TEAM JUPITERKATHERINE BLACKBURN· SETH BURLEIGH · JOSEPH

TRAN

LaAces 2009-2010Pre-Preliminary Design

Review

Our goal is to investigate the causes of atmospheric electrical conductivity as a function of altitude. The launch will take place at the Columbia Scientific Balloon Facility (CSBF), in Palestine, Texas on May 25, 2010.

MISSION GOAL

•Alpha Particles-ionizing forms of particle radiation•Aerosols-Small particles made up of atoms which

cling to nuclei in the atmosphere•Cosmic Ray-rays of highly energized particles from space•Humidity-Clouds, haze or other moisture

collection in the atmosphere• Laminar Flow-flow of particles in a uniform direction• Shot Noise-Noise in the voltage measurement due to ions directly striking the inner electrode

DEFINITIONS

• See if there exists any correlations between air conductivity and cosmic ray activity• Show uncharacteristic fluctuations in conductivity due to meteorological

events•Compare general profiles of temperature, pressure, humidity, and altitude with conductivity

SCIENCE GOALS

WHAT IS ATMOSPHERIC ELECTRICAL CONDUCTIVITY?

• The measure of positive and negative ions in the atmosphere• Generally increases with altitude

SCIENCE BACKGROUND

Figure 1- Altitude as a function of conductivity. Most of the potential drop of the atmosphere occurs near the surface. Adapted from Reference 2.

WHAT AFFECTS ATMOSPHERIC ELECTRICAL CONDUCTIVITY?

• Pollution level of air (e.g. aerosols)• Increased radiation in an area (e.g. cosmic

rays on the atmosphere)• Wind, pressure, moisture, and humidity

(i.e. factors that affect ion mobility)

IMPLICATIONS?• Cloud formations• Thunderstorms

SCIENCE BACKGROUND

PAST PROJECTS

• Pollution measurements based on surface conductivity in Mysore, India• Balloon payload in Antarctica (Figure 2)

SCIENCE BACKGROUND

Figure 2 – There is a quasi-sinusoidal behavior of the electrical field with respect to time as shown above. Adapted from Reference 2.

• Must be able to sense small changes to see

uncharacteristic changes from surface to 100,000 feet• Altitude and time must be measured• Cosmic ray intensity and atmospheric

conductivity data needs to be compared for possible correlations

SCIENCE REQUIREMENTS

•Measurement will occur from surface level to 100,000 feet• Target ascent rate is 1000 feet per minute•Altitude, temperature, cosmic ray count, windspeed, and humidity will need to be measured

TECHNICAL GOALS

TECHNICAL BACKGROUND

0 2 4 6 8 10 12 14 16 18 200

5

10

15

20

25

30 Voltage Decay Curves at Various Air Conductivity

5000 fS 800 fS

400fS 100 fS

25 fS

Time (second)

Bias

Vol

tage

THEORY OF OPERATION: VOLTAGE DECAY• Sample 1-2 Hz for 5-20 seconds•Reset Voltage

TECHNICAL BACKGROUND

Equation - Gerdien capacitor current given V (outer voltage- inner voltage), L (length), a (conductivity), b(inner radius), and a (outer radius)

Equation - Critical mobility - the minimum ion mobility (drift velocity/electric field) that will be captured by the gerdien capacitor

Equation 3 – Conductivity vs. exponential fit time constant

Equation 4 – Capacitor current vs. combined Gerdien and measurement capacitance and change in outer-inner cylinder voltage

Equation 5 – Conductivity

Equation 6 – Theoretical cylindrical capacitor capacitance

TECHNICAL BACKGROUNDCRITICAL MOBILITY,

ION CURRENT, BIAS VOLTAGE

• A voltage-sampling rate of 1 hertz (Hz) per 10 seconds (s)

•Memory of 4050 bytes

•At lower conductance (around 100 femtoSiemens) a 12 bit analog to digital converter with a 5 voltage (V)

• The end of the inner electrode must be bullet shaped to promote laminar flow

TECHNICAL REQUIREMENTS

ROLES AND STAFFING PLAN

Table 1 – Staffing PlanCategory: Team Member: Analysis Joseph TranCalibrations Joseph TranData Processing Seth BurleighDocumentation Katherine BlackburnElectronics Seth BurleighFlight Software Joseph TranIntegration Seth BurleighMechanical Seth BurleighProject Management Katherine BlackburnScience Requirements Katherine BlackburnSystem Testing Joseph Tran

1. K. Nagaraja, B.S.N. Prasad, N. Srinivas, M.S. Madhava, Electrical conductivity near the Earth's surface: Ion-aerosol model, Journal of Atmospheric and Solar-Terrestrial Physics, Volume 68, Issue 7, April 2006, Pages 757-768, (http://www.sciencedirect.com/science/ article/ B6VHB-4JDMR5M-1/2/607a27d56c6adbf8ce265ea1ad0d8e0a)

2. E.A. Bering, A.A. Few, J.R. Benbrook, The Global electric circuit, Journal of Physics Today, Volume 51, Issue 10, 1998, Pages 24-30

3. N. Ragini, T.S. Shashikumar, M.S. Chandrashekara, J. Sannappa, L. Paramesh, Temporal and vertical variations of atmospheric electrical conductivity related to radon and its progeny concentrations at Mysore, Indian Journal of Radio & Space Physics, Volume 37, August 2008, Pages 264-271

4. K.L. Aplin, A novel technique to determine atmospheric ion mobility spectra, Journal of Atmospheric and Oceanic Physics, January 2005, (arXiv:physics/0501129v1)

5. K.L. Aplin, Instrumentation for atmospheric ion measurements, University of Reading Department of Meteorology, August 2000, Pages 1-274

REFERENCES (1/2)

6. J.P. Scott and W.H. Evans, The electrical conductivity of clouds, Journal of Pure and Applied Geophysics, Volume 75, Issue 1, December 1969, Pages 219-232 (http://www.springerlink.com/content/x804k7123mqhn3r5/)

7. R.G. Harrison, A.J. Bennett, Cosmic ray and air conductivity profiles retrieved from early twentieth century balloon soundings of the lower troposphere, Journal of Atmospheric and Solar-Terrestrial Physics, Volume 69, November 2006, Pages 515-527

8. K.A. Nicholl, R.G. Harrison, A double gerdien instrument for simultaneous bipolar air conductivity measurements on balloon platforms, Journal of Review of Scientific Instruments, Volume 79, August 2008

9. K.L. Aplin, R.G. Harrison, A computer-controlled gerdien atmospheric ion counter, Journal of Review of Scientific Instruments, Volume 71, Issue 8, August 2000

10. B. Balsey, (2009). Aerosol size distribution . Retrieved from http://cires.colorado.edu/science/groups/balsley/research/aerosol-distn.html

REFERENCES (2/2)

QUESTIONS?