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1 Full Mission Simulation: Second Teleconference West Virginia University Rocketeers Student team: N. Barnett, R. Baylor, L. Bowman, M. Gramlich, C. Griffith, S. Majstorovic, D. Parks, B. Pitzer, K. Tewey, E. Wolfe Faculty advisors: Y. Gu, D.J. Pisano, D. Vassiliadis May 22, 2010
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2 Atmospheric/Plasma Science Payload 1. Atmospheric temperature. Processes: atmosphere heating/cooling mechanisms. Objective: identify layers based on temperature profile 2. Terrestrial magnetic field. Processes: field controls charged-particle motion. Objectives: –Measure vector B, dependence on altitude, geocentric distance. –For high S/N: detect low-frequency waves 3. Plasma and energetic particles. Processes: solar UV produces ionosphere >85 km. Cosmic rays produce avalanches of particles. Objectives: –Emit radio pulse which is reflected where index of refraction=0 –Measure density profile; identify E layer peak –For high-activity conditions: high-density patches descend to E- layer altitudes (“spread-F” effect) Echo Refracted rays n=0 n>0 n<0
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33 WVU in RockSat 2010: Functional Block Diagram Power Supply Thermistor uMag G uController Flash Memory RBF Swept-f Pulse Tx Power flow Comm/Con Data flow Z Accel Gyro Main BoardRadio Board Optical Port ADCADC Legend Fixed-f Pulse Tx Pre-amp & Power filter Super het LO Amplifier IF Inertial Sensor Regs G ANT Power C&DH Sensors RF in uController ADCADC Flash Memory ANT RF out
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4 Summary of Changes Since Last Report -Radio board (transmitter/receiver used to measure plasma density) -Receiver filter: several versions tested, some successful -PCB: v. 1 delivered. Revisions incorporated in v. 2. -Control and data acquisition software: in development -Main board (sensors: orbital and rotational motion, temperature, magnetic field) -Sensor calibration: ongoing -PCB v. 3 (minor changes from 2 nd ): ready to be ordered -Servo for energetic-particle detector included in PCB v. 3 -Independent testing by ABL.
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5 Receiver: main filter State-variable active filter: implemented with NJM1238 quad op amp, shown on perf board Stability issues: oscillations –Autonomous (similar to standing waves); input ignored –Clearest between op amps 2-3 and 2-4.
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6 Receiver: main filter (cont.) RLC passive filter: L=1 mH & C=10 pF f 0 =1.59 MHz. Combine with low R (~50-100 Ohm). Result: sharp (Q=15-20) response curve for several different configurations. Frequency generator; driving frequency shown in kHz Input signal and RLC response At/near central frequencyFar from central frequency
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7 Receiver: main filter (cont.) VCVS active filter (1 op amp): amplification over desired range, but broader rolloff than RLC High response near f 0 (~1.5 MHz) Circuit Rolloff example far from f 0 (here: 599 kHz)
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8 Receiver: main filter (cont.) 1 st -order Butterworth implemented as Thomas-1 active filter (3 op amps): unstable, similar to state-variable filter. Input (sinusoidal) vs. output (flat lines) Output unstable, sensitive to capacitive coupling; easily breaks up into nonlinear, autonomous oscillations Schematic
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9 Receiver: main filter (cont.) 1 st -order Butterworth implemented as Sallen-Key active filter (1 op amp): stable f<f 0: low response f~f 0 : amplification (filter~inverter) f>f 0 : lower response
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10 Main filter: summary of responses RLC, passive (0) VCVS, active (1) Butterworth as Sallen-Key, active (1) Butterworth as Thomas-1, active (3) = filter is a) stable, b) amplifies input, c) amplification occurs over bandpass region centered at design f 0
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11 Programmable Circuit Elements The ColdFire PIT is used to control the digital capacitor. Earlier we could only control one capacitor (images on right). Currently we can control simultaneously multiple capacitors: useful in extending range or resolution of effective capacitance.
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12 Radio PCB v.1 delivered Transmitter Receiver
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13 Radio PCB (cont.) Revisions incorporated into v. 2 (receiver shown below)
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14 Main Board Background: the main board was completed in April. Sensor calibration is ongoing. Data storage: transition to binary files, more efficient storage.
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15 Main Board: PCB v. 3 Minor revisions have been made based on feedback from tests on v. 2. In addition, to complement the plasma board operation, we have added an energetic- particle sensor operated by a servo. Image on right: PCB design without servo leads.
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16 Main Board: PCB v. 3 (cont.) Image on right: new PCB design including servo leads.
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17 Main Board: Other Tests Data acquisition of individual sensors. Top image: data acquisition from the high-rate sensors (gyro and accelerometer) on the breakout boards. Bottom image: the main board and several breakouts during the same run. The LED on the left represents a servo for the energetic- particle sensor (not connected).
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18 Main Board: Other Tests -Electrical interfaces/connectivity (transistor pins corrected; breakout headers added; analog I/O utilized for battery voltage sensor; connection to IMU resolved) -Mechanical fits (hole-fastener fits; breakout boards added; working area added where accel/gyro used to be; will be used for CR detector/other prototyping) -Sensor tests: completed (gyro replaced) -Data handling: completed (collected at 1000 Hz; verification LEDs blinking every ½ second; still need to save as calibrated binary data) -Calibration: not completed -End-to-end (flight) test: completed -Length of tests: 3-7 minutes -Software debugging: appears complete (Programmable Interrupt Timer/PIT used; all MOD analog and digital pins configured)
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19 Independent Testing at ABL Two students will take the main board to ABL; will participate in tests along with ABL staff. Tests planned: 1.Board inspection/connectivity of circuit cards by JSTD-certified engineer 2.Thermal/vacuum 3.Vibration: Sine sweep Random 4. Impulse/shock acceleration (classical shock or SRS). Test schedule: 2 days at end of May/beginning of June.
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20 Vibration Testing ABL will build a basic fixture to mount payload plate. We have provided them with specifications for plate and canister
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21 Vibration Testing (cont.) Alternatively the plate will be mounted on the canister, and the canister will be bolted on vibration platform
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22 Vibration Testing (cont.): Impulse Specification We have specified the impulse using the RockOn 2009 acceleration profile.
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23 Overall Analysis Launch readiness: we are still working on several issues related to the radio reception and control. We focus on two areas in particular: 1. We have several versions of stable filters in the frequency range of interest and we need to test them against each other. 2. The antenna transmission/reception tests indicate inductive (magnetic) rather than RF coupling. This is probably due to a mismatch in the circuit impedances. Otherwise we are now integrating the radio board!
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24 Lessons Learned Improvements: We are much more familiar with several sensor and electronics issues and know how to resolve them than we were a month ago. Logistics problems have improved and we are now in a good operational cycle. Unresolved issues: Instabilities in the radio filters are delaying the integration of the radio experiment.
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25 Conclusions Issues and concerns: –Stable active filters have been identified; final selection needs to be done. –Transmission/reception tests are continuing. Summary/Closing remarks: -The main board will be taken to independent testing at the end of the month. -There is additional work to be done on several radio board components.
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