Design and Implementation of Low-Cost Optical Telemetry to Support Radiometric Analysis of the

Atmosphere

University of Colorado at BoulderAlexandra Hickey, Evan Schomer, Rocky Marcus,

and Frank Erdesz3/14/2013

Mission Overview• Mini Cam Subsystem on Polar Cube• Low Cost• Data confirmation

– Through goe tagging– Contextual image comparison

• Provides simplified means for post launch recalibration

2

Design overview

• Three Subsystems – Structures – CDH– Power

• Goal– Compact– Easy to interface – Durable

This Semester

• Worked toward balloon launch • Not met due to technical difficulties that will

be talked about later by the different subsystems

Structures

Requirements/Overview

• fit with in a 1.4in x 1.2in x 1.14in volume• Weigh under 200g• Easily integrate into Polar Cube • Withstand at least 20g’s with a factor of safety of two• Maintain all components within operating

temperatures

6

The Design

• PCB structural members• Stand offs • Nylon washers

– Prevent moment about the stand offs • Reinforced holes for stand offs

Command and Data Handling(CDH)

Overview/Requirements

• CDH is handled with an AVR ATmega1284P microcontroller.

• CDH shall be able to handle image data streaming up 1Mbps from the image sensor as well as interfacing with memory and temperature sensors.

• CDH shall write any event or peripheral settings data to nv memory.

• CDH shall be able to locally store all data for an extended period.

• CDH shall be able to function as a satellite subsystem or standalone system.

Microcontroller and Peripherals

MicrocontrollerATmega1284P

Camera ModuleAptina MT9T111

NV Memory

JPEG DataStream

8-bit parallel

Command InterfaceI2C

Memory InterfaceSPI

Temperature Sensors(x3)

OneWire Interface

Image Capture Flow

Picture Trigger

• Check memory requirements• Prep buffer• Find address location of nv memory• Create image entry/start headers• Set camera settings if necessary• Gather timestamp and other data

Send Camera Capture Command

Load buffer into non-volatile memory

• Finish EOF headers on nv memory• Set low power mode on camera/memory• Increment photo ID• Add flight log data (time,settings,name)

Return

Receive camera data and store into vram buffer

Check Camera EOF

Data Storage

Images with a maximum size of 1.0 MB per photo at full color resolution will be collected. The camera may cycle through various modes affecting data output size up to 1.0 MB throughout the mission.

With a 256MB memory module, up to 254 images and supporting mission log data can be stored locally until uploaded to the main computer memory allowing for a data transfer to be postponed for an extended period.

Image Size JPG100 JPG903.1 MP2048x1536

1.0MB 504.4KB

Learned

• Processor bus read optimization for large data transfers.

• Find sufficient documentation for camera before purchasing.

• Interfacing with a complex and micro sized camera system and changing various settings through a command interface.

Power

Power Subsystem Requirements

• Will provide 5V to the microcontroller.• Will use 3.3V from PolarCube to power the

voltage regulator, DC-DC converter, and memory module.

• Will provide 2.8V and 1.8V to the camera module.

Functional Block Diagram

Schematics

Voltage Regulation

Microcontroller – Camera Interface

Lessons Learned

• Improvements on PCB design process• Learned more circuit debugging strategies

Schedule

Mini Cam BurnDown List Key   Met  In Progress

Test   Over DueThe Whip Test 25-Feb 25-Feb  Drop Test 25-Feb 25-Feb  The Stair Pitch Test 25-Feb 25-Feb  Day in the Life/ Cooler Test 12-Mar CANCELEDDay in the life/Cooler Test 2 2-Apr  Day in the Life/Vacuum Test 2-Apr  

MechanicalItem DateSolid Works Model Finalized 14-Feb 14-Feb  Parts Order for Prototype ordered 15-Feb 14-Feb  Prototype built 25-Feb 24-Feb  Whip test 25-Feb 25-Feb  Drop Test 25-Feb 25-Feb  The Stair Pitch Test 25-Feb 25-Feb  Design Revisions 4-Mar 27-Feb  Retesting 11-Mar 11-Mar  Design Finalized 12-Mar 11-Mar  Final Balloon sat Structure constructed 8-Apr  

ElectricalItem Date Date met Status1st board & parts ordered 14-Feb 14-Feb  

board and testing setup assembled 22-Feb 22-Feb  Testing: electrical, microcontroller, camera 27-Feb 28-Feb  Board v2 designed 27-Mar 27-Mar  

Board v2 ordered & parts ordered 27-Mar 27-Mar  Board v2 assembled 8-Apr  Board v2 electrical testing 9-Apr  

CDHItem DateSD Card/Temperature Working 23-Feb 23-Feb  

Last Day to get camera interface board for reasonable testing time 22-Feb 13-Feb  Camera Working 2-Apr  

Last Software Revision for testing 5-Apr  Deadline for software revision 5-Apr  Data anlyzation 19-Apr  

Conclusion

• Will provide a contextual image for geo tagging and general data confirmation

• Allows for easier resolution of anomalous readings

• Lowers overall Polar Cube mission risk