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.
http://science.nasa.gov/science-news/science-at-nasa/2009/01apr_deepsolarminimum/
http://science.nasa.gov/science-news/science-at-nasa/2009/29may_noaaprediction/
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.
What about earth´s GREEN JUNK?. They are a real menace to the world, naively thinking about controlling other people lives, trying them to follow their ideologized nightmares. This is serious. This is a very similar case like that pseudo religious leader who killed a lot of people at the Guyanas by making them commiting suicide by drinking poisoned Kool-Aid.
I believe the contraction of the atmosphere has been cited to be as great as 20%.
……..not a minor change.
Thank God for SciFi! This is old news for me having read the “Ring of Fire” series where the Maunder Minimum and its effects on the atmosphere, solar radiation, and radio waves is very well explained. I knew reading just for fun would come in handy some day.
Wind Rider says:
June 28, 2010 at 5:49 am
“…Then it simply enters a trajectory to be captured by the sun, or falls into the local gravity well and burns up.”
The normal disposition of geostationary satellites is to boost them to a higher orbit, where they can be perturbed into finally being captured by the sun, as Wind Rider states. But there is no atmosphere at geostationary altitude, therefore no drag effects, so there will be no gradual death spiral to eventual burnup. What will happen without disposition, however, is for an uncontrolled satellite to suffer orbital perturbations that will cause it to wander around its nominal location in larger and larger loops, constituting a collision hazard to other geostationary satellites (they are all packed into the equatorial plane at that altitude, as close as radiofrequency regulations permit).
Just out of interest, is there any atmospheric drag 600 miles up worth talking about?
Enough to slow down a satelite orbit by, say, three hours over 3 years?
Michael J Dunn and Wind Rider,
Satellites at less than GSO drop in altitude over time due to tidal drag/angular momentum exchange, until they get low enough to interact with the ionosphere and thermosphere, where they experience atmospheric/plasma drag.
Satellites above GSO tend to increase their orbital altitudes over time, also due to tidal drag/angular momentum exchange with Earth (same reason the Moon is getting further and further away each year).
Tidal drag effects are VERY small and take eons, even geological ages, to show significant effect. They are greatly overpowered by atmospheric drag effects in LEO, but up at GSO, they are, along with lunar and solar perturburances, and solar radiation pressure, the primary culprits for altitude and position change over time.
That said, there is a very interesting effect for satellites at GSO that is the cause of the present “zombiesat” issue. It seems that satellites in GSO prefer to drift to two areas of GSO. I am told they are at 105 East and 75 degrees West longitude, areas of the Earth which exhibit a “gravity trough” due to the slight non-spherical shape of the earth and of course differences in the tectonic system.
For this reason, 169 of the 1238 satellits in GSO have so far been captured by these two libration points, the Sargasso Seas of Space.
It is true that GSO is a much larger area of space, so actual impacts are not yet a serious issue. Nor have any nations developed an ASAT ability that can reach GSO to date, so intentional impacts are not presently possible. However, as the zombiesat case showed, a satellite set adrift by a space weather event that is still broadcasting can cause havoc with the entire communications network.
Carbon Dioxide,
There is some drag at 600 miles up. It increases the lower you get, of course. The ISS loses something like 3 miles of altitude each day due to drag, mostly from its huge solar panels. Hence why it needs frequent refuelling/resupply missions. The ISS varies between 173 and 286 miles altitude. Each Soyuz, Shuttle, and Progress tanker that visits uses some of its fuel to give the station a boost before they leave.
Jimbo,
Already has – try “Day after Tomorrow” for a taste of the new iceage due to “””climate change”””. I really did like the movie as a SF idea – but then realized people were walking out of the theater with their “suspension of disbelief” intact and shielded…oh my!
Mike
CO2 is never responsible for any “good” thing.
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Wouldn’t a shrinking atmosphere [due to lower solar activity] allow convective and radiative energy to be more efficient in cooling the earth because of the shorter path?
“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.”
Actually, that factoid is somewhat out of date, and perhaps optimistic. The Chinese ASAT test in 2007 just about doubled the count of catalogued LEO fragmentation debris from ~3500 to ~6500. However, on 10 Feb 09, two LEO commsats, Cosmos 2251 and Iridium 33, T-boned each other at ~11km/sec (24600 mph) — raising the LEO fragmentation debris count to over 8000. With the perigee of most of these objects at 700 km or higher, they’ll likely be there for decades, puffy atmosphere or not.
If the ISS loses 3 miles of altitude daily because of atmospheric drag smaller objects m which because of the square cube law, have much more surface area to mass (even taking into account the ISS’s solar panels) must de-orbit much faster.
It occurs to me that now is the ideal time to test ASAT, as long as you use the LEO opened up by the outer atmosphere’s contraction. There’s nothing else there, and when the atmosphere expands again, the debris orbits will decay quickly.
This is a crash at only 540 miles an hour
For orbital speeds you need something like this at 6400 miles an hour
Neil Craig says:
June 29, 2010 at 2:29 am
“If the ISS loses 3 miles of altitude daily because of atmospheric drag smaller objects m which because of the square cube law, have much more surface area to mass (even taking into account the ISS’s solar panels) must de-orbit much faster.”
No. Firstly you need to look at the ISS architecture. You have massive solar panels. Secondly, the core section modules have very little mass per cross sectional area partly because they are mostly-empty cans, but also because the depth to width ratio is so much shallower than for a smaller scale satellite.
Because of these architectural differences, the ISS exhibits far more drag for its mass.
However, one must also consider that its altitude is actually rather low. There are not many satellites that have an average altitude below 250 miles, those that do generally have a large thruster budget to keep in orbit, such as the GOCE satellite featured in the “Heavy Climate” article, which orbits at 254 km and needs an electric thruster operating constantly to keep it at the proper altitude and velocity.
The square cube law does still operate. For instance, the typical CubeSat put into orbit has an average life span of only 3-6 months. The CubeSat is a 10 cm cube massing 1 kg maximum.
Robert says:
June 29, 2010 at 8:00 am (Edit)
“This is a crash at only 540 miles an hour
For orbital speeds you need something like this at 6400 miles an hour”
Orbital speed is 17,400 mph in LEO. Space junk collisions can occur at speeds of less than 1 mph up to over 35,000 mph, depending on the relative orbital elements of the objects colliding.
Buzz Aldrin recently gave an interview to a Vanity Fair writer, in which he described having dumped some bags of his own human waste products overboard during a Gemini flight, only to realize after throwing them out that he’d given them a free return trajectory, so that, 1 orbit later, they came barrelling back at his capsule at the same speed he tossed them. Fortunately by that time his capsule was closed…. I am sure reentry cleaned up most of the mess.