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LA ACES Program Balloon Sat Payload: Light Emission Ratio(LER) Scientific Analysis. Zeb Menle Norberto Ríos Alexander Santiago. Goals. To collect temperature in °C and Light Intensity in Watts /m2. Accurate data Acquisition Recover the payload in near perfect conditions.
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LA ACES Program Balloon Sat Payload: Light Emission Ratio(LER)Scientific Analysis Zeb Menle Norberto Ríos Alexander Santiago MECN 3974
Goals • To collect temperature in °C and Light Intensity in Watts /m2. • Accurate data Acquisition • Recover the payload in near perfect conditions MECN 3974
Scientific Background • Electromagnetic Spectrum: 190nm-1100nm • The spectrum of the radiation emitted by the sun is close to that of a black body at a temperature of 5,900K. About 8% of the energy is in the ultra-violet region, 44% is in the visible region, and 48% is in the infra-red region. MECN 3974
Scientific Background • Electromagnetic Spectrum • EM waves are typically described by any of the following three physical properties: the frequency, f, wavelength, λ, and photon energy, E. Frequencies range from 2.4x1023 Hz (1 GeV gamma rays) down to tiny fractions of Hertz. • Photon energy is directly proportional to the wave frequency c = 299,792,458 m/s (speed of light in vacuum) and h = 6.62606896(33)×10−34 J·s (Planck's constant). MECN 3974
Scientific Background • Temperature Estimation MECN 3974
Scientific Background • Temperature Estimation MECN 3974
Scientific Background Light Intensity (W/m^2) MECN 3974
Scientific Background Light Intensity (W/m^2) • In order to obtain the relation between (W/m2) with current, we need to calculate the photon energy, the quantum efficiency. MECN 3974
Scientific Background Light Intensity (W/m^2) • The received Watts (light) is linear with the current, thus; I = (R)(P), where I is the photocurrent, R is the Responsivity, and P is the power. In our case: MECN 3974
Payload Design: Principle of Operation • Sensing and Storage System: • Sensors (Photodiodes and RTDs) • Data Acquisition subsystem (DAQ) • Controller Subsystem • Data Archive subsystem • Power System • Thermal system • Mechanical system MECN 3974
Payload Design: Principle of Operation Insulation Photodiode CAS Photo D. Micro-controller Analog BUS Logic RTC Peak Det. RTD ASW Voltage REF. Analog BUS BUS 3V Analog CAS RTD Mem. ADC Analog RTD Analog Analog Analog CAS Photo D. Analog ± 5V + 5V Photodiode MECN 3974
Payload Design: Principle of Operation MECN 3974
Data Result So, what do I have???
Data Result Massive Failure
Proof Plot: External Temperature vs. time
Proof Plot: Internal Temperature vs. time
Proof Plot: Light Intensity vs. Time Blue line (upper photodiode) & Brown line (bottom photodiode)
Possible Causes Poor PCB Design: Weak Connections Some cheap connectors, eventually will broke apart. It depends how many times you keep plug & unplug it.
Possible Causes Poor PCB Design: Weak Connections
Possible Causes Poor PCB Design: Thin routes
Possible Causes Poor PCB Design: unadjusted cables
Possible Causes Poor PCB Design: Inappropriate route repairs
Possible Causes Poor PCB Design: improper way of fixing the PBasic inside the box.
Possible Causes The Inner Temperature detector: is part of the Pbasic, so… It might be broken? Values were stable, but not in place. The blue potentiometer’s value, was not set correctly, in order to establish a proper feedback with the IC AD820
Possible Causes However, the Pbasic samples every 4 sec garbage for a period of ± 12 min. Then after, the EEPROM shows 0 on the debug screen until the POST-FLIGHT ends.
Possible Causes Did the batteries discharge very quickly? Impossible, PBasic battery was at 8.25V and –Vcc = 8.84V With batteries almost intact, and only 150 samples saved in memory, then a possible explanation is…
Conclusion Is a perfect example of “Go Home and do it Again”
Conclusion Suggestions: • When making PCB, it is recommended to draw the routes with a reasonable thickness. • Make the fabrication of the PCB as formal as possible. • You may use the PCB even with few minors repairs, otherwise, move on to construct another (you may consider change the drawing as well). • Buying cheap connectors, it’s just not a way to save money. • It is much better to tie up the PBasic and the PCB to the BOX.