Space junk, those bits and pieces dropped by astronauts, or resulting from explosion of upper stages, or collisions of satellites or ASAT tests, are a major safety hazard in Low Earth Orbit and are a growing issue in Geosynchronous Orbit, where we recently saw a “zombiesat” go on a wild murderous rampage (okay, it’s more of a slow drift, like any zombie, its not that hard to get out of the way of it) with a live tranceiver polluting the telecom spaceways with unwanted reruns of “The Jetsons” and “Plan 9 From Outer Space”.
Fortunately, the long term risks are dropping following the recent peak after the 2007 destruction by China of their Fengyun-1C satellite in an ASAT test, as there is now a proposed international convention requiring spacefaring nations to make their upper stages and satellites in LEO capable of deorbiting at the end of their service lives, and for those in GEO, to move to a graveyard parking orbit a few hundred miles beyond GEO. China recently agreed in principle to this, although while India has made a commitment, there is some noise they may do their own ASAT test to prove to China they aren’t pushovers. The threat in LEO could be decreasing as time goes on, provided new spacecraft comply with this new convention, however it is at an all time high due to the ASAT test fragmentation events.
Debris levels would be decreasing faster if the Sun was more active. NOAA and NASA have both released statements in the past year that the extended solar minimum is causing a major cooling in the upper atmosphere, causing it to contract in size, so that the ‘boundary’ to space has lowered by a number of miles for the time being. These agencies acknowledged that this means a great reduction in the amount of drag that satellites AND space junk in LEO experience, extending their ability to stay in orbit by a significant amount of time.
Companies and agencies operating satellites appreciate this, for it extends the life span of their satellites, saves them money in reduced replacement costs, and with reductions in orbital degradation, data coming from, for instance, earth observation satellites ice and temperature sensors should be more stable for a longer period of time. I don’t have any data on how this slowed orbital degradation is being accounted for or not by the various temperature and ice extent analysts, if people have details please provide.
However, the point of this post is to discuss a recent New Scientist story that is trying an attempt to revise scientific history, much as the Hockey Team has attempted with the LIA and MWP in the temperature record. New Scientist’s article is trying to claim that the cooler upper atmosphere and continued space junk problem is not due to the solar minimum at all, but due to CO2 induced Global Warming! Yes, that carbon dioxide is not just a car wax, a tooth polish, a paint remover AND an atmospheric warmer, it is also an atmospheric cooler…
“Arrun Saunders and Hugh Lewis, at the University of Southampton in the UK, studied the orbits of 30 satellites over the past 40 years, and recorded a gradual increase in the time they remain in orbit. They attribute this to the cooling and reduced density of the upper atmosphere caused by increasing carbon dioxide levels.”
Also, we can add Universe Today to the list of warmist weblogs, as I posted the following comment to their own piece echoing the New Scientist article, but after more than 32 hours waiting for moderation (in the interim, other comments have been approved by the moderators), this comment remains in limbo, so I’m posting it here:
Sorry but the claims in this story are absolute garbage. While Earth’s upper atmosphere has cooled and contracted, it is NOT because of CO2, it is because the Sun has been in a protracted solar minimum for several years with minimal 10.7 geomagnetic radio excitation of the upper atmosphere, minimal solar wind, and no solar flare activity.
NASA and NOAA state: “According to the forecast, the sun should remain generally calm for at least another year. From a research point of view, that’s good news because solar minimum has proven to be more interesting than anyone imagined. Low solar activity has a profound effect on Earth’s atmosphere, allowing it to cool and contract. Space junk accumulates in Earth orbit because there is less aerodynamic drag. The becalmed solar wind whips up fewer magnetic storms around Earth’s poles. Cosmic rays that are normally pushed back by solar wind instead intrude on the near-Earth environment.”
It is clear that NASA and NOAA disagree with Saunders and Lewis’ conclusions.
This said, we can’t really depend on solar activity related atmospheric drag to bring down space junk numbers. The Kessler Syndrome studies indicate that over time, the more junk that accumulates will start creating an increasing cascade of collision events, and higher altitude objects are significantly less impacted by atmospheric drag, instead depending on orbital perturbations to drag them down over decades.