The Sky’s the Limit: Monitoring the Earth’s Radiation Balance with Active Cavity Radiometers Calvin College Senior Design May 7, 2005 Calvin College Senior Design May 7, 2005 Llian Breen, Aaron Buys, and John Vander Weide

Team Members Aaron Buys John Vander Weide Llian Breen

Outline Project Objectives Motivation Design Overview Challenges Design Milestones Prototype Testing Project Assessment Acknowledgements Project Objectives Motivation Design Overview Challenges Design Milestones Prototype Testing Project Assessment Acknowledgements

Project Objectives Two-fold project goal: Design an Active Cavity Radiometer Test design in operating environment Two-fold project goal: Design an Active Cavity Radiometer Test design in operating environment

Global Warming Facts The average surface air temperature of the earth has increased over the past 100 years. 56 F (1900) 57 F (2000) The concentration of CO 2 has increased 285 ppm (pre-industrial) 365 ppm (current) Is there a correlation? The average surface air temperature of the earth has increased over the past 100 years. 56 F (1900) 57 F (2000) The concentration of CO 2 has increased 285 ppm (pre-industrial) 365 ppm (current) Is there a correlation?

increases Predictions of GW Models CO 2 Temp => CO 2 H2OH2O Temp CO 2 H2OH2O increases Increased Solar Absorption H2OH2O increases Increased Precipitation

How can we know? Current Tacks in Climatology Simulation and Modeling Direct Measurements Temperature Greenhouse gas concentration Precipitation RadiationRadiation Model vs. Measurement needs to observe long term trends Current Tacks in Climatology Simulation and Modeling Direct Measurements Temperature Greenhouse gas concentration Precipitation RadiationRadiation Model vs. Measurement needs to observe long term trends Computational Models Direct Measurement Temperature Gas concentrations Precipitation Radiation ? ACR And Us

Satellite Measurements Earth Surface ACR FOV Sat. Measurements Interpolated Fluxes 35 km Location ACR FOV Sat. Measurements Interpolated Fluxes 35 km Location Interpolations via Problematic Ground Cover & Radiative Models Interpolations via Problematic Ground Cover & Radiative Models 800 km

ACR Theory How does it measure radiation? Active control of cavity temperature Variation of outgoing radiation Cavity shutter measurement How does it measure radiation? Active control of cavity temperature Variation of outgoing radiation Cavity shutter measurement

Design Overview Cavity Earth Thermistors Battery Radiosonde Transmitter ReceiverComputer Heater ControlsSet Point Current and Volt Meter ACR Package Flight Package

Project Challenges Thermal Package Design Power balance estimation Heat leak estimation Cavity Design Cavity size Cavity heater Cavity coating Cavity thermal time constant Controls Design: PI Control Circuit debugging Joint thermo-electronic model Thermal Package Design Power balance estimation Heat leak estimation Cavity Design Cavity size Cavity heater Cavity coating Cavity thermal time constant Controls Design: PI Control Circuit debugging Joint thermo-electronic model

Milestones Thermal Package Design Algor © Thermal Model Ensure negligible radial heat leak with proper conductive and radiative insulation

Milestones Active Cavity Coating Design Cavity coating must absorb light over the longwave thermal spectrum Krylon UFB Krylon Ultra Flat Black Paint

Milestones Passive Time Constant Determination

Milestones Passive Time Constant Data Model Data curve fit provides characteristic heating time without active control τ p =154 sec

Milestones Tuning PI Circuit with Thermo-electric Model = Transfer Function: + Good Circuit Tuning Strange Magic Luck

Milestones Tuning PI Circuit with Thermo-electric Model VanBaak, D.A. Am. J. Phys. 60 (9), Sept 1992 Thermal Model Controls Model Couple Models Open Loop Testing Tuning Parameters

Milestones Tuning PI Circuit with Thermo-electric Model Determining Tuning Parameters Tuning PI Circuit with Thermo-electric Model Determining Tuning Parameters Steady State Temperature Variation with Heater Current

Milestones Tuning PI Circuit with Thermo-electric Model Comparison of passive and active cavity response Tuning PI Circuit with Thermo-electric Model Comparison of passive and active cavity response τ p =154 sec τ a =38 sec

Milestones Printed Circuit Board Layout

Milestones Printed Circuit Board Layout

Milestones Interfacing with Intermet Radiosonde System

Milestones Interfacing with Intermet Radiosonde System Antenna Receiver Cavity Controls Sonde To Software

Final Design Active Control

Prototype Design Radiometer Cross-Section Cavity Conductive Insulation Radiative Insulation Heat Sink Structural Shell

Prototype Design

Prototype Testing Grand Rapids 8:26pm Lansing 9:36pm Fowlerville 10:42pm

Prototype Testing

Jet Stream

Flight Data Jet Stream

Lessons Start models/prototypes early Define project early… and often Design is in the details… and in the big picture Start models/prototypes early Define project early… and often Design is in the details… and in the big picture

Acknowledgements Professor David Van Baak (Calvin) Professor Matthew Heun (Calvin) Professor Steven Vander Leest (Calvin) Robert Berrington (Intermet) Robert Houskamp (Intermet) NASA Institute for Advanced Concepts (NIAC) Senior Design Team 6 ( ) Professor David Van Baak (Calvin) Professor Matthew Heun (Calvin) Professor Steven Vander Leest (Calvin) Robert Berrington (Intermet) Robert Houskamp (Intermet) NASA Institute for Advanced Concepts (NIAC) Senior Design Team 6 ( )

Questions?

Stratospheric Balloon Measurements Earth Surface Balloon Measurements 35 km Location Balloon Measurements 35 km Location