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posted by janrinok on Wednesday September 04 2019, @07:31AM   Printer-friendly

About a week ago, the 18th Space Control Squadron, US Air Force, relayed warning data to the European Space Agency.

The data indicated that there was a non-negligible collision risk between ESA's Aeolus satellite and Starlink44, an active SpaceX satellite, at 11:02 UTC on Monday, 2 September.

As days passed, the probability of collision continued to increase, and by Wednesday, August 28, ESA's Ops team decided to reach out to Starlink to discuss their options. Within a day, the Starlink team informed ESA that they had no plan to take action at that point. By Thursday evening, ESA's probability threshold for conducting an avoidance manoeuvre had been reached, and preparations were made to lift Aeolus 350 meter in orbit. By Sunday evening, chances of a collision had risen to 1 in 1000, and commands were sent to the Aeolus satellite, which triggered a total of 3 thruster burns on Monday morning, half an orbit before the potential collision. About half an hour after the collision prediction time, Aeolus contacted base, and normal measurement operations could continue.

What the SpaceX satellite was doing in ESA's Aeolus orbit is not clear.

ESA has taken the opportunity to point out that, given SpaceX plans to put up 20,000 of those things, handling monitoring and avoidance semi-manually, and by mail, is no longer practical.


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  • (Score: 2) by Immerman on Thursday September 05 2019, @01:27PM (8 children)

    by Immerman (3985) on Thursday September 05 2019, @01:27PM (#890011)

    And is thermodynamics no longer science either? You know, because the overwhelming evidence has resulted in a near-total consensus among the people who once researched it?

    Climate change has become a political football, just as lead poisoning once was - but that doesn't change the science, just gets a whole lot of people who couldn't science their way out of a paper bag involved on both sides of the argument.

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  • (Score: 2) by deimtee on Friday September 06 2019, @12:39AM (7 children)

    by deimtee (3272) on Friday September 06 2019, @12:39AM (#890319) Journal

    Of course thermodynamics is science. It makes testable repeatable predictions and any situation that credibly violated those predictions would result in an investigation into what was wrong with (most likely) the experiment or (very unlikely) our understanding of thermodynamics.

    When chanting crowds crucify anyone who gets the "wrong" answer while measuring the enthalpy of an oxidation reaction then Thermodynamics will be a religion too.

    --
    If you cough while drinking cheap red wine it really cleans out your sinuses.
    • (Score: 2) by Immerman on Friday September 06 2019, @02:14AM (6 children)

      by Immerman (3985) on Friday September 06 2019, @02:14AM (#890353)

      You are again conflating the science with the throngs of people who've been rallied behind flags for or against it.

      The crowds are irrelevant to the science - and the science was settled long before there were any crowds.

      • (Score: 2) by deimtee on Friday September 06 2019, @03:34AM (5 children)

        by deimtee (3272) on Friday September 06 2019, @03:34AM (#890373) Journal

        "and the science was settled"
        Chanting a mantra does not actually make it true. Climate science is one of the least settled of the real sciences. It is incredibly complex and chaotic. Unbiased research would be great, but it doesn't seem likely, almost everyone involved has an agenda and any real science is lost in the noise.

        --
        If you cough while drinking cheap red wine it really cleans out your sinuses.
        • (Score: 2) by Immerman on Saturday September 07 2019, @12:29AM (4 children)

          by Immerman (3985) on Saturday September 07 2019, @12:29AM (#890781)

          Depends what exactly you're talking about. That human CO2 emissions are building up in the atmosphere and causing increased heat retention is long since settled.

          The full impacts of that, where exactly is the tipping point to a runaway transition to a hothouse-Earth, and whether there are as-yet-undiscovered negative feedback loops that will eventually mitigate our influence before we reach that point all remain to be seen. But at present none of the negative feedback loops that have been identified appear to be up to the task, and the positive feedback loops keep looking worse.

          So basically, at present we're faced with two choices: mitigate our influence in order to maintain the Earth in the relatively stable interglacial period that civilization arose in, or jump off the cliff and hope that something we haven't yet discovered will slow the process before catastrophic climate change decimates the global ecosystem, and us along with it.

          • (Score: 2) by deimtee on Saturday September 07 2019, @04:50AM (3 children)

            by deimtee (3272) on Saturday September 07 2019, @04:50AM (#890843) Journal

            Depends what exactly you're talking about.

            Definitely

            That human CO2 emissions are building up in the atmosphere

            Only about half as fast as they should be due to measured emissions.

            and causing increased heat retention is long since settled.

            Not settled at all. The IR window CO2 blocks is not that wide and adding extra CO2 doesn't really do very much over what is already there.

            The biosphere is strongly CO2 limited. At 200 ppm plants are right on the edge of starving. At 400 they are growing like they are having a good year in terms of water/fertilizer/sunlight. Higher CO2 also reduces a plant's need for water. At about 600ppm we are likely to get significant de-desertification. Would you like to see the Sahara being a verdant land again?

            I strongly support the use of nuclear/solar/wind power and I think we should be shutting down coal as fast as we can, but because of pollution and ecological damage, not the CO2 bogeyman.

            The problem with climate science is that lying about CO2 is being used by too many people with a political agenda and sufficient political power to make life uncomfortable for dissidents.

            You are again conflating the science with the throngs of people who've been rallied behind flags for or against it.

            You cannot be for or against science without being irrational. It's like marching around with a sign that says "Repeal the Law of Gravity". The illusion suffered by both sides that you can change facts by political action is one of the more damaging things about the CO2 industry, because of the effort and resources it wastes.

            Did you know that limestone deposition by shellfish removes 0.01% of all the carbon in the biosphere each year? Doesn't sound like much but if it wasn't for volcanoes and oil seeps life would have gone extinct about 10,000 years after molluscs developed shells.

            Almost the whole biosphere is limited by CO2. What we release is a temporary blip that it will gear up and eat in a very few years. If we are lucky we will end up with a greener planet with more life on it. If we are unlucky we will end up back at the current baseline with all the extra carbon sequestered.

            If you really want to make a difference to CO2 levels? Advocate for spraying 100,000 tons of iron compounds across the middle of the Pacific ocean each year. Maybe chuck some in the Atlantic as well. Trivial expense in terms of the CO2 industry and would massively increase the amount of life in the middle of the oceans. You get CO2 absorption and better fisheries. ("Save the whales!"). Middle of the ocean deserts are some of the few ecologies not limited by CO2, they are limited by the amount of iron - the main source is meteorite dust. I'm in favour of this mitigation because of the beneficial effects and because it will smooth out the 'hump' in the CO2 graph. Abrupt transitions are disruptive and slowing things down can be a good thing. Little bit conflicted because I would also like to see the 'Fertile Crescent' be fertile again but you can't have everything.
             

            --
            If you cough while drinking cheap red wine it really cleans out your sinuses.
            • (Score: 2) by quietus on Sunday September 08 2019, @11:57AM (1 child)

              by quietus (6328) on Sunday September 08 2019, @11:57AM (#891251) Journal

              At 200 ppm plants are right on the edge of starving. At 400 they are growing like they are having a good year in terms of water/fertilizer/sunlight. Higher CO2 also reduces a plant's need for water. At about 600ppm we are likely to get significant de-desertification.

              Strong statements require strong proof: care to donate some references to plant physiology articles?

            • (Score: 2) by Immerman on Tuesday September 10 2019, @02:01AM

              by Immerman (3985) on Tuesday September 10 2019, @02:01AM (#892004)

              >Only about half as fast as they should be due to measured emissions.
              Right we're pumping water into a pool at 10 gallons/minute, and the pool is filling at 5 gallons/minute. Doesn't matter how complicated any hidden plumbing is, it's a pretty safe bet that the pool wouldn't be filling without our contribution. Also, we have a pretty good idea where the extra CO2 is going - ocean acidification, etc. It's not like the atmosphere is an isolated system.

              > The IR window CO2 blocks is not that wide and adding extra CO2 doesn't really do very much over what is already there.
              IR isn't blocked, it's scattered - the same way blue light is scattered by the atmosphere so that the sky looks blue while the sun looks yellow, rather than black and white as they look from orbit. And every time a photon scatters off a CO2 molecule it's a 50/50 chance whether it's re-emitted towards space, or back towards Earth. And one of the features of scattering is that the more scatting substance you put in a solution (like the atmosphere), the more slowly scattered light escapes. 100% of the IR will always escape eventually, the question is how many times an average photon worth of energy ends up back on the surface before it finally makes it out of the atmosphere.

              As for the scattering band - the IR band CO2 scatters is separate from, and very roughly the same size as, the scattering band for water, which is the only other IR-scattering gas present in significant quantities in the atmosphere. Methane is the next most common, and there's ~200x more CO2 in the atmosphere than methane.

              There's ~50x as much water in the atmosophere as CO2. Water undeniably does most of the work: it averages somewhere around 2 to 2.5% (25,000ppm) of the atmosphere. It varies wildly from about 0 to 4%, but is self-regulating in the sense that the warming from increasing the average amount of water in the air by 1%, is never enough to let the air hold a full 1% more water. So the humidity percentage increases, and with it the chance of the water leaving the air as rain or snow.

              CO2 in comparison is tiny, now a bit over 400ppm, but that still makes it at least (400ppm/25,400ppm) = 1.6% of the total amount of greenhouse gasses. Not much, how big a difference can it really make? A reasonable guess would be 1.6% of all the greenhouse warming, so how much is that? Well, we can look at the moon for comparison, it's the same distance from the sun as us, but has no atmosphere. The average temperature of the moon at the equator is about -58C [58], as compared to the Earth's average temperature of about 15C. So greenhouse gasses are currently keeping the planet about 73C warmer than "normal" for our orbit. And probably much more - the Moon is quite dark colored and absorbs about 31% more solar energy than the Earth, plus I chose a nice warm place near the equator.

              So, there's at least 73C of current greenhouse-gas warming that's keeping our planet from being a frozen ball of ice. Even if we assume that CO2 is no more potent a greenhouse gas than water, 1.6% of 73C is about 1.2C of extra warmth laid directly at its feet.

              And CO2 has a crucial difference to water - it doesn't increase humidity. But any warming it does still increases the maximum amount of water the air can hold, and with it how much water needs to be in the air to have the same equilibrium humidity percentage.

              How strong is that effect? Well, at around 15C the maximum water content of air changes by about 7% per degree C. So, if CO2 causes 1.2C of heating on its own, then the air will have to carry (7%/C*1.2C=) 8.4% more water to maintain the same humidity So that ~1.6% of the total greenhouse gas of CO2 is potentially responsible for the presence of an extra 8.4% of the water in the atmosphere, for a combined 10% of the total greenhouse warming - or 7.3C of the total estimated warming. And the effect gets more dramatic at higher temperatures - get closer to 20C, and the amount of water required to maintain the same percentage humidity is increasing by 9% per degree C.