The Federal Communications Commission has proposed new rules to manage the risk of debris-generating explosions in space, but whether they go far enough for the new reality in orbit is a source of debate.
In May, FCC chair Jessica Rosenworcel put forward rules that would force applicants to assess and limit the probability of accidental explosions to less than one in a thousand for each satellite up for approval.
Assessing the explosion risk
Although the U.S. regulator already requires satellite licensees to affirm they have effectively mitigated this risk, it would be the first time this requirement is tied to a probability metric.
The metric is derived from NASA’s standard and would apply during and after the completion of mission operations — if a majority of the FCC’s five commissioners approve the rule-making.
Accidental satellite explosions are exceedingly rare. One contender in recent years is the Boeing-built Intelsat 29e satellite, which spewed out fuel in geostationary orbit after a sudden failure in 2019.
An investigation pinned that failure on either a meteoroid impact or a wiring flaw that led to an electrostatic discharge following heightened solar weather activity.
However, as SpaceX’s Starlink broadband constellation passes over 6,000 satellites in low Earth orbit (LEO), and tens of thousands of other spacecraft are in the works, there are warnings that a one-in-a-thousand risk threshold misses the mark.
“From a probabilistic perspective, small risks add up when dealing with large numbers of potential collisions,” a satellite executive said.
The total number of LEO satellites in a constellation, their aggregate mass and cross-sectional area all factor into the level of risk posed by a single network.
“The alternative is to come up with an appropriate aggregate risk metric for the entirety of a large constellation,” the person added, rather than one tied to a satellite-by-satellite basis.
The call joins a wider debate at the FCC over whether a satellite-by-satellite approach still makes sense for regulating the risk of collisions in orbit.
According to filings lodged with the regulator, proponents of some kind of aggregate risk metric include Eutelsat, SES and Viasat.
Opponents include SpaceX and large LEO constellation hopefuls Amazon and Telesat.
Moving away from a satellite-by-satellite basis would fail to adequately address the risk individual spacecraft pose, opponents have argued, and involve novel, untested methodologies.
Amazon told the FCC in July that “an aggregate risk framework is deeply flawed because it is premised on the assumption that a single authorized constellation creates more safety concerns than the same number of satellites spread across multiple constellations, when the opposite is more likely true.”
In allowing SpaceX to launch up to a quarter of its proposed 30,000 second-generation Starlink satellites in 2022, the FCC sought to manage aggregate collision risk with a “100 object years” rule.
This rule requires SpaceX to pause constellation deployment if the total number of years that each failed Gen2 Starlink remains in orbit passes 100 years.
However, even operators pushing for aggregate constellation risk measures have cautioned the FCC to move away from an object years approach.
“[S]uch metrics do not account for potential risks that may be realized in the future,” Viasat told the FCC in June, “and therefore may give a false sense that total risk had been limited effectively.
“For example, if subject only to a realized risk limit, an operator could launch an unlimited number of satellites with high collision probabilities in the event that they become non-maneuverable, but would be stopped from further launches only after some defined level of risk has actually been realized.”
By that point, Viasat said many more risky satellites with potentially fundamentally flawed designs could have already been deployed.
“There would be no way to put the genie back in the bottle,” Viasat wrote.
Learning from Europe
Meanwhile, across the Atlantic, an aggregate risk metric is currently being considered as part of the European Space Agency’s Zero Debris Charter.
Among targets to improve space sustainability, the charter calls for identifying a suitable aggregate risk threshold for LEO constellations to address the probability of debris-causing collisions and break-ups.
This article first appeared in the August 2024 issue of SpaceNews Magazine.
