JERUSALEM — Start-up satellite Internet provider OneWeb Ltd. on Oct. 15 said they will go far beyond what international guidelines recommend to reduce the chances that its 720-satellite constellation will create orbital debris.
The measures include provisioning extra fuel to deorbit its satellites at the end of their lives, including a mechanical fixture on the satellites to permit easier grappling by future debris-clearing hardware, and assuring that except in rare cases of failure all satellites are out of orbit no more than five years after retirement.
Current international guidelines ask that owners of satellites in low Earth orbit see to it that they either are driven or naturally fall out of orbit within 25 years of retirement.
Attending an orbital debris symposium as a surprise speaker here at the 66th International Astronautical Congress, OneWeb Fleet Operations Manager Mike Lindsay knew he was heading into hostile territory.
Lindsay said OneWeb, based in Britain’s Channel Islands, had already opened negotiations with the U.S. Air Force, operator of the Space Surveillance Network, about how to facilitate collision warnings with a constellation of unprecedented size.
OneWeb’s 150-kilogram satellites will operate in an orbit 1,200 kilometers in altitude, in 18 planes of 40 satellites each, with an inclination of 87.9 degrees relative to the equator. With its solar arrays deployed, each satellite will measure some 3.5 square meters.
Built by prime contractor Airbus Defence and Space of Europe, mostly at a factory yet to be identified in the United States, the OneWeb satellites will carry small electric thrusters instead of chemical propellant.
They will be launched by Russian Soyuz rockets into a 500-kilometer orbit and then use their thrusters to climb into the 1,200-kilometer operating orbit.
Once in service, the satellites are expected to last for around seven years. Lindsay said sufficient fuel will be reserved to assure that, on retirement, each satellite is powered into an orbit with an apogee of 1,100 kilometers – lower than the operating orbit – and a perigee of 200 kilometers. From this orbit they would be expected to be drawn into the Earth’s atmosphere and burn up in as little as a few months, but no longer than five years, according to OneWeb estimates.
Lindsay said the satellite design employs no tungsten and as little titanium as possible. Both metals resist disintegration on atmospheric re-entry.
Because satellites occasionally fail in orbit, OneWeb is designing onto its platforms a mechanical fixture that should make it easier for future active-debris-removal missions to grapple onto the satellites and remove them. Lindsay said OneWeb estimates that a dead satellite will be spinning relatively slowly, no more than 0.3 degrees per second, making it easier for debris removal.
“We don’t believe the rules that exist today are stringent enough,” Lindsay said. “The 25-year guideline is not strict enough. We want to get them down much more quickly – less than five years.”
Once the deorbit maneuver has begun with a retiring satellite, it should take between six months and two years.
Officials attending the session praised OneWeb for addressing head-on many of the concerns they had about a constellation of this size – and the prospect that it may be only one of several constellations in a similar orbit in the coming decade.
But not all were convinced. One official said OneWeb’s orbit concentrates so many satellites at the poles that it will make traffic management difficult even assuming a retooled U.S. Space Surveillance Network.
Several officials said any OneWeb attempt to maneuver a satellite on recept of a collision warning will raise as many problems as it resolves, with satellites ahead of and behind it in the same orbital plane, and with satellites in the cross planes – to say nothing of satellites from other operators.
OneWeb satellite launches are scheduled to start in 2017.
