May 16, 2011
On the way up to Greenland a few weeks ago, we discussed very briefly the science that has brought us here to Greenland this spring. Now that we have some pictures of our work, let’s discuss it in a bit more detail. As you already know, Matt and I were traveling about by snowmobile to establish GPS stations to measure ice sheet motion. The major goal of the project is to monitor the conditions at the bottom of the ice sheet and record how the environment down there changes with time. Our part of the project will record how the ice sheet velocity at the surface changes, by installing a network of GPS stations near Swiss Camp.
There has been a significant amount of research conducted in the Swiss Camp region over the past several decades. Among other work, researchers have mapped the ice thickness, the ice surface topography, the temperature and wind speed, and the ice sheet velocity. On the map, our GPS stations are indicated by the red dots, while the yellow stars indicate our two drilling locations. The blue triangles are monitoring sites maintained by Koni Steffen and measure the local meteorology as well as ice motion (in a long-term monitoring project by NASA scientist H.J. Zwally). The red curve represents a flow line — a path along which ice flows. If one were to put a marker on the flow line near the Swiss Camp station in the upper right of the map, it would travel down the ice sheet along the red path. Data indicate that ice flowing along our path ultimately ends in a fjord that connects to the ocean. The red dot on bedrock in the upper left (QING) is our base station — a GPS station placed on rock that is essentially immobile, at least over the time period of this study.
Our prior work in the area demonstrated that the surface velocity of the ice sheet is essentially the same between stations just 2 or 3 kilometers apart, but can be markedly different between points 5 or more kilometers apart. We also found that the velocity can change quickly during the summer, when lake drainages our common. The locations of our network of GPS stations (as shown on the map) are chosen to capture both the short term changes in velocity due to surface water drainage (which our sensors at the ice sheet bed should also record) as well as capture the spatial variability over a wide range of ice sheet surface elevation and ice thickness.
With luck, our GPS and borehole instrumentation will collect data for the rest of 2011 and well into 2012. Together, the data from the project will provide insight into how and why the ice sheet moves the way it does during the summer season. This is important because one of the major goals of the ice community is to better predict ice sheet changes in the coming decades and centuries. A critical part of this predictive ability is a solid understanding of how ice sheet velocity changes as the amount of melt on the ice sheet surface in the summer changes. The ROGUE project is designed to provide this insight, as well as set up a reference data set for large-scale ice modeling studies.
ROGUE: Real-time Observations of Greenland’s Under-ice Environment
The goal of the ROGUE project is to examine the nature and cause of short-term ice velocity changes near Swiss Camp, Greenland, by observing interactions between the ice sheet, the atmosphere and the bed.
MABEL: Flying on a high-altitude aircraft at the brink of space, the MABEL instrument is helping scientists to simulate measurements from NASA’s next ice-observing satellite, ICESat-2.
April 8, 2011
Today, I caught this video on the NASAexplorer channel on YouTube:
It covers Jake Bleacher’s work in understanding lava-sheet inflation
(see his video, which covers this interesting geologic process). On
MABEL’s last mission (4/5), we surveyed some of Jake’s sites in both
Arizona and New Mexico.
The lava sheets that Jake studies are very broad, flat regions. For
his work, he has kinematic GPS data across sections of these sheets.
We mimicked Jake’s traverses (from 65,000 feet up) to gather
ground-truth data for MABEL. Additionally, because MABEL samples in a
swath pattern, as opposed to just over a single point, we hope to
provide Jake with additional information about his survey areas.
MABEL is an airborne simulator of the laser altimeter that will be
aboard the ICESat-2 satellite. ICEsat-2 is designed to look at ice
sheets, not lava sheets. So this MABEL mission over Jake’s sites
represents the cooperative nature, typical of the different geoscience
disciplines, at Goddard Space Flight Center.
Well, we are pretty much finished out here. The engineers flew home
today and there are only a couple of us still here, flying out
tomorrow. We hope to return to the field with MABEL sometime later in
the summer.
MABEL: Flying on a high-altitude aircraft at the brink of space, the MABEL instrument is helping scientists to simulate measurements from NASA’s next ice-observing satellite, ICESat-2.
April 7, 2011
MABEL flew her final science mission of 2011 (4/5) over White Sands Missile Range. The weather over this area was clear when we flew it, however, weather rolled into the area just as the plane left our target.
White Sands was chosen as a MABEL target because we have been using the area as a ground-control site since ICESat was launched in 2003. Two ICESat tracks crossed in the center of the dune field; where they cross, ICESat researchers have recently planted reflectors that we hope to see in the MABEL data. These reflectors will help us validate MABEL’s elevation determination accuracy.
Also on this flight, we also attempted to collect data from deciduous trees in Arkansas. From Dryden Flight Research Center, to New Mexico, on to Arkansas, and then back to Dryden is a 9 hour mission.
However, between White Sands and Arkansas, MABEL’s laser stopped firing. This is not something that we were prepared to deal with in the field. So, given that we were already near the end of this mission, we decided we’d call this trip a success, given all that MABEL had already accomplished and given the science objectives that the instrument deployment had met:
1) Hit ground-control points set up at White Sands to validate MABEL
2) Collect tree data for ICESat-2 vegetation scientists
3) Collect snow data for ICESat-2 glaciologists
4) Collect data over the ocean and bright clouds for ICESat-2 instrument scientists
We are now headed home. We have had a fantastic time working with the pilots and mechanics here at Dryden Flight Research Center. They are great at what they do, making their components the smoothest parts of the complex MABEL equation. We might not have any other missions on the ER-2 this spring, but you can still follow their flight activities at their Twitter feed: @NASA_Airborne.
MABEL: Flying on a high-altitude aircraft at the brink of space, the MABEL instrument is helping scientists to simulate measurements from NASA’s next ice-observing satellite, ICESat-2.
April 5, 2011
We had another highly successful mission, this time to Colorado (4/1/2011).
Specifically, we targeted a field that usually holds snow late in the season. Additionally, we targeted SNOwpack TELemetry (SNOTEL sites), where we have good control with respect to snow cover. One last site we targeted was a SNOTEL site situated within Loveland Ski Area, which was reporting one new inch of snow in the past 24 hours.
The weather looked slightly spotty to the north, but the pilot reported that there were clear skies over our targets!
We can actually receive limited information from the instruments during flight. So during the flight we knew that MABEL was operating properly. Additionally, we can get a very good sense of the cloud cover by looking at real-time data from an instrument that is flying along-side MABEL. It’s called CPL, or Cloud Physics Lidar. CPL records a smaller volume of data and has very mature software, relative to MABEL. So it’s easy to use CPL as a real-time assessment of atmospheric conditions during the flight. So we tend to fly CPL regularly with MABEL.
Because our pilot had a ton of transit time between Dryden and our targets in Colorado, we asked him for a huge favor: We asked him to take photos for our project. Keep in mind that he is in a pressurized suit, so everything he does, he does wearing bulky gloves. So we were very happy when he returned these amazing photos. Phenomenal.
The pictures (above and below) were taken from 65,000 feet above sea level. At this elevation, you can clearly see the curvature of the earth. Additionally, you can see the thinning of the atmosphere (apparent in the change in color of the sky from light blue to dark blue).
MABEL: Flying on a high-altitude aircraft at the brink of space, the MABEL instrument is helping scientists to simulate measurements from NASA’s next ice-observing satellite, ICESat-2.
April 4, 2011
Palmdale, Calif. – Well, it took three tries, but we finally collected excellent MABEL data over a forested area in the Sierras.
While we were flying the first attempt (3/28), the detector temperature kept drifting out of the acceptable thermal range. So MABEL would temporarily shut down to cool itself. The temperature for the detector has to be remain very close to 32
degrees, so we need to keep very close control over the temperature of the instrument. After landing, it was determined that the problem stemmed from the fact that MABEL’s cooling system had not been completely flushed. That was fixed for the next flight.
At some point during the second flight over the Sierras (3/29), MABEL’s GPS failed. We use the GPS signal for precise positioning, but we also use it for very precise time. GPS satellites broadcast very precise time (which is also exploited by seismologists). We use the GPS signal to measure the exact time between the laser firing and the detector receiving that signal. So without the GPS data, our laser data was pretty much worthless.
Instrument issues are common during deployments. The engineers associated with MABEL are quick to address them so that the week’s flight schedule stays intact.
The third flight to the Sierras (3/30) was the clearest weather that MABEL had ever seen! It was what we had always been told was standard ‘southern California weather.’ And the flight itself went off without a hitch.
We are interested in a forest in the Sierras to assess MABEL’s ability to measure the top of the trees (the top of the tree canopy) and the ground beneath. These measurements give vegetation scientists an assessment of the biomass associated with these particular trees, which are evergreens. Later in the mission, we will try to collect similar data over Arkansas, or deciduous vegetation. Information from these flights will be incorporated into ICESat-2’s algorithms.
More from Dryden later!
