Optics: measuring and testing – Angle measuring or angular axial alignment – With photodetection remote from measured angle
Patent
1997-02-25
1998-10-27
Font, Frank G.
Optics: measuring and testing
Angle measuring or angular axial alignment
With photodetection remote from measured angle
250208, 356138, G01B 1126
Patent
active
058284478
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to orientation locating systems of an observation instrument.
2. Discussion of the Prior Art
It constitutes an improvement to a patent application with the same title and same inventors filed in France under No. 93 14872 and which described a system more particularly formed by an observation instrument, a source of a light pattern integral with the instrument, a system for reflecting the light from the source and a sensor of the light from the pattern. The reflecting system was formed by at least one mirror, whose function was to direct the light from the light pattern to the light sensor, which was equipped with an orientation reference. It could in particular be a stellar sensor, detecting at the same time as the pattern, the light of a star. The comparison of the positions of the images of the pattern and the star gave the angular deviation between the direction of the star and the emission direction of the light pattern before the reflecting system. The orientation of the instrument was deduced therefrom. In other designs, the light sensor affected by the pattern was integral with a stellar sensor or the like for supplying the reference, which gave the same result. However, a stellar sensor was preferred for giving the orientation reference due to the immobility of stars in a fixed reference mark and the sharpness of their appearance. In particular, preference is given to the measurement of the sighting direction with respect to the stars for a better precision.
The preference for a stellar sensor explains why the earlier invention was more particularly used in spacecraft such as satellites, interplanetary probes or space stations equipped with instruments for observing astrons such as the Earth, the same applying here.
The very precise knowledge of the sighting axis direction of an observation instrument is essential if it is wished to appropriately locate the observed location. At present, it is known to perfectly located an orbiting satellite (with uncertainties of 10 to 100 m for the GPS system and only 0.5 to 40 m for the DORIS system, as a function of conditions), whereas the global orientation of the sighting axis of the observation instruments is in practice only known with an uncertainty of at best 100 to 200 angular seconds, which corresponds to approximately 400 to 800 m position uncertainty on the ground for a satellite at a height of 800 km. Although this sighting orientation uncertainty is small in itself, it contributes to almost the entire location uncertainty and it is wished to reduce this.
In practice, there are three categories of instruments. The first are fixed to the craft, which must therefore be completely turned (deviated) so that the desired instrument is oriented in the desired direction. This design is not very advantageous more particularly due to the necessary energy costs. The uncertainty of the orientation of the sighting axis of the instrument is then more particularly dependent of the installation of the instrument on the craft and can be increased by disturbances such as vibrations or deformations due to localized heating produced on a single face of the craft by solar radiation.
Thus, the two other instrument categories comprise instruments equipped with mechanisms for orienting the instrument on the vehicle and, which is much more frequently encountered at present, the instruments fixed to the vehicle, but provided with sighting change mirrors placed in front of the instrument observation field and which modify at random its sighting direction when they are turned. The sighting axes are then directed much more simply. In all cases, the mobile mechanism or mirrors are responsible for supplementary orientation uncertainties.
U.S. Pat. No. 4,187,422 describes an orientation calibration system of a stellar sensor by projecting a light pattern through a source integral with the sensor towards a prism reflecting the image of the pattern onto the sensor. The position of the image on the sensor gi
REFERENCES:
patent: 3637312 (1972-01-01), Cantor et al.
patent: 4123164 (1978-10-01), Tambor
patent: 4154532 (1979-05-01), Emmerich
patent: 4159419 (1979-06-01), Wittke
patent: 4187422 (1980-02-01), Zoltan
Duchon Paul
Otrio Georges
Centre National d'Etudes Spatiales
Font Frank G.
Stafira Michael P.
LandOfFree
Orientation location system of an observation instrument does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Orientation location system of an observation instrument, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Orientation location system of an observation instrument will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1617890