07-09-002 an integrated software defined radio navigation system
TRANSCRIPT
An Integrated Software Defined Radio Navigation
System for Space Navigation
Alison Brown and Ben Mathewswww.navsys.com
ION GNSS 2007Session 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 SpacePCPC-104+
(400 MHz Celeron)
Ethernet
RF
1 PPS
Spacecraft I/F
NAVSYS Interface ModuleSPI
Microcosm
NAVSYS
MicroMakStar Sensor
ADL PC-104Power Supply
(5V & 12V Out)
Fujitsu Hard Drive(80 GB)
Oven Controlled Crystal Oscillator
12 VDCPower
MEMS IMU
PC/104 SDR Components
DAE Adapter and GPS DAE
PC/104+ CACXilxinx 2000FPGAs
P502 PowerPCMain Board
GMS IO Board
NAVSYS CustomPC/104+ AdapterBoard
NAVSYS Oscillator Board
Mounting Plate
GPS DAE Board
CAC FPGABoard
Pentium IVSBC
CristaMEMS IMU
MicroMakStar-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
orbit insertion and augmentation of star-tracker during satellite in-orbit maneuvering
InterNav Modular Inertial Navigation Product
• Integrates GPS, inertial, and a variety of other 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
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
Importance of Star-Tracker Input
2000 2200 2400 2600 2800 3000 3200-8
-6
-4
-2
0
2
4
6
8
10x 105
Atti
tude
Erro
r [m
icro
-rad]
Attitude Error: InterNav GPS/INS/ST vs. INSSIM Trajectory Truth
Receiver Time Since T0 = 475269.990 (s)
ΨxΨyΨzσ-xσ-yσ-zRequired
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