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S. Lehner et al.
used in navigation for maritime safety and in particular for collision avoidance. AIS
messages from ships are collected by coastal receivers too. The range of coastal AIS
receivers is typically 40 km offshore. For ships over 300 t in international waters,
and over 500 t in national waters, the use of AIS is mandatory.
Several institutions and companies have demonstrated that AIS signals can be
effectively received using space born systems. This fact makes SatAIS a powerful
data source to provide global situational awareness of ship positions, vessel and fleet
movements and traffic density mapping. AIS signal detection is possible in the entire
radio visibility range of a satellite equipped with an AIS payload. For a payload in
Low Earth Orbit (LEO) at an altitude of 650 km the distance from message source to
receiver varies between 2,800 km (very low elevation angle) and 650 km (space-based
receiver is directly over the ship in zenith). This means that the average field of view
of the payload is well above 20 million km
2 . The advantage of SatAIS is clearly
the possibility of complete global coverage and the availability in areas without
land based means of vessel detection. Moreover, SatAIS features the availability
of all information contained in the actual AIS messages as transmitted by ships,
providing a complete and extensive information source on all the parameters with
respect to individual ships. This enables a convenient and effective way of analysing
maritime traffic around the globe. The data received by SatAIS have demonstrated
the applicability of AIS data in maritime surveillance scenario’s underlining the
advantages as previously listed.
15.4.2 Automatic Identification System, Case Study
‘MV Sirius Star’
The hijacking of the super tanker “MV Sirius Star” by Somali pirates initiated a case
study to test the response time of the TS-X data acquisition as well as the rapid tasking
performance of the ground segment DLR-BN (Ground Station Neustrelitz, Germany)
for monitoring the situation. The supertanker was hijacked close to Somalia (Africa)
on November 18, 2008 and was released on January 9, 2009. With the detected
ship positions derived from large area ScanSAR and Stripmap search acquisitions,
follow up data takes in high resolution but at smaller coverage modes Spotlight and
High-Resolution Spotlight (HS) were planned.
The first two ScanSAR products from November 22, 2008 did not only yield a
clear detection at 4
◦ 35
35
N, 48
◦ 06
14
E but provided already enough details for
identification (Fig. 15.7). The subsequent HS data take on the 24th was placed at this
location, but showed no sign of the ship since it had moved in the meantime. This
initiated a new search acquisition revealing on November 27th, the new anchoring
site at 4
◦ 48
59
N, 48
◦ 15
52
E approximately 30 km North-East of the old position.
Several high resolution data takes were acquired of this area in the following weeks
and the ship was found to remain within 1000 m of this position until it was released
on January 9, 2009. The test case proved that the TS-X system is suited to task and
executes acquisitions based on the analysis of preceding products within 2–3 days
S. Lehner et al.
used in navigation for maritime safety and in particular for collision avoidance. AIS
messages from ships are collected by coastal receivers too. The range of coastal AIS
receivers is typically 40 km offshore. For ships over 300 t in international waters,
and over 500 t in national waters, the use of AIS is mandatory.
Several institutions and companies have demonstrated that AIS signals can be
effectively received using space born systems. This fact makes SatAIS a powerful
data source to provide global situational awareness of ship positions, vessel and fleet
movements and traffic density mapping. AIS signal detection is possible in the entire
radio visibility range of a satellite equipped with an AIS payload. For a payload in
Low Earth Orbit (LEO) at an altitude of 650 km the distance from message source to
receiver varies between 2,800 km (very low elevation angle) and 650 km (space-based
receiver is directly over the ship in zenith). This means that the average field of view
of the payload is well above 20 million km
2 . The advantage of SatAIS is clearly
the possibility of complete global coverage and the availability in areas without
land based means of vessel detection. Moreover, SatAIS features the availability
of all information contained in the actual AIS messages as transmitted by ships,
providing a complete and extensive information source on all the parameters with
respect to individual ships. This enables a convenient and effective way of analysing
maritime traffic around the globe. The data received by SatAIS have demonstrated
the applicability of AIS data in maritime surveillance scenario’s underlining the
advantages as previously listed.
15.4.2 Automatic Identification System, Case Study
‘MV Sirius Star’
The hijacking of the super tanker “MV Sirius Star” by Somali pirates initiated a case
study to test the response time of the TS-X data acquisition as well as the rapid tasking
performance of the ground segment DLR-BN (Ground Station Neustrelitz, Germany)
for monitoring the situation. The supertanker was hijacked close to Somalia (Africa)
on November 18, 2008 and was released on January 9, 2009. With the detected
ship positions derived from large area ScanSAR and Stripmap search acquisitions,
follow up data takes in high resolution but at smaller coverage modes Spotlight and
High-Resolution Spotlight (HS) were planned.
The first two ScanSAR products from November 22, 2008 did not only yield a
clear detection at 4
◦ 35
35
N, 48
◦ 06
14
E but provided already enough details for
identification (Fig. 15.7). The subsequent HS data take on the 24th was placed at this
location, but showed no sign of the ship since it had moved in the meantime. This
initiated a new search acquisition revealing on November 27th, the new anchoring
site at 4
◦ 48
59
N, 48
◦ 15
52
E approximately 30 km North-East of the old position.
Several high resolution data takes were acquired of this area in the following weeks
and the ship was found to remain within 1000 m of this position until it was released
on January 9, 2009. The test case proved that the TS-X system is suited to task and
executes acquisitions based on the analysis of preceding products within 2–3 days