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What I Did During

What I Did During. My Summer Vacation. NASA Wallops Trip. Opportunity to Fly APL L1/L2 Signal Sampler Goal: To Obtain Higher Resolution Ocean Reflected Data Not Successful!. GSFC, Code 596. Goddard Space Flight Center. Applied Engineering and Technology Directorate.

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What I Did During

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  1. What I Did During My Summer Vacation

  2. NASA Wallops Trip • Opportunity to Fly APL • L1/L2 Signal Sampler • Goal: • To Obtain Higher Resolution Ocean Reflected Data • Not Successful!

  3. GSFC, Code 596 Goddard Space Flight Center Applied Engineering and Technology Directorate Guidance Navigation and Control Center Hardware and Component Systems (Code 596)

  4. Code 596 & PiVoT • PiVoT Position Velocity Time • Space Flight Ready GPS Receiver • Radiation Hardened Components • Low Power • Gnucleus Embedded OS

  5. PiVoT 1.0 • Based on GPS Builder Card • Uses Mitel 2010/2021 Chipset • Software based on GPS Builder Card Software • Old, Buggy, Undocumented • Several Unresolved Bugs • Mix of Pipes & Shared Memory for Thread Communication • Low Performance

  6. PiVoT 2.0 • New Generation GPS Receiver • Totally In House • High Performance • Uses Motorola ColdFire™ Processor • 42 seconds TFF from Cold Start • Via FFT Acquisition • Implemented in Actel Rad-Hard FPGAs • Low Signal Level Tracking • 20ms Integration Time • 24 Correlators • Attitude Determination

  7. GPS Signal Sampler • Flexible, Low Cost Solution • Utilizes Off the Shelf Components • RF Front-End • 2 Signal Generators • A Couple of Band Pass Filters • A Few RF Amps • Downmixes GPS Signal to 35.4 MHz • EchoTek ADC Card • Samples GPS Signal at 2.048 MHz • High End PC w/ SCSI Raid Array

  8. PiVoT 2.0 Software • Decision to Abandon PiVoT 1.0 Code Base • Intellectual Property Issue • Code is a Monstrosity • Rewrite From Scratch • Utitilizing C++ OOP • Modular As Possible • 1 Method Of Thread Communication • Pipes

  9. Actual Work • Begin 2.0 Code Base • Goal: Produce Navigation Solution using Luke W.’s acquisition/tracking code, GPS Signal Sampler, and Real GPS Signal

  10. Results • Proved Validity of GPS Signal Sampler • Nav Solution Completed • ~2km Error • Proved Real-Time Software Correlators • ~50% CPU Usage for 12 Channels • Utilizing only MMX Optimizations • Further Improvement Expected from SSE/SSE2 Code

  11. This Fall • All Pieces in Place • Real Time Software Correlators • GPS Signal Sampler • Ability to Write Real Time Multithreaded Code • Code Base for Nav Solution • Goal: ~10m Real Time Nav Solution by End of Fall 2003 • Off of sampled data • Move to Real Time Operation (Directly Off of EchoTek Card) in Spring • Write a Paper

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