Common Ground: Cash Cows And Space Debris
by Richard DalBello
The answer may be 36,021 km + (1000 * CR * A/m). As to the question, well, we have to go back a couple of decades to when NASA began to worry about the discarded rocket stages and the odd bits of space junk that were whirring around in space. Physics is the basic problem here. It takes an awesome amount of energy just to get into space. The original energy imparted to the satellite gets translated into tremendous speed in a more or less fixed direction. A typical object in low earth orbit may be traveling at 10 km/s (a brisk 22,000 mph) with limited maneuvering capability. At these speeds, a 1 kg object packs the same punch as a fully loaded 35,000 kg truck moving at 190 km/h. Releasing that kind of energy in an uncontrolled fashion can be disastrous, since the resulting debris cloud creates opportunities for new collisions.
In the early 1990s, NASA’s engineers began to calculate the likelihood that something would accidentally punch a hole in their shiny new space station. This, everyone agreed, would be a very bad thing. The problem seemed to be growing in importance since the mobile satellite industry had just announced a raft of new satellite projects and the heavens, it seemed, would soon be filled with hundreds of new satellites.
So in 1995, at the request of the White House, an interagency report was drafted that concluded, among other things, that NASA and DoD should develop draft guidelines for orbital debris. Last month the FCC decided it was time to turn some of these guidelines into U.S. licensing requirements. In a densely written, 42-page Notice of Proposed Rulemaking (NPRM), the FCC began rethinking the orbital debris mitigation regime for commercial satellites. In the past, much of this process was done on a voluntary basis by the industry. Such “self-policing” action was clearly in the industry’s economic self-interest since failure to adopt stringent manufacturing, launch and operational practices could rapidly degrade the space environment. The FCC, while noting the past reliance on industry self-interest, expressed skepticism and asked “whether there are emerging satellite system designs that might call into question the adequacy of economic incentives.”
The NPRM opens a host of new and difficult questions: Should operators have to obtain insurance to cover debris damage? How about a mandatory pre-license assessment of orbital debris mitigation measures? Should their rules cover foreign launch vehicles? Can large LEO systems that rely on redundancy be relied on to ensure the quality of individual spacecraft? How about mandatory reporting for “end-of-life” fuel status? The list goes on and on.
The NPRM gives special focus to “end-of-life” maneuvers. Currently, the U.S. government and the ITU suggest geostationary satellites, at the end of their life, should be raised 300 km into a graveyard orbit. The Inter-Agency Space Debris Coordination Committee (IADC), representing about a dozen space agencies, had suggested that 235 km-435 km would be adequate. In 1997-1998, 38 spacecraft were retired from geostationary orbit. Thirteen exceeded the minimum IADC guidance, nine exceeded the U.S./ITU guidance, and 12 were abandoned in geostationary orbit. Of the abandoned satellites, only Telstar 401, which had an unexpected catastrophic failure, was U.S., the other 11 were either Chinese or Russian. No U.S. commercial satellites were involved in debris incidents.
In its NPRM, the FCC suggests replacing the 300 km guideline with a requirement to move the satellite to “an altitude of no less than: 36,021 km + (1000 * CR * A/m) where CR is the solar pressure radiation coefficient of the spacecraft, and A/m is the Area to mass ratio, in square meters per kilogram, of the spacecraft.” Whatever the merits of such precise calculation, the private sector has one question: “Am I turning off a perfectly good satellite before I need to?” Because satellites use the same fuel for stationkeeping that they use to accomplish their “end-of-life” transfers, the higher the graveyard orbit, the shorter the life of the satellite. In round numbers, for geostationary satellites, every additional 25 km of altitude required by the government results in one week less of life.
Now, satellite communications is a darn difficult business. Entry costs are high. Margins are thin. Investors are skeptical. Terrestrial competition has grown. Launch vehicles still blow up more than they should. Satellite manufacturers occasionally make technical decisions that don’t work. Therefore, the last thing you want to do with an operational, revenue-producing satellite is turn it off prematurely. A functional, reasonably occupied satellite near the end of its life has probably already paid for itself and is steadily producing revenue. It is the rarest of phenomena in the space business–a cash cow.
The U.S. satellite industry has a stellar record for safety and accountability. It is also an industry that is struggling through some difficult financial times. What we need now is the flexibility to innovate and to use new technologies to respond to the challenges of the space environment. Precise calculations that rely on decades-old technology may miss the point entirely.
Richard DalBello is the executive director of the Satellite Industry Association. His e-mail is firstname.lastname@example.org.