DE10302717A1 - Optical receiver used in a spacecraft has the incident emission received measured by sensors to provide input to controller input - Google Patents

Abstract

The optical unit has two aperture (14,15) with coupled filter (9) The received emission is detected by sensors (11) that measure intensity and these provide inputs to a control unit (10). Dependent upon the intensity the controller outputs signals to control the apertures.

Description

The present invention relates to a method and an arrangement for controlling the incidence of radiation into an optical receiver of a spacecraft. Spacecraft are in the sense of the invention all artificial Body, the for are designed for use in space, especially satellites, Space probes, space shuttle, Space stations or missiles. Optical receiver in the sense of the invention are all devices that are designed to emit optical radiation to receive and process, for example for the purpose of data exchange between spacecraft or between spacecraft and earth stations, or also for the purposes of recording, locating, measuring and / or Observation of objects that emit optical radiation.

The prior art is over DE 198 46 690 A1 an optical receiver device is known, which is designed in the form of a combined earth-star sensor. This is used for earth and star observation, whereby a three-axis position and position determination of satellites is made possible from the information obtained. Edge filters allow a long-wave portion of the radiation from earth and stars to be filtered out. The sensor allows a variable control of the exposure time, which is realized via a corresponding integration time of the sensor signals.

Out US 5,447,052 an earth sensor for satellites is known which has an array of IR detectors. Variations in the radiation of the earth are compensated for by an aperture (shutter) which is movably arranged in front of the lens or the IR detectors of the sensor and which, when closed, interrupts the radiation incident on the IR detectors. The closing of the diaphragm is controlled by a detector signal from one of the IR detectors.

Out DE 198 47 480 A1 an optical receiver device for optical inter-satellite connections is known. The corresponding optical receiver is in the DE 198 47 480 A1 described in sufficient detail. Such inter-satellite connections are used to exchange data between individual satellites, but can also, as in the case of DE 198 47 480 A1 , can be used to determine the position of a satellite.

A disadvantage of this prior art is, however, that there is always a constant incidence of radiation in the optical receiver occurs and as the only alternative, complete interruption the incidence of radiation is given. For this, however, an aperture must be used be moved mechanically. This is particularly important for space applications high source of error due to the risk of jamming the aperture is what can make the entire arrangement unusable. Besides, is especially variable control of the incidence of radiation the state of the art not possible.

Object of the present invention is an improved way to control the incidence of radiation in an optical receiver To provide spacecraft.

This task is solved by the characteristics of the claims 1, 9 and 10.

• – eine Eintrittsoptik
• – eine Detektoranordnung, die der Eintrittsoptik optisch nachgeschaltet ist,
• – mindestens ein Sensormittel zur Ermittlung des aktuellen Strahlungseinfalles.

A first subject of the invention is an arrangement for controlling the incidence of radiation in an optical receiver of a spacecraft, which has the following:

• - an entrance optic
• A detector arrangement which is optically connected to the entry optics,
• - At least one sensor means for determining the current incidence of radiation.

According to the present invention it is now provided that the detector device has at least one optical Filter means is optically upstream, in the case of control signals an optical state change can be generated and which signal technology with the at least one sensor means connected is.

So it is in the case of the invention no longer necessary, to move an aperture mechanically. Furthermore, the filter medium be designed so that only two states, namely open and closed, are no longer possible. All this is only achieved by using suitable filter media Control signals are transmitted, which bring about an optical change in the state of the filter, which then in turn influences the radiation passing through the filter medium. It can basically different parameters of the radiation alternatively or simultaneously be influenced like intensity, Polarization, wavelength, phase, Radiation direction. It is therefore at least within the scope of the invention an adaptive filter means used.

The filter medium can be on any suitable Place in the beam path in front of the detector arrangement (i.e. before the arrangement, which ultimately actually evaluates the incident radiation) his. The filter medium can either the total radiation incident influence the complete, analogous to how an aperture diaphragm Incidence of radiation influenced. It can also be just a part of the incident Radiation can be influenced, for example, by a certain visual field to select or influence in a targeted manner, analogous to one Field aperture by selecting a certain field of view only one affects a certain field of vision.

Optical receivers in the sense of the invention are all devices which are designed to receive and process optical radiation, for example for purposes of data exchange between Spacecraft or between spacecraft and earth stations, or for the purpose of detecting, locating, measuring and / or observing objects that emit optical radiation. Technical details for examples of such optical receivers can be found in the documents from the prior art mentioned above, in particular in the DE 198 46 690 A1 and the DE 198 47 480 A1 described.

According to a first training the invention provides that the at least one filter means such is formed by the optical change of state a changed one optical attenuation of the optical radiation passing through the filter means becomes.

On the one hand, it can now be provided be that the at least one filter medium as a bistable filter is trained. In this case, the filter has two stable optical ones conditions on. In such a case, short ones are sufficient Signal pulses to move the filter between the two optical states and switch on.

Alternatively, it can also be provided that the at least one filter medium ( 9 ) is designed such that a variable change in the optical state can be generated. Variable in the sense of the invention means that either more than two optical states of the filter means are possible (i.e. a quantized setting possibility of states), or that there is a continuous, freely scalable setting possibility of optical states, both at least for a defined partial area of a certain parameter Description of an optical state, such as, for example, a portion of the attenuation of the radiation intensity that passes through the filter means.

In particular, it can be provided that the filter medium as a liquid crystal filter is formed, for example as a ferroelectric liquid crystal filter or nematic filter. The technology of liquid crystal filters is for example at the website http://www.crlopto.com/technology/, in particular for ferroelectric Liquid crystal filter and nematic filter technology.

In particular, the filter medium directly connected to at least one sensor means for signaling purposes his. This can be done in particular by sensor means such as, for example Photocells can be realized, which are sufficient even with sufficient radiation intensity signal strength can deliver, which is enough to the desired in the filter medium change in condition to effect. But it can also be provided that at least a sensor means about a control electronics with the at least one filter means signal technology connected is.

As an example of an application of the Invention can be provided that the optical receiver as part a position and / or position determination device of a spacecraft is trained. For example, the optical receiver can be used as Earth sensor, star sensor or combined earth star sensor be, each entrance aperture having a filter means.

As an alternative application example of the invention, the optical receiver can be designed as part of a data communication device of a spacecraft. Technical details for the implementation of this application, especially for the design of the optical receiver, can be found in the already cited DE 198 47 480 A1 remove.

Another subject of the present Invention is a method for controlling the incidence of radiation into an optical receiver of a spacecraft, wherein at least one sensor means the current Incidence of radiation in the optical receiver is determined and the sensor means dependent on signals from the determined radiation incident to at least one Device for controlling the radiation incidence transmitted, which are signal-technically connected to the at least one sensor means is. According to the invention it is provided that at least one sensor means control signals transmitted to at least one optical filter means, which a detector device is optically upstream, and by the control signals an optical change in condition of the at least one optical filter means is generated. To further Explanations about this and possible Refinements to this procedure will be made within the framework of the arrangement according to the invention referred technical facts referenced.

In particular, the filter medium directly connected to at least one sensor means for signaling purposes his. However, the at least one sensor means can also control signals transmit to at least one control electronics and the control electronics in turn transmit control signals to at least one optical filter means.

Another subject of the present Invention is the use of an optical filter means in which an optical state change can be generated by control signals for Control of the incidence of radiation in an optical receiver Spacecraft, the optical filter means of a detector device is optically upstream and with at least one sensor means is connected by signal technology. For further explanations on this and possible Refinements to this procedure will be made within the framework of the arrangement according to the invention referred technical facts referenced.

In particular, the filter medium directly connected to at least one sensor means for signaling purposes his. However, the at least one sensor means can also control signals transmit to at least one control electronics and the control electronics in turn transmit control signals to the optical filter means.

The following is based on the 1 to 3 a special embodiment of the invention based on of a combined earth-star sensor, a control of the intensity of the radiation incidence being described here by way of example. 4 shows schematically an exemplary use of the invention for an optical communication receiver.

Show it:

1 : Combined earth star sensor according to the state of the art

2 : Combined earth star sensor with a device according to the invention for controlling the incidence of radiation

3 Combined earth star sensor with an alternative form of a device according to the invention for controlling the radiation incident

4 Optical communication receiver with a device according to the invention for controlling the incidence of radiation

1 shows a combined earth star sensor 5 for spacecraft such as in particular satellites, such as those from DE 198 46 690 A1 is known. This earth star sensor 5 has an entrance optic 1 on that mainly through a semi-transparent mirror 2 and a lens optic 3 is formed. This entrance optics is a detector device 4 optically downstream. The entrance optics 1 serves that of the earth 6 and the stars 7 overlaying outgoing optical radiation and together via the lens optics 3 on the detector device 4 map. The resulting picture 8th is in the 1 shown on the right.

2 now shows an earth star sensor improved in accordance with the present invention 5 , the area of the entrance optics 1 is shown enlarged. The entrance optics after 2 is analogous to the entrance optics 1 trained, with the representation of the lens optics 3 was omitted for the sake of simplicity. Also the detector device 4 is in for simplicity 2 not shown, but be analogous to 1 in the earth star sensor 5 intended.

How 2 shows, the combined earth-star sensor 5 two entrance apertures 14 . 15 on. In the area of these entrance apertures 14 . 15 is an optical filter medium 9 arranged, in which an optical change in state can be generated by control signals. These are preferably liquid crystal filters. These filter media 9 are via purely schematic signal lines 13 with control electronics also shown only schematically 10 connected, which in turn via signal lines 12 (also shown only schematically) with optical sensor means 11 are connected. The optical sensor means 11 capture the radiation intensities, each through the apertures 14 . 15 enter.

The sensor means 11 generate signals depending on the detected intensities and transmit these signals to the control electronics 10 where the signals are selective for each aperture 14 . 15 are detected and corresponding control signals to the respective filter means 9 the corresponding aperture to control the radiation intensity passing through. The optical sensor means 11 can be at any suitable point in the beam path of the earth star sensor 5 or also outside the beam path on the surface of the earth star sensor 5 be arranged. In 2 became two sensor means 11 schematically in the area of the semi-transparent mirror 2 shown arranged, one of the sensor means one of the two apertures 14 . 15 is assigned and the radiation intensity detected by this aperture 14 . 15 occurs. Of course, the sensor means 11 to be arranged in such a way that the radiation intensities or images of the earth or the stars on the detector are not impaired 4 he follows.

3 shows an alternative embodiment of the invention, in which no control electronics 10 is required. Here can be used as sensor means 11 for example photocells can be used. The photocells 11 can preferably on the surface of the earth star sensor 5 are arranged and are directly signal technology with the filter means 9 connected. This arrangement can be used, for example, to protect the detector arrangement from intense radiation such as direct sunlight, this arrangement being extremely simple and fail-safe since no further electronics are required. The photocells can generate sufficient voltage in a filter medium if there is sufficient radiation, as would result from direct sunlight 9 , for example a liquid crystal, to produce an optical change in state from transparent to opaque. In this way, the incidence of radiation into the optical receiver can be carried out in a simple and hardly error-prone manner 5 to be interrupted.

4 shows schematically the application of the invention in an optical receiver of an optical communication device, for example for realizing inter-satellite connections. This optical receiver 5 also has an entrance optic 1 on that mainly through an entrance aperture 14 and a lens optic 3 is formed. This entrance optics 1 is a detector device 4 optically downstream. In the area of this entrance aperture 14 is an optical filter medium 9 arranged, in which an optical change in state can be generated by control signals. These are preferably liquid crystal filters. This filter medium 9 is via a purely schematic signal line 13 with control electronics also shown only schematically 10 connected, which in turn via a signal line 12 (also shown only schematically) with an optical sensor means 11 are connected.

The optical sensor means 11 detects a desired radiation parameter through the aperture 14 incoming radiation such as radiation intensity, polarization, frequency or phase. The sensor means 11 generates signals depending on the detected parameters and sends these signals to the control electronics 10 where the signals are detected and corresponding control signals to the filter means 9 the aperture 14 to control the desired parameters of the radiation passing through. The optical sensor means 11 can be at any suitable point in the beam path of the optical receiver 5 be arranged.

The use of adaptive filters in the case of the combined earth-star sensor as well as in the case of 4 offers considerable advantages and possible extensions compared to the previously known systems. This should be explained using the example of the combined earth-star sensor:
The principle of the combined earth-star sensor lies in a joint observation of stars and earth by means of a sensor, the beam path being split into an “earth sensor” and a “star sensor”, for example by a partially transparent mirror. Since the apparent brightness of the earth is significantly greater than that of the observed stars, it makes sense to view it with a defined attenuation, which can be ensured by combining a filter with a beam splitter, which can, for example, reduce the earth's brightness by up to a factor 4000 can be weakened. Either a constant weakening can be provided, but adaptive weakening can also be provided.

The main advantage of an adaptive attenuation lies first in one opposite in the case of an always constant weakening of the earth's brightness susceptibility against stray light effects. These come to bear especially when the sun comes into the field of view of the earth sensor beam path. As well possible, however, the sun is less likely to enter the Star sensor beam path. Should Such a constellation can occur, for example, with the help the corresponding beam path is switched off by an adaptive filter, or can be darkened to such an extent that the interference influences the information of the other beam path. As a basic An alternative to a filter would be A mechanical shutter is also possible, but it has the disadvantages a mechanically movable arrangement, as already mentioned mentioned.

But it can also be the opposite Case, namely, that the edge of the earth appears so dark that it is always constant attenuation can no longer be clearly seen. Results from the invention now the opportunity the weakening to reduce the information about the center of the earth too available in such a case to be able to ask.

When using a system according to the invention with suitable adaptive filter means in both beam paths The sensor has the further advantage of being able to perform a large number of maneuvers To accomplish goal. This is shown in Tab. 1. With sufficient weakening of the corresponding beam path would be the sensor can even be used as a sun sensor. It is the same conceivable, both beam paths use as star sensors. This results in a higher position accuracy, if this is required and offers the decisive advantage that in this mode the orientations of the two beam paths are relative can be calibrated to each other. This reduces the deterministic inaccuracy of the system, such as for example, through change the alignment based on the start accelerations and vibrations can arise.

Tab.1: Anwendungsbeispiele für unterschiedliche Filterkombinationen

Tab. 1: Application examples for different filter combinations

A significant increase in the reliability of an earth-star sensor with a view to reducing downtimes and obtaining partial information (location) from the satellite / sensor can be expected if the two beam paths are protected against incorrect radiation. As described, the present invention solves this by using adaptive filters. In particular, the use of liquid crystal filters, such as ferroelectric liquid crystal filters or filters based on nematic technology, can be used. There are two types in particular: the "regular" liquid crystal filters, which can be influenced when the optical voltage of the filter is applied at a certain voltage such that the filter has a freely scalable degree of attenuation (for example up to approx. 300), and "bistable""Filters in which a voltage pulse between the optical states" transparent "and" closed "vice versa can be switched. For the "closed" state, this results in a weakening by approximately a factor of 1000. Both filter types can also be in one beam path (ie both filter types in one or both of the apertures 14 . 15 ) are attached. For example, these two filters can also be attached "back to back" in one beam path, that is to say with their rear sides adjoining one another, so that there is no disc otherwise customary for this type of filter, which can result in birefringence and weakening.

A special design of the adaptive filters described here are therefore filters which allow a stepped or freely scalable, continuous switching between optical states and thus allow an extreme dynamic range. This makes it possible to variably attenuate the radiation incidence, especially of the earth, in order to obtain optimal observation conditions for the earth's edge at different times of the day. In particular, the entire earth can be detected in the earth sensor part, including the entire earth edge. However, there is also an analogous advantage for the detection of stars in the star sensor part. Additionally or alternatively, it can be provided that one or both of the radiation inputs 14 . 15 "Switched off", namely can be largely optically blocked when the sun is in the field of view of one of the radiation inputs 14 . 15 comes in order not to impair (or as little as possible) the information content of the other beam path.This is essential insofar as this information would not be available if one of the beam paths were not closed, since the principle of the combined earth-star sensor Provides imaging on a single detector, which would then be overdriven.

Furthermore, it is when the "earth channel" (ie the entrance aperture) is completely open for the radiation emanating from earth) possible, a calibration of the System. For that should the earth first not be in the visual field of this entrance aperture. In particular, it can a search procedure was carried out be at first by closed filter (i.e. when the maximum attenuation of the Filters for the star input) to determine the orientation of the star sensor to then open Filters or opened Filter the stars from "Earth sensor" and "Star sensor" clearly assign to be able to. Then you can with the stars of the respective ray paths inertial position of the corresponding radiation inputs in the room and then their determine relative position to each other.

Claims (13)

Arrangement for controlling the incidence of radiation in an optical receiver ( 5 ) of a spacecraft, having an entrance optics ( 1 ), a detector arrangement ( 4 ) that match the entrance optics ( 1 ) is optically connected and at least one sensor means ( 11 ) to determine the current radiation incidence, characterized in that the detector device ( 4 ) at least one optical filter medium ( 9 ) is optically connected upstream, in which an optical change in state can be generated by control signals and which with the at least one sensor means ( 11 ) is connected for signaling purposes. Arrangement according to claim 1, characterized in that the at least one filter means ( 9 ) is designed in such a way that the optical change in state changes the optical attenuation of the filter medium ( 9 ) occurring optical radiation is achieved. Arrangement according to one of claims 1 or 2, characterized in that the at least one filter means ( 9 ) is designed as a bistable filter. Arrangement according to one of claims 1 or 2, characterized in that the at least one filter means ( 9 ) is designed such that a variable change in the optical state can be generated. Arrangement according to one of claims 3 or 4, characterized in that the filter means ( 9 ) is designed as a liquid crystal filter. Arrangement according to one of claims 1 to 5, characterized in that the at least one sensor means ( 11 ) via control electronics ( 10 ) with the at least one filter medium ( 9 ) is connected for signaling purposes. Arrangement according to one of claims 1 to 6, characterized in that that the optical receiver as Part of a position and / or position determination device Spacecraft is trained. Arrangement according to claim 7, characterized in that the optical receiver is designed as an earth sensor, star sensor or combined earth-star sensor and each entrance aperture ( 14 . 15 ) a filter medium ( 9 ) having. Arrangement according to one of claims 1 to 6, characterized in that that the optical receiver as Part of a data communication device of a spacecraft is. Method for controlling the incidence of radiation in an optical receiver ( 5 ) of a spacecraft, at least one sensor means ( 11 ) the current incidence of radiation in the optical receiver ( 5 ) determined and the sensor means ( 11 ) as a function of the radiation incident determined, signals to at least one device for controlling the radiation incident ( 9 ) transmitted with the at least one sensor means ( 11 ) is connected in terms of signal technology, characterized in that the at least one sensor means ( 11 ) Control signals to at least one optical filter means ( 9 ) which is sent to a detector device ( 4 ) is optically upstream, and the control signals cause an optical change in the state of the at least one optical filter means ( 9 ) is produced. A method according to claim 10, characterized in that the at least one sensor means ( 11 ) Control signals to at least one control electronics ( 10 ) transmitted and the control electronics ( 10 ) again control signals to at least one optical filter means ( 9 ) transmitted. Use of an optical filter medium ( 9 ), in which an optical change in state can be generated by control signals, for controlling the radiation incidence in an optical receiver ( 5 ) of a spacecraft, the optical filter means ( 9 ) a detector device ( 4 ) is optically upstream and with at least one sensor means ( 11 ) is connected for signaling purposes. Use according to claim 12, wherein the at least one sensor means ( 11 ) Control signals to at least one control electronics ( 10 ) transmitted and the control electronics ( 10 ) again control signals to the optical filter means ( 9 ) transmitted.