In 2017, Iridium began launching Iridium NEXT, a second-generation worldwide network of telecommunications satellites, consisting of 66 active satellites, with another nine in-orbit spares and six on-ground spares. These satellites will incorporate features such as data transmission that were not emphasized in the original design. The constellation will provide L-band data speeds of up to 128 kbit/s to mobile terminals, up to 1.5 Mbit/s to Iridium Pilot marine terminals, and high-speed Ka-band service of up to 8 Mbit/s to fixed/transportable terminals. The next-generation terminals and service are expected to be commercially available by the end of 2018. However, Iridium's proposed use of its next-generation satellites has raised concerns the service will harmfully interfere with GPS devices. The satellites will incorporate a secondary payload for Aireon, a space-qualified ADS-B data receiver. This is for use by air traffic control and, via FlightAware, for use by airlines. A tertiary payload on 58 satellites is a marine AIS ship-tracker receiver, for Canadian company exactEarth Ltd. Iridium can also be used to provide a data link to other satellites in space, enabling command and control of other space assets regardless of the position of ground stations and gateways.