A Taurus launch vehicle rose from California's Vandenberg Air Force Base in late February, ferrying the Orbital Carbon Observatory into space. The rocket streaked toward an orbit 705 miles above the Earth; from there the OCO and its single scientific instrument were to deploy to look back at the planet's surface, producing complete carbon dioxide maps of Earth every 16 days for two years.
Minutes into the flight, something went wrong. The satellite failed to shed its protective faring as it neared orbital velocity. Weighed down by the shielding material, the satellite never made it to orbit, but rather, crashed off the coast of Antarctica. "Most of it burned up in the atmosphere," said David Crisp of the Jet Propulsion Laboratory. After nearly a decade under development, the OCO would spend eternity underwater.
Crisp, the leader of the OCO scientific research team, said he received a call shortly after the mishap from halfway around the world. The director of Japan's GOSAT mission, launched a month earlier, wanted to borrow the OCO team's expertise to analyze data that he expected would soon come pouring in from Ibuki, the Japanese Space Agency's own greenhouse gas satellite.
"Not only do we have analysis capability they didn't have, we have a validation system they didn't have," he noted.
Crisp was happy to oblige, formalizing the spirit of cooperation among emissions monitoring projects worldwide. "Even though we didn't have an instrument flying we didn't lose the entire project. The part of it that was set up to analyze the OCO data was now available to work with the GOSAT team, and we're doing that right now."
NASA headquarters also called that day, directing Crisp to prepare a white paper outlining the urgency of a replacement OCO.
According to Crisp, even the most advanced carbon tracking satellites currently in service, including GOSAT, have little or no capability to detect CO2 over the oceans, leaving researchers in the dark about the location, the health and processes that drive the planet's most important carbon sinks.
Each day, the situation becomes more precarious. "Human beings are currently emitting about 30 billion tons of carbon dioxide into the air every year. Most of that comes from the burning of fossil fuels and other human activities, even cement manufacture," Crisp said. While the concentration of CO2 in the atmosphere has increased from about 280 to about 380 parts per million since the beginning of the industrial age, the oceans have absorbed most of the excess CO2 released by industrial activity, forestalling a runaway greenhouse gas scenario.
However, as a consequence of the added CO2, ocean chemistry has changed in the past 250 years "from a pH of about 8 to 7.9 — a bigger change than the oceans have seen, probably, since dinosaurs roamed the Earth," Crisp said.
In that light, he and other earth scientists wonder how much more carbon the oceans can take.
"Will it continue to absorb over 60 percent of the CO2 we're putting out, or will it actually start giving some of that back to us?" Crisp asks. The question was highlighted in two recent papers that looked at different data — and came to different conclusions about land and ocean carbon sinks, one saying the fraction absorbed was staying the same, the second that it was failing miserably.
To illustrate a troubling scenario, Crisp said that as the oceans warm due to climatic changes, "Some of the CO2 we put into the water over the past 250 years could start coming back out and actually defeat anything we try to do to reduce CO2 emissions."
And he said there is already evidence that "there are some parts of the world that want to start giving it back to us."
According to Crisp, researchers have observed one such mysterious carbon-rich upwelling off the coast of California, with CO2 emissions on the scale of a Los Angeles freeway.
"It's a worst-case scenario," he said.
But with OCO, "The other possibility is, we're out there flying around, and we find out that switch grass or hemp — something we're not thinking of — absorbs a tremendous amount of CO2," he speculated. Crisp said corn production in the Midwest provides an example as "it pulls CO2 levels down by 30 to 50 ppm, to 1970 levels, over the fields of Iowa every summer. There's a message there, that there are natural processes that are effective at absorbing carbon dioxide."
Crisp said if natural sinks could be found and carefully managed, that "could buy us more time to get off our fossil fuel diet."
Needle in a smokestack
Although NASA has several satellites in orbit that are capable of mapping CO2, they use a technology that only picks up CO2 abundance between about 16,000 feet to about 59,000 feet — the altitude at which planes fly — which Crisp said is exactly the level where CO2 is most efficient as a greenhouse gas. However, these satellites are not very good at spotting the variations in atmospheric CO2 concentrations associated with human emissions or natural sinks, which are, for the most part, near the surface.
"By the time the plumes of CO2 from the L.A. freeway rise up to where it can be detected by these satellites, they're over Arizona or Texas, having traveled a great distance downwind," Crisp said. Plus, earlier generation satellites lack the sensitivity to detect natural sinks.
According to Crisp a forest with the capacity to absorb an amount of carbon dioxide comparable to what comes out of an L.A. freeway every year could cover a couple of hundred square miles. "It takes a very sensitive measurement system to determine that the air is just a little bit lower in CO2 over this forest and to monitor that and quantify it over time."
He said OCO has the tools for the job. It has its greatest sensitivity to CO2 near the surface, but can make measurements of "the complete atmospheric column as high as planes fly."
The replacement OCO would follow a special orbit similar to the original flight plan, keeping pace with the afternoon sun. Wherever it carries out its observations it will always be 1:18 p.m. on the ground below, providing researchers with handy comparable measurements based on a standard time of day.
OCO's scientific instrument is comprised of three high-resolution spectrometers to capture sunlight reflected from the ground. By analyzing interference patterns in the spectrum caused by trace gases in the atmosphere, Crisp said the satellite "can, literally, count the CO2 molecules in the air column."
To calibrate OCO's measurements from the ground, Crisp said the research team has at its disposal a fleet of "about a dozen shipping containers" outfitted with state-of-the-art spectrometers that are about 20 times more powerful than those built into the satellite. These can drive around using tracking systems to point directly at the sun, while making corroborating measurements from land, from aircraft and at sea. "They are excruciatingly precise — they can make measurements to better than a tenth of a part per million on average."
Satellite on demand
NASA's official report on the February mishap was released in July 2009. Although no physical evidence was recovered, analysts traced the cause through deductive reasoning to a malfunction in one of four launch vehicle components. That report, however, concluded that with stringent quality control measures and a series of relatively minor technical modifications the difficulties encountered in February could be readily resolved.
According to Crisp, rebuilding the satellite based on the original blueprints should be relatively straightforward. He believes his team can deliver a new OCO satellite to Vandenburg's launch pad within 28 months, provided the contingency gets a jump-start in the budget process.
Crisp said part of the justification for a reflight is already before Congress. "The Waxman-Markey climate bill has 2012 as the reference year. Wouldn't it be nice to be able to get complete global measurements of carbon dioxide during that reference year to provide a solid baseline for planning by our government in carbon dioxide emissions controls? We could actually meet that deadline if we're allowed to start this year."
He points out further that the OCO would augment voluntary CO2 reporting programs such as the Vulcan Project and potentially play a valuable role in treaty enforcement.
"Ronald Reagan said, 'Trust but verify.' We've got the verification here. We can actually fly over the entire Earth and tell you how much carbon dioxide there is any place on the planet."
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