DEMOSAT MISSION TEAM LITTLE STAR Tully Baetz Raymond Dao Caleb Ogg 1

Mission Statement The DemoSat Project shall test several components of the ALL-STAR mission in order to reduce risks in those areas. Mission Objectives Compare the performance of epoxied and traditionally soldered solar cells by measuring output current and voltage. To test the ALL-STAR Star Tracker. 2

Mission Success Criteria Solar Cells Success is defined as measuring identical IV curves for both strings in identical pairs. That is, the epoxied solar cell measurements are in agreement and likewise for the soldered cells. Star Tracker Success is defined as detection of multiple stars in a single image. This is required if Star Tracker is to have a chance of identifying star arrangements. Success is also dependent on functionality and undamaged condition of Star Tracker after payload is recovered. Payload Recovery Payload must be recovered for data analysis 3

Structure Overview Foam Core Exterior 1 cm thick on each wall 1/8 in thick acrylic skeleton plates in interior Helps component interface and mounting Mounting points and holes for components/stand-offs Aids structural integrity Provides strength for flight tube assembly Flight String Assembly ¼ in inner diameter tube for flight string Washers and Metal Clips used for security of assembly 4

Final Acrylic Frame One edge panel removed Ease of access Mass constraints Attachment of components interface Holes added for stand-offs Baffle Created and interfaced Tooth and Grove design Added Structural Integrity 5

Assembled View (Labeled) 6 Photodiode 1 Photodiode 2 Photodiode 6 Solar Cells MOSFET PCB Star Tracker Camera/baffle Flight String DE2 PCB

Baffle 7

Payload Attachment Washers will be used as the anti-abrasion brushings Washers will be attached to the acrylic frame. The flight string will pass through a ¼ inch plastic tube Metal wire will be run through the tube to limit rotation of the satellite. Metal wiring will also help prevent flight string line from slipping through payload.

Overview of Electrical System Arduino based system 2 types of solar panels PCB Photodiode array Star Tracker FPGA Camera and baffle Heating System 9

Solar Panels Two strings, one soldered and one epoxied Data read and converted by PCB 10V, 40mA max output 10

PCB and Arduino PCB of own design, based off of DANDE’s solar circuit Arduino Uno, with microSD shield for storage Provides us with all the analog and digital pins needed to control the whole system Each component powered by one 9V battery 11

Data Flow Structure PCB

Data Storage We calculated the data storage needed for the IV curves to be GB or MB We will use a microSD card attached to the Arduino to store all our data. All temperature and relativity humidity data will be Stored on the HOBO Data logger Current mission ops require flying an additional temperature sensor to determine altitude for the star tracker. However the reordered data for this sensor will not be logged since it is redundant.

Photodiode Array 6 Photodiodes Attached to analog in 3.3V power Data stored as a 6 bit integer to display position of sun 14

Star Tracker Consists of DE2-115 FPGA and camera board Star tracking software provided by ALLSTAR loaded on DE2 Camera board connected to and powered by DE2 12V power provided to DE2 Receives one line from Arduino to allow control of when pictures are taken Will start taking photos at 1 hour after launch 15

Star Tracker Positioning The Star Tracker must be positioned to maximize star viewing potential Must not be obscured by balloon or pointed at Earth. Calculated ideal Star Tracker tilt based on balloon dimensions and Star Tracker’s field of view. Maximum Balloon Diameter: 90 ft Distance Between Balloon and Payload: 50 ft Star Tracker’s Max Field of View: 25 ° Star Tracker will be tilted at a 37-41° angle above the horizontal. This provides a ° “buffer” on the balloon side for the minor variations in payload tilt. 16

Heating Circuit consisting of 6 batteries and 6 heating resistors Placed centrally to evenly distribute heat 17

Software Overview The software has four main functions. It reads the data from the analog ambient light sensors It reads the data from the ADC while varying the value of the DAC It stores all read data on the microSD card for processing later At a predetermined altitude the software turns on the star tracker camera for picture taking Since speed is of the essence for generating a lot of IV curves during flight the software has been designed and built to take a data point once every 2 milliseconds. 18

Quality Assurance During development, we put the payload through a series of tests to better prepare for conditions that will be encountered on launch day. Drop Test – Structural test simulating landing Whip Test - Structural test for strength flight string attachment Flat Sat Testing – Electronics test for individual component functionality. Day in the Life Test – Electronics test for long term success of all component functionality Cold Test – Systems test simulating cold environment 19

Quality Standards Secure Flight String Assembly(Whip Test) Structural Integrity(Drop Test) No damage to inner components Thermal Heating(Cold Test) Maintain temperature above 0˚C Component Functionality and Interface (Flat Sat Testing) Everything works Day in The Life Testing Electronics work for estimated duration of flight 20

Flight and After Recovery Payload rose to altitude of 89,000 feet. Program crashed ~30 seconds into flight. Faulty and Loose wiring caused the crash Recovery Structure performed extremely well No Cracks discovered in plastic skeleton Only a few exterior abrasions and cuts from landing 21

Organizational Chart Emily Proano Project Manager Sean Rivera Lead Systems Engineer Tully Baetz Structures Lead Caleb Ogg Systems Lead Raymond Dao Structures Vignesh Muralidharan Electrical Lead Edward Lowe Electrical Eric Jacobson Structures William Whiteneck Systems 22

Appendix Slides Included Testing Details Whip Test Drop Test Star Tracker Test Photo Diode Test Solar Cell Test Flat Sat Testing Day in the Life Testing Cold Test Trigonometric Analysis Memory Calculation 23

Whip Test TopicDetails Purpose Determines whether or not the current structure can hold on to the flight string and not detach from it. The flight string was attached using knots, ¼ inch diameter tube, and pins. Test Details Spin structure (by flight string) at high speeds to simulate forces during flight LimitationsComponents were simulated with masses and locations Results Flight String Assembly held on for the duration of the test. Test showed that the assembly was strong enough to hold the weight. 24

Drop Test TopicDetails PurposeDetermines whether or not the current structural design can withstand impact with ground while keeping components functional and undamaged. Test DetailsDrop payload from 6 meters onto concrete surface to simulate worst case landing. LimitationsPayload landed on bottom, which is not guaranteed during real landing. Mock Ups were used for the components ResultsFoam core and insulation remained intact. Acrylic frame was shattered into only a few places 25

Drop Test Pictures Exterior after Drop TestInterior After Drop Test 26

Star Tracker Testing Not tested with DE2 because ALLSTAR is still working on star tracker Arduino system emits +5volt at 1 hour after launch on the attached pin to tell DE2 to start taking photos Tested with multi-meter This means our project has been tested to meet ALLSTAR’s requirements 27

Photodiode Test Photodiodes were taken into direct sunlight Slowly moved from direct sunlight to only receiving ambient light Once in ambient light the distinguishing constant was changed accordingly A baffle and grate will still be needed to limit exposure to direct sunlight 28

Solar Panel Test Solar Panels emit voltage + current when hit with sunlight Tested using multi-meter Already tested previously to be operational by ALLSTAR team Load is varied by the Arduino and works 29

Flat Sat Testing Flat Sat Testing has found the photodiodes to work Photodiodes have been calibrated to detect sunlight no longer detect ambient light Flat Sat Testing has gotten the PCB to output the correct voltage and current 30 minute data trial test showed all systems to be operational and the data was checked to be correct Flat Sat Testing has shown the microSD card can store data All data was stored correctly and did not exceed memory limits 30

Flat Sat Test Sample data is shown below showing data is recorded for 3.3 hours, until which the old battery died. This was replaced by new batteries 31

Flat Sat Testing Details Flat Sat testing included all components required for measuring solar cells: PCB Board + Arduino + Internal Power Source + SD Card shield. Flat Sat testing did NOT include any components related to Star Tracker. DEMOSAT has tested that we can provide the Star Tracker with a +5 volt signal and power it with our linear regulator. We were not provided with the Star Tracker in time to incorporate it into flat sat testing. 32

Day in the Life Testing Flat Sat was operated for 4 hours to make sure the program didn’t crash or components didn’t fail after being continuously operated. Day in the life Test passed while powered externally. Day in the life failed while powered internally. Corrected, was due to insufficient power. 33

Cold Test TopicDetails Purpose To simulate the low temperature conditions the payload will experience during flight. Test Details -20 lbs. of dry ice placed in a 6 ft 2 thermally isolated box. -Climate will be simulated to -65˚ C Success Criteria The inside of the payload must stay above 0 ̊ C. LimitationsComponents were simulated with masses and locations ResultsResults will be shown after cold test 34

Specifications for Cold Test All relevant electrical components functioning and placed inside payload for Cold Test Baffle Hole and Baffle were cut and created. Foam Insulation was cut precisely to seal vertices. Flight String Assembly accounted for 35

Cold Test Minimum Interior Temperature reached: -45 ̊ C Total Time Elapsed: 5 hours 36

Results of Cold Test Temperature was at zero only after three hours Expected flight time in high altitude is far below 3 hr. Showed that enough heat was on board The external temperature sensor was placed at the very top of the box, thus having a lower than actual reading Internal Temperature drops below External Temperature External Temperature Readings were only at -5 ̊ C 37

Trigonometric Analysis m m Arc of View: 25 ° Horizon 64 ° ° ° 38

Memory Calculation Each port on the ADC has 12 bit accuracy in the returned data. 12 bit data, if converted to an integer, can give numbers up to 4 digits large. Each digit will the be converted into a char to be saved by the program in a text file. Therefore, every millisecond we will receive at most 32 different chars since there are 8 ports with a possibility of 4 digit numbers from all of them.

Memory Calculation The photodiodes output will be taken as at most a 2 digit number since there are only 6 of them and they are treated as single bits (ie. return 1 if facing the sun, otherwise return 0) Therefore the maximum amount of digits created in a millisecond is 34 Each data point shall be broke up with a comma, and a millisecond will be broken up with apostrophe With identifiers, which allow for easier data processing, the total comes to 43 digits created every millisecond Therefore there are digits of data created every second

Memory Calculation digits/second = digits/hour digits/hour = digits over the course of the flight. Each digit of data is a byte in size Therefore, we generate bytes of data or.4644 GB of data total.