BANGALORE, India — Building small geostationary-orbiting telecommunications satellites has become perhaps the most dynamic segment of the commercial satellite-manufacturing industry in the past five years.

Several builders of large spacecraft — including Lockheed Martin Commercial Space Systems, Space Systems/Loral and Thales Alenia Space — have adapted their production lines to maintain the capacity to provide spacecraft with a launch mass of less than 3,500 kilograms and a power output of less than 5 kilowatts.

Joining the competition in this market segment are Orbital Sciences Corp., Astrium Satellites of Europe and its joint venture with India’s Antrix Corp., and still-emerging efforts at Surrey Satellite Technology Ltd. of Britain and OHB System of Germany backed with European Space Agency funding.

Dulles, Va.-based Orbital Sciences plans to deliver five of its pioneering Star satellite platforms this year. The company has 10 of these models in its backlog, including three orders won so far in 2007.

Orbital Sciences Chief Executive David W. Thompson estimates that of the 25 commercial geostationary telecommunications satellites expected to be ordered this year, between eight and 10 will fit the small-satellite definition. Orbital expects to win about five of these orders, he said.

Thompson said the decline of the U.S. dollar relative to the euro and other currencies should help Orbital, but that the competition remains tough.

Among the newcomers that already have made their presence felt is the joint venture between Astrium Satellites and Antrix, the commercial arm of the Indian Space Research Organisation (ISRO). The venture landed its first two contracts last year for satellites that will feature Indian satellite platforms outfitted with European-built payloads.

ISRO has begun work on the satellites, ordered by Eutelsat of Paris and Avanti Screen Media of the United Kingdom. Eutelsat’s W2M and Avanti’s Hylas satellites will be based on ISRO’s standardized I-3K and smaller I-2K platforms, respectively.

Both ISRO platforms were originally designed for India’s domestic telecommunications and meteorological satellite needs. The I-2K satellite, with a liftoff mass in the 2 to 2.4 metric ton range, was designed to be lofted by current versions of India’s Geostationary Satellite Launch Vehicle (GSLV). Satellites based on the roughly 3-metric ton I-3K platform — the workhorse of India’s current Insat telecom fleet — have been launched exclusively on European Ariane vehicles to date, although ISRO is working on larger variants of the GSLV to handle satellites of that size.

K.R. Sridharamurthi, executive director of Antrix, based here, said the W2M and Hylas programs will not require significant modifications to the ISRO platforms since both the I-2K and I-3K are “more or less tuned” to the needs of the marketplace. All of ISRO’s satellites, he said, “are adaptable to the varying needs of missions and payloads and capable of catering to the new challenges,” he said.

For example, while the I-3K platform originally was designed to provide 4 kilowatts of payload power, it was adapted to India’s Insat-4-series satellites to provide up to 5.5 kilowatts of power, Sridharamurthi said.

For ISRO, the joint venture manufacturing process begins at the ISRO Satellite Centre in Bangalore with the construction of structural panels embedded with heat-conducting pipes. These panels are then sent to Astrium’s facilities in France for payload integration, Sridharamurthi said.

Astrium mounts the transponders, waveguides, switches, filters and antennas on the panels before shipping them back to Bangalore. There, ISRO integrates the panels with the rest of the satellite structure, which includes the thermal-control, attitude-control and propulsion systems, as well as the solar panels, batteries and other power systems, Sridharamurthi said.

“We do the assembling and testing in presence of representatives of our partner and customers,” Sridharamurthi said. He added that ISRO has video links with its partners in France so that technical experts on both sides can interact during the assembly process.

S. Krishnamurthy, a spokesman for ISRO, said W2M is scheduled for delivery in October 2008, with Hylas to follow in December.

Small to medium-sized platforms are attractive to satellite operators because they can be manufactured relatively quickly and because they can serve as on-orbit backups for larger satellites, Sridharamurthi said. He also said ISRO can deliver a satellite in about 24 months.

Sridharamurthi said India’s domestic demand for satellites varies from year to year but averages about two geostationary platforms and two I-1K remote sensing platforms.

ISRO built a brand new satellite assembly, integration and testing facility two years ago. The facility can handle four to six satellites at a time, Krishnamurthy said.

“We do not foresee any need to expand the manufacturing facility for the next four or five years,” Sridharamurthi said. “Facilities are unlikely to become a limiting factor to meet expected demand for space craft, but manpower might.”

ISRO, like many other space-related organizations, has had trouble in recent years replacing departing engineers with top-flight talent.

Antrix ultimately would like to market its satellites in conjunction with GSLV launches but Sridharamurthi said this service will have to wait until the GSLV-Mark 3 variant, capable of lifting 4 tons to geostationary transfer orbit, comes on line. According to ISRO’s annual report for 2006-2007, the first developmental flight of this vehicle will not take place before 2009 or 2010.

Sridharamurthi said existing GSLV versions can launch I-2K-class spacecraft but added that India will only produce enough of these launchers in the next few years to meet its domestic needs.

Sridharamurthi said he does not envision extending the joint venture with Astrium into remote sensing satellites, noting that the European company already offers its Proteus platform in this market. However, ISRO is looking for export opportunities for its proven remote sensing platforms.

ISRO has built more than a dozen remote sensing satellites and currently operates a fleet of six including Cartosat-2, which launched in January and can take pictures with 1-meter resolution. The satellites are based on ISRO’s standard I-1K platform and typically have a liftoff mass of about 1 metric metric ton, compatible with India’s Polar Satellite Launch Vehicle.

“Till now we have only been marketing the imagery obtained by our remote sensing satellites,” Sridharamurthi said. “We want to fully exploit the capability that ISRO has built up in remote sensing and that includes the complete satellite. We may build more of these satellites as we foresee opportunities in marketing these in two to three years.”