The TV crew went out to two different islands on two different helicopters today to check off the very last items on the "shoot list" (i.e. the list of things they wanted to tape.) Erica went back to the island of Legan to tape retrieval of data from the acoustic microphone. Jeff Nystuen needed to leave directions for somebody else to download data, because Jeff's stay on Kwajalein didn't coincide with any days that helicopters were flying. John Hubbert was designated as the person to download data and so when John got off the plane from Honolulu yesterday, we handed him the directions and told him to meet the helicopter at 6:45 AM. What a way to start a trip!

Rich and I flew to Meck in order to tape the tethersonde operation. This picture captures much of the operation. The tethersonde is simply an instrument that measures wind, pressure, temperature and humidity (the sonde part) that is hanging from a balloon that is attached to a cable (the tether part). In this picture the balloon is at a "parking height" of 30 meters. The aim is to get the balloon up to 1,000 meters altitude. The cable is 1,200+ meters long because the balloon is always blown sideways by the wind and so the cable needs to be longer than the 1,000 meter goal. The balloons that I will be releasing next week (radiosondes) are hooked to a helium balloon that rises through the atmosphere until it bursts. The tethersonde allows the researcher to set the sonde and different altitudes and leave it there for a period of time.

Here is the sonde that hangs down from the balloon. In this picture, the sonde has just been hooked to the cable where the cable is coming out of a series of pulleys. To haul the balloon up and down to 1,000 meters there is an electric winch that does most of the work. One balloon was destroyed early in KWAJEX by a storm that smashed the balloon into the ground from its normally-safe parking height. Now when severe storms are forecast the crew hauls the balloon down by hand for the last 30 meters. That job requires four people to handle safely. The winch sure makes normal operations a lot easier!

One obvious advantage of a tethersonde is that one can retrieve the sonde. Radiosondes are released and used only once. Making the sonde retrievable means you can pack more powerful (and more expensive) instruments. Here is the inside of the white canister portion of the sonde. That is a small palmtop computer inside, collecting all the data from the sensors. Needless to say, one would not be able to put such a computer on a single-use sonde!

As if handling the balloon weren't enough, the tether sonde project also runs this 10-meter tower with sensors that sample water vapor and carbon dioxide at four different heights, and plus wind direction and speed, temperature, pressure and humidity. That allows a cross-check, so that sensors on the tower and sensors on the sonde are compared at the beginning and the end of each launch of the balloon. If those sensors don't agree, the problem can be diagnosed and hopefully fixed promptly. Of course, when the sensors do agree (and they almost always do) then we have more confidence in BOTH sensors than we could possibly have in just a single sensor.

This trip also gave me a chance to check out the island of Meck from the ground. Meck gives you the feel that you are on an island in the middle of the Pacific. Kwajalein and Roi have been developed enough so that you get a bit of a feel that they are a community, even close to suburbia in parts. Meck is a rock with buildings and concrete. Meck is a place to work. Right now, the Meck radiosonde operation is not functioning. But parts arrived yesterday and will be installed tomorrow and hopefully all will be well. If so, I will be back to Meck in just a few days releasing radiosondes six times a day! The TV crew left today. My radiosonde training begins tomorrow....

Alan Nelson