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"Interplanetary navigation."
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Analytical Methods in Triangulation-Based Celestial Localization
Optical measurements are a key part of modern interplanetary navigation. This work applies the statistically optimal Linear Optimal Sine Triangulation (LOST) algorithm to the problem of celestial navigation. In addition to optimal triangulation methods, celestial navigation requires the consideration of target ephemeris errors, light aberration, and light time-of-flight. In most cases, only light aberration and light time-of-flight change the expected direction of the measured line-of-sight. These effects are found to be non-negligible at typical observer velocities (for light aberration) and planet velocities (for light time-of-flight). The effects of the position uncertainty of planets are only important when the observer is close to them. The LOST framework provides a mechanism to conveniently consider all of these effects.
Journal Article
X-ray Pulsar Signal Denoising Based on Variational Mode Decomposition
Pulsars, especially X-ray pulsars detectable for small-size detectors, are highly accurate natural clocks suggesting potential applications such as interplanetary navigation control. Due to various complex cosmic background noise, the original pulsar signals, namely photon sequences, observed by detectors have low signal-to-noise ratios (SNRs) that obstruct the practical uses. This paper presents the pulsar denoising strategy developed based on the variational mode decomposition (VMD) approach. It is actually the initial work of our interplanetary navigation control research. The original pulsar signals are decomposed into intrinsic mode functions (IMFs) via VMD, by which the Gaussian noise contaminating the pulsar signals can be attenuated because of the filtering effect during signal decomposition and reconstruction. Comparison experiments based on both simulation and HEASARC-archived X-ray pulsar signals are carried out to validate the effectiveness of the proposed pulsar denoising strategy.
Journal Article
Autonomous optical navigation using nanosatellite-class instruments: a Mars approach case study
This paper examines the effectiveness of small star trackers for orbital estimation. Autonomous optical navigation has been used for some time to provide local estimates of orbital parameters during close approach to celestial bodies. These techniques have been used extensively on spacecraft dating back to the Voyager missions, but often rely on long exposures and large instrument apertures. Using a hyperbolic Mars approach as a reference mission, we present an EKF-based navigation filter suitable for nanosatellite missions. Observations of Mars and its moons allow the estimator to correct initial errors in both position and velocity. Our results show that nanosatellite-class star trackers can produce good quality navigation solutions with low position (<300m) and velocity (<0.15m/s) errors as the spacecraft approaches periapse.
Journal Article
Reconstructing the cruise-phase trajectory of deep-space probes in a general relativistic framework: An application to the Cassini gravitational wave experiment
Einstein’s theory of general relativity is playing an increasingly important role in fields such as interplanetary navigation, astrometry, and metrology. Modern spacecraft and interplanetary probe prediction and estimation platforms employ a perturbed Newtonian framework, supplemented with the Einstein-Infeld-Hoffmann
n
-body equations of motion. While time in Newtonian mechanics is formally universal, the accuracy of modern radiometric tracking systems necessitate linear corrections via increasingly complex and error-prone post-Newtonian techniques—to account for light deflection due to the solar system bodies. With flagship projects such as the ESA/JAXA BepiColombo mission now operating at unprecedented levels of accuracy, we believe the standard corrected Newtonian paradigm is approaching its limits in terms of complexity. In this paper, we employ a novel prototype software, General Relativistic Accelerometer-based Propagation Environment, to reconstruct the Cassini cruise-phase trajectory during its first gravitational wave experiment in a fully relativistic framework. The results presented herein agree with post-processed trajectory information obtained from NASA’s SPICE kernels at the order of centimetres.
Journal Article
Single-point position estimation in interplanetary trajectories using star trackers
This study provides a single-point position estimation technique for interplanetary missions by observing visible planets using star trackers. Closed-form least-squares solution is obtained by minimizing the sum of the expected object-space squared distance errors. A weighted least-squares solution is provided by an iterative procedure. The weights are evaluated using the distances to the planets estimated by the least-squares solution. It is shown that the weighted approach only requires one iteration to converge and results in significant accuracy gains compared to simple least squares approach. The light-time correction is taken into account while the star-light aberration cannot be implemented in single-point estimation as it requires knowledge of the observer velocity. The proposed method is numerically validated through a statistical scenario as follows. A three-dimensional grid of test cases is generated: two dimensions sweep through the ecliptic plane and the third dimension sweeps through time from January 1, 2018 to January 1, 2043 in 5-year increments. The observer position is estimated at each test case and the estimate error is recorded. The results obtained show that a large majority of positions are well suited to position estimation by using star trackers pointing to visible planets, and reliable and accurate single-point position estimations can be provided in interplanetary missions. The proposed approach is suitable to be used to initiate a filtering technique to increase the estimation accuracy.
Journal Article
Finding the ET Signal from the Cosmic Noise
This paper highlights a methodological approach designed to enhance the search for extraterrestrial intelligence (SETI) by hypothesizing that a transmission technosignature would likely have two features: 1) be wideband in the microwave or higher frequency range that originates from a hub within a supposed ET interplanetary navigation/communication (nav/comm) network, and 2) contain x-ray pulsar-based navigation (XNAV) metadata. Potential contributions to the field include improved accuracy in finding transmission technosignatures and other technosignatures in the electromagnetic spectrum, a common standard in reaching a Schelling Point (a mutual realization of how we and ETs can find each other), and operationalizing models such as the Drake Equation.
Paper
An Autonomous Vision-Based Algorithm for Interplanetary Navigation
The surge of deep-space probes makes it unsustainable to navigate them with standard radiometric tracking. Self-driving interplanetary satellites represent a solution to this problem. In this work, a full vision-based navigation algorithm is built by combining an orbit determination method with an image processing pipeline suitable for interplanetary transfers of autonomous platforms. To increase the computational efficiency of the algorithm, a non-dimensional extended Kalman filter is selected as state estimator, fed by the positions of the planets extracted from deep-space images. An enhancement of the estimation accuracy is performed by applying an optimal strategy to select the best pair of planets to track. Moreover, a novel analytical measurement model for deep-space navigation is developed providing a first-order approximation of the light-aberration and light-time effects. Algorithm performance is tested on a high-fidelity, Earth--Mars interplanetary transfer, showing the algorithm applicability for deep-space navigation.
Paper
An Image Processing Pipeline for Autonomous Deep-Space Optical Navigation
A new era of space exploration and exploitation is fast approaching. A multitude of spacecraft will flow in the future decades under the propulsive momentum of the new space economy. Yet, the flourishing proliferation of deep-space assets will make it unsustainable to pilot them from ground with standard radiometric tracking. The adoption of autonomous navigation alternatives is crucial to overcoming these limitations. Among these, optical navigation is an affordable and fully ground-independent approach. Probes can triangulate their position by observing visible beacons, e.g., planets or asteroids, by acquiring their line-of-sight in deep space. To do so, developing efficient and robust image processing algorithms providing information to navigation filters is a necessary action. This paper proposes an innovative pipeline for unresolved beacon recognition and line-of-sight extraction from images for autonomous interplanetary navigation. The developed algorithm exploits the k-vector method for the non-stellar object identification and statistical likelihood to detect whether any beacon projection is visible in the image. Statistical results show that the accuracy in detecting the planet position projection is independent of the spacecraft position uncertainty. Whereas, the planet detection success rate is higher than 95% when the spacecraft position is known with a 3sigma accuracy up to 10^5 km.
Paper
Variations of the harmonic components of the X-ray Pulse Profile of PSR B1509-58
We used the Fourier decomposition technique to investigate the stability of the X-ray pulse profile of a young pulsar PSR B1509-58 by studying the relative amplitudes and the phase differences of its harmonic components with respect to the fundamental using data from the Rossi X-Ray Timing Explorer. Like most young rotation powered pulsars, PSR B1509-58 has a high spin down rate. It also has less timing noise allowing accurate measurement of higher order frequency derivatives which in turn helps in study of the physics of pulsar spin down. Detailed investigation of pulse profiles over the years will help us establish any possible connection between the timing characteristics and the high energy emission characteristics for this pulsar. Further, the study of pulse profiles of short period X-ray pulsars can also be useful for using them as means of interplanetary navigation system. The X-ray pulse profile of this source has been analysed for 15 \\( \\rm years \\) (1996-2011). The long term average amplitudes of the first, second and third harmonics (and their standard deviation for individual measurements) compared to the fundamental are 36.9 % (1.7 %), 13.4 % (1.9 %) and 9.4 % (1.8 %) respectively. Similarly, the phases of the three harmonics (and standard deviations) with respect to the fundamental are 0.36 (0.06), 1.5 (0.2), 2.5 (0.3) \\(\\rm radian \\) respectively. We do not find any significant variation of the harmonic components of the pulse profile in comparison to the fundamental.
Paper