An Integrated Software Defined Radio Navigation System for Space - - PowerPoint PPT Presentation

An Integrated Software Defined Radio Navigation System for Space Navigation

Alison Brown and Ben Mathews www.navsys.com ION GNSS 2007 Session C5: Software Receivers 1 September 28, 2007

Problem Statement

• Existing space-qualified attitude control and

navigation solutions are not suitable for deployment on microsatellites due to size, weight, power, and cost constraints

• Small spacecraft require higher bandwidth

attitude control authority due to faster response needed to counter disturbance forces

• A small, flexible, and low-cost attitude control

and navigation solution is required to support future microsatellite missions and applications

Benefits of a Software Defined Radio (SDR) Navigation Approach

Flexible waveform processing using FPGAs Multiple Frequencies supported by flexible RF/Digital Transceivers Software control of SDR configuration and operation Easy integration of additional sensors and components

Integrated GPS / INS / Star-Tracker

GPS Antenna ADL855 PC-104 (Windows, RTX) PC-104 CAC Board PC-104 GPS DAE (L1) / DAE Passive Adptr Parvus SpacePC PC-104+ (400 MHz Celeron) Ethernet RF 1 PPS Spacecraft I/F NAVSYS Interface Module SPI

Microcosm NAVSYS

MicroMak Star Sensor ADL PC-104 Power Supply (5V & 12V Out) Fujitsu Hard Drive (80 GB) Oven Controlled Crystal Oscillator

12 VDC Power

MEMS IMU

PC/104 SDR Components

DAE Adapter and GPS DAE PC/104+ CAC X ilxinx 2000 FPGAs P502 Pow erPC M ain Board GM S IO Board NAVSYS Custom PC/104+ Adapter Board NAVSYS Oscillator Board M

• unting Plate

GPS DAE Board CAC FPGA Board Pentium IV SBC Crista MEMS IMU MicroMak Star-Tracker

Digital Antenna Element and Correlator Accelerator Card

• Digital Antenna Element
• Front-end down-conversion

and digitization

• Frequency/waveform agile
• Beamsteering/Beamforming
• GPS Correlator Accelerator Card
• Firmware-based correlations under SW control
• Can support other signal processing besides GPS
• Snapshot acquisition for external post-processing

Integrated Navigation Filter

• Must gracefully fuse data from multiple and

disparate sensors into an integration attitude and navigation solution

• GPS – Satellite pseudorange / carrier-phase

measurements

• Star-Tracker – Low-rate, high precision

attitude estimates for in-orbit operations

• IMU – High rate inertial information during
• rbit insertion and augmentation of star-

tracker during satellite in-orbit maneuvering

InterNav Modular Inertial Navigation Product

• Integrates GPS, inertial, and a variety of
• ther sensor data
• PR/DR or Pos/Vel
• ∆θ, ∆V from gyros and accels
• Modular design facilitates integration of

different sensors

• Was modified under this effort to integrate star-

tracker data into the combined navigation solution

• Performs inertial navigation functions
• Uses Kalman Filter for applying GPS updates
• Can be configured to optimize performance

based on sensor characteristics

Filter Implementation

v ∆ θ ∆ v ∆

N b

Q INS X

G ˆ

INS X

G ˆ

∆

NAVSYS Advanced GPS Hybrid Simulator (AGHS)

• Simulator control provided

through Matlab/Simulink interface

• Open architecture to facilitate

integration with trajectory generators

• Precise digital signal generation

under software control

• Multiple antenna elements for

wavefront simulation (8+)

• Jammer simulation
• Simulated inertial output
• Simulated star-tracker output

AGHS Simulink Interface

• Provides a user-friendly

interface for simulation control and analysis

• Open, flexible

architecture supports easy modification for prototyping – This architecture was leveraged for rapid insertion of star-tracker simulation capability

AGHS Test Set-Up

AGHS HWIL Test Architecture

D/A and Tune to RF Phase-Coherent Mixing AGHS Control Logic

GPS Tracking Results

Integrated Filter Test Results

Importance of Star-Tracker Input

2000 2200 2400 2600 2800 3000 3200

• 8
• 6
• 4
• 2

2 4 6 8 10 x 10

Attitude Error [micro-rad] Attitude Error: InterNav GPS/INS/ST vs. INSSIM Trajectory Truth Receiver Time Since T0 = 475269.990 (s) Ψx Ψy Ψz σ-x σ-y σ-z Required

With Star-Tracker Without Star-Tracker

Conclusions

• Prototype integrated space navigation

receiver has been developed and tested

• Benefits of star-tracker integration into

navigation filter have been shown

• Provides an affordable navigation option

for low-cost microsatellite missions

• Future efforts are focusing on radiation

hardening and incorporation of NAVSYS IMU

Questions?