NASA preps environmental satellite for launch

CBS News

Getting a second chance after a 2009 launch failure, environmental researchers are eagerly awaiting launch early Tuesday of a $468 million mission designed to precisely measure carbon dioxide levels in Earth's atmosphere to shed light on how the greenhouse gas affects climate change.

"It's absolutely fantastic to get another opportunity to actually conduct these incredibly important scientific measurements," said David Crisp, science team leader for NASA's Orbiting Carbon Observatory 2 mission. "It's been a long, hard road but boy, I'm glad to be back."

NASA's Orbiting Carbon Observatory 2 will measure carbon dioxide levels with unprecedented accuracy, giving researchers insights into how the greenhouse gas may contribute to climate change. (Credit: NASA)

The original OCO mission was lost in a 2009 launch mishap when a protective nose cone fairing failed to separate during the climb to space atop an Orbital Sciences Corp. Taurus XL rocket. The OCO satellite, also built by Orbital, fell back to Earth in a $275 million failure.

Given NASA's increasingly tight budgets, second chances are hard to come by. But NASA managers, scientists and engineers decided the mission was too important to cast aside and the agency approved development of a second OCO spacecraft.

This time around, following a second Taurus nose cone separation failure, NASA managers decided to put the replacement satellite on a more expensive United Launch Alliance Delta 2 rocket, a workhorse medium-class booster with a long track record and one of only five left in the company's inventory.

Switching to the Delta 2, along with necessary satellite upgrades, pushed the cost of the second OCO mission to $467.7 million.

"The loss of the original OCO mission was a tremendous heartbreak for all of us, it was truly devastating," said Ralph Basilio, OCO-2 project manager at NASA's Jet Propulsion Laboratory. "We are excited about this golden opportunity to be able to finally complete some unfinished business. This launch doesn't signal the end of the road, but it's the next step in a very important mission."

Said Crisp: "We've done everything humanly possible this time, as before, to ensure a safe and successful launch. ... I'm looking forward to getting past this step. It's been a long run up to the starting line of this race, but we're ready to start now."

Liftoff from Space Launch Complex 2 at Vandenberg Air Force Base, Calif., was targeted for 5:56:44 a.m. EDT Tuesday (GMT-4; 2:56 a.m. local time), the opening of a short 30-second launch window. Forecasters predicted fog in the area but nothing that would prevent an on-time launch.

Equipped with three solid-fuel strap-on boosters for extra power for the climb out of the dense lower atmosphere, the Delta 2's trajectory was designed to carry the spacecraft away to the south over the Pacific Ocean and into an orbit tilted 98.2 degrees to the equator.

After two firings of the Delta 2's second stage engine, the 990-pound OCO-2 satellite was expected to be released into a nearly circular 430-mile-high orbit about 56 minutes after launch. In such polar orbits, satellites fly over the entire planet as it rotates below.

After six to seven weeks of tests and checkout, along with on-board rocket firings to raise its altitude another nine miles or so, the OCO-2 satellite will kick off a two-year mission, passing over nearly every point on the Earth's surface every 16 days. The satellite will join four others in the same orbit that are studying other aspects of Earth's environment.

The solar-powered OCO-2 satellite is equipped with a single instrument, a high-resolution grating spectrometer. Operating in the infrared region of the electromagnetic spectrum, the instrument will break reflected sunlight down into its component colors, precisely measuring the intensity in three wavelength regions. Specifically targeted colors lose intensity when high levels of CO2 are present and brighten when levels are lower.

Every orbit, OCO-2's spectrometer will make 69,000 measurements, or 8 million each 16-day cycle. Researchers also will collect data from ground stations once each day to verify the accuracy of the satellite's readings.

"With that one instrument, we're going to collect hundreds of thousands of measurements each day, which will then provide a global description of carbon dioxide in the atmosphere," said Betsy Edwards, OCO-2 program executive at NASA Headquarters. "It's going to be an unprecedented level of coverage and resolution."

Carbon dioxide is considered a greenhouse gas because it helps trap heat in the atmosphere. A major question mark is how CO2 generated by human activity might play into climate change and contribute to increasing global temperatures.

Crisp said plants emit about 440 billion tons of carbon dioxide every year while the oceans contribute around 330 billion tons. Most of that naturally occurring CO2 is emitted and then re-absorbed as the seasons change.

"The new players on the block are us," Crisp said. "Since the beginning of the industrial age, we've been burning fossil fuels, also practicing deforestation and other things that have been emitting carbon dioxide into the atmosphere at an ever growing rate.

"Human beings are now emitting about 40 billion tons of carbon dioxide into the atmosphere every year. That's about five-and-a-half tons for every man, woman and child on the Earth. That input into the atmosphere isn't balanced by an uptake like the oceans and the (plants). So we're basically building up the carbon dioxide in the atmosphere of the Earth, slowly, but at an ever increasing rate."

Recent measurements indicate CO2 concentrations of 400 parts per million, believed to be the highest levels in the past 800,000 years. OCO-2 is capable of detecting concentrations as low as 1 part per million.

"There's a steady increase in atmospheric carbon dioxide concentrations with time," said Mike Gunson, OCO-2 project scientist at JPL. "Human beings have released hundreds of billions of tons of carbon into the atmosphere. ... We're releasing something like 40 billion tons of carbon dioxide each year. And this is increasing."

But CO2 levels follow an annual cycle, "dropping every summer as the northern hemisphere forests and plants start to grow," Gunson said. "This is the Earth breathing. But it's not just the planet's plants and forests. The oceans play an equal role as well in absorbing some of this carbon dioxide."

As it turns out, about half of the carbon dioxide generated by humans also is re-absorbed each year, but scientists don't understand where it goes or whether the "sinks" that take up the CO2 will continue to operate in the same way down the road.

Given that industrial carbon dioxide emissions appear to be steadily climbing, re-absorption by whatever means cannot keep pace. Understanding the details of the carbon cycle will help inform decision makers about the threat posed by CO2 and its potential impact on climate change.

"It's absolutely critical that we learn what processes are absorbing carbon dioxide in our system today, over half of the carbon dioxide we're emitting, because we need to understand, first of all, how much longer they might continue to do us that great favor," Crisp said.

"The other thing, though, is that while our inputs have been growing slowly but steadily over time, the amount that stays in the atmosphere varies dramatially from year to year. ... We don't know why. We need to understand those processes as well in order to understand how carbon dioxide will build up in our system in the future and how we might manage carbon dioxide buildup if that's what our policy makers decide to do."