The A-Train is a series of five satellites that orbit Earth in single-file formation 700km above the planet's surface. In July 2014, NASA's OCO-2 satellite will join the A-Train formation to monitor atmospheric carbon dioxide as part of understanding its role in climate change. OCO-2 will measure global CO2 concentrations with unprecedented accuracy to better understand natural and human-caused CO2 sources and "sinks" that absorb CO2. The satellite was transported from Virginia to California for launch aboard a Delta II rocket from Vandenberg Air Force Base into a polar orbit to join the A-Train constellation.

1. Scientists called it “The A-Train.” even though convoy would a be more rigorous
description for a series of five satellites orbiting Earth in single file along the same path,
~700km-high over our planet and passing above its north and south poles.
[AUDIO] Dr.BasilioOCO-2ProgramMgr..wma
[[Audio – Dr. R. Basilio
Interview Excerpt]]
____________________
HD Embedded Audio ... . .
[[Video – OCO-2 searching
for CO2 Sources and “Sinks”]]
____________________
HD Embedded Video . .
Double-Click Icon Double-Click Icon
Their names? Aqua, Calypso, Cloudsat, and Aura. They all launched from Vandenberg
Air Force Base, Calif., and by early July 2014, if all goes according to schedule, they will
be joined by another Earth-monitoring craft: NASA’s OCO2, short for Orbiting Carbon
Observatory.
This new environmental sentry in the sky in part gets its name from the chemical
formula for carbon dioxide, the same gas humans and countless living organisms
sharing our planet release through physiological processes.
For those familiar with elemental chemistry, the structural formula for carbon dioxide is
written out as O=C=O. All it means is that one carbon atom is holding on to two oxygen
atoms, which turns out to become the gas getting our atmosphere increasingly warmer.
Over the past 200 years, starting with the Industrial Revolution – about two centuries
ago – humans have been depending on the constant and ever-increasing consumption
of fossil fuels: from coal, to gasoline, to methane.
The OCO-2 mission “meets a science imperative,” says Dr. Ralph Basilio, Mission
Manager at JPL. The scientific measurements are particularly important since the

2. concentration levels of CO2 in the atmosphere is up to unprecedented level of 400 parts
per million. That’s unprecedented in recorded history, even going back 800,000 years
studying air bubbles trapped in ice core samples from the Antarctic.
We have air data records, air samples, showing CO-2 levels were hovering around 300
parts per million. Currently, human activities contribute to the discharge of some 30
billion tons of carbon dioxide into the atmosphere. However, this startling figure pales
when compared with some 770 billion tons of CO2 naturally released into the
atmosphere each year by natural processes on land and in the oceans.
What processes?
Among the major sources of natural CO2 emissions are volcanoes – from those found
on Earth’s continents to those erupting onto the ocean floor of our planet – spewing
lava and releasing noxious gases as they bubble their way out of ocean waters into the
atmosphere.
Scientists estimate that for each ton of carbon, humans consume 3.7 tons of CO2,
hardly a a small amount, but it makes up only for a small fraction (4%) of the total CO2
emitted by natural phenomena.
This is a key point, as recent scientific evidence seems to indicate that carbon dioxide
released into the atmosphere as a result of natural phenomena gets reabsorbed almost
entirely into the aforementioned “sinks”.
Atmospheric CO2 measurements gathered by a network of surface stations located all
over the world, indicate that natural CO2 “sinks” not only absorb almost all of the CO2
emitted by natural processes – They absorb about half the CO2 resulting from fossil fuel
combustion, resulting from industrial activities and other non-natural sources.
Arid ecosystems like deserts provide a "major sink" for atmospheric carbon dioxide,
researchers have said.
According to scientists at Washington State University, arid areas soak up an
unexpectedly large amount of CO2, giving researchers a better understanding of our
planet's carbon budget.
Published in the journal Nature Climate Change, research leader R Dave Evans
commented on the study: "It has pointed out the importance of these arid ecosystems.
They are a major sink for atmospheric carbon dioxide, so as CO2 levels go up, they'll
increase their uptake of CO2 from the atmosphere.
"They'll help take up some of that excess CO2 going into the atmosphere. They can't
take it all up, but they'll help."

3. Earth's carbon budget looks at how much CO2 in the atmosphere contributes to global
warming and how much gets absorbed by the planet.
To establish how deserts act as CO2 sponges, the team spend 10 years exposing plots
of land in the Mojave Desert to elevated CO2 levels, similar to what is expected in 2050.
The team then removed the soil and plants to measure how much CO2 had been
absorbed.
How much land-based ecosystems absorb CO2 has been a long-standing mystery
within the scientific community. Ecosystems consider arid receive less than 10 inches of
rain per year and run in a wide band at 30 degrees north and south latitude.
Forest ecosystems can absorb a lot more CO2, but researchers say the vast areas of
Earth covered by arid land mean they have a greater role to play in global warming and
the absorption of CO2.
Researchers dug up plots around 75ft in diameter. CO2 with a special chemical
fingerprint was fed in through PVC pipes. On analyzing the soil, researchers looked at
the CO2 fingerprint to establish that arid ecosystems account for between 15% and 28%
of the amount currently being absorbed by land surfaces.
Increasing CO2 levels will also increase the amount soaked up by arid lands so they
account for up to 8% of current emissions. "I was surprised at the magnitude of the
carbon gain, that we were able to detect it after 10 years, because 10 years isn't very
long in the life of an ecosystem," Evans said.
Explaining the implications of their findings, the team said the planet will be working in
overdrive to soak up CO2 by 2050, and that with a growing population leading to
further land development for homes, there is a great concern ecosystems will not cope.
"Land is extremely valuable," Evans said. "A lot of growth may occur in these areas that
are fairly arid and we don't know what that's going to do then to the carbon budget of
these systems."
General Launch and Mission Information for OCO-2
Q&A – (Answers from Interview with Alicia Mendoza-Hill -- MIM)
Satellite weight: ~ 530 Kg (1,165 lbs.)
OCO-2 will plot atmospheric concentrations of human-activities-produced carbon
dioxide (CO2) to help ascertain its effects on Earth’s environment.
OCO-2 Managed by JPL. Will join the so-called “A-Train” of environmental satellites –
preceding the “Aqua” spacecraft by 15 minutes – along same polar orbit – inclined 98.2
degrees on equator. Altitude: 705 km (440 miles).

4. Launch site choice fell on VAFB, Calif. as it’s most suitable for polar orbit launches –
without risk for communities along the coast – reason rockets launch heading south.
How the spacecraft arrived at VAFB (preparation)
Where spacecraft came from? How was the spacecraft transported? Was there anything
during the transportation or the arrival of the spacecraft that were challenging?
Orbital Sciences Corp. (OSC) built spacecraft at own plant in Dulles, Virginia, then
shipped to OSC’s facility in Gilbert, AZ for integration and testing. The satellite traveled
on an open flat-bed tractor trailer, inside enclosed pallet. Accelerometers monitored any
stress during transport. From AZ, OCO2 will travel to Payload Processing Facility at VAFB
for final processing.
Spacecraft Processing
Final processing will take about a month, then spacecraft will be moved for mating with
Delta II rocket on launch pad.
Is there a process for the transition of the spacecraft to enter the cleanroom
Yes. The satellite is removed from enclosed pallet. Wrapping material cleaned up before
taking it into PPF. Unwrapping follows. Final preparations can begin.
Why a particular cleanroom was chosen
Satellite is small: no special arrangements for particular facility. Clean room (Positive
Pressure) to prevent dust/dirt from entering. It meets cleanliness standards for this kind
of spacecraft (no delicate optical instruments). Specifically, the Payload Processing
Facility (Astrotech West High Bay) follows the so-called ISO9 standard, meaning the
maximum number of impurity particles can be:
100,000/cubic meter – i.e. [105/28.3e3 ft.]
What were the special challenges or issues of the mission?
One particular challenge was modifying the equipment and hardware originally
designed to link the satellite to the Taurus rocket.
Following launch problems with two Taurus rockets came the decision to use Delta II for
OCO-2 launch, instead. Challenging part was ensuring the satellite could withstand
launch dynamic stress (such as vibrations) aboard Delta II
Examples: Contamination, spacecraft sensitivity, unique process requirements

5. OCO-2 requiring standard non-contamination environment (see above) since it’s not
equipped with any particular (for example) optical instruments that would require
maximum cleanliness care.
Spacecraft processing time
Processing time at VAFB facility is expected to last one month.
Launch, Location, and Window
Only five Delta II rockets are still available – and all will launch from VAFB. They were
built using parts still available at plant, even though productions had stopped.
The first of the last five Delta II rockets is set to take to the California skies from VAFB’s
Space Complex 3 is on July 1, 2014, sometime between 2:56 a.m. and 2:58 a.m. PDT –
5:56 and 5:58 a.m. EDT. The launch Window is not quite a window, it’s just an instant,
and will change only by a few seconds per day. VAFB’s range will be available to support
the launch all the way to the end of July.
Propelled by its standard main engine burning a kerosene-like, liquid hydrocarbon mix,
and assisted by three solid-fuel booster rockets, the Delta rocket will lift off assisted by
three solid fuel booster rockets. Once expended, they will drop off 99 seconds after
launch.
Overall, the first stage will run for 2 min. 24 seconds, before separating and diving into
the Pacific. The second stage engine will then take over, burning for 4 min. 38 sec.
As the rocket performs its task, the shroud encasing the spacecraft at its top will split in
half and fall away, as the atmosphere now is rarefied (thin) enough for OCO2 to be
exposed to space environment.
Securely perched atop its propulsion system, OCO-2 will coast for 51 minutes – an
amount of time longer than originally intended – had the satellite flown aboard a
Taurus rocket.
The switch represented a challenge for the spacecraft team, which devised and develop
a plan to ensure the satellite will have a healthy load of battery power all the way to its
operational orbit.
For that to occur, the second stage of the Delta II will restart and burn for 5 minutes and
1 second. Then, automatic commands will be imparted so that all ties holding OCO-2
and the Delta upper stage together are severed, and the satellite set free.
Finally, the solar panels will deploy, and start providing all the energy OCO-2 needs to
begin and carry out its mission.