Satellite communications provider Globalstar and its partner ADS-B Technologies have successfully completed what Globalstar says is the most rigorous demonstration to date of dual-link, space-based automatic dependent surveillance-broadcast (ADS-B) services.

The statement follows a late August flight by Anchorage-based ADS-B Technologies’ Piper Navajo Chieftain twin-engine test aircraft in a flight from Anchorage to Fort Myers, Florida, and back. The aircraft carried two ADS-B systems: a Garmin GDL 90 universal access transceiver (UAT), which is an ADS-B solution primarily for aircraft flying at 18,000 ft. or below, and a Garmin GTX 330 Mode 1090ES transceiver with extended squitter, a surveillance solution for airlines. The companies’ ADS-B Link Augmentation System (ALAS) uses a coaxial coupler to tap into the output from an existing ADS-B "out" unit near the ground-facing antenna, routing a new cable to a paperback book-sized, low-profile L-band antenna atop the aircraft. Position and other selectable signal "payloads" are sent out at a 1 sec. rate to Globalstar’s 24-satellite constellation, where the payloads are redirected via a "bent-pipe" method down to Globalstar-built ground stations. In an operational scenario, the ground stations would belong to air navigation service providers tracking aircraft.

Globalstar completed its constellation in 2013, with 24 operational satellites in low Earth orbit now providing a range of voice, data and other services to about 600,000 customers. Globalstar also offers the portable Spot Trace tracking device that sends out its position through the satellite network as often as every 2.5 minutes, a safety aid used in the general aviation community. Globalstar chief executive Jay Monroe says the total delay in the aircraft-to-ground station transmission through the network is 500 milliseconds or less.

Space-based ADS-B services are contingent on ADS-B technologies gaining certification for the ALAS, which the company expects to take about 18 more months, says Skip Nelson, president of ADS-B Technologies. Nelson says the primary marketing targets for ALAS are air navigation service providers or civilian aviation authorities in countries where ground infrastructure for ADS-B may not be a viable option for financial reasons. Nelson says that as ADS-B is increasingly mandated, ANSPs will need ground stations for the satellite links, for aircraft surveillance and for other services, and airlines will need the space-based ADS-B avionics to comply with mandates.

The recent test flight was another step in the road to FAA certification. Included were simultaneous and individual transmissions from 1090ES and UAT units through Globalstar, bank angles to 45 degrees without loss of connection to the satellites, and transitioning between three Globalstar ground stations, or gateways along the route. Nelson says the flight ideally would have been conducted on an oceanic route, however the piston-powered Chieftain was more suitable for shorter legs over water, including some areas over the Gulf of Mexico where no radar or ground-based ADS-B coverage exists.

ALAS will go head-to-head with the Aireon system, providing its surveillance service through the Iridium NEXT satellite network, set for first launches next year.