UAVSonde for NearSys Station, 19 February 2017

UAVSonde data were collected at 7:10 AM. Here are the data.

Altitude 2260 feet
Temperature 36 *F
Relative Humidity 100%
Pressure 1002.9 mb

Altitude 2637 feet
Temperature 40 *F
Relative Humidity 100%
Pressure 985.0 mb

Fun with Electrostatics Class: Day 1

The first day of Fun with Electrostatics taught students the history of electrostatics (briefly), the background on the nature of electrostatic charge, and the triboelectric series. The students then did basic experiments to reinforce what they were taught. These experiments included charging objects by friction, polarization, and conduction and seeing that like charges repel each other.

Kurt levitating a plastic ring using only electrostatic charge.
It's science magic! 

    

Great Horned Owl

On many of my recent evening walks, I have caught the hooting call of two Great Horned Owls. I have even managed to catch sight of one of them. This evening's walk was a little different in the owl decided to stay in place as I used my cellphone camera to get a picture of him or her.

Ever get the feeling you're being watched?

A modification to the BalloonSat Recording Photometer expanded it's capabilities to function as a Photopolarimeter. A Photopolarimeter is a device to measure the intensity of light in different wavelengths and their amount of polarization. Most people are familiar with the fact that the brightness of light varies throughout the day, but not to the fact that the sky polarizes sunlight and how it can change throughout the day. The images below show how sky brightness varies as a Polaroid filter is rotated 90 degrees.

The experiment run at NearSys Station on February 11, 2017 was an attempt to detect both changes in polarization and intensity of sunlight in the eight different spectral bands listed below.

Infrared (940 nm)
Infrared (890 nm)
Red (660 nm)
Orange (620 nm)
Yellow (595 nm)
Green (505 nm)
Blue (470 nm)
Violet/UV (400 nm)

Polarization was measured in the North-South direction and then the East-West direction by comparing the intensity of sunlight in the above eight spectral bands as a polarizing filter was rotated over the light sensors. During the experiment, the Photopolarimeter was pointed due south and at an elevation of close to 45 degrees.

Sunrise occurred at 7:48 AM and sunset at 6:11 PM (18:18 hours). The sun was due south at 1:00 PM (13:00 hours). The sun's elevation at 1:00 PM was 32.5 degrees.

The Photopolarimeter slipped at 2:17 PM (14:17 hours) and remained pointing up until corrected at 2:41 PM (14:41 hours). However, the angle the Photopolarimeter was reset to was slightly lower in elevation that before.

Here are some things to notice.

1. From sunrise to 10:00 AM, sunlight has greater polarization in the East-West direction than North-South direction. At 10:00 AM, the sun was located at an azimuth of 133 degrees (southeast) and elevation of 19.5 degrees.

2. From 10:00 AM to 1:00 PM, sunlight has greater polarization in the North-South direction than the East-West direction. At 1:00 PM, the sun was located at an azimuth of 180 degrees (south) and elevation of 32.5 degrees.

3. From 1:00 PM to 4:15 PM, sunlight has greater polarization in the East-West direction than North-South direction. At 4:15 PM, the sun was located at an azimuth of 230 degrees (southwest) and elevation of 17.2 degrees.

4. After 4:15 PM, sunlight has no preferential polarization.

5. The amount of polarization is greatest at yellow (595 nm) and weakest at infrared (940 nm and 890 nm) and violet/UV (400 nm).

6. The intensity of red (660 nm) and infrared (890 nm and 940 nm) spiked from 5:35 PM to sunset. This peak was not observed in any other colors. At 5:35 PM, the sun was located at an azimuth of 246 degrees (west-southwest) and elevation of 6 degrees.

The Photopolarimeter will run several more days, weather permitting. The next experiment will involve placing the Photopolarimeter straight up. Later, the experiment will be run a third time with the Photopolarimeter pointing at the horizon. Later experiments will point it to the north.

An Update
After a discussion with Mr. Forrest Mims, I came to realize that Polaroid film is designed to be most effective at particular wavelengths. Since the Polaroid film I used is designed for eyeglasses, it should be more effective in the green-yellow portion of the electromagnetic spectrum (where human eyes are most sensitive). That may explain the greater polarization seen by the green and yellow LEDs.

Photons in the blue end of the spectrum have wavelengths so short that they can pass through the Polaroid film in either vibration orientation. Photons in the red end have wavelengths so large they can't be effected by the Polaroid film.

So off to find new polarization films.

You can read what Mr. Mims is up to at his website, forrestmims.org.

UAVSonde for NearSys Station, 11 February 2017

UAVSonde data were collected at 5:15 PM. Here are the data.

Altitude: 2226 feet
Temperature: 43 *F
Relative Humidity: 33%
Pressure: 1016.0 mb

Altitude: 2624 feet
Temperature: 43 *F
Relative Humidity: 25%
Pressure: 1014.0 mb

This is the first UAVSonde to detect no change in air temperature at altitude.

UAVSonde for NearSys Station, 4 February 2017

UAVSonde data was collected at 4:15 PM. Here are the data.

Altitude 2283 feet
Temperature 47*F
Relative Humidity 46%
Air Pressure 1012.7 mb

Altitude 2676 feet
Air Temperature 50*F
Relative Humidity 42%
Air Pressure 994.9 mb

The data shows a temperature inversion over NearSys Station. Data further indicates that the relative humidity peaked at 54% at an altitude of 2375 feet. This is the first time I recall seeing the relative humidity peak during ascent like this. I will need to watch this more closely on future sonde flights.

Community Education Class on Electrostatics

I'm preparing my next Community Education with the Boise School District. This class begins on February 15th and teaches an introduction to electrostatic. Like my other classes, this one will also be strongly project based. The image below shows all the projects my students will build as they learn about electrostatics.

Students taking Introduction to Electrostatics will build and test the following items.

1. Charging items through friction, induction, and conduction.
2. Electrophorous
3. Leyden Jar
4. Versorium
5. Electroscope
6. Paschen Want
7. FET Electrometer

You still have to sign up for this class. Visit BoiseLearns.org for information and registration.