How does pulsar-based localization work for spacecraft navigation at relativistic speeds?
Answered at 4:27 in Ep 66 - Pulsar Localization & Digit's Digits · Automate It: A Robotics Podcast
How does pulsar-based localization work for spacecraft navigation at relativistic speeds?
Pulsars pulse at relatively unique and identifiable frequencies, allowing localization within a certain range. If you observe multiple pulsars and know their cosmological positions, you can identify your location. However, optical resolution limits (the Rayleigh limit) constrain accuracy to roughly plus or minus a million kilometers in any direction. At relativistic speeds, you must account for both special and general relativity, Doppler shifts, and the vectors of moving stars to achieve accuracy. Dead reckoning combined with pulsar tracking—knowing your speed, heading, and initial position—can narrow localization to usable frames of reference of possibly meters over time.
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In short
Pulsars pulse at relatively unique and identifiable frequencies, allowing localization within a certain range.
Guest · Ep 66 - Pulsar Localization & Digit's Digits · Automate It: A Robotics Podcast · answer at 4:27
Key takeaways
- Pulsars pulse at relatively unique and identifiable frequencies, allowing localization within a certain range.
Quote to remember
“Localization is the real problem because that, in robotics, whatever problem you want to work on is the hardest problem.”
The full answer · about 4 min
Pulsars pulse at relatively unique and identifiable frequencies, allowing localization within a certain range. If you observe multiple pulsars and know their cosmological positions, you can identify your location. However, optical resolution limits (the Rayleigh limit) constrain accuracy to roughly plus or minus a million kilometers in any direction. At relativistic speeds, you must account for both special and general relativity, Doppler shifts, and the vectors of moving stars to achieve accuracy. Dead reckoning combined with pulsar tracking—knowing your speed, heading, and initial position—can narrow localization to usable frames of reference of possibly meters over time.
Key facts
- Localization accuracy with four pulsars: plus or minus one million kilometers in any direction due to Rayleigh diffraction limits
- Orientation accuracy with pulsar tracking: roughly one thousandth of a degree
- GPS/GNSS accuracy for position: plus or minus 30 meters for cheap dash cameras, despite speed discrimination being highly accurate
- Travel time to nearest star at speed of light: approximately four years; at 20% speed of light: roughly 20 years
- Kilohertz range: pulsar brightness changes occur at kilohertz frequencies, requiring fast camera sensors