The Sky’s the Limit:

Monitoring the Earth’s Radiation Balance with Active Cavity Radiometers

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

Llian Breen, Aaron Buys, and John Vander Weide

Team

Members

Team

Members

AaronBuys

John Vander Weide

LlianBreen

Outline

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

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

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 CO2 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 CO2 has increased •285 ppm (pre-industrial)•365 ppm (current)

•Is there a correlation?

http://education.arm.gov

increases

Predictions of

GW

Models

Predictions of

GW

Models

CO2 Temp=>

CO2 H2O

Temp

CO2

H2O

increases

Increased SolarAbsorption

H2O increases

Increased Precipitation

http://www.pnl.gov/

How can

we know?

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

ComputationalModels

Direct Measurement

TemperatureGas concentrations

Precipitation

Radiation

?

ACRAnd Us

Satellite

Measurements

Satellite

Measurements

Earth Surface

ACR FOVSat. MeasurementsInterpolated Fluxes35 km Location

ACR FOVSat. MeasurementsInterpolated Fluxes35 km Location

Interpolations viaProblematic

Ground Cover& Radiative Models

Interpolations viaProblematic

Ground Cover& Radiative Models

800 km

ACR Theory

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

Design

Overview

Cavity

Earth

Thermistors

Battery

Radiosonde Transmitter

Receiver Computer

Heater

Controls Set Point

Current and Volt MeterACR

Package

FlightPackage

Project

Challenges

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

Milestones

•Thermal Package Design

•Thermal Package Design

Algor© Thermal Model

Ensure negligible

radial heat leak with proper

conductive and radiative insulation

Milestones

Milestones

•Active Cavity Coating Design

•Active Cavity Coating Design

Cavity coating must absorb light over the

longwave thermal

spectrum

http://master.jpl.nasa.gov/reference/paints.htm

Krylon UFB

Krylon Ultra Flat Black

Paint

Milestones

Milestones

•Passive Time Constant Determination

•Passive Time Constant Determination

Milestones

Milestones

•Passive Time Constant

•Passive Time Constant

Data

Model

Data curve fit provides

characteristic heating time

without active control

τp=154 sec

Milestones

Milestones

•Tuning PI Circuit with Thermo-electric Model

•Tuning PI Circuit with Thermo-electric Model

=

Transfer Function:

+Good CircuitTuni

ngStrange Magic

Luck

Milestones

Milestones

•Tuning PI Circuit with Thermo-electric Model

•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

Milestones

•Tuning PI Circuit with Thermo-electric Model

•Determining Tuning Parameters

•Tuning PI Circuit with Thermo-electric Model

•Determining Tuning ParametersSteady State Temperature Variation with Heater Current

Milestones

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

τp=154 sec

τa=38 sec

Milestones

Milestones

•Printed Circuit Board Layout

•Printed Circuit Board Layout

Milestones

Milestones

•Printed Circuit Board Layout

•Printed Circuit Board Layout

Milestones

Milestones

•Interfacing with Intermet Radiosonde System

•Interfacing with Intermet Radiosonde System

Milestones

Milestones

•Interfacing with Intermet Radiosonde System

•Interfacing with Intermet Radiosonde System

Antenna

Receiver

Cavity

Controls

Sonde

To Software

Final

Design

Final

Design

•Active Control

•Active Control

Prototype

Design

Prototype

Design

•Radiometer Cross-Section

•Radiometer Cross-Section

Cavity

Conductive Insulation

Radiative Insulation

Heat Sink

Structural Shell

Prototype

Design

Prototype

Design

Prototype Testing

Prototype Testing

Grand Rapids 8:26pm

Lansing 9:36pm

Fowlerville 10:42pm

Prototype Testing

Prototype Testing

Prototype Testing

Prototype Testing

Jet Stream

Flight

Data

Flight

Data

Jet Strea

m

Lessons

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

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 (2003-04)

•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 (2003-04)

Questions?

Questions?

Stratospheric

Balloon

Measurements

Stratospheric

Balloon

Measurements

Earth Surface

Balloon Measurements35 km LocationBalloon Measurements35 km Location