As the ISS circles Earth, it has begun tracking individual ships crossing the seas beneath. An experiment hosted by ESA’s Columbus module is testing the viability of monitoring global traffic from the Station’s orbit hundreds of kilometres up.
The ship-detection system under test is based around the Automatic Identification System (AIS), the marine equivalent of the air traffic control system.
All international vessels, cargo ships above certain weights and passenger carriers of all sizes must carry ‘Class A’ AIS transponders, broadcasting continually updated identification and navigation data.
AIS allows port authorities and coastguards to track seagoing traffic, but the system relies on VHF radio signals with a horizontal range of just 40 nautical miles (74 km). This makes it useful within coastal zones and on a ship-to-ship basis but open ocean traffic remains largely untracked. However, AIS signals travel much further vertically – all the way up to the International Space Station.
Global overview of maritime traffic
“The COLAIS (Columbus AIS) experiment was switched on at the start of June,” said Karsten Strauch, ESA’s project manager.
“To give an idea, more than 90 000 Class A AIS messages were gathered between 19:00 GMT on 2 June and 09:00 GMT the following day, giving a global overview of maritime traffic.”
With commissioning completed, the experiment is run remotely and the results are routed via the Columbus Control Centre in Oberpfaffenhofen, Germany to COLAIS teams.
“We are currently testing the NORAIS receiver, built by the Norwegian Defence Research Establishment and Kongsberg Seatex,” explained Mr Strauch.
“In three months’ time the Station crew will switch it with a second receiver called LUXAIS, the work of Luxembourg companies Luxspace and Emtronix. For the next two years we will go on swapping between these receivers.”
The Station’s orbit crosses all major shipping lanes. The main challenge is simply that far too many vessels are detected at once, leading to signal overlaps and interference. The Station’s 7 km/s speed also distorts the signal. The receivers therefore need to be capable of high-performance signal detection and message decoding.
Being hosted on the ISS, COLAIS can be kept updated in the future simply by astronauts swapping receivers, or fixing any problems that arise.
Integrating AIS information with other satellite data, such as from remote-sensing satellites, should significantly improve maritime surveillance and boost safety and security at sea.
ESA is planning a dedicated initiative in this area as part of its Advanced Research in Telecommunications Systems (ARTES) programme.
“We performed the COLAIS integration with external and internal hardware and software within a very short timeframe,” explained Horst Koenig, Head of ESA’s ISS System Engineering Section, who was in charge of overall integration.
“We had very close cooperation with NASA and the Radio Amateur Satellite Corporation (AMSAT). The AIS antenna was provided to ESA by AMSAT, along with an additional antenna for the Amateur Radio on International Space Station (ARISS) group.”
The receivers were delivered to the ISS by Japan’s H-II Transfer Vehicle in September 2009, while the external AIS antenna came up by Shuttle in November 2009.
Astronauts were instrumental in enabling the experiment. Columbus was not originally outfitted with the VHF antennas to capture the AIS signals; they were installed on the outside of the module by Randy Bresnik during a spacewalk, showing again the flexibility of the Station as a multi-purpose tool for a large variety of experiments.
The remaining piece of the system was the ‘ERNObox’ control computer, delivered on last month’s Russian Progress spacecraft. Finally, on 21 May, it was installed inside Columbus, along with the NORAIS receiver, by astronaut Timothy Creamer.
ERNObox, in itself an orbital demonstration of a new class of space computers being developed by Astrium Gmbh, Germany, was originally launched with Columbus in 2008. However, it was returned to Earth in the summer of 2009 when electronic problems were identified, for modifications and adaptation to COLAIS.
About COLAIS
COLAIS is an In-Orbit Demonstration project of ESA’s General Support Technology Programme, aimed at providing Europe’s space sector with opportunities for flight-testing new technologies.
Astrium Bremen in Germany was responsible for overall system integration, and contributed the ERNObox and a grappling adaptor (GATOR), used to attach the AIS antenna to Columbus. Antennas for both AIS and ARISS were built by AMSAT.
“Integrating COLAIS on the ISS and in Columbus required a substantial amount of work and coordination with the many parties involved,” said Daniele Laurini, the Mission Manager for the current ISS Increment.
“The early positive results of this experiment are a good reward for all those involved and further reinforces the need to use this incredible platform, the ISS, in all possible ways, not only for scientific reasons.”
