50 February 2018
APPROACHING THE FINAL FRONTIER
would block the light from the sun. I connected an LM335
temperature sensor to a flight computer and then placed
the sensor outside in the open air. The results can be seen
in the graph.
The chart shows the changes in the air temperature
pausing between the troposphere and stratosphere (at
between 40,000 and 50,000 feet). The boundary between
the troposphere and stratosphere is called the tropopause
because changes in the air temperature pause during this
transition. My balloon flights don’t always detect the pause,
but the eclipse flight did.
If there was an atmospheric temperature effect from
the eclipse, then the tropopause is hiding it. Due to bad
timing on my part, the balloon was in the wrong place at
the wrong time for this experiment.
Another successful experiment on the eclipse flight
was conducted with my eight-channel LED photometer.
The photometer is based on the work of Forrest Mims
who discovered that LEDs produce a small current when
exposed to light close to the color they emit. This makes
them color-selective and an inexpensive way to measure
the intensity of light in specific frequencies.
The BalloonSat carrying this experiment oriented the
LEDs of the photometer straight up. However, rocking and
spinning of the BalloonSat resulted in the LEDs changing
their pointing direction throughout the flight.
As I said, the photometer has eight channels.
Those came from the eight different LEDs built into the
photometer. The LED colors were violet/
ultraviolet, blue, green, yellow, orange, red,
infrared at 890 nm, and infrared at 940
nm. Blue and violet light are most strongly
scattered by the atmosphere (hence, our blue
sky) and red is the least scattered. Therefore,
I was expecting to see the brightness of the
sky change at different rates for the colors of
the spectrum (red most affected and violet
least affected). As some of the photometer
charts show, the sky affected all the colors of
the spectrum equally.
I suspect the wider variation in violet-UV intensity below 20,000 feet and above
60,000 feet is due to the sensor getting
saturated. Otherwise, the way the intensity
of these three colors changed is basically
identical. You can see as the balloon
approached totality at 44,000 feet, the
sky’s intensity in every color went to zero
— regardless of the photometer’s pointing
My Next Solar Eclipse Launch
The next total solar eclipse to cross the United States
occurs on April 8, 2024. The path of totality begins in
Texas and travels northeast to Lake Erie and Lake Ontario.
This eclipse will take place on a Monday, which means it’s
a school day. Therefore, I’m going to need to take some
vacation days if I want to study this eclipse.
Because of my experience with last August’s eclipse, I
want to make the following changes for the next one. First,
I’ll launch multiple balloons. It’s important to cover a range
of altitudes during the eclipse. That way, data can tease out
subtle effects the eclipse may have on Earth’s atmosphere.
Besides, launching redundant payloads on balloons is
an insurance policy for the possible failure of any one
Next, I’ll add a second Geiger counter to the balloon
(or balloons). The random nature of cosmic radiation
makes it difficult to measure small variations in the number
of particles detected per minute. With multiple Geiger
counters, I can isolate variations that appear regardless of
their altitude. Even if the Geiger counters were on the same
balloon, I would expect to have better luck measuring
variations in the cosmic ray flux.
Third, I’ll make a video recording of the neutron
detector during the flight. By relating the time a bubble
appears with the time of the mission, I can determine the
altitude that each detection takes place. According to
Bubble Tech, the bubbles appear rapidly, so their detection
in the resulting video will be easy. Unfortunately, it will be a
boring process of watching over two hours of video of just
Totality occurred when the balloon was between an altitude of 43,000
and 45,000 feet. Unfortunately, there’s no sign of an unexpected
temperature change between those altitudes.