GNSS)
  • Sensors: magnetic field, acceleration, temperature, humidity, pressure
  • Data memory: 512 Mbyte
  • Battery capacity: 70 / 60 / 45 mAh
  • GaAs solar cell (top-performing technology at this time)
  • Transmit power: 6 mW
  • Transmit frequency: 402.25 MHz, 1.1 MHz bandwidth
  • Receive frequency: 468.1 MHz
  • Transmitted data set: 223 bytes/ISS contact

Some ongoing and planned ICARUS projects

Global songbird migration - Billions of songbirds migrate between continents twice a year. Songbirds are valuable to the ecosystem, but their numbers have declined by 30 % over the past 20 years. It is unclear how they can be protected – which is why there is interest in learning more about their living conditions.

Understanding the lost years - The most difficult time for most animals comes when leaving their place of birth. For many species, the young animals disappear off the radar screens of biologists for years. ICARUS should help to close this knowledge gap. The focus is on mammals as well as turtles and seabirds.

Animals protecting animals - Rangers are important for protecting wild animals since they can keep poachers at bay. Although they cannot be everywhere simultaneously, the animals can. Based on their collective behavior, it is possible to draw conclusions about the presence of predators or poachers, allowing rangers to be deployed as needed.

Movement of human/animal communities - Since early history, humans have traveled with certain livestock animals. These joint migrations can still be observed in some remote locations. Exactly who is leading and who is learning from whom? Researchers are preparing to study these questions in Bhutan (Himalayas), the southern Sahel region, Bolivia and the High Arctic.

Pandemic prediction - As the habitat for many animals is increasingly encroached upon, both the frequency and intensity of contacts between people and wildlife are increasing. Pathogens can cross species as a result. COVID-19 is suspected to have entered the human population in this manner. In the animal kingdom, the usual suspects"include bats. However, they are only an intermediary. ICARUS should help to identify the original sources of diseases.

Movement of shorebirds and seabirds - Many shorebirds serve as a link between the earth’s hemispheres. During their long journeys, they rely on coastal regions to nourish themselves. However, suitable regions are becoming increasingly rare due to the omnipresence of humans. Where should protected areas be established? Seabirds are among the most puzzling species. Which maritime regions do they prefer? How do they navigate? How do they sleep? Seabirds are also good for monitoring climatic phenomena like El Niño. They can continuously measure winds, salinity and ocean currents and provide information about where the next typhoon or hurricane is forming.

Prof. Dr. Martin Wikelski

"For us as scientists, new and exciting findings are all that really matters. After the major technical success of ICARUS, we immediately began working with our Russian and international partners to equip animals worldwide with transmitters and deploy the ICARUS tags. Every day counts for us."

Prof. Dr. Martin Wikelski