StarNavAdvanced CMOS Star Trackers:

enhanced accuracy, reliability and speed

John L. JunkinsTexas A&M University

May 16, 2002

May 16, 2002 GIFTS Software TIM, College Station, TX Slide No. 2

StarNav I, II, and III Advanced Star Tracker Systems

• The StarNav sensors combine novel hardware and software to establish a new generation of smart navigation sensors– Outputs 5 rad 3 axis accuracy

– Split field of views optics means one camera sees two orthogonal starfields simultaneously => cost reductions, accuracy improvements

– CMOS Active Pixel Sensor => rad. tolerance and high frame rates

– Fast/reliable star identification algorithm for lost in space (LIS) case, first algorithm capable of reliable LIS star ID for magnitude six stars in a small fraction of a second.

– Recursive on-orbit autonomous self-calibration => greatly enhanced reliability, autonomy and accuracy, esp. for long missions.

• StarNav I: Proof of Concept Experiment for STS 107 (July ’02)

• StarNav II: 10 HZ GIFTS Mission StarTracker (Circa 2003)

• StarNav III: 60HZ Gyroless Attitude and Rate Sensor (SLI)

May 16, 2002 GIFTS Software TIM, College Station, TX Slide No. 4

STARNAV: Recent Legacy

  

STARNAV I: Lab Test ConfigurationMICRO STAR TRACKER CAMERA HEAD FRAME GRABBER SITe SIA502AB 512 x 512 CCD array peak quantum efficiency 0.85

LENS

SINGLE BOARD COMPUTER 586-133, 32 Mb DRAM, 40 Mb FLASH

Research and development at TAMU from laboratory brassboard to flight prototype

1999

STS 107 StarNav I Flight Experiment

2002

STARNAV I – On-orbit demonstration of advanced “Lost in Space” algorithms and data collection for recursive on-orbit calibration implementation.

• A Micro-Star Tracker for Micro-Spacecraft

• A self-calibrating Smart Sensor, outputs attitude, not image data

• Striving for Significant Advances:• Low Cost

• Light Weight

• Low Power

• High Accuracy

May 16, 2002 GIFTS Software TIM, College Station, TX Slide No. 5

The StarNav II camera simultaneously images star fields from two parts of the sky, real-time identification of the star patterns, and determination of 3 axis attitude with a precision of 5 rad (1).

StarNavII Split Field of View Star Camera for the EO-3 GIFTS Mission

May 16, 2002 GIFTS Software TIM, College Station, TX Slide No. 6

FOV 1

FOV 2

Patents applied for.

• Two star field images are superimposed onto a single image plane.

• This concept eliminates the unavoidably poor sensitivity of a single star tracker in resolving rotations about the optical axis without incurring the mass penalty of a second star tracker.

• The star images of each field-of-view are “tagged” optically via cylindrical meniscus lenses, resulting in elliptical star images. Spots are then sorted by shape to determine the FOV of origin.

Dual Field-of-ViewStar Tracker Concept

Tom Pollock’s night sky expmt, Oct, 2000

STARNAV II (TCP’s EO-3 Prototype)Dual Field of View Tech Demo Success!

May 16, 2002 GIFTS Software TIM, College Station, TX Slide No. 7

Dual Field-of-ViewStar TrackerEngineering Modelfor Concept Verification

Status: assembledbench testednight sky tested

STARNAV Dual FOV Testbed