PARIS — Swedish Space Corp. authorities are reporting a near-100 percent success for their two-satellite Prisma mission so far, including the demonstration of a new satellite thruster system that its developers say is safer, less costly and more efficient than conventional hydrazine.

The two Prisma satellites were launched in June on a yearlong mission to test several new technologies alongside the principal mission of performing formation-flying maneuvers between the two spacecraft. A key mission goal is to demonstrate high autonomy for the “active” satellite as it operates around the other, smaller satellite, which is in passive mode.

Staffan Persson, Prisma project manager at the Swedish Space Corp., said that aside from a propellant-feed anomaly that has ended an experiment in micropropulsion thrusters, the Prisma satellites are operating as designed and are beginning to test their formation-flying and satellite-autonomy missions after separating in orbit.

“We are now in autonomous formation-flying mode where the decisions are really taken by the satellite on its own,” Persson said in a Sept. 3 interview. “Further tests, particularly of the CNES formation-flying sensor, will come, but as of now things look good.”

In addition to the contribution of the French space agency, CNES, the Prisma mission includes a GPS-based navigation package provided by the German space agency, DLR.

Prisma will be Europe’s first mission with formation-flying technology as a principal objective. Aside from paving the way for future scientific satellites, formation-flying technologies are viewed as key elements on the way to rendezvous and docking in space.

The 18-nation European Space Agency (ESA) is planning to launch a mission called Proba-3 to further test formation-flying systems, although the financing for that mission has yet to be secured since Sweden pulled out for budget reasons.

Swedish authorities are offering other agencies or industrial interests the possibility of taking over Prisma to perform their own experiments starting next spring when the Swedish national mission is scheduled to be complete. Persson said estimates of the fuel supply have concluded that the Prisma mission could last for around six months after the Swedish mission is completed.

The on-board fuel supply was not materially affected by a July maneuver to avoid collision with a piece of the retired Russian Cosmos 2251 satellite that in 2009 collided with an operational Iridium mobile communications spacecraft, resulting in one of the worst debris-creating events in space history.

In the July incident, U.S. Air Force authorities operating the U.S. Space Surveillance Network of ground sensors informed Swedish officials that a piece of Cosmos 2251 junk was on a possible collision course with Prisma, with impact the following day.

“We used only a few seconds of thrust to get out of the way,” Persson said. “The maneuver went very nicely.” The Cosmos 2251 debris passed Prisma at a distance of some 2 kilometers.

A less-known system being tested on Prisma is a novel satellite-propulsion system developed by Ecological Advanced Propulsion Systems (Ecaps) of Solna, Sweden, a wholly owned subsidiary of Swedish Space Corp.

The High-Performance Green Propulsion (HPGP), based on ammonium dinitramide, was developed with Swedish Space Corp. and ESA funding to provide an alternative to conventional hydrazine fuel.

Mathias Persson, chief executive of Ecaps, said the demonstrations conducted since the Prisma launch have already proved that the HPGP system has a higher specific impulse than hydrazine in addition to providing more thrust per fuel volume — an important factor, particularly for small satellites.

Beyond its performance characteristics, HPGP is not toxic, meaning that satellite teams need not don spacesuit-type protective gear to handle it.

“At Yasny we were fueling Prisma while the CNES people were working on their satellite, and nobody was wearing protective gear, only the normal clean-room clothing,” Mathias Persson said in a Sept. 3 interview. The Prisma satellites were launched on a Russian-Ukrainian Dnepr rocket from Russia’s Yasny spaceport. The vehicle also carried the French Picard science satellite.

Mathias Persson said Ecaps estimates that handling HPGP can be done at one-third the cost of hydrazine.

Ecaps hopes that once the Prisma results are known, the HPGP system will find a commercial market. The company already has booked its first commercial sale, contracting with Broad Reach Engineering of Golden, Colo., for eight engines in a deal valued at $450,000.

Broad Reach and GeoOptics LLC of Pasadena, Calif., are designing a constellation of satellites to collect meteorological data. Mathias Persson said the eight-engine order is for two demonstration satellites for the constellation, called Cicero.

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