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April 6, 2022 – 07:25 am
Globalstar 11500 Full

Globalstar satellites are simple "bent pipe" analog repeaters, unlike Iridium.

A network of ground gateway stations provides connectivity from the 40 satellites to the public switched telephone network and Internet. A satellite must have a Gateway station in view to provide service to any users it may see. Twenty Four Globalstar Gateways are located around the world, including 7 in North America. Globalstar Gateways are the largest cellular base stations in the world with a design capacity for over 10, 000 concurrent phone calls over a coverage area that is roughly 50% of the size of the USA. Globalstar supports CDMA technology such as the rake receiver and soft handoffs, so a handset may be talking via two spot beams to two Gateways for path diversity.

Globalstar users are assigned telephone numbers on the North American Numbering Plan in North America or the appropriate telephone numbering plan for the country that the overseas gateway is located in, except for Brazil, where the official Globalstar country code (+8818) is used. The use of gateway ground stations provides customers with localized regional phone numbers for their satellite handsets. But if there are no gateway stations to cover certain remote areas (such as areas of the South Pacific and the polar regions), service cannot be provided in these remote areas, even if the satellites may fly over them. As of May 2012, voice and full-duplex data service is currently non-functional over much of Africa, the South Asian subcontinent and most mid-ocean regions due to lack of nearby gateway earth stations.

The Globalstar system uses the Qualcomm CDMA air interface; however, the Ericsson and Telit phones accept standard GSM SIM cards, while the Qualcomm GSP-1600/1700 phones do not have a SIM card interface, but use CDMA/IS-41 based authentication. Therefore, the Globalstar gateways need to support both the CDMA/IS-41 and the GSM standards.

Globalstar has roaming agreements with local cellular operators in some regions, enabling the use of a single phone number in satellite and cellular mode on multi-mode Globalstar handsets. These cellular roaming agreements are not in place in North America. Because of improvements in cellular phones and networks and the limitations inherent to satellite phones, the newest Globalstar handset (released in 2006) does not include cellular connectivity as Globalstar does not expect subscribers to carry it as their only mobile phone.

First Generation Satellites[edit]

Globalstar orbits have an orbital height of approximately 1400 km and latency is still relatively low (approximately 60ms).

A Globalstar satellite has two body-mounted, Earth-facing arrays. First-generation Globalstars weigh approximately 550 kg, However, the second-generation Globalstar design will gain significant mass.

In 2005, some of the satellites began to reach the limit of their operational lifetime of 7.5 years. In December 2005, Globalstar began to move some of its satellites into a graveyard orbit above LEO.

First-Generation satellite problems[edit]

According to documents filed with the amplifiers used on its satellites for two-way communications are occurring at a rate faster than expected, possibly eventually leading to reduced levels of two-way voice and duplex data service in 2008. The company's simplex data services used to support the asset tracking products as well as the SPOT Satellite Messenger are not affected by the S-band satellite issue mentioned above. Globalstar also launched eight ground spare satellites in 2007 to help reduce the impact of the issue.

In the filing, Globalstar made the following statements:

"Based on data recently collected from satellite operations, the Company has concluded that the degradation of the amplifiers is now occurring at a rate that is faster than previously experienced and faster than the Company had previously anticipated."

"Based on its most recent analysis, the Company now believes that, if the degradation of the S-band antenna amplifiers continues at the current rate or further accelerates, and if the Company is unsuccessful in developing additional technical solutions, the quality of two-way communications services will decline, and by some time in 2008 substantially all of the Company’s currently in-orbit satellites will cease to be able to support two-way communications services." [1]

Industry analysts speculate the problem is caused by radiation exposure the satellites receive when they pass through the South Atlantic Anomaly in their 876-mile (1414 km) altitude orbits.

"The S-band antenna amplifier degradation does not affect adversely the Company’s one-way “Simplex” data transmission services, which utilize only the L-band uplink from a subscriber’s “Simplex” terminal to the satellites."

"The Company is working on plans, including new products and services and pricing programs, and exploring the feasibility of accelerating procurement and launch of its second-generation satellite constellation, to attempt to reduce the effects of this problem upon its customers and operations. The Company will be able to forecast the duration of service coverage at any particular location in its service area and intends to make this information available without charge to its service providers, including its wholly owned operating subsidiaries, so that they may work with their subscribers to reduce the impact of the degradation in service quality in their respective service areas. The Company is also reviewing its business plan in light of these developments."

"The Company’s liquidity remains strong. At December 31, 2006, in addition to its credit agreement, the Company had unrestricted cash on hand and undrawn amounts under the Thermo Funding Company irrevocable standby stock purchase agreement of approximately $195 million."

Globalstar's interim solution[edit]

In 2007, Globalstar launched eight spare satellites for its existing constellation with a view to reducing the gaps in its two-way voice and data services pending commercial availability of its second-generation satellite constellation, scheduled for initial launch in the second half of 2009. Globalstar will continue to operate its existing satellite constellation to provide and support services until the second-generation Globalstar satellites are available for service.

Until the new second-generation Globalstar satellite constellation is operational, Globalstar is offering its Optimum Satellite Availability Tool (OSAT) on its Internet site, which subscribers may use to predict when one or more unaffected satellites will be overhead at any specific geographic location.

Second-generation satellites[edit]

In December 2006, Globalstar announced that Alcatel Alenia Space, now Thales Alenia Space in its Cannes headquarters, has been awarded a €661 million contract for the second-generation constellation. The satellites were designed with a life expectancy of 15 years, significantly longer than the design life of Globalstar’s first-generation constellation. The second generation constellation will consist of 24 satellites.

In addition, Globalstar announced on April 3, 2007 that it has signed a €9 million agreement with Thales Alenia Space to upgrade the Globalstar satellite constellation, including necessary hardware and software upgrades to Globalstar’s satellite control network facilities.

In August 2008, Thales Alenia Space began production assembly, integration and testing of the second-generation flight model satellites, in its Rome factory, for launch as early as Q3 2009.

Source: en.wikipedia.org

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