PARIS — Europe’s Ariane 5 ECA rocket on July 1 successfully placed the TerreStar-1 mobile communications satellite — the largest commercial spacecraft ever built — into geostationary transfer orbit from the Guiana Space Center in French Guiana.

The 6,910-kilogram TerreStar-1, built by Space Systems/Loral of Palo Alto, Calif., is designed to provide mobile voice and data communications in North America to smartphone-size handsets using the 2-gigahertz, or S-band, portion of the radio spectrum. The system is designed to function with a network of ground-based signal amplifiers to permit service in areas the satellite cannot reach, such as urban canyons and areas outside the line-of-sight view of the spacecraft.

The launch was the third of a planned seven Ariane 5 ECA launches in 2009. Because of its size, TerreStar-1 was the sole payload on board the vehicle, which typically is used to place two telecommunications satellites at a time into geostationary transfer orbit.

In addition to its size, TerreStar-1 is distinguished by its 18-meter-diameter unfurlable S-band antenna, built by Harris Corp. of Melbourne, Fla. The antenna will be unfurled in the coming weeks, and the satellite is expected to be put through several months of ground tests before entering commercial service toward the end of the year, according to officials from Reston, Va.-based TerreStar Networks Inc. TerreStar-1 will operate from 111 degrees west longitude.

With its satellite now launched, TerreStar faces some of the same challenges that ICO Global, also of Reston, faced following the launch of its S-band mobile communications satellite in mid-2008: How to secure the remaining investment needed to deploy the network of ground repeaters, called the Ancillary Terrestrial Component, which are crucial to making the service work. It is an investment likely to total at least several hundred million dollars. ICO has since filed for Chapter 11 bankruptcy protection as it seeks to reorganize its debt.

Peter B. de Selding was the Paris bureau chief for SpaceNews.