Notes from the Field

Looking Forward

August 22nd, 2011 by Joanne Howl

Wallops Island, Virginia  9 p.m. EDT

From Jon Ranson:

It’s a beautiful evening here at Wallops Island!  I’m here to join our Eco-3D team, and I’m sure looking forward to starting our flight campaign tomorrow morning.  I’m really excited to be a part of the mission, and expect to have a good week gathering great data.

My name is Jon Ranson, and I’m one of the science investigators with the DBSAR.  In this blog, I’ll be the one speaking to you, but I’m not actually doing the writing.   I’ve discovered that on field campaigns that the science team- and usually me especially – stay too busy to spend time in the evening sitting down and writing.   We can write – and we do – but while we’re in the field, we have other work to do.   What I’ve found works best for everyone is to let a writer carry our story for us.   For this effort, our writer is Joanne Howl.  She will be staying at the home office in Maryland, taking our phone calls, and telling our story in a blog that will appear hear as near-real-time as conditions allow.

The Eco-3D mission focuses on measuring the three dimensional structure of vegetation. To accomplish this, we are combining three innovative instruments to take simultaneous measurements from a single platform – something that has never before been done.

We plan to collect aerial data from over many very diverse sites – several in the northern U.S., several in the south, and several in Maryland.  We also are going to be using ground truth measurements collected on the ground at those same sites to help validate our instruments.

We currently have a crew in Maine taking forest measurements there in advance of our flight, and hopefully will be measuring as we fly overhead, too.  We’ll also collect data from other recently measured sites, such as measurements make a few months ago by scientists working with the Carbon Monitoring System biomass pilot program.  Their measurements support their efforts to quantify carbon in forests as well as defining the accuracy of their estimate, and we consider their field work very valuable and helpful for our own efforts.  We also hope to provide them valuable data for their own research.

So why do we want to measure three-dimensional structure of vegetation?  Well, let me first say that by measuring vegetation – and forests in particular – we can estimate aboveground biomass.  If we know the biomass of a forest, then we can estimate the carbon stored in that forest.  The more accurate the measurements, the more certain the carbon estimates.

Traditional remote sensing instruments have relied on two dimensions – length and width – just about forever.   This type of measurement gives us a lot of information about forest structure and biomass, but it’s still missing quite a bit –it’s missing the entire third dimension. It’s missing height.

So why is height important?  Imagine you have a photo taken at the top of a cliff, looking down.   You’ve got length and width in that photo, so it’s two dimensional.  Now imagine that image suddenly becomes three-dimensional.   As your brain processes the added data and your mind measures the sheer drop, the image would appear more nearly real, and you might feel dizzy or frightened.  That third dimension allows for a better estimate of the reality of the scene.   In science, the third dimension will allow us to make a much better estimate of the height of the trees, and that is a powerful measurement to have when trying to estimate biomass.

We are carrying three instruments on the P3 aircraft,  We have the Digital Beamforming Synthetic Aperture Radar (DBSAR), the Slope Imaging Multi-polarization Photon-counting Lidar (SIMPL), and the Cloud Aerosol Radiometer (CAR).  DBSAR collects polarimetric and interferometric data to validate biomass estimates. SIMPL is a multi-beam, micropulse, single photon ranging laser altimeter, and will provide measurements of forest canopy structure with very high spatial resolution.  It also will collect two-color polarimetry data that can be used to differentiate stand types.  CAR is an airborne multi-wavelength scanning radiometer that can measure spectral directional reflectance over uniform forests, homogenous clouds, and bright targets. We’re interested in biomass, so during our campaign, CAR will be employed to derive the Bidirectional Reflectance Distribution Function (BRDF) and the vegetation clumping index.

These instruments are great, but they are new versions of older instruments, and do not have a long history of field use in this manner.  They’ve only been flown together once before, and that was just this summer.  The data from those flight lines look really good, but it’s not realistic to think that the installation and testing of these instruments would go entirely smoothly.  And it hasn’t.

Last week our engineers began to install instruments on the NASA P3 Orion.  That went well. The engineering check out flights showed the instruments and the plane can work well together, with no problems.  The instrument check out, however, uncovered some hitches, some with each instrument. The engineers have fixed most of the issues, but we still seem to have an intermittent problem with the DBSAR.  Most of the time it works fine, but occasionally it loses bits of data. The tough thing is that it only seems to have problems when it’s in the air, so that’s a real challenge to figure out.  But we have great minds here, and I’m sure the engineers will get the job done, whatever it takes.

We’re planning an early morning take-off, and we’ll run an instrument check out first thing.  If the problem appears again, we’ll return to Wallops and fix it.  When the DBSAR works, we’ll head to Maine and start making our measurements.   So I’m off to bed – tomorrow will start early and may well end up being a very long day.

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