he recent progress report by the multinational Inter-Agency Space Debris Coordinating Committee (IADC) on disposal practices for geostationary-orbiting satellites is encouraging. It appears that satellite operators are getting more serious about keeping the geostationary-orbit arc – where most telecommunications spacecraft operate – reasonably clear of potentially hazardous clutter.
That satellite operators – both commercial and governmental – are increasingly sensitive to the problem of space debris is evident in their actions. According to the IADC, whose membership includes the world’s major spacefaring nations, 11 of 12 geostationary-orbiting satellites taken out of service in 2007 were disposed of in a manner consistent with guidelines the group adopted in 1997. That means the satellites were boosted into higher orbits that will keep them out of the geostationary arc for at least 200 years.
2007 is only one year, of course, but it nonetheless represents a dramatic improvement over 2006, when only eight of 17 mothballed satellites were placed in graveyard orbits high enough to prevent them from becoming future hazards to operational spacecraft.
Properly disposing of a geostationary-orbiting satellite is not an easy thing to do, technically or financially. Not only must operators be able to estimate a satellite’s on-orbit fuel levels with enough precision to determine when they can wait no longer to safely execute the orbit-raising sequence; they also must resist the temptation to forgo the maneuver altogether in order to squeeze the maximum possible revenue from their investment.
In that regard, the pan-African Rascom organization – a relative newcomer to the satellite operating community – deserves credit for its handling of the situation with its first satellite. Rascom QAF1, launched Dec. 21, has a leak in its fuel pressurization system that prevented controllers from using the satellite’s main kick motor to raise it from a parking orbit to its final operating orbit. Instead, they were forced to use the satellite’s attitude control thrusters, which require less pressure. But the decision to perform this maneuver, which will give Rascom about two and a half years’ use of the satellite, was made only after company officials were convinced that there would be sufficient pressure left over to properly dispose of the satellite.
By contrast, Russia’s satellite disposal practices are a matter of concern. Of the satellites that were retired in 2007, only Russia’s Gorizont 26 was not boosted into an orbit high enough to prevent it from returning relatively soon to the geostationary arc. Of the satellites that were not correctly re-orbited in 2006, three were Russian and one of these, Raduga 29, was simply abandoned in the geostationary arc.
Russian representatives to the IADC point out that Gorizont 26 was launched some five years before the disposal guidelines were adopted and have pledged to do a better job with more recent satellites. As a major builder and operator of geostationary-orbiting satellites, Russia has every incentive to improve in this area – as do all satellite operators. International organizations like the IADC, along with companies that do business with Russian satellite operators, should monitor this situation closely and use their influence to hold Russia to its promise.
There will always be crippling on-orbit failures and in these cases there is little that can be done to prevent the affected satellites from becoming permanent obstacles in the geostationary landscape – barring the emergence of an economically viable space-rubbish removal service. Preventable clutter is another matter, however. While there has been marked improvement in the last year, satellite operators must stay vigilant and keep looking for more reliable ways to keep the geostationary arc clear – not only for themselves but for future generations.