Pathfinder Balloon Launch

One of the reasons scientists want us to fly their payloads over Antarctica is that they can get a long time at float, as much as 43 days. In the summer a high pressure center sets up in the stratosphere over the South Pole. This is true in the Northern Hemisphere as well in it's summer. It takes a while for the old winter low pressure system to be replaced by the high. The 24 hours of daylight continually warms the thin air of the stratosphere until it reaches a point where a nice concentric high pressure system is anchored near the Pole. Since winds in the southern hemisphere flow in a counterclockwise direction (clockwise in the northern hemisphere) that means we can launch from LDB Camp (at about 77.8 degrees South) and the balloon will float at about 120,000 feet and circle around and come back almost right back over us. In some case science groups want a longer time at float and choose to go around again. The downside to that is that the further from LDB Camp we bring the payload down, the longer it takes to recover it. In some cases the group might have to wait a year to get it back as it takes a lot of resources to recover a payload on the Antarctic Plateau or near the South Pole.

We have satellite derived wind charts available that give us an idea of what the winds are doing in the stratosphere, but these need to be verified with real measurements using balloons. Normal meteorological balloons launched from McMurdo, South Pole, and a few other stations around Antarctica rarely get above 100,000 feet. In order for us to measure winds to 120,000 to 130,000 feet we launch a small plastic balloon (small by our standards) with an instrument package attached that reports back it's altitude, latitude/longitude, and time. From this information we calculate wind speed and direction. This balloon will float for about 7 days before the package runs out of battery life. It tells us a lot during that time.

As you can see from the pathfinder track below the circulation center is over the Ross Sea and isn't over the Pole yet. That agrees with the satellite derived wind analysis. The satellite derived wind chart is valid at a pressure level of 5 millibars(mb) or 5 hectopascals(hPa) which at this time is pretty close to 120,000 feet. What that means is that conditions are not right in the stratosphere for launch of the big science payloads, but they are acceptable for launch of a smaller test balloon flight. We will try to launch that tomorrow.

BESS Flight Track from 2007:


Pathfinder Launch:


Current Pathfinder Track:


Satellite Derived Wind Chart (Data is courtesy Climate Prediction Center):