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Forget The Moon: Mostly Pointless Carbon Emission Satellite To Be Re-Flown Instead

From @NASA on Twitter

Good news for climate science in Obama’s NASA budget out yesterday: We plan to rebuild & refly the Orbiting Carbon Observatory.

Will that compensate for the indefinite postponement of any flight beyond Earth orbit? I guess not, especially after reading some wonderful details about the Orbiting Carbon Observatory (OCO) (the first attempt failed to reach orbit on Feb 24, 2009):

  • flown in a near polar orbit [observing] most of the Earth’s surface at least once every sixteen days
  • OCO measurements would record changes in CO2 abundance over annual seasonal cycles
  • fly in Sun synchronous orbit so that all observations took place at about 1:18 PM
  • planned operational life of 2 years

Let’s forget for a minute that 2 years are nothing at all in terms of climate (a problem affecting most Earth observation platforms dedicated to climate science, it seems)….still, a quick computation reveals the grand total amount of observations from OCO for any particular spot on the planet is expected to be 45. That is, around 11 per “seasonal cycle”. And all of them, at 1:18PM local time.

No further comment is necessary.

0 replies on “Forget The Moon: Mostly Pointless Carbon Emission Satellite To Be Re-Flown Instead”

You should note that OCO will observe *at least* once every 16 days. Typically such orbits observe alternately once every 2 days and then 16 days, so you’re under estimating the actual number of observations by close to a factor of 2. Operational lifetimes are typically low ball estimates of instrument lifetime. Our instrument, for instance, has greatly exceeded expectations in terms of lifetime and this has been the case for most instruments on board our satellite.

Even then, I’m not sure you can dismiss these observations as a waste of time quite so quickly. It took extremely careful and in depth analyses from the science team on OCO to show that their data would be useful. So I’m going to side with their in-depth and convincing analysis over what appears to be a totally baseless assertion.

You’re framing the question of whether the observations will be useful in the totally wrong way. Should we expect high spatial variability in CO2 concentrations? Or would expect high degrees of spatial auto-correlation? Empirical evidence would support the latter. Hence why this satellite will be useful for constraining regional scale emissions. Of course if their claims were that they were going to resolve all point sources of CO2 across the globe I might agree, but this isn’t the case at all.

For anyone who’s interested I recommend this:

NASA Orbiting Carbon Observatory: measuring the column averaged carbon dioxide mole fraction from space. 2008. JOURNAL OF APPLIED REMOTE SENSING, 2: 023508.

thank you for visiting and comment Paul.

As I wrote on Feb 5, “Of course [OCO] will greatly increase our almost non-existent knowledge…that’s why I called it “mostly” pointless rather than “totally” pointless“. So rest assured I am not dismissing its observations as a waste of time. And the data will be useful.

Thank you also for clarifying the number of observations. They’ll be 22 per seasonal cycle instead of 11. Not yet anything to celebrate.

As for operational lifetime, OCO is going to be in LEO. I would expect the orbit to decay long before any instrument does. Please note that my main concern is exactly about the length of the observational period, not the spatial resolution.

Apart from the obvious reason, do you know of any other about why OCO will fly so low?

At least within the domain I work, where proposals for satellites costing hundreds of millions of dollars to build are considered, “mostly pointless” isn’t much different from “a waste of time”, or, indeed, money. If you’re going to win a proposal for a mission like OCO you need to show, prior to any money being handed over, that the science objectives are actually of interest and are achievable with the instrument design. This process is extremely rigorous, time consuming and incredibly competitive. The science objectives of OCO, to resolve CO2 fluxes at the regional scale over the lifetime of the instrument, certainly are meaningful, novel and would greatly increase our knowledge of carbon cycle science. Perhaps you getting mixed up with observations of global temperature, which has significant inter-annual variability, and therefore needs to be observed over a long period of time in order to create a meaningful trend. The primary mission of OCO is not make trends but to simply observe where CO2 is moving around at the moment to a higher level of detail than is achieved at the moment. OCO would represent a step forward scientifically in that regard. We don’t even know if there is significant interannual variability in the sinks and sources of CO2. Judging by the surface background observations it doesn’t seem that way, but OCO might show us that there is such variability, which would be a new finding, which woul be exciting, which would make a mission, like the type you seem to favour, much likely to get funded. Therefore, I would urge you think very carefully about the decisions that go into building and designing these things and ask some critical questions. For instance, would scientists and engineers really be able to get millions of dollars just like that to build something that is mostly pointless?

On LEO orbits. If you want significant and regular spatial coverage you need to go LEO. I don’t think you should be so concerned about the decaying orbit issue. Of the satellites I am familiar with, the instruments are going to die approximately a third to half way into the orbit lifetime of the satellite.

“Thank you also for clarifying the number of observations. They’ll be 22 per seasonal cycle instead of 11. Not yet anything to celebrate.”

Using twice every 18 days I get 40.5 obs per year or 91 obs over 2 years. As stated, that 2 year lifetime is almost certainly a low ball estimate.

“Please note that my main concern is exactly about the length of the observational period, not the spatial resolution.”

Actually the spatial sampling and spatial auto correlation issue I mentioned is an important one in this context of you claiming there are not enough observations over 2 years. Becasuse of the relative homogeniety in the CO2 concentrations, and the stated aims to investigate CO2 sources and sinks on regional scales, fact that OCO would measure at X one day and then a few km from X at Y in a few hours and so on greatly informs us about the likely CO2 at X owing to the spatial autocorrelation of CO2. X and Y wil likely be quite similar. This can be considered in far more formal mathematical contexts that would allow you make genuine scientific statements about the likely variability of CO2 over a wider region. Of course, there are limits to this spatial auto-correlation, else you could just measure at one place and infer what was going on everywhere. My backgorund is in shorter lived gases, but I would hazard a ball park figure for this phenomena to be important on scales of 50-100 km. That is why the focus of OCO is on regional fluxes of CO2.

“Let’s forget for a minute that 2 years are nothing at all in terms of climate…”

This confuses climate trends with climate equilibrium. Radiative equilibrium can be computed from just a few observations. See, for example, Barton Paul Levenson’s excellent “How to Estimate Planetary Temperatures” ( Computing trends requires 20-30 years of annual data.

OCO will be useful for pinpointing CO2 sources and sinks with much greater accuracy than they’re known today. For $170 million (a tiny fraction of returning to the moon), it’s an excellent investment.

Jim – climate change is about trends not single observations. Every pinpointed source (or sink) might as well have become a sink (or source) in two years’ time…the only way for OCO-class satellites to be useful would be to have at least 50-100 of them flying at the same time, and with an expected life of 2 years you’d also need to launch them 15 times or more. Hugely impractical to say the least

It’s certainly the case that climate *change* is about trends, but estimating climate at equilibrium requires only a few measurements, which is why we can say with confidence that we understand the climates of, for example, Venus, Mars, and Titan, with only a few in-situ instruments.

OCO is necessary to observe carbon fluxes at the scale of continents and ocean basins, which we currently can’t do with surface stations. Clearly, on this scale, sudden sign changes of sources and sinks will not occur; a two-year snapshot will greatly increase our knowledge of processes that regulate the exchange of CO2 between the atmosphere, the oceans, and the biosphere.

Of course it will greatly increase our almost non-existent knowledge…that’s why I called it “mostly” pointless rather than “totally” pointless 😎

So it would be preferable to remain ignorant and not launch OCO?

It would be better to embark in a sustainable CO2 space observation programme, with a few satellites launched at very long intervals, like the Meteosat series has done for weather observation.

ADDENDUM – by the above I mean, satellites capable to observe CO2 sources and sinks from orbits far above the atmosphere, and therefore capable to operate for much longer periods of time, rather than the few hundred km above ground that doom OCO to relatively fast oblivion

I agree that it would be great to launch some long-duration missions that are dedicated to studying Earth’s climate (e.g., Triana). But we will still learn a great deal from OCO, even over a two-year span, since there’s no other way to characterize regional carbon fluxes of both signs.

Details here:

The Need for Atmospheric Carbon Dioxide Measurements from Space: Contributions from a Rapid Reflight of the Orbiting Carbon Observatory

Would this be the relaunch of the same failed satellite that your High Priest Monckton lamented as to its loss on the basis that it would have disproved AGW? And that its loss was done deliberately by the pro-AGW NASA (who rtealised it would disprove AGW) and subsequently covered up. (Like all good denialists, Monckton does love his conspiracy theories!)

If so, I find it rather bizarre that you would be against the relaunch of such a stallite…

PKD – would you mind please finding any website whatsoever (nevermind this blog) where I have espoused Monckton’s theories or in any way shown or vaguely hinted that he is my High Priest? 😎

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