LSU 06/04/2007 Student Payload Experiments 1

Student Payload Choices

Ballooning Unit, Lecture 5

LSU 06/04/2007 Student Payload Experiments 2

Your balloon payload

• Limited to about 500 grams weight

• Roughly a cube with 15 cm to 20 cm long sides

• Mechanical structure constructed from foam core board

• Vehicle interface is a pair of strings, separated by ~17 cm, that pass through the payload unbroken and secured with spring clips.

Payload mechanical interface

• Need to conduct some kind of science or technology experiment

• Designed, built, tested and shown to be fully “space worthy” by May of next year.– Will have about 14 weeks to complete this phase.

• 48 hours after launch you will need to have calibrated science results from your flight and present your results to an audience of professional scientists and engineers.

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Need to begin thinking now!

• Given the constraints, you need to think about and address issues throughout the academic year

• Here we discuss some example payloads that have either been previously developed and flown or which should be feasible to develop and fly within the limitations of this program– You need to choose one of these payloads to work on!

• During the current “skill building” phase then …– Research the scientific background for your payload– Think about how a particular activity / concept applies to your payload

(I guarantee that they ALL apply) and keep track of these in a payload “design” notebook

– Determine who in your group has similar interest or complimentary skills and begin developing a team

– Develop hardware / software prototypes as an activity extension

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Potential Payload Topics

• “Look up” experiments– Cosmic ray intensity

– Cosmic ray components

– UV transmission through atmosphere

– IR emission

• “In-situ” experiments– Atmosphere temperature,

pressure profile

– Atmosphere ozone profile

– Atmosphere humidity profile

– Atmosphere “trace gas” profile (more difficult)

• “Remote sensing” experiments– Imaging the ground and/or limb

– Multispectral (filtered) imaging of the ground

• “Technology” experiments– Balloon payload dynamics

– Solar cell efficiency

– Video camera imaging (live or recorded)

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Cosmic Ray Intensity• Cosmic rays are high energy nuclei

that originate outside our solar system.

• CR interact in Earth’s atmosphere producing a shower of particles

• The intensity of this radiation varies with altitude

• This payload would determine the radiation flux as a function of altitude on ascent and descent

• Simple to implement detector system by using a hand-held radiation monitor

• Most effort will be in understanding what “flux” is and doing the appropriate calibrations to convert your measurement to flux.

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Cosmic Ray Components

• Cosmic rays include electrons, protons, heavy nuclei (He to beyond Iron) plus interaction products such as neutrons, pions, muons, etc.

• This payload would try to measure the relative abundances of some of these components.

• Use multiple detector systems with different thresholds.– Geiger-Muller tube for electrons, protons– Plastic scintillator with a photodiode for higher energy

deposits produced by heavy ions

• To compare multiple detector system it will be critical that you can determine the correct “flux” for each detector.

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Transmission through atmosphere

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UV Transmission• UV is absorbed by ozone in the upper atmosphere• Payload would measure the UV intensity as a

function of altitude and infer the vertical distribution of ozone

• One or more sensors (or the appropriate wavelength sensitivity) would monitor UV from the Sun.

• The signal from the sensor would need to be conditioned and converted to a digital number by an ADC

• You will need to take into account rotation of the balloon craft

• Calibrations of sensor and ADC will be needed to determine flux

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Infrared Emission

• Sun energy is absorbed by objects on Earth (ground, clouds, atmosphere) and emitted in the infrared wavelengths (8 – 15 microns), further astronomical objects, such as the Sun, emit infrared energy.

• This payload would implement an infrared sensor to measure the temperature of some particular object.

• The signal from the sensor will need to be conditioned and converted to a digital number by an ADC.

• You will need to take into account rotation of the ballooncraft.• You may also need to account for temperature dependences in

your sensor and/or electronics.• The trick here is to understand what your sensor is looking at and

to have the calibrations necessary to convert your measurement to a temperature.

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Atmospheric Structure

Typical max balloon altitude ~ 30 km

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Temperature, Pressure Profile

• The temperature and pressure of the atmosphere varies as a function of altitude.

• Temperature initially decreases with increasing altitude, then increases as UV is absorbed in the atmosphere.

• Pressure decreases in an exponential manner

• This payload would implement temperature and pressure sensors to measure this variation.

• Need to understand sensor & ADC range & accuracy.

• Compare with standard atmosphere model

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The Distribution of Ozone• The ozone layer, located between 15 – 50 km

altitude, shields the Earth from high frequency UV components by absorbing this radiation.

• Payload would use a standard electrochemical concentration cell (ECC) to measure the ozone density as a function of altitude

• Will also need to measure temp. and pressure

• ECC is based upon an iodide – iodine redox reaction using a potassium iodide solution, so you will need to keep your sensor from freezing.

• Calibration of your sensor is essential• This is a more challenging experiment, but

doable.

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Absolute Humidity

• The amount of water vapor in the stratosphere may be directly dependent upon interactions between ozone, UV and methane. There are few in-situ studies of humidity at high altitude and a poor understanding of the mechanisms that control it.

• Payload would include humidity and temperature sensors to obtain the absolute concentration of water vapor as a function of altitude

• May also want auxiliary measurements to look for possible causal relationships.– Include UV and/or methane sensor– Collaborate with another team doing UV or methane measurements

• Will need to condition sensor signals and use an ADC to obtain digital information

• Will need to understand sensor / ADC range and accuracy

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Trace gas profiles

• There are many other components in the atmosphere that could be interesting to measure as a function of altitude– Methane, Carbon Dioxide, Chlorofluorocarbon compounds

• Requires an appropriate sensor that could fit within the balloon payload power, size and weight constraints

• Likely to be temperature dependent, so will need to monitor temperature and calibrate sensor for flight conditions.

• May need to monitor pressure to obtain absolute levels

• Could collaborate with multiple teams, each measuring a single component.

• This would be a challenging payload

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High Altitude Imaging

• Payload would fly a digital camera and be automatically controlled to take a series of images

• May need to include a polarizing filter to cut down on glare• Need to record images on non-volatile media to avoid loss during

power off• Will need thermal-vacuum testing to assure system will function

correctly.

• Provide aerial view of ground or Earth limb from low to high altitude

• ACES program has yet to achieve high quality images from high altitude

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Multi-spectral Imaging

• Remote sensing images taken of the same area but in different frequency bands can be used to distinguish between healthy vegetation, water features, surface roughness and other characteristics.

• Payload would include multiple cameras each of which would take a image through a different “color” filter. (e.g. IR, “green”, UV)

• Alternate payload would have one camera and a wheel that would include multiple filters. Software would then rotate the wheel one increment prior to taking the image

• Camera will need different exposure times depending upon which filter is used.

• This will be a very interesting and challenging experiment!

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Technical Payloads

• Measure the dynamics of the payload through use of accelerometers and/or tiltmeters.– Form basis of an inertial position sensing system– Investigate use of balloon payload for g experiments

• Measure the efficiency of various solar cells– Can balloon payloads be powered by solar cells?– Record voltage and current for each cell

• Develop a compact video camera payload and record specific events during the flight– Main problem here is weight– Telemeter video signal down to ground?

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Your Own Idea

• You can also develop an alternative payload based upon your own idea.

• However, keep in mind that your payload must have a relevant “science / technical” goal and must be feasible given the payload weight, power, budget and time constraints.

• The payloads identified here can be developed so they fit within these constraints.

• In any event you need to begin your payload planning now!