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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

Full Mission Simulation: Second Teleconference

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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. - PowerPoint PPT Presentation

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Page 1: Full Mission Simulation: Second Teleconference

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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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Atmospheric/Plasma Science Payload1. 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

Refracted rays

n=0n>0

n<0

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WVU in RockSat 2010: Functional Block Diagram

Power SupplyPower Supply

Thermistor

uMag

G

uController

FlashMemory

RBF

Swept-fPulse Tx

Power flow

Comm/Con

Data flow

Z Accel

Gyro

Main Board Radio Board

OpticalPort

ADC

Legend

Fixed-fPulse TxPre-amp &

Power filter

Superhet

LO

Amplifier

IF

InertialSensor

Regs

G

RegsANT

Power

C&DH

Sensors

RF in

uControllerADC

FlashMemory

ANT

ANT

RF out

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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 2nd): ready to be ordered

- Servo for energetic-particle detector included in PCB v. 3

- Independent testing by ABL.

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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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Receiver: main filter (cont.)

RLC passive filter: L=1 mH & C=10 pF f0=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 frequency Far from central frequency

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Receiver: main filter (cont.)

VCVS active filter (1 op amp): amplification over desired range, but broader rolloff than RLC

High response near f0 (~1.5 MHz)

Circuit Rolloff example far from f0 (here: 599 kHz)

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Receiver: main filter (cont.)

1st-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 oscillationsSchematic

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Receiver: main filter (cont.)

1st-order Butterworth implemented as Sallen-Key active filter (1 op amp): stable

f<f0: low responsef~f0: amplification (filter~inverter) f>f0: lower response

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Main filter: summary of responses

RLC,passive (0)

VCVS,active (1)Butterworth as

Sallen-Key, active (1)

Butterworth asThomas-1,active (3)

= filter is a) stable, b) amplifies input, c) amplification occurs over bandpass region centered at design f0

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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.

Capacitance (pF)

0

2

4

6

8

10

12

14

0 5 10 15 20 25 30 35

Number of Pulses

Capacitance (pF)

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Radio PCB

• v.1 delivered

Transmitter

Receiver

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Radio PCB (cont.)

• Revisions incorporated into v. 2 (receiver shown below)

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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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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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Main Board: PCB v. 3 (cont.)

• Image on right: new PCB design including servo leads.

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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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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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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

engineer2. Thermal/vacuum3. 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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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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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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Vibration Testing (cont.):Impulse Specification

• We have specified the impulse using the RockOn 2009 acceleration profile.

Position wrt Time

020000400006000080000

100000120000140000

0 2000 4000 6000 8000 10000 12000

Time ( .1 seconds)

Alti

tude

(m)

Series1

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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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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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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.