Earth Stations on Vessels (ESV) are stabilized VSAT antennas installed on large marine craft. ESV lock onto a satellite and track it counterbalancing the movement of the ocean waves. However, several conditions, including the vessel’s unpredictable gyrations, can cause a stabilized antenna to drift from the intended satellite and cause harmful interference to adjacent satellites.  

• Auto Shut-Off.  The system must shut off transmissions if the antenna deviates more than 0.5 degrees from the target satellite.  The time to shut off must not exceed 100 milliseconds.  The system must not initiate transmissions until the antenna is within 0.2 degrees from the intended satellite.
   
• Power Density.  The stabilized antenna must meet certain off-axis power density radiation patterns as outlined by the FCC. 
   
• Vessel Tracking.  The system must be able to track vessel location at 20 minute intervals or less.  

•  Vessel Weight.  To restrict the operation of ESVs in narrow water paths and to protect incumbent microwave systems, antennas can only be installed on vessels heavier than 300 gross tons.

• Space Segment. Each ESV operator may coordinate up to 36MHz of uplink capacity per satellite, on up to two satellites.  Collectively, all ESV operators in a given geographic area are limited to 180MHz of coordinated bandwidth. 

1. ESVs installed in non U.S.-registered vessels communicating with U.S. hubs.
2. ESVs installed in non US-registered vessels communicating with non U.S. hubs, but operating within 300Km of the U.S. coastline.