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Full Mission Simulation Test Report West Virginia University Rocketeers Students: N. Barnett, R. Baylor, L. Bowman, M. Gramlich, C. Griffith, S. Majstorovic, D. Parks, B. Pitzer, K. Tewey, E. Wolfe Faculty: Y. Gu, D.J. Pisano, D. Vassiliadis May 12, 2010 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 Elayer altitudes (“spread-F” effect) n>0 Refracted rays n=0 n<0 Echo Refracted rays WVU in RockSat 2010: Functional Block Diagram Main Board Radio Board Power Supply G Power Supply RBF RF in G ANT Regs Flash Memory Inertial Sensor A uController D Regs Fixed-f Pulse Tx Pre-amp & Power filter uMag LO Optical Port ANT RF out Super het IF Swept-f Pulse Tx ANT Thermistor C Amplifier Z Accel Gyro Flash Memory A D C uController Legend Power Power flow C&DH Comm/Con Sensors Data flow 3 Changes Since Subsystem Integration - Main board (sensors for: orbital and rotational motion, temperature, magnetic field) - - All sensors and electrical interfaces: tests completed Flight software, incl. data acquisition and storage: tests completed Servo for CR detector included in PCB Sensor calibration: ongoing Independent testing by ABL: electrical, mechanical, vibration. 3rd version of PCB (minor changes from 2nd): ready to be ordered Radio board (sensors for plasma density) - Receiver (Rx) active filter: redesigned (two versions: state-variable and VCVS), in testing phase - Rx detector: two designs (analog circuit with diode vs. AD637 converter) compared; analog circuit was chosen - Tx/Rx antennas: several prototypes constructed; in testing phase - PCB: completed - Control and data acquisition software: in development - Canister replica completed Main Board • The main board was completed in April. • Since then the flight software, incl. sensor control, and data acquisition/storage, was finished and tested. • The main board has been mounted on the Makrolon along with power supply, G switch and accelerometer/gyro board Radio Board: PCB Design • Several board components have been redesigned • Top image: PCB design • Bottom image: the PCB showing the microprocessor and flash memory, power supply, RBF and G switch, and receiver active filter. The detector has since been added at the center. Test Description: Main Board - - - 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) Test Description: Radio Board - - Active filter: comparison of 3 designs (state-variable, biquad, VCVS; electrical connectivity (breadboard vs. perf board); choice of op amp types (operating voltages; slew rates) Detector: comparison of two designs Antenna: Inductive vs. RF coupling Calibration: not completed End-to-end test: not completed Software: control of digital components (cap is close to completion; potentiometer incomplete) Test Results - In the following slides we present and discuss selected results from the two boards. Test Results (1): Main Board • Testing the flight software on the main board. • Shown on the right is the disassembled board during such a test. Test Results (2): Main Board Sensors • 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 assembly during the same run. The LED on the left represents a servo (not connected here). Test Results (3): Circuit Elements • In order to tune the Tx/Rx pair we use digital circuit elements. • Image on right: debugging the digital resistor. Test Results (3): Circuit Elements • The ColdFire PIT is used to control the digital capacitor and the serial peripheral interface (SPI) is used for the resistor. • Top image: running a test on the MAXIM capacitor and recording the reactance. • Bottom image: results from a test on the capacitor: PIT pulses delivered versus measured capacitance. Capacitance (pF) 14 12 10 8 Capacitance (pF) 6 4 2 0 0 5 10 15 20 Number of Pulses 25 30 35 Test Results (4): Detector Design 1. Analog circuit (detector with backdiode): 2. AD637 converter: • Green: high-pass filter • Red: half wave rectifier • Blue: low-pass filter • Brown: AD8099 op amp w/ squaring FB loop • The receiver’s detector rectifies the active-filter voltage and turns it into DC (right image). • Two alternative designs (top images) were compared. Digital oscilloscope output illustrating half-wave rectification of AC input Test Results (4): Detector Design The ideal detector output is 1) DC, 2) constant over a wide frequency range, and 3) linear (or at least monotonic) with input amplitude. Below are 2 results from the analog circuit: • Red is the output voltage when frequency scan was performed at 3V p-p, while blue is at 2V p-p. • The wobble is well within measurement error, no more than one millivolt. • The output amplitude is monotonic (actually linear) with input • However, only over a narrow input voltage range Conclusion from these and other tests: analog circuit is satisfactory, chosen over converter. Overall Analysis Launch readiness: we are still working on several issues related to the radio reception and control. The following issues are problematic: • The active filter in two realizations (state-variable, biquad) is not stable above 1.1 MHz (needs at least 1.6 MHz). We may resort to the simpler VCVS version which is more stable. • The antenna reception is weak and indicates inductive (magnetic) rather than RF coupling. • Otherwise the board is very similar in hardware (PCB, processor, data acquisition, etc) to the main board which has been ready for some time. Lessons Learned Improvements: • Logistics problems have improved and are now in a good timing. • We are much more familiar with several sensor and electronics issues and know how to resolve them than we were a month ago. • Task allocation has improved, but is still not perfect. Unresolved issues: • Basic-research complications in some components are delaying the construction of the radio experiment. Conclusions Issues and concerns: – Active filter design is evolving. – Transmission/reception tests are continuing. Summary/Closing remarks: - The main board tests have been completed and independent testing has been scheduled. - There is additional work to be done on several radio board components.