1. Remote Atmospheric Sensing Device Team UNO

2. Donald Swart Donald Swart Cindy Gravois Cindy Gravois René Langlois René Langlois UNO Advisor Lawrence Blanchard Lawrence Blanchard

3. Objectives Using the measurable quantities of UV intensity: Using the measurable quantities of UV intensity: Measure total column thickness of the ozone layerMeasure total column thickness of the ozone layer Measure relative ozone concentration as a function of altitudeMeasure relative ozone concentration as a function of altitude Measure UVB and UVC as it is transmitted and attenuated through the stratosphere Measure UVB and UVC as it is transmitted and attenuated through the stratosphere

4. Background What is Ultraviolet (UV) radiation What is Ultraviolet (UV) radiation How does UV help to detect ozone? How does UV help to detect ozone? Absorption cross sections Absorption cross sections Ozone measurements Ozone measurements Beer-Lambert’s Law Beer-Lambert’s Law

5. Discovery of UV Johann W. Ritter Johann W. Ritter 1801 projected sunlight through a prism 1801 projected sunlight through a prism Chloride in each color to see the outcome Chloride in each color to see the outcome Evidence of another wave form just barely higher than the violet of visible light Evidence of another wave form just barely higher than the violet of visible light

6. What is UV? Ultraviolet (UV) radiation is part of the electromagnetic spectrum from approximately 10nm-400nm that is emitted by the sun. Ultraviolet (UV) radiation is part of the electromagnetic spectrum from approximately 10nm-400nm that is emitted by the sun. UV rays can be made artificially by passing an electric current through a gas or vapor, such as mercury vapor. UV rays can be made artificially by passing an electric current through a gas or vapor, such as mercury vapor. UV accounts for approximately 7% of total solar radiation UV accounts for approximately 7% of total solar radiation Wavelengths: Wavelengths: UVA - 320 to 400 nmUVA - 320 to 400 nm UVB - 280 to 320 nmUVB - 280 to 320 nm UVC - 200 to 280 nmUVC - 200 to 280 nm Vacuum or Far UV – 10 to 200 nmVacuum or Far UV – 10 to 200 nm

7. Determining total ozone layer thickness Recording ground intensities Recording ground intensities Using literature values for amount of UV within a specified wavelength range Using literature values for amount of UV within a specified wavelength range Using a longer wavelength sensor Using a longer wavelength sensor Beer-Lambert Law Beer-Lambert Law

8. Beer-Lambert Law  Light transmission has an exponential dependence on:  Concentration or thickness of the gas  Path length of the light  Wavelength of light  m represents the path length of light  σ represents the wavelength dependence The value of the absorption coefficient σ varies between different absorbing materials and also with wavelength for a particular material. I 0 is the intensity of the incident lightintensity I is the intensity after passing through the material m is the distance that the light travels through the material (the path length)path length A is the concentration of absorbing species in the materialconcentration  is the absorption coefficient of the absorber.

9. Determining relative concentration Rates of Change Rates of Change Density functions Density functions Relation of UV intensity to column thickness Relation of UV intensity to column thickness

10. How do we use UV measurement to determine ozone amounts? Variation of absorption levels due to different wavelengths of UV Variation of absorption levels due to different wavelengths of UV UVA is completely transmitted through ozone UVA is completely transmitted through ozone UVB is partially transmitted through ozone. UVB is partially transmitted through ozone. UVC is totally attenuated by ozone. UVC is totally attenuated by ozone.

11. Ozone Absorption cont.  “Screening” effect  Ozone peak absorption between 250 and 280 nm

12. Absorption Cross Sections Elements and compounds absorb certain wavelengths of light unique to each Elements and compounds absorb certain wavelengths of light unique to each Ozone (O 3 ) absorbs primarily UVB and UVC Ozone (O 3 ) absorbs primarily UVB and UVC The wavelengths of light (energy) absorbed is referred to as an absorption cross section The wavelengths of light (energy) absorbed is referred to as an absorption cross section

13. Ozone Absorption Cross Section Y-axis: absorption cross section in cm 2 /molecule Y-axis: absorption cross section in cm 2 /molecule X-axis: light wavelength in nm X-axis: light wavelength in nm Hartley band 210 – 380 nm Hartley band 210 – 380 nm Effectively creates a light “screen” that blocks light at certain wavelengths better than others Effectively creates a light “screen” that blocks light at certain wavelengths better than others Nearly constant values for 255 ± 10 nm Nearly constant values for 255 ± 10 nm

14. Atmospheric Cross Sections Ozone primarily absorbs between 200 and 325 nm Ozone primarily absorbs between 200 and 325 nm Other gasses responsible for shorter wavelength absorption Other gasses responsible for shorter wavelength absorption Almost no absorption at wavelengths > 350 nm Almost no absorption at wavelengths > 350 nm

15. Air mass m= sec  m= sec   Determined from the prerecorded solar zenith angles.  Expresses the path length traversed by solar radiation to reach the earth’s surface.

16. Measuring Ozone Typical unit of ozone thickness is the Dobson Unit (DU) Typical unit of ozone thickness is the Dobson Unit (DU) Defined such that 1 DU is.01 mm thick at STP and has 2.687e20 molecules/m 2 Defined such that 1 DU is.01 mm thick at STP and has 2.687e20 molecules/m 2 STP is pressure at Earth’s surface (avg.) 101.325 kPa, and a temperature of 273 K STP is pressure at Earth’s surface (avg.) 101.325 kPa, and a temperature of 273 K

17. Payload Design Electrical System Electrical System Mechanical System Mechanical System Detection Array Detection Array Power System Power System Thermal System Thermal System

18. Electrical Design Detector Array Detector Array Filtered Photo diodesFiltered Photo diodes Dark Current CompensationDark Current Compensation Controller Controller PIC16F917PIC16F917 8 16 Kb FRAM units8 16 Kb FRAM units Pressure Detection Pressure Detection Temperature Detection/Regulation Temperature Detection/Regulation

19. Electrical cont. PIC16F917Circuitry solder connections

20. Mechanical Design  Box  8x6x5 inches  Allows space for all components  Reflective tape to prevent overheating  Insulation  Styrofoam sheets  1 inch of exterior foam retains heat  Provides support for inner electronics

21. Detection Array  Photodiodes  2 filtered  Detect 255 ± 7 nm  2 unfiltered  Detect 230 – 305 nm  Arrayed opposing each other at upper box corners  Connectors  Quick disconnect male/female connector

22. Power System  Main Payload and Diodes  Energizer CR 2025 batteries  3 V, 170 mAh each  Heater  Energizer CR 2025 batteries  Stacked to provide 6V  CR 2025 are very lightweight  9 total used, less mass than standard 9 V battery  Can last 5 hours with a constant draw of 30 mA

23. Thermal System  Heat Source  4 Ω power resistors in series  Power Source  4 CR 2025 batteries  6 V, 340 mAh  Heat provided primarily to the microcontroller  Radiation

24. Sensor Calibration  UV Source  Hg, quartz envelope, lamp  Calibration  1000 watt quartz-halogen tungsten coiled-coil filament lamp Standard of Spectral Radiance .320 m spectrograph using a diffraction grating  600 grooves/mm blazed at 300 nm.  Calibrated according to NIST standards to ±2.23%  Lamp was calibrated to within ±.25Å

25. Calibration cont.  Source cont.  253.7 nm peak  Power per steradian ~ 9e-11 W ste -1  Solid angle of sensor as seen from diode:  A sensor /distance 2  Diodes  Filtered  Gain set such that 1.98e-16 W produced 1.5 V  1.32e-19 W/mV  Unfiltered  Gain set such that 1.98e-16 W produced 2.7 V  7.33e-20 W/mV  Voltage changes were inversely proportional to the square of the distance

26. Data Analysis  Data Acquisition  In situ intensity measurements  Pressure  Other Data  Solar zenith angles  Initial intensity (outer atmosphere)  Absorption cross section of ozone

27. Data Analysis cont. Ground measurements Ground measurements Total ozone columnTotal ozone column In situ measurements In situ measurements Track changes in intensityTrack changes in intensity Determine relative ozone concentrationDetermine relative ozone concentration

28. Expected Results  Flight profile:  0 to 30km  Approximately 90 minute flight  Increasing UV intensity with increasing altitude  Largest change at about 15km  The curve shown on this graph represents ozone density as a function of altitude  Using ozone coverage estimates for the area of Palestine, TX provided by NOAA and taken over the last 3 years during this week we should see about 320 DU of ozone coverage.

29. References “Atmospheric Absorption Spectrum.” HELIOSAT-3. 20 March 2007. “Atmospheric Absorption Spectrum.” HELIOSAT-3. 20 March 2007. http://www.heliosat3.de/e- learning/radiative- transfer/rt1/AT622_section10.pdfhttp://www.heliosat3.de/e- learning/radiative- transfer/rt1/AT622_section10.pdf Bevington, Philip. Data reduction and error analysis for the physical sciences. 1969. McGraw-Hill. Bevington, Philip. Data reduction and error analysis for the physical sciences. 1969. McGraw-Hill. Caroll, Bradley, and Ostlie, Dale. An Introduction to Modern Astrophysics. Second Edition. 2007. Addison Wesley. Caroll, Bradley, and Ostlie, Dale. An Introduction to Modern Astrophysics. Second Edition. 2007. Addison Wesley. Finlayson-Pitts, Barbara. Chemistry of the upper and lower atmosphere: theory, experiments, and applications. 2000. Academic Press. Finlayson-Pitts, Barbara. Chemistry of the upper and lower atmosphere: theory, experiments, and applications. 2000. Academic Press. Hamatsu Corporation. Photodiode Technical Guide. 2003. March 2007 http://sales.hamamatsu.com/assets /html/ssd/si-photodiode/index.htm Hamatsu Corporation. Photodiode Technical Guide. 2003. March 2007 http://sales.hamamatsu.com/assets /html/ssd/si-photodiode/index.htm http://sales.hamamatsu.com/assets /html/ssd/si-photodiode/index.htm http://sales.hamamatsu.com/assets /html/ssd/si-photodiode/index.htm Jacob, Daniel. Introduction to atmospheric chemistry. 1999. Princeton University Press: New Jersey. Jacob, Daniel. Introduction to atmospheric chemistry. 1999. Princeton University Press: New Jersey. Jacobson, Mark Z. Atmospheric Pollution; 2002. Cambridge University Press Jacobson, Mark Z. Atmospheric Pollution; 2002. Cambridge University Press Kistler.Piezoelectric theory and applications. 2003. March 2007. http://www.designinfo.com/kistler/ref/ tech_theory_text.htm Kistler.Piezoelectric theory and applications. 2003. March 2007. http://www.designinfo.com/kistler/ref/ tech_theory_text.htm http://www.designinfo.com/kistler/ref/ tech_theory_text.htm http://www.designinfo.com/kistler/ref/ tech_theory_text.htm Mauersberger, K. Barnes, J. Hanson, D. Morton, J. “Measurement of the ozone absorption cross-section at the 253.7 nm Mercury line.” Geophysical Research Letters 13.7 (1986): 671 – 673. Mauersberger, K. Barnes, J. Hanson, D. Morton, J. “Measurement of the ozone absorption cross-section at the 253.7 nm Mercury line.” Geophysical Research Letters 13.7 (1986): 671 – 673. NASA. Studying Earth's Environment From Space(SEES). June 2000. March 2007 http://www.ccpo.odu.edu/SEES/ozone /class/Chap_9/9_6.htm NASA. Studying Earth's Environment From Space(SEES). June 2000. March 2007 http://www.ccpo.odu.edu/SEES/ozone /class/Chap_9/9_6.htm http://www.ccpo.odu.edu/SEES/ozone /class/Chap_9/9_6.htm http://www.ccpo.odu.edu/SEES/ozone /class/Chap_9/9_6.htm

30. References cont. Physics Equations. 20 March 2007. Eric Weisstein’s World of Physics. 20 March 2007. Physics Equations. 20 March 2007. Eric Weisstein’s World of Physics. 20 March 2007. http://scienceworld.wolfram.co m/physics/http://scienceworld.wolfram.co m/physics/ Solar Zenith Angles. 20 March 2007. Solar Radiation Research Laboratory. 20 March 2007. Solar Zenith Angles. 20 March 2007. Solar Radiation Research Laboratory. 20 March 2007. http://www.nrel.gov/midc/solpo s/spa.htmlhttp://www.nrel.gov/midc/solpo s/spa.html The Aerospace Corporation. Microengineering Aerospace Systems. April 2006. March 2007. http://www.aero.org/publications /helvajian/helvajian-1.html The Aerospace Corporation. Microengineering Aerospace Systems. April 2006. March 2007. http://www.aero.org/publications /helvajian/helvajian-1.html http://www.aero.org/publications /helvajian/helvajian-1.html http://www.aero.org/publications /helvajian/helvajian-1.html Total Ozone Mapping Spectrometer. 5 March 2007. NASA. 20 March 2007. http://jwocky.gsfc.nasa.gov/dobs on.html Total Ozone Mapping Spectrometer. 5 March 2007. NASA. 20 March 2007. http://jwocky.gsfc.nasa.gov/dobs on.html http://jwocky.gsfc.nasa.gov/dobs on.html http://jwocky.gsfc.nasa.gov/dobs on.html Ultraviolet radiation. 19 March 2007. Wikipedia. 20 January 2007. Ultraviolet radiation. 19 March 2007. Wikipedia. 20 January 2007. http://en.wikipedia.org/wiki/Ultr aviolethttp://en.wikipedia.org/wiki/Ultr aviolet UV Index. 11 January 2006. National Oceanic and Atmospheric Administration. 20 March 2007. UV Index. 11 January 2006. National Oceanic and Atmospheric Administration. 20 March 2007. http://www.cpc.ncep.noaa.gov/ products/stratosphere/uv_index/u v_information.shtmlhttp://www.cpc.ncep.noaa.gov/ products/stratosphere/uv_index/u v_information.shtml Warneck, Peter. Chemistry of the Natural Atmosphere. Second edition. 1999. Academic Press. Warneck, Peter. Chemistry of the Natural Atmosphere. Second edition. 1999. Academic Press. Ozone coverage. 5 March 2007. Total Ozone Mapping Spectrometer. 17 May 2007. Ozone coverage. 5 March 2007. Total Ozone Mapping Spectrometer. 17 May 2007.