The Orbiting Carbon Observatory-2 is a satellite tasked with tracking carbon sequestration around the world. It could revolutionize climate science, if only it could get into orbit. The original satellite crashed into the ocean, while the replacement's launch was scrubbed in the final minute of countdown.
Timelapse of the Mobile Service Tower (MST) rollback to reveal the Delta II with the OCO2 payload. Credit: NASA/Bill Ingalls
The Orbiting Carbon Observatory-2 (OCO2) is the first satellite to specifically track carbon on a global scale. If it sounds familiar, that's because the first satellite to use this name failed horribly during launch in 2009, ending the mission before it had a chance to get started. Half a decade later, the replacement is ready to go.
Once the observatory gets into orbit, this mission is the key to getting data on how carbon distributions change over space and time, identifying areas and processes most important to sequestration. Even better, that data will also be able to constrain complex climate models, giving fixed points of hard data and reducing the number of free variables.
In its mechanics, the observatory is a straightforward satellite design, made special not by its design but by its incredible sensitivity.
Nothing about the satellite design is inherently spectacular: spectrometers will measure light absorption by carbon dioxide in the atmosphere to track carbon levels. What will be ground-breaking is the data: as this data piles up day after day and month after month, it will create a picture of how carbon sequestration works on our planet with relation to geography and time. This is a moment of "We don't even know what we don't know," where the opportunities to learn about important processes for carbon sequestration is wide-open.
The observatory has a trio of spectrometers that captures light for a third of a second, using the equivalent of a photographer's f:1.8 stop. That light is guided through a diffraction grating to break it into tiny colour divisions with ridiculous sensitivity. The three spectrometers capture three different narrow bands of the Near-Infrared spectrum associated with different gas absorption wavelengths: weak carbon dioxide (CO2 at 1.61 µm), strong carbon dioxide (CO2 at 2.06 µm), and oxygen (O2 at 0.76 µm).
All three measurements will be taken simultaneously for the same location. Oxygen concentrations are a known constant in our atmosphere, so oxygen level will be used as a reference point to confirm that OCO2 is taking accurate measurements. The weak CO2 band is representative of surface carbon dioxide concentrations, while the strong CO2 band provides an independent measurement of carbon dioxide that is sensitive to aerosols, pressure, and humidity.
Carbon dioxide has a very specific spectral pattern but with incredibly slight variation, alternating from transparent to opaque over a very small set of wavelengths. To compensate for this, the light is directed through a diffraction grating, spreading the spectrum into a wide array of narrow wave-bands, sorting light into 17,5000 colours. By contrast, a consumer digital camera splits that same range of light into just 3 colours.
The sensitivity of this beast is ridiculous. The golf-ball sized detectors are designed for a noise ration of a thousand to one (1000:1). That isn't a typo: it really can cope with just a handful of misplaced electrons per pixel before getting swamped. To help protect the instruments from being overwhelmed by noise, the optics will be passively cooled to -5°C, while the detectors are mechanically dropped by cryogenics down to -120°C. Immediately after launch, the craft will operating in "warm" mode, with heat shed by radiators and a variable conductance heat pipe that automatically cycles open and closed every 10 to 15 minutes to maintain a steady temperature, but without functioning cryogenics.
The observatory undergoing laboratory testing prior to launch. Image credit: JPL/NASA
Along with optics and detectors, OCO2 has a space-hardened on-board computer to control the craft and instruments. It has the standard S-band telecommunications link, while data will be transmitted by the higher-frequency X-band. The higher frequency allows for greater rates in anticipation of the deluge of carbon data that will be coming our way in the next few months. It also has a small star-tracker telescope, an inertial measurement unit, and a GPS to help determine exactly where the craft is and its attitude, and a set of tiny momentum wheels to act as thrusters keeping the satellite pointed in the right direction. The "right direction" can mean one of two things: directly down in Nadir Mode, or obliquely at the sun's reflection when in Glint Mode.
The entire spacecraft is a hexagonal structure made of honeycomb aluminium sheeting wrapped in a thermally insulating blanket. It works out to about a meter in diameter and two meters tall: the size of the Doctor's Tardis, but constrained to normal space-and-time dimensions. (During a NASA Social briefing, one of the project scientists lamented about how many more instruments he could squeeze on if the observatory also shared the Tardis' characteristic of being bigger on the inside!) The entire package of spacecraft and instruments weighs in at 450 kilograms, making OCO2 a high-density science project.
Artist's impression of the observatory peering at the planet. Image credit: NASA
After the spacecraft is launched and separates from its rocket, a pair of solar panels will unfold 3 meters on either side of the craft, bringing OCO2 up to a 7-meter wingspan. These arrays will provide electrical power to the observatory, and charge up a battery to keep the satellite working when it passes into the Earth's shadow.
Unfolding wings is a special point in the launch sequence: everyone from NASA Administrator Charles Bolden through Vehicle Systems Engineer Mic Woltman listed the moment of deploying wings as the moment they will be able to start relaxing a tiny bit and breath easy that the launch succeeded.
Once launched, OCO2 will take up a solitary orbit 15 kilometers below the Afternoon-train (or A-train) constellation of Earth-observing satellites. The A-train is home to a fortune of functional satellites: NASA's Aqua, CloudSat, Aura, and CALIPSO satellites and JAXA's GCOM-W1.
The A-train constellation of satellites circles the earth north-south in a sun-synchronous orbit.
Before getting too close to millions of dollars of scientific instruments travelling at 17,000 miles per hour, the observatory will run through a testing period to prove that it's fully cooperative and capable. Once the tests are completed weeks to months after the launch date, the team will bring it up slowly and carefully with a series of nudging adjustments, merging into the polar sun-synchronous orbit at the head of the train. From then on, OCO2 will be passing over the equator at 1:35 local time twice a day (am and pm), with the other A-train satellites observing the same locations moments later.
This coordinated train of satellites is not just logistically easier for juggling around the massive mess of things in Low Earth Orbit, but will also make it easier for researchers to combined data from multiple sources in their analysis. Together, the satellites complete a north-south orbit every 98.8 minutes, precessing around the planet to cover the same locations every 16 days. Early on in the mission, these repeat measurements will be more about calibration and validation, ensuring that the instruments are performing as well in space as they did on the ground. Later, the data will provide a time-element to carbon-tracking, observing seasonal changes along with the impact of extreme events like droughts.
While the OCO2 mission duration is currently listed at two years, it has enough fuel on board to make orbital adjustments to stay in position for a decade after that. Once the fuel is almost-exhausted, the retirement plan for this craft after the end of its operational lifespan isn't to head up to the satellite graveyard, but down to burn out in a blaze of glory. It's small enough to burn up completely on re-entry, so can be de-orbited with less caution than larger satellites that need to be aimed at unoccupied oceans.
This mission has been a long time coming; the original OCO went down in a torrent of sorrow when the payload fairing system failed to separate from the launch vehicle back in February 2009. When the rocket came diving down into the ocean, it brought the satellite with it, taking its payload to a watery grave. While it doesn't pack the visceral gut-punch of the loss of a crewed capsule, the loss of an entire satellite is still devastating. It represents years of work, ideas, technology, devotion, money, and time, all gone in an instant.
The ill-fated launch carried the original OCO to watery depths. Image credit: NASA
Work on the replacement started just over a year later in March 2010. The basic concept is the same, but some of the replacement instruments were upgraded from their ill-fated earlier incarnation. Most importantly, this mission was mounted on a Delta II rocket, the well-tested workhorse by United Launch Alliance that doesn't even use the same fairing systems that failed with the first project.
While touring the facility, I met two members of the project team who had devoted nearly a decade and a half to the Orbiting Carbon Observatory, working on the project from the first failed satellite through to its replacement. Vehicle Systems Engineer and Launch Services Program Mic Woltman and OCO-2 Project Architect Randy Pollock presented a calm facade in the hours leading up to launch, but it was easy to tell that it took a concentrated effort.
As Project Architect, Pollock's final checks were already complete by the time I met him, with nothing left to do but be present and watch. During a break, he explained to me that the control center for the satellite is actually in Virginia, but that he'd travelled out to California to avoid any gremlins mucking up last-minute communications. The day before the originally-scheduled launch, he had timed out a window after the solar panels were fully extended and initial systems checks completed when the satellite would enter a five-hour communications dead zone. If everything looked good, he planned on using that time to hop on a plane back to the east coast, touching down and getting to the control center just in time for a wake-up call from the satellite. And if things looked sketchy? He'd cancel the flight and stay put, doing what needed to be done to make this mission a success.
I joined a NASA Social event dedicated to the observatory at Vandenberg Airforce Base in southern California. Once at Vandenberg, you know I had to stick around for the launch, jittery with excitement and anticipation.
The experience was totally surreal, and unmistakably fantastic. With a launch date just a whisper before 3 am, I needed to be on-location by 1:30 am to track the final countdown. A sensible person would look at that schedule, and head to bed early for a long nap before waking up, but I dare you to be sensible when awaiting a launch. Instead, I paced, tried to stargaze through the coastal fog, researched local military history, debated the merits of particular Instagram filters when I don't even have a username, pretended to read, painted my nails, and otherwise frittered away time until it was late enough to head out to the viewing location.
OCO2 and the Delta II rocket, all conditions green at t-15 minutes. Image credit: NASA
I was attending the launch with a small cadre of other space-enthusiasts, so in the wee hours of the night, I piled into a rental car and tried to play navigator through sleepy country roads. Our viewing location was on a road that Google Maps insists doesn't exist, a turn down an unmarked driveway past ominous fenced-in buildings awaiting the zombie apocalypse. Finally stumbling over soft sand to reach a field with eerily-lit bleachers added to the surrealism, darkness and fog smothering details of the landscape between us and the rocket 3.8 miles away.
We passed around a jar of peanuts, joining in the long-standing Jet Propulsion Laboratory tradition birthed during the Ranger missions years ago. It missed a few people, and the call went out to pass them back, make sure everyone who wasn't deathly allergic got a handful of peanuts to munch as even scientists became superstitious. Spirits high, visiting Canadians celebrated Canada Day thanking American taxpayers for making the rocket launch possible, and each radio check announcing conditions were green and systems were go were met with cheers and applause.
NASA Social participants, live-reporting the countdown whenever they caught a glimmer of cellular service. Image credit: NASA/Stephanie Smith
After resuming the countdown at t-4 minutes, the lights flipped off, plunging us into darkness. A falsetto duet spontaneously broke out with a rendition of the theme from The Final Countdown. The radio checks grew quicker, voices clearly excited as the name of each system provoked an echoing "Go!" so quickly they piled on top of each other. At the terminal count, waves of silence quieted the bleachers, quickly broken by the rustle of everyone standing to face the foggy horizon.
At less than t-1, a bare 46 seconds before the start of the launch window, a voice on the radio called Hold! It was a failure of the launch pad water flow. The disappointment was audible as the control center started reading from the manual, calling out the steps to power off and reset.
The launch window for the mission was just 30 seconds long, starting at 2:56:44 am local time. Any time past 2:57:14, and the orbital dynamics wouldn't align to slip the payload into position at the front of and just below the A-train of Earth-observing satellites. By the time mission control read through one step in the trouble-shooting process, it was already too late: it was past 2:57:14 am, the window was closed, and the launch was scrubbed.
The launch for OCO2 was scrubbed with just 46 seconds left in the countdown.
In the stunned silence, a voice called out, "Alright, who didn't eat the peanuts?" Laughter broke the tension, and we started trying to work out what happened. NASA Social coordinator Stephanie Smith embraced the positive side, telling us "Better a good scrub than a bad launch," before packing away her jar of peanuts.
We tried asking Larry Hill, the public affairs representative for the 30th Air Wing, what a water flow failure meant. He gave his best impression of a deer-in-the-headlights stare, downplaying his years of experience at Vandenberg with the quip, "I'm a trumpet player from Albuquerque."
As we made our way back to homes and hotels, engineers stayed up late on base to place the satellite and rocket into a safe configuration and begin offloading the liquid oxygen fuel. Someone stayed at the keyboard, using the NASA account to explain, "[T]he water system provides sound suppression to dampen acoustic waves at liftoff and protects a launch pad flame duct." At a briefing the following morning, the explanation was confirmed: the launch had been scrubbed due to the launch pad's protective water systems failing to flow, endangering the pad infrastructure. While it sounds silly to scrub a flight on the potential of being too noisy, undamped acoustic vibration can be damagingly strong, while after touring the base to ogle flame ducts, I'm rather terrified of the concept of one of those enormous ducts belching unquenched redirected rocket flames into the landscape. Best of all, repairing pad infrastructure sounds a lot more manageable than troubleshooting a malfunctioning rocket, increasing the probabilities that the error will be repaired before the next launch window.
Assuming that the swarm of engineers can assess and repair the failure in time, the next launch window is 30 seconds in the wee hours of July 2nd, or July 3rd, or July 4th, or however long it takes to get a good, clean launch and boost this satellite into orbit. If a 30-second launch window sounds utterly bonkers, try this on for context: it isn't the shortest launch window by a long shot. That title is held by a Mars mission, with a launch window of just one second duration.
Running under the tagline, "You can only manage what you can measure," once it makes it into orbit, the Orbiting Carbon Observatory has the potential to make a massive difference. By identifying carbon sources and sinks, and how sequestration changes over space and time, the OCO2 data will give us some solid observations to constrain wide-open climate models. This satellite is a targeting tool for future graduate students, identifying locations and processes important to carbon sequestration that we don't even know we don't know about yet.
OCO2 satellite and Delta II rocket on the pad at Vandenberg Airforce Base. Credit: Image Credit: NASA/Bill Ingalls
We're not going into this totally blind: we know that growing forests are carbon sinks and bustling cities produce a lot of gas. We have a notion that carbon sequestration rates changes with the seasons, although how much, to what degree, and how it varies with respect to extremes like El Niño and La Niña is very thoroughly To Be Determined. The longer this mission lasts, the more data we'll have on what the normal variation in carbon sinks and sources is.
This data won't do anything to progress the false debate about climate change — we've already pretty thoroughly concluded any ongoing debate is a matter of opinion where facts are irrelevant. What this will do is provide solid, detailed data on carbon distribution. And with that, the rest of us can get on with improving science-based climate models, monitoring cap-and-trade treaty agreements, and otherwise adapting to this changing world of ours.
Here's hoping that they fix the water systems, and the satellite is carried in a good, clean launch in the first few hours of Wednesday morning!