SpaceX founder Elon Musk made a splash in January when he announced plans to circle the globe with a consolation of Internet-delivery satellites. Since then, additional details have been relatively few and far between. Credit: SpaceNews illustration by Lance Marburger

Updated at 9:22 a.m EDT

PARIS — Satellite fleet operator Intelsat asked U.S. regulators to block a SpaceX launch of two small satellites to test technologies for a future low-orbiting Internet-delivery constellation, claiming SpaceX has refused to disclose sufficient information relating to potential frequency interference and collision risk.

SpaceX has apparently accepted at least part of Intelsat’s argument and has disclosed specific data on how its satellites will avoid interference with Intelsat and other geostationary-satellite fleet operators.

In a July 9 filing with the FCC, Intelsat says SpaceX has kept secret the information Intelsat and other geostationary operators need to determine how its satellites will avoid interference

Hawthorne, California-based SpaceX is in the early phase of development of a constellation of small satellites – as many as 4,000, company Chief Executive Elon Musk has said – to speed the transport of large chunks of data around the world, avoiding the detours and bottlenecks of terrestrial fiber networks.

The company has filed, through the government of Norway, an initial notification to the International Telecommunication Union, a United Nations agency that assigns orbital slots and broadcast frequencies. The notification, under the names STEAM-1 and STEAM-2 is for Ku- and Ka-band-frequency broadcasts.

SpaceX has filed a separate application to the U.S. Federal Communications Commission (FCC) to launch 6-8 satellites testing Ku-band transmissions, with the first two to launch by 2016. SpaceX’s first two identical satellites, called MicroSat-1a and MicroSat-1b, are designed to operate in a circular 625-kilometer orbit, inclined at 86.6 degrees relative to the equator, and to operate for up to a year.

The satellites would be visible for around 10 minutes every 22 hours from SpaceX’s ground stations, to be operated from the company’s Hawthorne site; from the Fremont, California headquarters of the Musk-run Tesla Motors; and from SpaceX’s new satellite facility in Redmond, Washington.

The schedule of the satellites’ launches has likely been upended by the June 28 failure of a SpaceX Falcon 9 rocket. The investigation into the failure is ongoing, and SpaceX has not set a return-to-flight date beyond suggesting that it’s likely sometime this year.

The Falcon 9 failure investigation will defer revenue from customers until launches resume and result in additional charges to SpaceX. Whether this will slow operational ramp-up of the Redmond facility is unclear.

In the time since SpaceX made its initial FCC filing in May, competitor OneWeb LLC of Britain’s Channel Islands, whose constellation will also use Ku-band frequency, has selected a builder of its 648-satellite system, contracted with a launch-service provide and raised $500 million in cash.

Among the investors is Luxembourg- and Washington-based Intelsat, which has taken a $25 million equity stake in OneWeb and is working on the technically challenging scenario of permitting users to shift seamlessly between Intelsat’s satellites at 36,000 kilometers over the equator and the OneWeb constellation at 1,200 kilometers.

Current satellite regulations oblige low-orbiting constellations to steer clear of any interference with satellites in geostationary orbit, which have higher priority. Typically interference is avoided by lowering power levels, particularly over the equator, so as not to disturb the geostationary-satellite signals.

In a July 9 filing with the FCC, Intelsat says SpaceX has kept secret the information Intelsat and other geostationary operators need to determine how its satellites will avoid interference. Intelsat further claims that SpaceX has declined to make public its plans for avoiding potential collision between its satellites and geostationary satellites that move through low Earth orbit — including the SpaceX satellites’ altitude — just after launch, on the way to their operating destinations.

SpaceX had requested confidential treatment for much of its satellite operating data by saying the data includes proprietary commercial and technical information.

Intelsat said the company should not be able hide this information, including details of its satellites’ operating frequencies that are necessary to enable Intelsat and others to pinpoint the source of any future interference.

In an unusual step, Intelsat on July 9 filed a Freedom of Information Act Request to the FCC asking that the SpaceX data be made available.

On July 20, SpaceX responded, dismissing many Intelsat allegations but agreeing to make available additional technical details. “[I]n the interests of facilitating the commission’s review of the MicroSat-1a/b application, SpaceX is providing additional information in an expanded and publicly available” exhibit attached to its application, the company said.

“It is helpful that SpaceX has provided additional technical information,” Intelsat said in a July 22 statement in response to SpaceNews inquiries. “We are continuing to review their submission to determine if it is adequate for us to complete a thorough analysis of the potential impact.”

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