Closing the Flight Campaign

September 20th, 2011 by Joanne Howl
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Goddard Space Flight Center    12:30 p.m.

Charles Gatebe:

I’m calling in from my office at Goddard Space Flight Center today.  We finished our flights for CAR yesterday, on Monday.  I did try to call in my report late in yesterday evening as I was driving home from Wallops.  I missed the connection at that time – but today’s a good time to catch up.

This has been a hectic, hectic time for me.  I came back to my office to work today for the first time in at least a month.  We’ve been flying that long!  Before that, I was working on getting the instrument on the aircraft, so it’s been more like six weeks since I’ve done much work in the office.  I did stop in from time to time, between flights, but only for an hour or two.  So now I have plenty of office work to do here!

The Flux Tower at Harvard Forest. The CAR instrument acquired data at this site on September 19, 2011 on the last day of the Eco3D campaign.

Flight campaigns are very long and very busy.  Work for the campaigns start weeks before the flights themselves.  To get ready to fly, you first have to have your instrument ready.  Then you integrate the instrument into the plane.  When you think that is done, then you let the pilot fly with the instruments all loaded, to make sure that they don’t fall down in takeoff, landing or flying.  Then you finally get to go and check the instrument itself to see how it performs in flight.   So when a flight campaign lasts a month, you can be sure that the work started well before that time.

We started very early in the morning yesterday and had a really long and really good day.  I left from my house in Silver Spring at 3 a.m. and then drove to Wallops, which is over 3 hours away.   After the flights, I drove home the same day and arrived about 7 p.m.  Friday was worse, I flew 8 hours, left home at 3 a.m., and then drove back home after that flight.  It was a 14-15 hour day on Friday.

Yesterday, we had wheels-up at 8 a.m.  Once we were in the air, we flew a few lines over Wallops, then  made one more run for SIMPL, and then we headed out to Massachusetts.  We made good measurements under clear skies there all morning.  The site in Massachusetts is Harvard forest, and we had identified it as a backup site, early on.  It wasn’t a primary site, but it was a place we wanted to fly if we could.   Finally we got the chance.

Our first choice yesterday would have been to fly directly to Howland, but we heard it might be very cloudy there, which isn’t good for CAR or SIMPL.   Because Bartlett Forest is fairly close to Howland, we thought the cloud cover might extend out there early in the morning, too.  That’s why we decided to go to our backup site, Harvard Forest, which was predicted to have clear skies.  And it did – the skies were nice and clear.

We made a lot of measurements for SIMPL over the forests, and then we went to the Harvard Tower to take measurements for CAR.  The tower is a flux tower in Harvard Forest that was installed in 1989.  It has instruments on it which can provide a long-term record of net ecosystem CO2 exchange, evaporation, and energy flux (energy change).  They can make measurements hourly.  So it’s an interesting and well-studied site.

Because we wanted to make our measurements over that tower, I had the pilot circle the tower there while CAR acquired data.  I guess it must have looked like we were hovering over the tower, and we were there long enough that apparently people started to notice us flying not-too-high in a clear blue sky over their heads.  We made the newspaper in a local town, and a photographer took a great photo of the P3 at work.

When we finished our measurements at Harvard Forest, we flew to Bartlett to see if we could make measurements there.   We had lost our earlier chance at Bartlett, in New Hampshire, because the hurricane made us leave early.  When we got there, we found the sky to be very clear, and we were able to fly our mission and acquire very good data there, too.  It was very nice – I really enjoyed going there and finding no clouds in the sky.  About the time we finished making our measurements, a few cloud cells began to form, but that wasn’t too bad.  We had finished what we wanted to do.  And so that was when we headed straight back to Wallops – and we were done with measurements for this flight campaign.

We had about 6 hours of flying time yesterday.  That’s long enough to fly from coast to coast, isn’t it?  But instead of going from one coast to another, we made measurements instead, mostly flying lines and in circles.  Sometimes you don’t realize how long you are flying when you are working, because you are very busy making sure the instrument is collecting good data and making observations. It seemed like a very long day at the end, but while working, the time seemed to go fast.

It is very intense when you are flying a science mission.  It is like you are in a laboratory.  You want to be alert and making observations the entire time, so that later on, when you analyze the data, you can tie the observations into the measurements the instrument has collected.  The entire time we are in the air, I am making notes.  When I am doing the analysis, I can go back and tie the data back to what I noted.  Also, I take a lot of pictures.  They will all be time-tagged, so you can look at the log, the data and the photos and know what happened at what time.

When I fly, I sit in a bubble window.  At my station, I have the computer and the window, too, because I really need to see where we are flying.  I want to be able to know if there are clouds or the sky is clear, if we are flying over buildings or what the ground might look like.  I also am able to talk to the pilot.  Sometimes I can see things he doesn’t notice.  If we are flying into thin clouds, for example, the pilot might not notice and keep flying into them.  I can call him and ask him to go elsewhere.

It is a busy, busy, busy time in the air.  I tell my students that it’s not just a good time.  You must make observations.  You must note issues or problems that arise.  It is so important to be curious.  That’s how things are discovered – and there is so much to be discovered!

Charles Gatebe and Kurt Rush working at the CAR station prior to take-off on an early flight. Charles sits next to a bubble window, from which he can make constant visual observations of the area while in flight. Acquiring data on a flight campaign is no honeymoon - it is a busy time of very hard work running the instrument, making observations out the window, taking detailed notes and capturing time-tagged photographs in order to enable a full and detailed analysis of the data after the flight campaign ends.

Let me give an example.  There was recently a study published – an interesting study – that began from an unexpected observation.  We were over the Pacific Ocean trying to gather data for an experiment that wanted clear skies.  But we kept flying into ship plumes – and those plumes affect the instrument.  Toward the end of that experiment, the skies over the ocean appeared beautifully clear and I asked the pilot to orbit over that clear area.  I started making measurements, with no ships in the area, and was very, very happy.  I said that it was a good, classic experiment and that was excellent.

Then I looked and there was a ship plowing through the area of my measurements.  I wasn’t happy, but I kept collecting data. And I made careful notes – when the ship appeared and when we it left the area.  So when the data was being analyzed, my Quality Assurance person came and showed me some bad data – there was a huge increase in albedo.  I say, “This isn’t possible” and the QA people said, “But that is what the data says”.  So we thought we had a serious problem with the data.  We went and matched this to the log, and found that the big, surprising increase in albedo was caused by that ship itself – it wasn’t bad data.  It was an important observation.

So we saw that the wake of a ship makes the ocean tremendously brighter – over 100 times brighter than clear ocean.  I made that observation while collecting data, and if I hadn’t we would have missed an important finding, one that has led to a second study.   It’s observation that leads you to other things. I emphasize to my students, when they get to come on a flight, that this is no honeymoon – it is hard work.  I want to stay focused, stay busy and make notes.  There are so many things that need to be discovered out there. If you don’t pay attention, then you don’t see it.

I like to think of my instrument as a set of eyes.  CAR is measuring radiation in the ultraviolet, the visible and the near infrared frequencies.  This instrument can “see” things that our eyes can see, and so much more. So imagine having that set of eyes – you are looking and observing with amazing power, when you have those kinds of eyes.  So I need to compare my own eyes with the instrument eyes – UV, visible and near infrared.  I can use my own eyes to help interpret what we see.  When we look at the data, we see that some objects may seem to reflect one part of the light – or absorb it – much more strongly that we would expect.  And that type of thing is what we want to capture.  When you find something unexpected, it’s phenomenal.

So that’s the main point I want to make.  It’s important to be very, very observant.

We had some instrument issues on this flight campaign, especially with the DBSAR which is fairly new.  For me, I am flying an instrument that has flown for many years, so there are not so many surprises with CAR.

The biggest challenge, when we set out, was that we had very low expectations of what measurements we would take.  We thought we’d measure just Howland, maybe Wallops, but not a lot more.  But we had the opportunity to gather a lot more data.  We did get our measurements over Howland, but we also took in New Hampshire and Massachusetts sites, and others.  Many of these sites have on-going measurements, and that will help us make very strong conclusions about our data.  When we went to Florida, we realized that those sites were really very, very interesting, too.  So from low expectations, we rose pretty high and have had a very successfully campaign.

I did have one big surprise with the instrument.  At first, it was failing all of the check flights.  It never fails check flights – I know this instrument, and it works well.  It shouldn’t fail any check flights.  But it failed so bad, that they just about dumped me from the mission.

So let me tell you about my instrument. It rotates almost 360 degrees.  It sits on the nose of the plane, and with this 360 degree rotation, I can observe the skies anywhere.  I can see a cloud at any angle at all. When we are on a flight, I start with an objective.  Sometimes I just want to look at the surface of a cloud, or I’ll want to look just at vegetation, I will move it around.  I can sweep from one side to another and get a view almost like a carpet – it is a fantastic view.

The part that moves the instrument, there is a collar on it to control the movement.  When the pilot was doing the flight checks, he felt uncomfortable.  He thought that he might not be able to control it.  And he thought it was my problem.  And they were going to take me off the flight – no work at all.  That was August 19, when they said we couldn’t pass the flight test, and so we couldn’t fly.

But I said no, it wasn’t my instrument but that collar that they added.  I know this, because we have never failed a flight check before. It took quite a lot of convincing, but we took the collar off and it was fine.  We were able to demonstrate that the instrument was harmless.   And so we were back on the flight – it was close, but we made it!

A QuickLook image of BRDF from Howland Forest. An aircraft platform provides a convenient and efficient means of obtaining complete bidirectional reflectance distribution function (BRDF), which defines how light is reflected on a surface in all the directions. To measure BRDF, the aircraft assumes a closed circular flight pattern over any surface of interest. The pilot attempts to maintain a constant altitude at a selected height above ground, over land, water or cloud with a constant aircraft speed and a roll angle of 20-30°. Unlike any ground based BRDF measuring instrument, which characterizes BRDF over an area no larger than tens of meters in diameter, CAR can survey the BRDF characteristics of a region on the order of kilometers in diameter as demonstrated in this taken over Howland Forest in Maine on August 31.

The only other surprise was that halfway through the fights, the instrument broke down.  I could not find out why. I was sure it was in the wiring.  So I spent a long two or three hours in the air, looking at every wire and troubleshooting everything I could find.  I couldn’t find anything there.  But on the ground, I found there was something small wrong in the instrument itself, and I got it fixed really fast.  That was a very happy moment for me!

Now, I have some pictures I’ll post on this blog.  But if you want to read more details about the CAR instrument, and more details about the campaign, we have a website.  There you can see the instrument as well as each of the campaigns.  The site is car.gsfc.nasa.gov. When you go there, you can click on Data, and then find Eco3D.   Then you can go to each flight day and see our map (the lines we flew), our log, photos from the flight as well as data we acquired.   Not all of that is up yet, but some of it is and we will be adding to the website just as soon as we get the data processed.

Well, this is the end of the flight campaign.  We flew over just over 69 hours in four weeks – at the end of the day yesterday that was the total.  My instrument went through that with only very minor issues, and we survived very well.  All in all, we only lost about two or three hours of data.  So it was a very long campaign, but very productive.   From here, we go on to analyze the data.  That is a great deal of work, too, but I am looking forward to doing that work, too.

One Response to “Closing the Flight Campaign”

  1. drew fenton says:

    Dear Charles Gatebe and Kurt Rush: You have the best job in the world! It seems you are very excited and interested in this important work. Can you do the Pacific Redwood coast? I’m a big fan observing your information. TO NASA: keep this program funded!
    From the public, drew
    Big Basin, Santa Cruz