1. Terrain Relative Navigation for Pinpoint Landing using Cubesats
Mars Cubesat Workshop
Swati Mohan,
Andrew Johnson,
Nikolas Trawny
November 21, 2014
Copyright 2014 California Institute of Technology. Government sponsorship acknowledged.
For planning and discussion purposes only. Cleared for unlimited release (CL# ).

2. LVS is an extension of MER-DIMES
MER-DIMES (2004) was the first use of descent images for navigation during EDL.
descent image
reference map
position
knowledge error before TRN
knowledge error after TRN
TRN automatically matches features in a descent image to landmarks in a map to obtain a position fix.
landmarks
image features
DIMES tracked features between descent images to estimate velocity.
Champollion, MER, NMP/ST9, Mars Tech Program
First Pair Tracking
Second Pair Tracking
TRN is an extension of MER-DIMES to estimate position for accurate landing.
Horizontal Velocity
:  For Planning and Discussion Purposes Only.

3. LVS TRN Implementation
VISINAV: Batch Initialization
VISINAV: Extended Kalman Filter x
outlier
Threshold x x x x x x x
Residuals x x x x x x x x x x x x x
Time
TRON: coarse matches
TRON: coarse matches
TRON: coarse matches
TRON: fine matches
TRON:
fine
matches
fine match image templates
coarse match image templates
IMU
IMU
Image 1
IMU
Image 2
IMU
Camera
Image 3
Image 10
Image 4
Image 5
Map
move later
add performance requirements
outlier
IMU
Batch update
EKF update
EKF update
Propagate
Propagate
Propagate
Propagate
Remove Large Position Uncertainty (50m 1-σ)
Improve Position Accuracy (20m 1- σ)
:  For Planning and Discussion Purposes Only.

4. Prototype LVS Block Diagram
LVS Compute Element
compact PCI backplane
LEON 3 Flight Processor
RTEMS OS
Batch Init Estimator
Extended Kalman Filter
Image Processing Control
Homography Generation
Outlier Rejection
Data Sequencing
Lander GN&C
initial state (p+perr,q,v+verr,A)M_B
(position correction)M_B
data products, data
Data Logger
Virtex 5 FPGA
AMBA Bus
Homography Warp
Image Normalize
FFT Correlation
Interest Operator
Spatial Correlation
Sensor Timing
Camera I/F IMU I/F
accel, angular rates
LVS IMU
grayscale image
LVS Camera
SDRAM with map
legend
LVS
LVS Technology
S/C
:  For Planning and Discussion Purposes Only.

5. Implementation on a Cubesat
Hardware
Compute Element:
Existing TRN boards are larger than Cubesat scale
Requires time and money to scale down to scale to a Cubesat size
JPL developed IRIS radio includes Cubesat scale Virtex 5 implementation
Deep space Cubesat processor in development in JPL Sec. 349
IMU:
Current TRN designs use LN200 or MIMU
Cubesat scale IMUs exist with similar performance
Examples are BCT MEMS gyro, KVH FOG gyro
Camera:
Current TRN design use a 1024x1024 array with 90 deg field of view
Cubesat scale detectors exist with similar performance
Example: KAI (2048x2048)
Optics would need to be designed for each mission
Software
TRN algorithms have been implemented and field tested
Mission specific development needs to occur:
Porting to the mission processor
Interfacing with the mission GN&C
Obtaining and implementing maps for mission landing site
:  For Planning and Discussion Purposes Only.

6. Possible Mission Applications
Technology Advancement
Technology demonstration of pinpoint landing
Technology demonstration of hazard detection
Science
Precision placement of probes ( seismometers, weather stations, etc.)
Mapping of Phobos or Deimos
Landing Site Support
Pre-cursor probes to confirm “worthiness” of potential landing site targets
And many more…!
:  For Planning and Discussion Purposes Only.