WO1990000257A1 - Attitude measuring device - Google Patents

Attitude measuring device Download PDF

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Publication number
WO1990000257A1
WO1990000257A1 PCT/NL1989/000054 NL8900054W WO9000257A1 WO 1990000257 A1 WO1990000257 A1 WO 1990000257A1 NL 8900054 W NL8900054 W NL 8900054W WO 9000257 A1 WO9000257 A1 WO 9000257A1
Authority
WO
WIPO (PCT)
Prior art keywords
detector
signal
space
field
attitude
Prior art date
Application number
PCT/NL1989/000054
Other languages
French (fr)
Inventor
Daniel Fischer
François MATHET
Maurice Tissot
Original Assignee
N.V. Philips' Gloeilampenfabrieken
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by N.V. Philips' Gloeilampenfabrieken filed Critical N.V. Philips' Gloeilampenfabrieken
Priority to BR898907019A priority Critical patent/BR8907019A/en
Priority to DE3990729T priority patent/DE3990729T1/en
Priority to DE3990729A priority patent/DE3990729C2/en
Publication of WO1990000257A1 publication Critical patent/WO1990000257A1/en

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S3/00—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received
    • G01S3/78—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received using electromagnetic waves other than radio waves
    • G01S3/782—Systems for determining direction or deviation from predetermined direction
    • G01S3/785—Systems for determining direction or deviation from predetermined direction using adjustment of orientation of directivity characteristics of a detector or detector system to give a desired condition of signal derived from that detector or detector system
    • G01S3/786—Systems for determining direction or deviation from predetermined direction using adjustment of orientation of directivity characteristics of a detector or detector system to give a desired condition of signal derived from that detector or detector system the desired condition being maintained automatically
    • G01S3/7868—Systems for determining direction or deviation from predetermined direction using adjustment of orientation of directivity characteristics of a detector or detector system to give a desired condition of signal derived from that detector or detector system the desired condition being maintained automatically using horizon sensors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64G—COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR
    • B64G1/00—Cosmonautic vehicles
    • B64G1/22—Parts of, or equipment specially adapted for fitting in or to, cosmonautic vehicles
    • B64G1/24—Guiding or controlling apparatus, e.g. for attitude control
    • B64G1/244—Spacecraft control systems
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64G—COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR
    • B64G1/00—Cosmonautic vehicles
    • B64G1/22—Parts of, or equipment specially adapted for fitting in or to, cosmonautic vehicles
    • B64G1/24—Guiding or controlling apparatus, e.g. for attitude control
    • B64G1/36—Guiding or controlling apparatus, e.g. for attitude control using sensors, e.g. sun-sensors, horizon sensors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S3/00—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received
    • G01S3/78—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received using electromagnetic waves other than radio waves
    • G01S3/782—Systems for determining direction or deviation from predetermined direction
    • G01S3/789—Systems for determining direction or deviation from predetermined direction using rotating or oscillating beam systems, e.g. using mirrors, prisms

Definitions

  • the invention relates to a measuring device placed on a first object in space to evaluate its attitude with respect to a second object in space, said first object being or not in motion relative to said second object, the said device comprising an optical sensor whose instantaneous field of view periodically scans said second object and which receives the emission of its radiation in a determined spectral band to transform it into an electrical signal by means of a detector.
  • an optical sensor whose instantaneous field of view periodically scans said second object and which receives the emission of its radiation in a determined spectral band to transform it into an electrical signal by means of a detector.
  • attitude angles are identified with respect to the instantaneous axes of rotation of said first object (the telecommunication satelli ⁇ te in the aforementioned application) in roll (axis tangent to the orbit) and in pitch (axis perpendicular to the orbital plane) .
  • the angles are calculated from the information provided by said detector during periodic scanning of said second object (the terrestrial disc in the above-mentioned application) by the instantaneous field of the sensor.
  • the scanning movement is actuated by an optico-mechanical device.
  • the detected signal follows exactly the evolution of the convolution of the luminance profile with the instant field of view of the sensor.
  • This signal is then filtered in a bandpass filter, the response of which consists of two pulses of the same amplitude, one of positive signal during the transition between space and the second object (input second object), the other of negative sign during the transition between the second object and the space (second object exit).
  • One threshold detection makes it possible to obtain the transition instants g (second object input) and tg (second object output).
  • the output pulse then starts at an instant after the instant when the signal leaves the luminance profile of the second object.
  • the negative pulse at the output of the bandpass filter starts before the positive pulse has returned to zero.
  • the distortion of the response is itself a function of the length of the scanning path, that is to say of the actual attitude of the satellite. This therefore results in: - a non-linearity of the response function of the sensor
  • the object of the invention is to prevent most of the causes of error listed above in order to overcome the defects that they cause.
  • said attitude measurement device comprises, after said detector, a high-pass filter followed by a member separating the increasing part and the decreasing part. of said signal, each of said parts being introduced into a low-pass filter whose response is a positive pulse - for the increasing part of the signal and a negative pulse for the decreasing part of the signal, each of said pulses being introduced into a threshold detector S which determines the transition time tg of said field of view between space and the entry of said second object on the one hand, the transition time tg of said field of view between the exit of said second object and space on the other hand, with an accuracy independent of the time interval separating said instants, the values of which are related to the corresponding attitude angles.
  • the threshold S is chosen independently for the input and for the output of the second object, at a constant fraction of the amplitude of the corresponding pulses obtained during previous scans.
  • the detector which receives the radiation emitted by said second object is for example a bolometer placed behind an IR filter.
  • the IR filter will operate, for example, in the absorption band of C0 2 around 15 ⁇ m.
  • - Figure 1 a satellite in Earth orbit.
  • - Figure 2 the scanning mode of the terrestrial disc by the instantaneous field of view of the sensor.
  • FIG. 1 represents a satellite represented by a parallelepiped 1 which moves in space 2 around the earth 3 describing the orbit 4.
  • Time measurements made by means of a sensor ambushed on the satellite allow to determine at all times its angular deviations around its instantaneous axes of roll 5 (tangent to the orbit) and pitch 6 (perpendicular to the orbital plane), that is to say its angular attitude with respect to the Earth.
  • FIG. 2 shows the trace 7 of the instantaneous field of view of the sensor in the plane of the terrestrial disc seen at a certain distance. This field scans the disc following the chord 8 of length 1 at the distance x from the center c.
  • the sensor targets space it radiates according to its own temperature and loses energy. Its field of view is located outside the terrestrial disc. As soon as this field enters the disc and travels through the cord 8, the sensor receives the energy radiated by the earth.
  • the emitted radiation is transformed into an electrical signal by means of a detector.
  • This signal varies as a function of time according to the response curve in solid line 10 of FIG. 3a superimposed on the signal corresponding to the profile of the earth drawn in solid lines 11.
  • This latter signal varies abruptly at the transitions entered and exit ; its convolution product with the instantaneous field of view of the sensor gives the trapezoidal variation of the signal at the output of the detector with a rise time and a fall time fixed by the angular value of the field, the time constant of the detector being assumed to be negligible.
  • the value of the half-sum i_ (tg + tg) corresponds to the instant of passage of the instantaneous field of view of the sensor through the midpoint of the scanning string.
  • the value of _ (tg + tg) corresponds to a angle measured in the plane containing the scan line.
  • the deviations in orientation are measured with respect to a reference value.
  • Figure 5 gives the block diagram of the device of the invention which includes the detector D represented by an electric generator in series with a resistor and connected to a high-pass filter F which is itself connected to the separator S.
  • the separator separates the two parts of the aforementioned signal.
  • the positive part is processed in the positive channel via the low-pass filter F + and the threshold detector D + .
  • the negative part is processed in the negative channel via the low-pass filter F "and the threshold detector D ⁇ .
  • the instants tg and tg are thus obtained at the output of D + and D ⁇ respectively.
  • FIG. 6a the time diagrams in FIG. 4a have been transferred, indicating by the references 13 'and 13 "the two parts of the overall response curve 13 of the detector.
  • the partial response 13 ′ of the detected signal coming from the separator provides after filtering and separation, the 15 'pulse.
  • the setting of the threshold S in the detector D + determines the instant tg.
  • the partial response 13 "of the detected signal provides after filtering and separation, the pulse 15".
  • the setting of the threshold S 'in the detector D ⁇ determines the instant t s .

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  • Engineering & Computer Science (AREA)
  • Remote Sensing (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Automation & Control Theory (AREA)
  • Navigation (AREA)
  • Radar Systems Or Details Thereof (AREA)

Abstract

Measuring device placed on a first object in space for evaluating its attitude relative to a second object in space and including an optical sensor, the instantaneous field of vision of which periodically scans said second object, the sensor receiving the radiation of said second object and transforming it into an electrical signal by means of a detector (D). The increasing and decreasing part of said electrical signal are separated in a separator (S) and processed independently by filtration (F?+, F?-) and detection (D?+, D?-) relative to a threshold which determines the transition times (tE? and tS?) corresponding to scanning by the field of the sensor for the input and output of said second object. The angles of attitude are calculated from said transition times. Application to communication satellites.

Description

DESCRIPTION DESCRIPTION
"Dispositif de mesure d'attitude""Attitude measuring device"
L'invention concerne un dispositif de mesure placé sur un premier objet de l'espace pour évaluer son attitude par rapport à un second objet de l'espace, ledit premier objet étant ou non en mouvement par rapport audit second objet, le- dit dispositif comportant un capteur optique dont le champ de vue instantané balaye périodiquement ledit second objet et qui reçoit l'émission de son rayonnement dans une bande spectrale déterminée pour la transformer en un signal électrique au moyen d'un détecteur. On tel dispositif trouve une application par exemple dans un satellite de télécommunication dont les antennes doi¬ vent être constamment pointées vers la terre avec une certaine tolérance angulaire. Il faut donc que la plateforme qui sup¬ porte ses antennes soit elle-même orientée convenablement et en permanence dans la bonne direction, ce qui nécessite la me¬ sure précise de l'attitude du satellite par rapport à la ter¬ re. Cette mesure est effectuée par l'intermédiaire dudit cap¬ teur qui détecte les limites entre le disque terrestre et l'espace. Les angles d'attitude sont repérés par rapport aux axes instantanés de rotation dudit premier objet (le satelli¬ te de télécommunication dans l'application précitée) en roulis (axe tangent à l'orbite) et en tangage (axe perpendiculaire au plan orbital). Le calcul des angles est effectué à partir des informations fournies par ledit détecteur lors du balayage pé¬ riodique dudit second objet (le disque terrestre dans l'appli¬ cation précitée) par le champ instantané du capteur. Le mouve¬ ment de balayage est actionné par un dispositif optico-mécani- que. Lorsque la constante de temps du détecteur est né¬ gligeable par rapport à l'intervalle de temps mis par le champ de vue du capteur pour traverser le second objet de l'espace tout en y étant inclus en totalité, le signal détecté suit exactement l'évolution de la convolution du profil de luminan¬ ce avec le champ de vue instantané du capteur. Ce signal est ensuite filtré dans un filtre passe-bande dont la réponse est constituée de deux impulsions de même amplitude, l'une de si¬ gne positif lors de la transition entre 1'espace et le second objet (.entrée second objet), l'autre de signe négatif lors de la transition entre le second objet et l'espace (sortie second objet) .The invention relates to a measuring device placed on a first object in space to evaluate its attitude with respect to a second object in space, said first object being or not in motion relative to said second object, the said device comprising an optical sensor whose instantaneous field of view periodically scans said second object and which receives the emission of its radiation in a determined spectral band to transform it into an electrical signal by means of a detector. Such a device finds an application for example in a telecommunications satellite whose antennas must be constantly pointed towards the earth with a certain angular tolerance. It is therefore necessary that the platform which supports its antennas is itself oriented properly and permanently in the right direction, which requires the precise measurement of the attitude of the satellite with respect to the earth. This measurement is carried out via said sensor which detects the limits between the terrestrial disk and space. The attitude angles are identified with respect to the instantaneous axes of rotation of said first object (the telecommunication satelli¬ te in the aforementioned application) in roll (axis tangent to the orbit) and in pitch (axis perpendicular to the orbital plane) . The angles are calculated from the information provided by said detector during periodic scanning of said second object (the terrestrial disc in the above-mentioned application) by the instantaneous field of the sensor. The scanning movement is actuated by an optico-mechanical device. When the time constant of the detector is negligible compared to the time interval set by the field of view of the sensor to cross the second object of space while being fully included therein, the detected signal follows exactly the evolution of the convolution of the luminance profile with the instant field of view of the sensor. This signal is then filtered in a bandpass filter, the response of which consists of two pulses of the same amplitude, one of positive signal during the transition between space and the second object (input second object), the other of negative sign during the transition between the second object and the space (second object exit).
One détection à seuil permet d'obtenir les instants de transition g (entrée second objet) et tg (sortie se¬ cond objet) .One threshold detection makes it possible to obtain the transition instants g (second object input) and tg (second object output).
Si l'hypothèse habituellement faite, consistant à négliger la constante de temps du détecteur vis-à-vis de l'in¬ tervalle de temps mis par le champ du capteur pour balayer le second objet n'est pas satisfaite, cela peut résulter :If the assumption usually made, consisting in neglecting the time constant of the detector vis-à-vis the time interval set by the field of the sensor to scan the second object is not satisfied, this may result:
- soit du choix d'un détecteur à grande constante de temps, fournissant souvent un plus grand rapport signal à bruit ; - soit du choix d'une fréquence de balayage plus élevée, en vue d'augmenter la fréquence de mesure ;- either the choice of a detector with a large time constant, often providing a greater signal-to-noise ratio; - or by choosing a higher scanning frequency, in order to increase the measurement frequency;
- soit du fait d'un plus faible parcours de balayage, ce qui - se produit par exemple lorsque le satellite est notablement dépointé. II s'ensuit que le signal fourni par le détecteur après l'entrée second objet, n'a pas le temps d'atteindre son niveau asymptotique avant la sortie second objet : l'impulsion de sortie démarre alors à un instant postérieur à l'instant où le signal sort du profil de luminance du second objet. De plus l'impulsion négative en sortie du filtre passe-bande démarre avant que l'impulsion positive ne soit re¬ venue à zéro.- either due to a shorter scanning path, which - occurs for example when the satellite is significantly depointed. It follows that the signal supplied by the detector after the entry of the second object does not have time to reach its asymptotic level before the exit of the second object: the output pulse then starts at an instant after the instant when the signal leaves the luminance profile of the second object. In addition, the negative pulse at the output of the bandpass filter starts before the positive pulse has returned to zero.
Ces deux défauts constituent des causes d'erreur de mesure de l'instant de transition de sortie second objet, et par conséquent des deux angles d'attitude du satellite par rapport à ce second objet : - erreur déterministe liée au décalage temporel et à la défor¬ mation de la réponse ;These two faults constitute causes of measurement error of the second object transition transition instant, and consequently of the two angles of attitude of the satellite with respect to this second object: - deterministic error linked to the time difference and to the deformation of the response;
- plus grande sensibilité au bruit sur la détection de l'ins¬ tant de sortie, du fait de la dégradation de la pente du si- gnal.- greater sensitivity to noise upon detection of the output moment, due to the degradation of the slope of the signal.
Il faut noter que la déformation de la réponse est elle-même fonction de la longueur du parcours de balayage, c'est-à-dire de l'attitude réelle du satellite. Il en résulte donc : - une non-linéarité de la fonction de réponse du capteurIt should be noted that the distortion of the response is itself a function of the length of the scanning path, that is to say of the actual attitude of the satellite. This therefore results in: - a non-linearity of the response function of the sensor
(fonction reliant l'attitude vraie à l'attitude mesurée) ;(function linking the true attitude to the measured attitude);
- un couplage entre les deux axes, roulis et tangage, selon lesquels l'attitude est mesurée.- a coupling between the two axes, roll and pitch, according to which the attitude is measured.
Le but de l'invention est de prévenir la plupart des causes d'erreur énumérées ci-dessus afin de pallier les défauts qu'elles occasionnent.The object of the invention is to prevent most of the causes of error listed above in order to overcome the defects that they cause.
A cet effet, l'invention est remarquable en ce que ledit dispositif de mesure d'attitude comporte à la suite du¬ dit détecteur, un filtre passe-haut suivi d'un organe sépara- teur de la partie croissante et de la partie décroissante du¬ dit signal, chacune desdites parties étant introduite dans un filtre passe-bas dont la réponse est une impulsion positive - pour la partie croissante du signal et une impulsion négative pour la partie décroissante du signal, chacune desdites impul- sions étant introduite dans un détecteur à seuil S qui déter¬ mine l'instant de transition tg dudit champ de vue entre l'espace et l'entrée dudit second objet d'une part, l'instant de transition tg dudit champ de vue entre la sortie dudit second objet et l'espace d'autre part, avec une précision in- dépendante de l'intervalle de temps séparant lesdits instants dont les valeurs sont reliées aux angles d'attitude correspon¬ dants.To this end, the invention is remarkable in that said attitude measurement device comprises, after said detector, a high-pass filter followed by a member separating the increasing part and the decreasing part. of said signal, each of said parts being introduced into a low-pass filter whose response is a positive pulse - for the increasing part of the signal and a negative pulse for the decreasing part of the signal, each of said pulses being introduced into a threshold detector S which determines the transition time tg of said field of view between space and the entry of said second object on the one hand, the transition time tg of said field of view between the exit of said second object and space on the other hand, with an accuracy independent of the time interval separating said instants, the values of which are related to the corresponding attitude angles.
Pour tenir compte de variations éventuelles de la luminance dudit objet (le disque terrestre par exemple), va- riations très lentes en fonction du temps et variations spa- tiales le long du disque, le seuil S est choisi indépendamment pour l'entrée et pour la sortie second objet, à une fraction constante de l'amplitude des impulsions correspondantes obte¬ nues au cours des balayages précédents. Le détecteur qui reçoit le rayonnement émis par le¬ dit second objet est par exemple un bolomètre placé derrière un filtre IR . Dans le cas où ledit second objet est la terre, le fitre IR fonctionnera par exemple dans la bande d'absorp¬ tion du C02 autour de 15μm. L'invention sera mieux comprise à l'aide de la des¬ cription suivante d'un mode de réalisation d'un dispositif donné à titre d'exemple non limitatif, ladite description étant accompagnée de dessins qui représentent :To take account of possible variations in the luminance of said object (the terrestrial disc for example), very slow variations as a function of time and spatial variations tials along the disc, the threshold S is chosen independently for the input and for the output of the second object, at a constant fraction of the amplitude of the corresponding pulses obtained during previous scans. The detector which receives the radiation emitted by said second object is for example a bolometer placed behind an IR filter. In the case where said second object is earth, the IR filter will operate, for example, in the absorption band of C0 2 around 15 μm. The invention will be better understood using the following description of an embodiment of a device given by way of nonlimiting example, said description being accompanied by drawings which represent:
- figure 1 : un satellite en orbite terrestre. - figure 2 : le mode de balayage du disque terrestre par le champ de vue instantané du capteur.- Figure 1: a satellite in Earth orbit. - Figure 2: the scanning mode of the terrestrial disc by the instantaneous field of view of the sensor.
- figure 3 : les diagrammes de temps des signaux électriques en sortie du détecteur et en sortie du filtre dans le cas du fonctionnement idéal. - la figure 4 : les diagrammes de la figure 3 dans le cas pra¬ tique du fonctionnement.- Figure 3: the time diagrams of the electrical signals at the detector output and at the filter output in the case of ideal operation. - Figure 4: the diagrams of Figure 3 in the practical case of operation.
- figure 5 : le schéma synoptique du dispositif de l'inven- - tion.- Figure 5: the block diagram of the device of the invention.
- figure 6 : les diagrammes de temps des signaux électriques résultant du traitement séparé, selon le dispositif de l'in¬ vention, des parties croissantes et décroissantes du signal issu du détecteur.- Figure 6: the time diagrams of the electrical signals resulting from the separate processing, according to the device of the invention, of the increasing and decreasing parts of the signal from the detector.
La figure 1 représente un satellite figuré par un parallélépipède 1 qui se déplace dans l'espace 2 autour de la terre 3 en décrivant l'orbite 4. Des mesures temporelles ef¬ fectuées au moyen d'un capteur embusqué sur le satellite per¬ mettent de déterminer à chaque instant ses écarts angulaires autour de ses axes instantanés de roulis 5 (tangent à l'orbi¬ te) et de tangage 6 (perpendiculaire au plan orbital), c'est- à-dire son attitude angulaire par rapport à la terre. La figure 2 montre la trace 7 du champ de vue ins¬ tantané du capteur dans le plan du disque terrestre vu à une certaine distance. Ce champ balaye le disque suivant la corde 8 de longueur 1 à la distance x du centre c. Lorsque le capteur vise l'espace il rayonne suivant sa propre température et perd de l'énergie. Son champ de vue est situé à l'extérieur du disque terrestre. Dès que ce champ pénètre dans le disque et parcourt la corde 8, le capteur re¬ çoit l'énergie rayonnée par la terre. Le rayonnement émis est transformé en un signal électrique au moyen d'un détecteur.FIG. 1 represents a satellite represented by a parallelepiped 1 which moves in space 2 around the earth 3 describing the orbit 4. Time measurements made by means of a sensor ambushed on the satellite allow to determine at all times its angular deviations around its instantaneous axes of roll 5 (tangent to the orbit) and pitch 6 (perpendicular to the orbital plane), that is to say its angular attitude with respect to the Earth. FIG. 2 shows the trace 7 of the instantaneous field of view of the sensor in the plane of the terrestrial disc seen at a certain distance. This field scans the disc following the chord 8 of length 1 at the distance x from the center c. When the sensor targets space it radiates according to its own temperature and loses energy. Its field of view is located outside the terrestrial disc. As soon as this field enters the disc and travels through the cord 8, the sensor receives the energy radiated by the earth. The emitted radiation is transformed into an electrical signal by means of a detector.
Ce signal varie en fonction du temps selon la cour¬ be de réponse en trait plein 10 de la figure 3a superposée au signal correspondant au profil de la terre tracé en traits in¬ terrompus 11. Ce dernier signal varie de façon abrupte aux transitions entrée et sortie ; son produit de convolution avec le champ de vue instantané du capteur donne la variation en forme de trapèze du signal en sortie du détecteur avec un temps de montée et un temps de descente fixés par la valeur angulaire du champ, la constante de temps du détecteur étant supposée négligeable.This signal varies as a function of time according to the response curve in solid line 10 of FIG. 3a superimposed on the signal corresponding to the profile of the earth drawn in solid lines 11. This latter signal varies abruptly at the transitions entered and exit ; its convolution product with the instantaneous field of view of the sensor gives the trapezoidal variation of the signal at the output of the detector with a rise time and a fall time fixed by the angular value of the field, the time constant of the detector being assumed to be negligible.
A partir de l'instant où le champ de vue du capteur pénètre dans le disque terrestre, il met le temps Δti pour at¬ teindre sa valeur de palier qu'il conserve pendant le temps Δt2. Le passage de ce signal dans un filtre passe-bande fournit les impulsions de même amplitude 12' et 12" représen¬ tées sur la figure 3b. L'impulsion positive correspond au temps de montée du signal lors de la transition espace-terre et l'impulsion négative correspond au temps de descente du si- gnal lors de la transition terre-espace. smax étant l'amplitude de l'impulsion, on peut convenir de fixer les instants d'entrée et de sortie du champ de vue ins¬ tantané du capteur aux transitions de la terre et de l'espace, à partir d'un seuil S représentant une fraction de cette am- plitude. Avec |S|=Smax/2 par exemple, on obtient les ins¬ tants tg et tζ indiqués sur la figure. La longueur 1 de la corde de balayage 8 (figure 2) est directement proportionnelle à la différence tg-tg. Il est donc possible de calculer la distance x (distance qui sé¬ pare la ligne de balayage du centre du disque terrestre) c'est à dire l'orientation angulaire du satellite dans la direction perpendiculaire à la ligne de balayage en fonction de tg-tg et par conséquent les variations éventuelles de cet¬ te orientation par rapport à une valeur de référence.From the moment the field of view of the sensor enters the terrestrial disc, it takes time Δti to reach its level value which it keeps for the time Δt 2 . The passage of this signal in a bandpass filter provides the pulses of the same amplitude 12 'and 12 "shown in FIG. 3b. The positive pulse corresponds to the time of rise of the signal during the space-to-earth transition and the negative pulse corresponds to the descent time of the signal during the earth-space transition, s max being the amplitude of the pulse, we can agree to fix the instants of entry and exit of the field of view ins¬ tantane of the sensor at the transitions of the earth and space, from a threshold S representing a fraction of this amplitude. With | S | = S max / 2 for example, we obtain the instants tg and tζ indicated in the figure. The length 1 of the sweeping rope 8 (FIG. 2) is directly proportional to the difference tg-tg. It is therefore possible to calculate the distance x (distance which separates the scanning line from the center of the terrestrial disc), that is to say the angular orientation of the satellite in the direction perpendicular to the scanning line as a function of tg- tg and consequently the possible variations of this orientation with respect to a reference value.
La valeur de la demi-somme i_ (tg+tg) correspond à l'instant de passage du champ de vue instantané du capteur par le point milieu de la corde de balayage. Lorsque la mesure des instants de transition est reliée à la position angulaire du champ de vue instantané le long de la ligne de balayage, par exemple par l'intermédiaire d'un codeur angulaire, à la valeur de _(tg+tg) correspond un angle mesuré dans le plan contenant la ligne de balayage. Pratiquement, on mesure ici encore les écarts d'orientation par rapport à une valeur de référence.The value of the half-sum i_ (tg + tg) corresponds to the instant of passage of the instantaneous field of view of the sensor through the midpoint of the scanning string. When the measurement of the transition instants is linked to the angular position of the instantaneous field of view along the scanning line, for example by means of an angular encoder, the value of _ (tg + tg) corresponds to a angle measured in the plane containing the scan line. In practice, here again, the deviations in orientation are measured with respect to a reference value.
On a déjà mentionné ci-dessus que l'allure de la courbe de réponse du signal détecté est liée à différents fac¬ teurs : temps de réponse du détecteur, fréquence du balayage et distance balayée sur le disque terrestre. On dispose ac- - tuellement de détecteurs ayant une constante de temps de quel¬ ques millisecondes avec un bon rapport signal à bruit. Pour une fréquence de balayage de 1 Hz la réponse du détecteur est encore acceptable, mais si l'on désire améliorer les condi¬ tions de mesure en portant par exemple cette fréquence à 10 Hz, le signal en sortie du détecteur est très déformé.It has already been mentioned above that the shape of the response curve of the detected signal is linked to different factors: response time of the detector, frequency of the scan and distance scanned on the terrestrial disk. There are currently detectors having a time constant of a few milliseconds with a good signal-to-noise ratio. For a scanning frequency of 1 Hz the response of the detector is still acceptable, but if it is desired to improve the measurement conditions by bringing this frequency to 10 Hz for example, the signal at the output of the detector is very distorted.
On a porté sur la figure 4a la variation en fonc- tion du temps du signal effectivement obtenu 13 avec un détec¬ teur et une fréquence de balayage déterminés. Le niveau asymp¬ totique de ce signal n'est pas atteint avant que le champ de vue du capteur ne soit sorti du disque terrestre.The variation as a function of time of the signal actually obtained 13 has been shown in FIG. 4a with a determined detector and scanning frequency. The asymmetric level of this signal is not reached before the sensor's field of view has left the terrestrial disc.
Le passage de ce signal dans un filtre passe-bande fournit l'impulsion d'entrée 14' et l'impulsion de sortie 14" représentées sur la figure 4b. Cette dernière impulsion de plus faible amplitude démarre à l'instant t* postérieur à l'instant Δtι+Δt2 correspondant à la somme du temps de montée et de la durée du palier sur la courbe de réponse idéale 10 de la figure 3a reportée sur la figure 4a et tracée en traits in¬ terrompus. De plus, l'impulsion négative 14" démarre avant que l'impulsion positive ne soit revenue à zéro. Ces défauts sont les causes essentielles des erreurs de mesures d'attitude déjà citées. L'idée de l'invention consiste à traiter séparément les parties du signal de réponse du détecteur située de part et d'autre de l'instant t*, c'est-à-dire les parties ayant respectivement une pente positive et une pente négative. On élimine ainsi au moins partiellement les causes d'erreurs liées aux défauts de non linéarités et aux décalages temporels de la réponse globale.Passing this signal through a bandpass filter provides the input pulse 14 'and the output pulse 14 " shown in Figure 4b. This last pulse of lower amplitude starts at the instant t * posterior to the instant Δtι + Δt 2 corresponding to the sum of the rise time and the duration of the plateau on the ideal response curve 10 of FIG. 3a transferred to Figure 4a and drawn in broken lines. In addition, the negative pulse 14 "starts before the positive pulse has returned to zero. These faults are the main causes of the attitude measurement errors already mentioned. The idea of the invention consists in treating separately the parts of the detector response signal located on either side of the instant t *, that is to say the parts having a positive slope and a negative slope respectively. This therefore at least partially eliminates the causes of errors related to non-linearity faults and time shifts in the overall response.
La figure 5 donne le schéma de principe du disposi¬ tif de l'invention qui comporte le détecteur D représenté par un générateur électrique en série avec une résistance et relié à un filtre passe-haut F qui est lui-même relié au séparateur S. Le séparateur effectue la séparation des deux parties du signal précitées. La partie positive est traitée dans la voie positive via le filtre passe-bas F+ et le détecteur à seuil D+. La partie négative est traitée dans la voie négative via le filtre passe-bas F" et le détecteur à seuil D~. On obtient ainsi en sortie de D+ et D~ les instants tg et tg respec¬ tivement.Figure 5 gives the block diagram of the device of the invention which includes the detector D represented by an electric generator in series with a resistor and connected to a high-pass filter F which is itself connected to the separator S. The separator separates the two parts of the aforementioned signal. The positive part is processed in the positive channel via the low-pass filter F + and the threshold detector D + . The negative part is processed in the negative channel via the low-pass filter F "and the threshold detector D ~. The instants tg and tg are thus obtained at the output of D + and D ~ respectively.
Sur la figure 6a on a reporté les diagrammes de temps de la figure 4a en indiquant par les repères 13' et 13" les deux parties de la courbe de réponse globale 13 du détec¬ teur.In FIG. 6a, the time diagrams in FIG. 4a have been transferred, indicating by the references 13 'and 13 "the two parts of the overall response curve 13 of the detector.
Sur la figure 6b on montre les diagrammes de temps séparés des voies positive et négative.In Figure 6b we show the separate time diagrams of the positive and negative channels.
Ainsi la réponse partielle 13' du signal détecté issue du séparateur fournit après filtrage et séparation, l'impulsion 15'. La fixation du seuil S dans le détecteur D+ détermine l'instant tg.Thus the partial response 13 ′ of the detected signal coming from the separator provides after filtering and separation, the 15 'pulse. The setting of the threshold S in the detector D + determines the instant tg.
De la même manière, la réponse partielle 13" du si¬ gnal détecté fournit après filtrage et séparation, l'impulsion 15". La fixation du seuil S' dans le détecteur D~ détermine l'instant ts. In the same way, the partial response 13 "of the detected signal provides after filtering and separation, the pulse 15". The setting of the threshold S 'in the detector D ~ determines the instant t s .

Claims

REVENDICATIONS : CLAIMS:
1. Dispositif de mesure placé sur un premier objet de l'espace pour évaluer son attitude par rapport à un second ob¬ jet de l'espace, ledit premier objet étant ou non en mouvement par rapport audit second objet, ledit dispositif comportant un capteur optique dont le champ de vue instantané balaye pério¬ diquement ledit second objet et qui reçoit l'émission de son rayonnement dans une bande spectrale déterminée pour la trans¬ former en un signal électrique au moyen d'un détecteur, carac- térisé en ce que ledit dispositif comporte à la suite dudit détecteur, un filtre passe-haut dont la réponse est introduite dans un organe séparateur de la partie croissante et de la partie décroissante dudit signal, chacune desdites parties étant introduite dans un filtre passe-bas dont la réponse est une impulsion positive pour la partie croissante du signal et une impulsion négative pour la partie décroissante du signal, chacune desdites impulsions étant introduite dans un détecteur à seuil S qui détermine l'instant de transition tg dudit champ de vue entre l'espace et l'entrée dudit second objet d'une part, l'instant de transition tg dudit champ de vue entre la sortie dudit second objet et l'espace d'autre part, avec une précision indépendante de l'intervalle de temps sépa-- rant lesdits instants dont les valeurs sont reliées aux angles d'attitude correspondants. 1. Measuring device placed on a first object in space to assess its attitude with respect to a second object in space, said first object being or not moving relative to said second object, said device comprising a sensor optics whose instantaneous field of view periodically scans said second object and which receives the emission of its radiation in a determined spectral band to transform it into an electrical signal by means of a detector, characterized in that said device comprises, following said detector, a high-pass filter, the response of which is introduced into a member separating the increasing part and the decreasing part of said signal, each of said parts being introduced into a low-pass filter, the response of which is a positive pulse for the increasing part of the signal and a negative pulse for the decreasing part of the signal, each of said pulses being introduced into a d threshold detector S which determines the instant of transition tg of said field of view between the space and the input of said second object on the one hand, the instant of transition tg of said field of view between the output of said second object and l space on the other hand, with a precision independent of the time interval separating the said instants whose values are related to the corresponding attitude angles.
2. Dispositif selon la revendication 1, caractérisé en ce que ledit seuil de détection S est choisi indépendamment pour l'entrée et la sortie dudit second objet, à une fraction constante de l'amplitude des impulsions correspondantes.2. Device according to claim 1, characterized in that said detection threshold S is chosen independently for the input and the output of said second object, at a constant fraction of the amplitude of the corresponding pulses.
3. Dispositif selon la revendication 1, caractérisé en ce que ledit détecteur recevant par l'intermédiaire dudit capteur optique le rayonnement émis par ledit second objet est par exemple un bolomètre placé derrière un filtre IR fonction¬ nant dans la bande d'absorption du C02 autour de 15μm.3. Device according to claim 1, characterized in that said detector receiving via said optical sensor the radiation emitted by said second object is for example a bolometer placed behind an IR filter operating in the absorption band of C0 2 around 15μm.
4. Dispositif selon les revendications 1 à 3, caracté- risé en ce qu'il permet l'utilisation d'un détecteur à grande constante de temps et/ou une fréquence de balayage plus élevée et/ou un plus faible parcours de balayage. 4. Device according to claims 1 to 3, characterized in that it allows the use of a detector with a large time constant and / or a higher scanning frequency and / or a shorter scanning path.
PCT/NL1989/000054 1988-07-01 1989-07-03 Attitude measuring device WO1990000257A1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
BR898907019A BR8907019A (en) 1988-07-01 1989-07-03 MEDICATION DEVICE
DE3990729T DE3990729T1 (en) 1988-07-01 1989-07-03 Position measuring arrangement
DE3990729A DE3990729C2 (en) 1988-07-01 1989-07-03 Measurement of satellite attitude in space

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8808921A FR2633714B1 (en) 1988-07-01 1988-07-01 ATTITUDE MEASURING DEVICE
FR88/08921 1988-07-01

Publications (1)

Publication Number Publication Date
WO1990000257A1 true WO1990000257A1 (en) 1990-01-11

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JP (1) JPH03500335A (en)
BR (1) BR8907019A (en)
DE (2) DE3990729T1 (en)
FR (1) FR2633714B1 (en)
WO (1) WO1990000257A1 (en)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2273285A1 (en) * 1974-06-03 1975-12-26 Hughes Aircraft Co
US3936629A (en) * 1974-10-07 1976-02-03 U.S. Philips Corporation Horizon sensor for a satellite in geostationary orbit
US4328421A (en) * 1980-02-25 1982-05-04 Barnes Engineering Company Horizon sensor
US4627724A (en) * 1983-07-08 1986-12-09 The United States Of America As Represented By The Secretary Of The Army Radiation scanning and detection system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2273285A1 (en) * 1974-06-03 1975-12-26 Hughes Aircraft Co
US3936629A (en) * 1974-10-07 1976-02-03 U.S. Philips Corporation Horizon sensor for a satellite in geostationary orbit
US4328421A (en) * 1980-02-25 1982-05-04 Barnes Engineering Company Horizon sensor
US4627724A (en) * 1983-07-08 1986-12-09 The United States Of America As Represented By The Secretary Of The Army Radiation scanning and detection system

Also Published As

Publication number Publication date
FR2633714A1 (en) 1990-01-05
JPH03500335A (en) 1991-01-24
DE3990729C2 (en) 1998-09-03
FR2633714B1 (en) 1991-03-15
BR8907019A (en) 1990-12-26
DE3990729T1 (en) 1995-06-01

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