NASA Earth Science Field Campaign Transcript – Dr. Petya Campbell

Section 1: Field Safety and Emergency Preparedness (0:05-3:14)

Field safety includes a list of everyone in the party, where you’re going, and who’s the emergency contact that’s not with you. We designate a communications point person who has an InReach for satellite text messaging because we’re going to be in places without cell coverage. Actually, we’re pretty much out of cell coverage here at Patuxent, but seriously, when you’re on the North Slope of Alaska, you want to have some way of getting information out.

I go through with everyone on the team how the communication device works, how to turn it on, how to set off the alarm. If I’m incapacitated, then somebody else can use it. We identify a health response person – first aid or first responder. As we introduced ourselves, we found out that Caitlyn has the highest level of medical training among the group, and she has a very complete first aid kit. If somebody has been bitten by a bear or whatever – I’m serious – she has the tourniquet and bleed stop kit and everything. Liz and I have the second level of medical training, so if Caitlyn is incapacitated, we’re prepared to handle that.

One of the really important things is driving. I always check – Caitlyn, you drove the Suburban up the haul road with this team in it. Where are the keys? We identify a second in command like Liz, who knows how to drive a Suburban on the haul road, knows all the safety procedures and CB radio calls. We document all this with a field pencil.

Would you bring a second one for redundancy?

Absolutely. One is none and two is one. We would have at least two complete first aid kits.

Section 2: Field Campaign Planning and Instrumentation (3:26-8:39)

We’re going to use ASD and STELLA to look at pigments. For instruments we need STELLA – which STELLA are we going to use? I want to use a 1.2 and a Q2. So we have those two, plus ASD and chlorophyll meters. Ideally we want to measure leaf area index (LAI), but we’ll put that as TBD for now.

Who’s going to measure with STELLA? Mike will set up the STELLAs and prepare them. Jesse will set up the ASD and panels. We need tripods for the panels. Let’s meet directly at OPE at 9 AM. I’ll go earlier to mark the five sites with flags, separating three measurement points so we can assemble the data properly.

This is why we do the panel measurement sandwich – STELLA measures irradiance, not digital numbers. We do this because we want reflectance. Reflectance is a ratio between the panel measurement and the measurement from the target. We do multiple measurements because the sun is changing position – at 9 AM the sun is here, but at 9:30 it moves up. We need to know the incoming solar radiation at the time of measurement. If you take too long after the panel measurement, you need to take another panel reading.

Section 3: Field Preparation and Experience (8:44-12:03)

For longer campaigns, we’d prepare food. Everyone comes with covered toes – no sandals and flip-flops. I’ve had students show up in shorts and flip-flops, and there are ticks. Socks need to go over the pants so ticks climb up, then when you go home, you check carefully and remove everything. You need hats, water, sunscreen.

Interviewer: How many field campaigns have you been on?

I’m a forester by background. I started in college, then worked for the Ministry for Environmental Protection in Bulgaria, surveying protected areas and looking at plants and animals. I did my dissertation in the Czech Republic doing forest health surveys. I have a doctorate in Remote Sensing for Environmental Applications. I teach at the University of Maryland Baltimore County and do research here at NASA Goddard on vegetation function and health. That’s what makes me happy and drives me in science. I started at Goddard in 2000.

Section 4: Site Selection and Agricultural Context (12:03-17:05)

What makes a good spot to measure? We want it representative of the field. Look at the field out there – we want to measure spots that represent the field. If you turn to the other field, you’ll see it’s nothing like this field. They’re very different. We’ll measure three repetitions here because some areas are denser, some are not, some have more soil cover.

Why are we taking three measurements at each spot? If we have three measurements and some are not good and representative, we can get rid of them. These are soybeans. This field has nitrogen treatments – they fertilize with different amounts: 0, 25, 50, 100. They know what’s optimal for this soil, water, and natural nitrogen content for corn to grow. This area looks like 150 nitrogen treatment because it’s very tall. Over there the corn is smaller and yellowish because the nitrogen is low.

What we do is create equations for satellite products. Satellites get zeros and ones – digital numbers. We need to make it into products like chlorophyll or amount of water in leaves or height of canopy. People need to measure on the ground and make equations to derive the product and make the maps.

Section 5: Technical Measurement Coordination (17:05-25:07)

We’ll assemble the data in files. Make sure Mike tells you the file name for STELLA data. Going from irradiance to radiance is non-trivial – you need distance and field of view for that calculation. But Digital Numbers to radiance is a simple multiplier table. The ASD has a different sensor than STELLA, so the amount of photons it collects is different, but the curves should be the same because they’re relative. That’s why reflectance is always going to be the same.

We’ll coordinate measurements carefully. Before every plot, we put instruments over the white spectralon panel to get the baseline 100% number for reflectance calculations. The measurement sequence is important because the sun is rising and we’ll have differing values. We need the same order of operations between instruments. I suggest people with Q2s first, then the 1.2 last because it takes longer to cycle.

When I take the first data point in the plot, the next person should be over the panel. We want one data point per panel on STELLAs because they take much longer – 20 measurements each.

Section 6: Active Field Data Collection (25:07-33:13)

We’re taking chlorophyll measurements to understand if STELLA can provide information relevant to chlorophyll. Don’t shade the white panel when taking data. If we shade part of it, it’s not getting 100% sunlight like the plants. The white panel is essentially 100% reflective. This is a perfect day because there are no clouds and minimal haze.

Keep the white panel clean without touching it because touching smears things into the porous surface. This is called a Lambertian surface – once light gets in, it reflects in all directions evenly. A pure Lambertian surface reflects at all angles evenly, but nothing is pure Lambertian. This is the closest there is.

Keep your STELLAs at the same height to get similar field of view areas. We want to measure soybeans, not dirt, so position carefully over the plants. We measure the smaller corn because the leaves are less green – they didn’t get as much nitrogen as the others.

This is what I do – this is my work.