A disaster response team in Florida calls for emergency aid using a mobile phone, even though cell antennas and networks in the area have been destroyed by a hurricane. On the same day, a soldier in a Mid-East war zone picks up a mobile phone and talks to her daughter about her first day of school. Mobile communications in remote areas beyond cellular and landline service take place around the world every day at petroleum companies, mining operations, commercial fishing boats, construction sites, utilities, forestry services, government, military and individual users hiking, mountain climbing or otherwise moving about in extremely remote locations.
Such voice calls – as well as Internet data connections –are made on mobile telephones that connect to orbiting satellites instead of terrestrial cell towers. A leader in this rapidly evolving telecommunications field is Globalstar – the world’s largest provider of mobile satellite voice and data services with over 375,000 subscribers in 120 countries around the world. The company uses a constellation of 48 low-Earth-orbit satellites circling the globe about every 90 minutes at an altitude of 1,414 km. Each satellite has a set of solar panels for electrical power and two earth-facing antenna arrays for two-way communications.
Like small relay stations in the sky, the satellites receive signals, then amplify and transmit them back to gateway ground stations that process voice or data calls and distribute them to local telephone networks or the Internet. Several satellites pickup the same signal, preventing call interruption by handing off communication to one another through the Globalstar network when phone signals are blocked by buildings or terrain. The constellation and ground network currently provide coverage to most inhabited places of the Earth, excluding only south-central Asia and central and southern Africa. Globalstar has plans to extend service to these areas in the coming years.
Nearing the end of their operational life, the original Globalstar satellites are scheduled to be replaced starting in the third quarter of 2010, when a three-stage Soyuz rocket will lift the first six second-generation satellites into orbit.
These new satellites are designed with greater reliability, increased power and a life expectancy of 15 years – double that of the first-generation hardware. The new constellation and the upgraded ground network that will follow are intended to provide more reliable service and faster data speeds required to support next-generation Internet-protocol-based services.
Satellite assembly, integration and test
Prime contractor for this huge project is Thales Alenia Space, Europe’s largest satellite manufacturer. Being at the forefront of orbital infrastructures, Thales Alenia Space is a joint venture between Thales (67 percent) and Finmeccanica (33 persent) and forms with Telespazio a Space Alliance. Thales Alenia Space is a worldwide reference in telecom, radar and optical earth observation, defense and security as well as navigation and science. Thales Alenia Space has 11industrial sites in 4 European countries (France, Italy, Spain and Belgium) with over 7,200 employees worldwide.
Thales Alenia Space has primary responsibility for the design, manufacture, test and delivery of 48 second-generation satellites for the Globalstar constellation. The company is also upgrading the Globalstar Satellite Operations and Control Center as well as Telemetry and Command Units and In-Orbit Test hardware and software located in Globalstar gateway ground stations around the world.
Technicians work on the assembly line of second-generation Globalstar
satellites at the Thales Alenia Space offices in Rome. Globalstar is a
low Earth orbit (LEO) satellite constellation for satellite phone and
low-speed data communications.
With Europe’s only integrated manufacturing and test center for satellite assembly and integration, Thales Alenia’s three Assembly, Integration and Test (AIT) Centers are located in Rome, Italy, and in Cannes and Toulouse, France. The multi-site capability is particularly well-suited for handling large satellite constellation projects, with specialized capabilities for transporting sensitive hardware between facilities and for delivering assembled satellites and related data acquisition systems directly to launch sites.
One of the critical roles of these facilities is testing satellites to ensure that highly sensitive components can withstand the thunderous acoustics and jarring vibrations of vehicle launch. Engineers focus on the thousands of individual parts and subsystems that absolutely must remain intact, connected and fully operational – delicate structural components deploying solar arrays and antennas, for example, as well as highly sensitive and complex on-board electronic systems with interconnected circuit boards, semiconductor chips, signal processors, and other components. Such testing is critical in the satellite business, since failure of anyone of these parts can jeopardize an entire mission.
All three AIT Centers perform various phases of these environmental tests. For the Globalstar project, sine vibration and acoustic qualification tests are done in Cannes. Acoustic flight model tests performed just prior to satellite assembly and delivery to the launch pad are done in Rome. Verification testing on the antennas is done in Toulouse, France and L’Aquila, Italy.