Debra Werner 2017-09-09 00:58:20
From mega-constellations to zombie-sats, there’s plenty of space traffic ahead but precious little management Space traffic management — such as it exists — is at a turning point. Miniature electronics coupled with low-cost launch options are prompting companies to devise constellations of hundreds of satellites. “We have three mega-constellations that all want to be at 1,200 kilometers and they all want to be at different inclinations,” said Edward Swallow, senior vice president for the Aerospace Corp.’s civil systems group, which is working with the U.S. Federal Aviation Administration to study space traffic. “Just one of these mega-constellations is expected to have 2,000 to 3,000 conjunction warnings per day, of which eight to ten are within 100 meters and two to three are within 50 meters.” If any of those spacecraft collide, the resulting debris could jeopardize commercial and national security space activities, said William LaPlante, senior vice president and general manager of Mitre Corp.’s National Security Sector. “The number of events where you have to actively deconflict before potential collisions is going up and it feeds off itself because once you have a collision you have debris and the debris threatens other activities in space,” said LaPlante, former U.S. Air Force assistant secretary for acquisition. “It’s becoming more urgent.” Collisions in orbit could also impede global communications and harm financial markets, which rely on Global Positioning System satellites to provide precise timing information for financial transactions. “All it will take is a couple of collisions and people will be saying, ‘Why aren’t we doing something about this?’” LaPlante said. WINGING IT Before that happens, government and industry officials are discussing a series of measures individual nations and international groups could take to ensure spacecraft operate safely, are suitable for their planned activities and equipped with transponders to broadcast their location. “Somebody has to do something about all the bricks people are launching,” Swallow said. People trying to figure out how to make space traffic run smoothly often look to air traffic management and the mechanisms countries use to prevent mid-air collisions. For example, civil aviation authorities evaluate aircraft models and award airworthiness certificates to the ones that meet safety standards. Once a model is certified airworthy, the agency does not inspect each aircraft of that type. That certification process does not yet exist for satellites and launch vehicles but “there needs to be some threshold of a vehicle’s safety because it can ultimately be a safety hazard for people on the ground,” LaPlante said. Similarly, governments will have to decide whether to certify the spaceworthiness of each spacecraft designed to carry people into orbit or to certify spacecraft types. Another mechanism the space community hopes to borrow from aviation are the transponders planes use to broadcast their position. “If you look at what the FAA has been doing to bring down the cost of modernizing the air traffic management system, Automatic Dependent Surveillance-Broadcast has been a critical element,” Swallow said. For spacecraft, the Aerospace Corp.’s Innovation Lab has developed a 150-gram prototype “pinger” that fits in a 1.5-centimeter slice of cubesat and uses its own battery power to announce the precise location of its host satellite and whether the satellite is functioning. “Nobody has ever put one together for a spacecraft before,” Swallow said. “Spacecraft have transponders for their telemetry, tracking and command, but they don’t tell everybody at all times, ‘I’m here and my host is able to or not able to maneuver should it have to.’” Those maneuvers are becoming more frequent with the rising popularity of low Earth orbit. Spacecraft operators in geosynchronous orbit, meanwhile, are steering clear of debris and malfunctioning communications satellites like fleet operator SES’s AMC-9, which is drifting in orbit, and PT Telkom of Indonesia’s Telkom-1 satellite that generated a cloud of debris Aug. 25 when it stopped working. “The biggest challenge in space traffic management right now is we have no agreement on how it is going to be managed,” Swallow said. “At some point there has got to be a global summit. Like there was when the International Civil Aviation Organization (ICAO) was formed.” ICAO, a United Nations agency established in 1947, publishes standards and recommendations that are widely adopted by civil air navigation authorities around the world. Before a global space summit can be held, a working group will need to draft proposed “rules of the road” for spacecraft operators and suggest mechanisms the community can use to modify the rules over time, Swallow said. That won’t happen until someone agrees to lead the effort. While the United States is a likely candidate, U.S. government agencies are busy sorting out their own space traffic management issues. The U.S. Department of Defense, which has been tracking satellites and debris, analyzing where orbits are likely to cross and contacting spacecraft operators to warn them of possible collisions, is working with the FAA to hand off some of those responsibilities. “In the long term, I don’t think we are going to be able to leave it to the military to manage traffic in space just like we couldn’t leave it to the military to manage the thousands and thousands of airplanes in airspace,” LaPlante said. COLLISION COURSE The 1956 midair collision of commercial passenger planes over the Grand Canyon prompted Congress to create the FAA, which establishes air traffic routes and employs the air traffic controllers who guide pilots. “If you want to fly westbound on route Kilo, you’re going to be on an odd number altitude and your slot in time and position is going to be authorized by the Oklahoma en-route center,” Swallow said. Spacecraft don’t follow rules like that, but that may change. “If you put up three mega-constellations at 1,200 kilometers, you’re talking about guaranteed collisions on a daily basis unless somebody starts separating them by saying one of them gets 1,160 kilometers, one gets 1,200 kilometers and one gets 1,240,” Swallow said. “Forty kilometers is the minimum separation you need otherwise they’ll bang together when the reach either the northern or southern poles. That’s where all the paths converge.” But who gets which one and who decides? Those questions are trickier than ever to answer. That’s because unlike in the past when individual satellites were built and launched by a single government organization or corporation, space is an increasingly international business with constellations managed, funded, built and launched in different parts of the world. Swallow said the whole problem reminds him of a rug sliding around on a polished wood floor. “You’ll never get it laid out flat and straight so everybody can see what it looks like until one corner of it is nailed down and nobody has figured out which corner is going to get nailed down yet,” he said. “I think of space traffic management as that rug sliding around on the floor. We are trying to figure out, ‘Can we get some part of it to settle down so everybody to agree on some standard?’”
Published by Space News Inc. View All Articles.
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