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Science BackgroundScience Background
• Cosmic rays are high Cosmic rays are high energy particles energy particles hitting the Earth’s hitting the Earth’s atmosphereatmosphere
• The initial particle The initial particle breaks into a breaks into a multitude of different multitude of different particlesparticles
• We’re interested in the We’re interested in the gamma rays that gamma rays that result from this showerresult from this shower
Science Background, Science Background, continuedcontinued
• Lead-shielded GM Lead-shielded GM tube specialized for tube specialized for detecting gamma detecting gamma radiationradiation
• Gamma radiation Gamma radiation accounts for about accounts for about one-third of the one-third of the cosmic ray countcosmic ray count
Mission GoalsMission Goals
• To measure the flux of cosmic radiation To measure the flux of cosmic radiation (excluding gamma rays) as a function of (excluding gamma rays) as a function of altitudealtitude
• To measure the flux of overall radiation To measure the flux of overall radiation as a function of altitudeas a function of altitude
• To determine the flux of gamma To determine the flux of gamma radiation versus altituderadiation versus altitude
• To determine the ratio of gamma rays To determine the ratio of gamma rays to overall flux as a function of altitudeto overall flux as a function of altitude
Payload DesignPayload Design
• Flight control unit: BalloonSAT®Flight control unit: BalloonSAT®• Power source: three 3.6V AA lithium Power source: three 3.6V AA lithium
batteriesbatteries• Geiger Müller (GM) tube to measure cosmic Geiger Müller (GM) tube to measure cosmic
ray countray count• Lead-shielded GM tube to determine Lead-shielded GM tube to determine
gamma ray countgamma ray count• Insulation and padding for structureInsulation and padding for structure
System DesignSystem Design
• Balloon to payload Balloon to payload interface: straws interface: straws and stringsand strings
• Batteries power GM Batteries power GM tube boards & tube boards & BalloonSAT®BalloonSAT®
• GM tube boards GM tube boards connect to pins P2 connect to pins P2 (shielded) and P6 (shielded) and P6 (unshielded)(unshielded)
Electrical DesignElectrical Design
• Powered by three Powered by three 3.6V AA lithium 3.6V AA lithium batteriesbatteries
• BalloonSAT® is the BalloonSAT® is the flight control unitflight control unit
• Geiger-Müller tubes Geiger-Müller tubes connect to the FCU connect to the FCU via pads P2 and P6via pads P2 and P6
• Fuse rated to ensure Fuse rated to ensure safe operationsafe operation
Component Current Draw (mA) Voltage (V) Power (mAh)Gamma Ray Sensor 5 10.8 20Cosmic Ray Sensor 5 10.8 20BalloonSAT 50 10.8 200Total 60 10.8 240
Thermal DesignThermal Design
• Thermal tests were Thermal tests were conducted with various conducted with various Fom-Cor® set-ups and Fom-Cor® set-ups and polystyrenepolystyrene
• Polystyrene was Polystyrene was chosen since it is both chosen since it is both insulating and insulating and lightweightlightweight
• Recycled blown-in Recycled blown-in insulation is added insulation is added
• Reflective tape outsideReflective tape outside
Foam Tests
-80
-60
-40
-20
0
20
40
0 500 1000 1500 2000
Cell Number
Tem
per
atu
re (*
C)
Test 1: Black Foam w/o Inner Reflective Tape
Test 2: Black Foam Only
Test 3: Only White Foam
Test 4: Only Insulation
Test 5: White Foam and Insulation
Test 6: Yellow Foam
Test 7: Polystyrene Insulation
Mechanical DesignMechanical Design
• Lead thickness is Lead thickness is 0.6cm to detect 0.6cm to detect about 2/3 of the about 2/3 of the gamma raysgamma rays
• Sheets of lead form Sheets of lead form a partial cylinder a partial cylinder shield around the shield around the GM tubeGM tube
• Total weight: 615gTotal weight: 615g
Interaction Percentage vs. Mass
0
20
40
60
80
100
0 100 200 300 400 500
Mass (g)
Inte
racti
on
Perc
en
tag
e (
%)
Series1
Weight (in g) Component
64 Radiation sensor
64+Lead(163) Gamma Ray sensor
63 Balloon Sat
58 Power (Batteries)
69 Polystyrene InsulatingStructure
81 Wires and extras
53 Recycled Blown inInsulation
615 Total
Mechanical Design, cont.Mechanical Design, cont.
• Top view with vertical insertTop view with vertical insert• Recycled blown-in insulation added in Recycled blown-in insulation added in
open spaces (in plastic baggies)open spaces (in plastic baggies)
Mechanical Design, cont.Mechanical Design, cont.
• Top view, cont.Top view, cont.
• Side viewSide view
SoftwareSoftware
• Geiger modeGeiger mode• 256Kb memory chip 256Kb memory chip • Reset Basic Stamp programReset Basic Stamp program• Data acquisition program:Data acquisition program:
• time is set to standard time (Greenwich) to time is set to standard time (Greenwich) to synchronize with altitude datasynchronize with altitude data
• sampling intervals (each 18.1 seconds per sampling intervals (each 18.1 seconds per interval)interval)
• timestamp to correlate with altitudetimestamp to correlate with altitude
Software, cont.Software, cont.
• Data Retrieval:Data Retrieval:• certain steps need to be taken to get the raw certain steps need to be taken to get the raw
data into Exceldata into Excel• data for each tube is organized into four data for each tube is organized into four
columnscolumns
• Program to correlate counts with altitudeProgram to correlate counts with altitude• Filtering of data: Filtering of data:
• organization of Excel spreadsheetorganization of Excel spreadsheet• averaging three consecutive counts to yield an averaging three consecutive counts to yield an
average count per intervalaverage count per interval
Temperature TestTemperature Test
• Confirm the power source could last in upper Confirm the power source could last in upper atmosphere temperaturesatmosphere temperatures
• Confirm that there is no dependence of the Confirm that there is no dependence of the measurement on temperature measurement on temperature
• Payload passed the testPayload passed the test• was working when we took it out of the dry ice was working when we took it out of the dry ice
chamberchamber• data showed no dependency on the cold data showed no dependency on the cold
temperaturestemperatures
Pressure TestPressure Test
• Because our vacuum source was not Because our vacuum source was not operational, a pressure test was impossibleoperational, a pressure test was impossible
• We verified that each material would not We verified that each material would not “blow up” in the low pressure environment“blow up” in the low pressure environment
• We determined from past flights using the We determined from past flights using the same materials that we would not encounter same materials that we would not encounter any issuesany issues
Shock TestShock Test
• The payload was dropped from a height of The payload was dropped from a height of 10 feet to simulate the force felt upon 10 feet to simulate the force felt upon landing because the nominal descent rate is landing because the nominal descent rate is approx. 20 feet/sec.approx. 20 feet/sec.
• The drop moved the switches on the GM The drop moved the switches on the GM tubes, so we put electrical tape on the tubes, so we put electrical tape on the switches to hold them in place.switches to hold them in place.
• Nothing was damagedNothing was damaged