Globalstar

Globalstar provides global mobile satellite telephony and data services using a constellation of low Earth orbit (LEO) satellites. The original Globalstar constellation, completed in February 2000, consisted of 48 operational satellites in circular orbits at an altitude of approximately 1,414 km, providing end-to-end voice delays of about 60 ms. The satellites were arranged in eight orbital planes, separated by 45° in right ascension, with an inclination of 52°. An additional four satellites were deployed as in-orbit spares at a lower altitude of approximately 920 km.

Between 2010 and 2013, 24 second-generation satellites were launched into the same 52°-inclination orbital configuration to replenish and restore system capacity. A small number of first-generation satellites have remained in orbit, primarily serving as in-orbit spares. Owing to its moderate inclination, Globalstar does not provide coverage in polar regions, with practical service coverage limited to approximately ±67° latitude.

Globalstar offers a range of mobile satellite services, including voice telephony, SMS text messaging, low-rate circuit-switched data (up to 9.6 kbps), packet-switched data services, and device geolocation with typical accuracies on the order of tens of kilometers. Services are accessed via dual-mode handheld terminals that operate on both satellite and terrestrial cellular networks.

The Globalstar system employs a bent-pipe satellite architecture using CDMA air-interface technology. User signals are relayed transparently via the satellite to a terrestrial gateway, where calls and data are routed through local telecommunications networks. Channel bandwidths are 1.23 MHz, with maximum user data rates of 9.6 kbps. Satellite-to-mobile links operate in S-band (2.4835–2.500 GHz) for the downlink and L-band (1.610–1.62135 GHz) for the uplink.

Each satellite carries an S-band transmit phased-array antenna and an L-band receive phased-array antenna. The S-band antenna forms 16 spot beams covering the satellite footprint, enabling frequency reuse and adaptive power control. Transmit power is dynamically controlled by both the satellite and user terminals. Signals may be received simultaneously from multiple satellites and beams, allowing receivers in both gateways and terminals to exploit spatial diversity for improved link reliability and seamless beam-to-beam and satellite-to-satellite handover. A global network of approximately two dozen gateways connects the satellite constellation to terrestrial networks; at least one gateway must be within view of a satellite for service to be provided to users within that satellite’s footprint.

First-generation Globalstar satellites have a launch mass of approximately 450 kg, while second-generation satellites have a launch mass of about 700 kg and a design life of 15 years. All satellites are three-axis stabilized and use hydrazine monopropellant propulsion for orbit raising and station maintenance. Power is provided by two deployable, Sun-tracking, multi-segment solar arrays, supplying approximately 2.4 kW at beginning of life (about 1.5 kW at end of life).

The first Globalstar satellites were launched in February 1998, though service was delayed following a September 1998 launch failure that resulted in the loss of 12 satellites. Limited commercial service commenced in December 1999, with full commercial service beginning in February 2000 following completion of the initial constellation. After experiencing financial difficulties, Globalstar entered bankruptcy protection in February 2002. The company was subsequently acquired by Thermo Capital Partners in April 2004, after which the subscriber base steadily increased, exceeding 400,000 subscribers across more than 120 countries by late 2023.

In September 2022, Apple announced a partnership with Globalstar enabling satellite-based emergency messaging for iPhone 14 users in regions without cellular coverage. This capability was expanded in 2024 to support broader satellite messaging functionality via Apple’s operating system when terrestrial networks are unavailable. ¹