Last week, the NASA DC-8
flew three flights over the California Central Valley to test the performance
of a laser-based instrument designed to measure methane in Earth’s atmosphere. The Methane Sounder Instrument, built by Haris Riris and his
team from the Goddard Space Flight Center, may one day map methane from a
future Earth or Mars orbiting satellite.
On Earth, methane is an
important greenhouse gas produced by certain types of bacteria in soils and in
the digestive tracts of some animals. Large quantities of methane are also
produced as a result of forest fires and human industrial processes. Knowledge of the global distribution
and abundance of methane is important for understanding global climate
change.
Methane has also been recently
detected on Mars. Because methane
is rapidly destroyed in Mars’ atmosphere, it must have been produced relatively
recently. While geological
processes can produce methane, another exciting possibility is that Mars’ methane is
produced by life. Determining the abundance and locations of methane sources on
Mars is therefore extremely important for understanding recent geological (and
perhaps biological) processes occurring on the Red Planet.
Before instruments are
installed on satellites or spacecraft, many are first tested from NASA
airplanes. The Methane Sounder instrument team spent two weeks at the Dryden Aircraft Operations Facility in
Palmdale, CA installing and testing their instrument on the NASA DC-8. They spent several days aligning and
testing the instrument from the airplane on the ground before finally testing
its performance on three flights over the California Central Valley.
Methane Sounder instrument PI Haris Riris (left) and Stewart
Wu (right) test the alignment of the laser underneath the DC-8 at the NASA
Dryden Aircraft Operations Facility.
Before flying their instrument on the DC-8, they fired its laser from
the parked airplane toward the ground, reflected the laser off of a mirror
underneath the airplane (above), and aimed at a nearby building. The infrared laser is invisible to the
human eye.
Inside the DC-8, while parked at the Dryden Aircraft
Operations Facility, Haris Riris (center) and Martha Dawsey (left) align the
laser for the Methane Sounder instrument.
The laser is fired straight down through a port on the underside of the
aircraft. To test the alignment,
it was reflected off of a mirror (see above) and then off of the side of a nearly
building.
The Methane Sounder Instrument
detects methane with an infrared laser beam. The laser emits light at a wavelength (color) that is too
red for the human eye to detect (1.65 microns). This
wavelength corresponds to one of the wavelengths that the methane molecule
absorbs light. As the laser passes through the atmosphere and bounces off of the
ground, methane molecules in the atmosphere absorb some of the light from the
laser. Measuring the amount of absorption that occurs as the instrument passes
over different locations allows the team to build methane maps.
Although current Earth-orbiting
satellites have instruments that can detect and map Earth’s methane, the laser-based
system of the Methane Sounder will enable much higher accuracy methane
detections and higher resolution methane maps than are possible with current
non-laser based instruments. With some
modifications, the laser system could also be used for a Mars-orbiting satellite.
The NASA DC-8 early morning before takeoff for the Methane
Sounder Instrument test flight on August 24, 2011.
To test the instrument, the
team flew at a variety of altitudes over a large methane source (a cattle
feedlot) in the California Central Valley.
Flight track (in red) for August 24, 2011. The DC-8 took off from Palmdale,
California, flew northwest to the California Central Valley and flew in a large
racetrack pattern around a cattle feedlot.
Altitude profile of the DC-8 from August 24, 2011. The DC-8 took off from Palmdale, flew
at 10,000 feet toward the cattle feedlot and then increased in altitude in 5000-foot
increments while flying in a racetrack pattern over the California Central
Valley (see flight track map above).
Haris Riris (right) and his group from the Goddard Space
Flight Center watch as they acquire data with the Methane Sounder Instrument onboard
the NASA DC-8.
Cattle feedlot near Coalinga, Central California seen from
10,000 ft from the NASA DC-8. Due
to the large number of cattle concentrated in such a small area, this feedlot
is a large methane source.
The instrument performed
outstandingly well, detecting the presence of methane in the atmosphere at all
altitudes. “The Methane Sounder is the first demonstration of methane detection
using lasers from an aircraft flying above 30,000 ft," said Riris. "It should be a
valuable tool for monitoring greenhouse gas emissions, especially in the
Arctic.”
The Methane Sounder instrument team is all smiles in flight
onboard the DC-8 as their instrument performs well.
Funding for the Methane
Sounder was provided by the NASA Astrobiology Science and Technology for
Instrument Development program with support from the ASCENDS CO2 Instrument Incubator Program.
On Sunday August 7, 2011, NASA’s DC-8 aircraft took off from the Dryden Aircraft Operations Facility in Palmdale, California for an eight-hour flight along the west coast of North America. The flight was part of a series of flights testing laser instruments that may be selected to fly on a future satellite mission to measure atmospheric carbon dioxide. For more information about the ASCENDS II campaign, please see this recent article: “NASA’s DC-8 Flying Lab Validates Laser Instruments”
NASA DC-8
flight track (in red). The DC-8
took off from the NASA Dryden Aircraft Operations Facility in Palmdale, Calif.,
flew north through the Cascade Mountains and into southern British Columbia, Canada
during an eight-hour flight on Sunday August 7, 2011.
The pilots, crew, and scientists met at 6:30AM inside the hangar at the NASA Dryden Aircraft Operations Facility. After the flight briefing, we boarded the DC-8 and took off at 8AM, heading north from Palmdale. One of the goals of this flight was to test the performance of the instruments over a wide variety of terrains, including vegetated surfaces and surfaces covered with snow and ice. In order to find snow in August, we flew to the northern Cascade Mountains in Washington State and British Columbia, Canada.
Crew and
scientists prepare for takeoff inside the NASA DC-8 on Sunday August 7, 2011 (Image
credit: E. Schaller)
After takeoff, we traversed the California Central Valley to test the performance of the instruments over vegetated terrain. We continued north through California over the Cascade Mountain Range, flying through Oregon, Washington, and Southern British Columbia, Canada. Along the way, we saw many famous peaks of North America including Mt. Shasta, Mt. St. Helens, Mt. Rainier, and Mt. Baker.
Mt. Baker
in northern Washington State seen from the NASA DC-8 (Image credit: E.
Schaller)
We then crossed into Canadian airspace and continued northwest, flying over numerous glaciers and snowfields. All of the instruments were performing well, which afforded many of the scientists and crew the opportunity to step away from their computers and consoles and look out the windows at the beautiful scenery passing by below us.
DC-8
flight track through Canada
A glacier in British Columbia, Canada near 51.4N 125.8W (Image credit: E. Schaller)
Another goal of the mission was to directly sample carbon dioxide in the atmosphere to compare with the remote carbon dioxide values measured by the laser systems. We flew in slow ascending and descending spiral patterns while directly measuring carbon dioxide as we increased or decreased in altitude. Once we re-entered Washington State after flying over the Canadian glaciers, mountains, and snowfields, we flew in a descending spiral pattern, decreasing in altitude from ~20,000 ft down to ~2000 feet. We then flew a planned missed-approach over a small airport near Forks, Washington (Quillayute Airport). After the missed-approach, we climbed back up to 12,000 ft, flew to another small airport near Toldeo, Washington (Ed Carlson Memorial Field), and flew another missed-approach.
Flight track in Washington State showing the spiral patterns near Forks, WA and Toledo, WA
Following the second missed-approach, we flew another spiral pattern, this time steadily increasing in altitude until we reached 31,000 ft. This last spiral pattern allowed everyone onboard to see Mt. Rainier, Mt. Adams, and Mt. St. Helens multiple times.
Mt. St
Helens seen from the NASA DC-8 during the ascending spiral pattern (Image
credit: E. Schaller)
Finally, we flew south back to Palmdale along nearly the same track as we had flown north in the morning. Though we almost landed twice, we did not actually touch the ground until we returned to Palmdale eight hours and 3500 miles later (roughly the distance between New York and London.)
Though a bit tired from the 8-hour flight, all onboard were very excited with the quality and abundance of data that was collected.