The Effects of Clock Drift on the Mars Exploration Rovers

Ali, Khaled; Vanelli, Charles A.

doi:10.2514/6.2012-5229

Cited by 3 publications

(1 citation statement)

References 11 publications

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“…In addition, errors in the SAPP pitch estimate while driving lead to inaccuracies in the estimation of changes in the rover's vertical position. 2 A technique to reverse the clock drift is currently under development. This technique reduces the error in the spacecraft clock value by a few seconds each sol, responding to concerns that a large instantaneous change in clock value may cause undesirable secondary effects.…”

Section: B Accumulated Error In Rover Attitude Estimationmentioning

confidence: 99%

Mars Exploration Rovers 2004-2013: Evolving Operational Tactics Driven by Aging Robotic Systems

Townsend

Seibert

Bellutta

et al. 2014

SpaceOps 2014 Conference

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Over the course of more than 10 years of continuous operations on the Martian surface, the operations team for the Mars Exploration Rovers has encountered and overcome many challenges. The twin rovers, Spirit and Opportunity, designed for a Martian surface mission of three months in duration, far outlived their life expectancy. Spirit explored for six years and Opportunity still operates and, in January 2014, celebrated the 10th anniversary of her landing. As with any machine that far outlives its design life, each rover has experienced a series of failures and degradations attributable to age, use, and environmental exposure. This paper reviews the failures and degradations experienced by the two rovers and the measures taken by the operations team to correct, mitigate, or surmount them to enable continued exploration and discovery.

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Section: B Accumulated Error In Rover Attitude Estimationmentioning

confidence: 99%

Mars Exploration Rovers 2004-2013: Evolving Operational Tactics Driven by Aging Robotic Systems

Townsend

Seibert

Bellutta

et al. 2014

SpaceOps 2014 Conference

View full text Add to dashboard Cite

show abstract

Time synchronisation for millisecond-precision on bio-loggers

Wild,

Wilbs,

Dechmann

et al. 2024

Mov Ecol

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Time-synchronised data streams from bio-loggers are becoming increasingly important for analysing and interpreting intricate animal behaviour including split-second decision making, group dynamics, and collective responses to environmental conditions. With the increased use of AI-based approaches for behaviour classification, time synchronisation between recording systems is becoming an essential challenge. Current solutions in bio-logging rely on manually removing time errors during post processing, which is complex and typically does not achieve sub-second timing accuracies.We first introduce an error model to quantify time errors, then optimise three wireless methods for automated onboard time (re)synchronisation on bio-loggers (GPS, WiFi, proximity messages). The methods can be combined as required and, when coupled with a state-of-the-art real time clock, facilitate accurate time annotations for all types of bio-logging data without need for post processing. We analyse time accuracy of our optimised methods in stationary tests and in a case study on 99 Egyptian fruit bats (Rousettus aegyptiacus). Based on the results, we offer recommendations for projects that require high time synchrony.During stationary tests, our low power synchronisation methods achieved median time accuracies of 2.72 / 0.43 ms (GPS / WiFi), compared to UTC time, and relative median time accuracies of 5 ms between tags (wireless proximity messages). In our case study with bats, we achieved a median relative time accuracy of 40 ms between tags throughout the entire 10-day duration of tag deployment. Using only one automated resynchronisation per day, permanent UTC time accuracies of ≤ 185 ms can be guaranteed in 95% of cases over a wide temperature range between 0 and 50 °C. Accurate timekeeping required a minimal battery capacity, operating in the nano- to microwatt range.Time measurements on bio-loggers, similar to other forms of sensor-derived data, are prone to errors and so far received little scientific attention. Our combinable methods offer a means to quantify time errors and autonomously correct them at the source (i.e., on bio-loggers). This approach facilitates sub-second comparisons of simultaneously recorded time series data across multiple individuals and off-animal devices such as cameras or weather stations. Through automated resynchronisations on bio-loggers, long-term sub-second accurate timestamps become feasible, even for life-time studies on animals. We contend that our methods have potential to greatly enhance the quality of ecological data, thereby improving scientific conclusions.

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Time synchronisation for millisecond-precision on bio-loggers

Wild,

Wilbs,

Dechmann

et al. 2024

Preprint

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Time-synchronised data streams from bio-loggers are becoming increasingly important for analysing and interpreting intricate animal behaviour including split-second decision making, group dynamics, and collective responses to environmental conditions. With the increased use of AI-based approaches for behaviour classification, time synchronisation between recording systems is becoming an essential challenge. Current solutions in bio-logging rely on manually removing time errors during post processing, which is complex and typically does not achieve sub-second timing accuracies. We first introduce an error model to quantify time errors, then optimise three wireless methods for automated onboard time (re)synchronisation on bio-loggers (GPS, WiFi, proximity messages). The methods can be combined as required and, when coupled with a state-of-the-art real time clock, facilitate accurate time annotations for all types of bio-logging data without need for post processing. We analyse time accuracy of our optimised methods in stationary tests and in a case study on 99 Egyptian fruit bats (Rousettus aegyptiacus). Based on the results, we offer recommendations for projects that require high time synchrony. In our case study with bats, we achieved a median relative time accuracy of 40 ms between tags throughout the entire 10-day duration of tag deployment. During stationary tests, our low power synchronisation methods achieved median time accuracies of 2.72 / 0.43 ms (GPS / WiFi), compared to UTC time, and relative median time accuracies of 5 ms between tags (wireless proximity messages). Using only one automated resynchronisation per day, permanent UTC time accuracies of ≤ 185 ms can be guaranteed in 95% of cases over a wide temperature range between 0 to 50°C. Accurate timekeeping required a minimal battery capacity, operating in the nano- to microwatt range. Time measurements on bio-loggers, similar to other forms of sensor-derived data, are prone to errors and so far received little scientific attention. Our combinable methods offer a means to quantify time errors and autonomously correct them at the source (i.e., on bio-loggers). This approach facilitates sub-second comparisons of simultaneously recorded time series data across multiple individuals and off-animal devices such as cameras or weather stations. Through automated resynchronisations on bio-loggers, long-term sub-second accurate timestamps become feasible, even for life-time studies on animals. We contend that our methods have potential to greatly enhance the quality of ecological data, thereby improving scientific conclusions.

show abstract

The Effects of Clock Drift on the Mars Exploration Rovers

Cited by 3 publications

References 11 publications

Mars Exploration Rovers 2004-2013: Evolving Operational Tactics Driven by Aging Robotic Systems

Mars Exploration Rovers 2004-2013: Evolving Operational Tactics Driven by Aging Robotic Systems

Time synchronisation for millisecond-precision on bio-loggers

Time synchronisation for millisecond-precision on bio-loggers

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