Centroid and Apparent Diameter Optical Navigation on Mars Orbit

2021 ◽  
pp. 1-13
Author(s):  
Thibaud Teil ◽  
Hanspeter Schaub ◽  
Daniel Kubitschek
Keyword(s):  
Optical Navigation ◽  
Apparent Diameter

The 3-Dimensional Molecular Structure of the Actin Filament Revisited

1985 ◽  
Vol 43 ◽  
pp. 480-481
Author(s):  
U. Aebi ◽  
R. Millonig ◽  
H. Salvo
Keyword(s):  
Actin Filament ◽  
Supramolecular Assembly ◽  
Specimen Preparation ◽  
X Ray Diffraction ◽  
Single Filament ◽  
X Ray ◽  
3 Dimensional ◽  
Filament Diameter ◽  
Preparation Conditions ◽  
Apparent Diameter

To date, most 3-D reconstructions of undecorated actin filaments have been obtained from actin filament paracrystal data (for refs, see 1,2). However, due to the fact that (a) the paracrystals may be several filament layers thick, and (b) adjacent filaments may sustantially interdigitate, these reconstructions may be subject to significant artifacts. None of these reconstructions has permitted unambiguous tracing or orientation of the actin subunits within the filament. Furthermore, measured values for the maximal filament diameter both determined by EM and by X-ray diffraction analysis, vary between 6 and 10 nm. Obviously, the apparent diameter of the actin filament revealed in the EM will critically depend on specimen preparation, since it is a rather flexible supramolecular assembly which can easily be bent or distorted. To resolve some of these ambiguities, we have explored specimen preparation conditions which may preserve single filaments sufficiently straight and helically ordered to be suitable for single filament 3-D reconstructions, possibly revealing molecular detail.

Optical Navigation for Lunar Exploration Missions

2006 ◽  
Author(s):  
Markus Landgraf ◽  
G. Thiele ◽  
D. Koschny ◽  
B. Udrea
Keyword(s):  
Lunar Exploration ◽  
Optical Navigation

The Starry Universe of Jacques Cassini: Century-old Echoes of Kepler

2021 ◽  
Vol 52 (2) ◽  
pp. 147-167
Author(s):  
Christopher M. Graney
Keyword(s):  
18Th Century ◽  
The Sun ◽  
Johannes Kepler ◽  
Apparent Diameter ◽  
Early 18Th Century ◽  
Made In

This paper discusses measurements of the apparent diameter and parallax of the star Sirius, made in the early 18th century by Jacques Cassini, and how those measurements were discussed by other writers. Of particular interest is how other writers accepted Cassini’s measurements, but then discussed Sirius and other stars as though they were all the same size as the sun. Cassini’s measurements, by contrast, required Sirius and other stars to dwarf the sun—something Cassini explicitly noted, and something that echoed the ideas of Johannes Kepler more than a century earlier.

scholarly journals Comparison of 3 Optical Navigation Systems for Computer-Aided Maxillofacial Surgery

2008 ◽  
Vol 134 (10) ◽  
pp. 1080 ◽  
Author(s):  
E. Bradley Strong ◽  
Amir Rafii ◽  
Bettina Holhweg-Majert ◽  
Scott C. Fuller ◽  
Marc Christian Metzger
Keyword(s):  
Maxillofacial Surgery ◽  
Navigation Systems ◽  
Optical Navigation ◽  
Computer Aided

scholarly journals Optical navigation for nanosatellite star trackers

2021 ◽  
Author(s):  
Harry (Ming Qi) Zhang
Keyword(s):  
Optical Navigation ◽  
Position Errors ◽  
Compact Size ◽  
Design Case ◽  
Simulation Results ◽  
Design Case Study ◽  
Navigation Filters ◽  
Great Resolution ◽  
Key Parameter

This thesis looks at the effectiveness of using nanosatellite class star trackers to perform optical navigation. Although star trackers used for these missions lack the accuracy and sensitivity of sensors employed on larger spacecraft, they offer great resolution relative to its compact size. Two Extended Kalman Filter-based navigation filters illustrate the applications of this class of sensor. The first filter looks at horizon-based techniques using observations of Mars and its moons to assist the navigation filter in a hyperbolic approach. Results show low position (< 300 m) and velocity (< 0:15 m/s) errors as spacecraft reaches periapse. The filter formulation serves as a basis for a design case study exploring different possible sensor configurations for this mission type. The second filter looks at landmark-based techniques using absolute and relative landmarks as observations. Measurement frequency appears as a key parameter in this study, simulation results show position errors in the order of tens of kilometers, or better even if absolute landmarks are only available every 30 minutes. The accuracy of the results are validated through series of Monte Carlo simulation.

Ground Calibration System Design of High-Precision Star Sensor

2013 ◽  
Vol 694-697 ◽  
pp. 1068-1073
Author(s):  
Jie Duan ◽  
Zhi Yong An ◽  
Xiang Yang Sun
Keyword(s):  
High Precision ◽  
Optical Transmission ◽  
Angular Distance ◽  
Star Sensor ◽  
Optical Navigation ◽  
Calibration System ◽  
Large Size ◽  
High Magnitude ◽  
Design Plan ◽  
Ground Calibration

In order to meet the high precision calibration requirements of precision angular distance and high magnitude to the optical navigation sensor, A new style of high precision star simulator with large caliber, and long-focus, is presented. And then the main compositions of this simulator are designed in detail referring to the simulator, the steering mirror, the standard simulated targets and so on. According to the simulator characteristics of large size lens and multi lens, the structural of lens cone uses the tube sleeve and inner sleeves fixed together means. To eliminate the mirror deformation, the design plan based on the tiny stress is applied in steering mirror. In order to achieve a high magnitude, the light targets are simulated by optical transmission from OLED to high precision drone with fibers. Its degree ≤1〞,simulated magnitude≥5 that meet calibration requirements of the current high-precision optical navigation sensor.

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