CONSTELLATION SIMULATOR, SYSTEM AND METHOD FOR CALIBRATING A STAR SENSOR

Abstract

The present disclosure relates to a calibrated constellation simulator, a system and a method for calibrating and/or testing a star sensor assembled on a spacecraft. The calibrated constellation simulator comprises an optical device configured to project a defined star formation (IRF) of a star catalog onto a star sensor assembled on a spacecraft. Further, the calibrated constellation simulator comprises an alignment unit with a position and/or location reference (ARF) of the calibrated constellation simulator configured to detect a position and/or location of the calibrated constellation simulator in space, wherein the defined star formation (IRF) and the position and/or location reference (ARF) are in a first fixed calibrated rotation (Q.sub.OSPS) with respect to one another. The calibrated constellation simulator improves the calibration of the star sensor as an independent calibration standard. The constellation simulator becomes a calibration standard.

Claims

1. A calibrated constellation simulator for calibrating and/or testing a star sensor assembled on a spacecraft, comprising: an optical device configured to project a defined star formation (IRF) of a star catalog onto the star sensor assembled on the spacecraft, and an alignment unit having a position and/or location reference (ARF) of the calibrated constellation simulator configured for detecting a position and/or location of the calibrated constellation simulator in space, wherein the defined star formation (IRF) and the position and/or location reference (ARF) lie in a first fixed calibrated rotation (Q.sub.OSPS) relative to one another.

2. The calibrated constellation simulator according to claim 1, wherein the optical device has at least one optical unit together with a light source and a static constellation mask with the defined star formation (IRF) of the star catalog or a static or dynamic display unit for representation of the defined star formation (IRF) of the star catalog.

3. The calibrated constellation simulator according to claim 1, wherein the fixed calibrated rotation (Q.sub.OSPS) is implemented in a quaternion metric (Q.sub.OSPS) or in a rotation matrix (A.sub.OSPS).

4. The calibrated constellation simulator according claim 1, wherein the alignment unit has or is designed to have at least one unit from the following group of units: one or more mirror cubes, one or more prisms, one or more polished surfaces, and/or one or more reflective elements.

5. A system for calibrating and/or testing a star sensor assembled on a spacecraft, having: the star sensor, which is assembled on the spacecraft and has sensor optics, wherein the sensor optics has an alignment reference (BRF) and the star sensor has a mechanical position and/or location reference (MRF) with respect to the spacecraft, and wherein the alignment reference (BRF) and the mechanical position and/or location reference (MRF) lie in a second rotation (Q.sub.STR) with respect to one another; the calibrated constellation simulator according to claim 1, arranged in space around the spacecraft; and a detection unit assembled on the spacecraft, configured to detect at least one feature of the alignment unit of the calibrated constellation simulator, wherein the system is configured to calibrate the star sensor and the calibrating comprises determining at least one feature of the alignment unit by the detection unit after converting the alignment reference (BRF) to the position and/or location reference (ARF) using the second rotation (Q.sub.STR) and the fixed calibrated rotation (Q.sub.OSPS).

6. The system according to claim 5, wherein the system is configured in such a manner that detecting the least one feature by the detection unit comprises optical detection using an optical detection unit.

7. The system according to claim 6, wherein the system is configured in such a manner that the optical detection is performed using autocollimation.

8. The system according to claim 5, wherein the fixed calibrated rotation (Q.sub.OSPS) are or are implemented in a quaternion metric (Q.sub.OSPS) or in a rotation matrix (A.sub.OSPS).

9. The system according to claim 5, wherein the system is configured in such a manner that a transfer is determined by the following formula: $Q_{ARF}\left(\mathrm{BRF},\mathrm{IRF}\right)=\mathrm{Inv}\left(Q_{STR}?Q_{\mathrm{OSPS}}\right)$ wherein Q.sub.ARF represents the transfer, Inv the operator for the inversion of a quaternion, Q.sub.STR the quaternion output by the star sensor, ? the operator for the quaternion multiplication, and Q.sub.OSPS the calibrated rotation.

10. The system according to claim 5, wherein the system is configured in such a manner that the calibration of the star sensor is performed to a reference system (SCRF) of the spacecraft.

11. The system according to claim 5, wherein the spacecraft is designed as a satellite, or a space capsule.

12. A method of calibrating and/or testing a star sensor assembled on a spacecraft using a calibrated constellation simulator, comprising the following method steps: detecting a second rotation (Q.sub.STR) resulting from a relative alignment reference (BRF) and a mechanical position and/or location reference (MRF), wherein the alignment reference (BRF) is a reference of sensor optics of the star sensor and the mechanical position and/or location reference (MRF) is a reference of the star sensor with respect to the spacecraft; converting the alignment reference (BRF) to a position and/or location reference (ARF) of a calibrated constellation simulator using the second rotation (Q.sub.STR) and a first fixed calibrated rotation (Q.sub.OSPS), and calibrating the star sensor by detecting at least one feature of an alignment unit of the calibrated constellation simulator by a detection unit assembled on the spacecraft.

13. The method according to claim 12, further comprising: reading out of the fixed calibrated rotation (Q.sub.OSPS), which results from a defined star formation (IRF) of a star catalog and the position and/or location reference (ARF) of an alignment unit of the calibrated constellation simulator.

14. A computing unit having a processor unit, a communication interface and a storage unit for calibrating and/or testing the star sensor assembled on the spacecraft for use in the calibrated constellation simulator according to claim 1.

15. A computer program, wherein the computer program is loadable into the storage unit of the computing unit according to claim 14 and has program code portions for causing the computing unit to execute the method for calibrating and/or testing the star sensor assembled on the spacecraft when the computer program is executed in the computing unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Exemplary embodiments of the disclosure are described in more detail below with reference to figures, in which the following are shown schematically and by way of example:

[0031] FIG. 1 shows a schematic diagram of a calibrated constellation simulator in accordance with one embodiment of the disclosure;

[0032] FIG. 2 shows a schematic diagram of a system in accordance with one embodiment of the disclosure;

[0033] FIG. 3 shows a flow chart of a method in accordance with one embodiment of the disclosure, and

[0034] FIG. 4 shows a schematic diagram of a computing unit in accordance with one embodiment of the disclosure.

[0035] The accompanying figures are intended to provide a further understanding of the embodiments of the disclosure. They illustrate embodiments and serve to explain the principles and concepts of the disclosure in connection with the description. Other embodiments and many of the advantages mentioned are shown in the figures. The elements of the figures are not necessarily shown to scale. In the figures, identical, functionally identical and identically acting elements, features and components are each provided with the same reference numerals, unless otherwise stated.

DETAILED DESCRIPTION

[0036] FIG. 1 shows a schematic diagram of a calibrated constellation simulator in accordance with one embodiment of the disclosure; In FIG. 1, reference numerals 110 denotes the calibrated constellation simulator according to the disclosure. The constellation simulator 110 is designed to calibrate and/or test a star sensor assembled on a spacecraft 130, for example a satellite, a space capsule or a spacecraft. The calibrated constellation simulator 110 comprises an optical device 111 and an alignment unit 113. The optical device 111 is configured to project a defined star formation IRF of a star catalog, in embodiments, onto a star sensor 120 assembled on a spacecraft 130 (see FIG. 2). Further, the constellation sensor 110 comprises the alignment unit 113 with a position and/or location reference ARF of the calibrated constellation simulator 110 configured for detecting a position and/or layer of the calibrated constellation simulator 110 in space, wherein the defined star formation IRF and the position and/or location reference ARF are in a first fixed calibrated rotation Q.sub.OSPS with respect to one another.

[0037] With the constellation simulator 110 according to the disclosure, a mirror cube assembled on the star sensor can be dispensed with, and thus also the time-consuming alignment measurement as part of the manufacture of a star sensor. Embodiments of the present disclosure enable a higher production throughput to be achieved, as is necessary for a constellation program. Further, time, cost and mass savings can be achieved for the star sensor. Embodiments of the present disclosure provide the constellation simulator 110 according to the disclosure with an alignment reference. The constellation sensor 110 thus comprises an optical reference comprising an alignment unit 113. The alignment unit 113 may have or be designed to have one unit from the following group of units: one or more mirror cubes, one or more prisms, one or more polished surfaces, and/or one or more reflective elements, e.g. adhesive pads. The optical reference is designed to measure its layer in space.

[0038] The transformation Q.sub.OSPS (IRF->ARF) inherent in the constellation simulator 110 as a fixed rotation between the star formation IRF (inertial reference frame) comprising a real star pattern from a star catalog and the position and/or location reference ARF of the alignment unit 113 (alignment reference frame) is used to reference the alignment unit 113 on the constellation simulator to the BRF of the star sensor Q.sub.STR (IRF->BRF) via its common quaternion Q.sub.STR. Thus, the star sensor 120 BRF can be connected to the constellation simulator 110 ARF via the measured quaternion Q.sub.STR and the calibrated rotation Q.sub.OSPS as follows:

[00002]$Q_{ARF}\left(\mathrm{BRF},\mathrm{IRF}\right)=\mathrm{Inv}\left(Q_{STR}?Q_{\mathrm{OSPS}}\right)$

[0039] The calibrated rotation Q.sub.OSPS can be executed in a quaternion metric Q.sub.OSPS or in a rotation matrix A.sub.OSPS. Thus, the constellation simulator 110 according to the disclosure becomes a calibration standard for calibrating and/or testing star sensors 120 on a spacecraft 130 (see FIG. 2) by means of an integrator to the reference system of the spacecraft SCRF (see FIG. 2). It may be provided that the constellation simulator 110 is calibrated once by the manufacturer. Here, each side of the alignment unit 113 receives a clearly assignable calibration rotation, for example in the form of a rotation matrix or a quaternion. By means of the optical device 111, a known star formation from a star catalog can be projected onto the star sensor 120 (see FIG. 2) by an optical system of the optical device 111. The calibrated constellation simulator 110 may be used to calibrate and/or test a star sensor 120 already assembled on a spacecraft 130.

[0040] FIG. 2 shows a schematic diagram of a system in accordance with one embodiment of the disclosure; In FIG. 2, reference numerals 100 denotes the system according to the disclosure with a spacecraft 130. A star sensor 120 is assembled on the spacecraft 130. Further, the spacecraft 130 has a detection unit 150. In addition, the system 100 has the calibrated constellation simulator 110 according to the disclosure.

[0041] The star sensor 120 is in embodiments assembled on the spacecraft 130 and has sensor optics 121. The sensor optics 121 has an alignment reference BRF. The star sensor 120 has a mechanical position and/or location reference MRF with respect to the spacecraft 130. The alignment reference BRF and the mechanical position and/or location reference MRF are in a second rotation Q.sub.STR to one another.

[0042] The calibrated constellation simulator 110 may be arranged in space around the spacecraft 130. In particular, the calibrated constellation simulator 110 may be arranged and/or mounted on the star sensor 120. The detection unit 150 is assembled on the spacecraft 130 and configured to detect at least one feature of the alignment unit 113 of the calibrated constellation simulator 110. The system 100 is configured for calibration, which comprises a determination of at least one feature of the alignment unit 113 by the detection unit 150 after a transfer of the alignment reference BRF to the position and/or location reference ARF using the second rotation Q.sub.STR and the fixed calibrated rotation Q.sub.OSPS.

[0043] The system 100 further has the computing unit 140 according to the disclosure. The computing unit 140 can be arranged centrally or decentrally and can be in data communication with the system 100 and/or the constellation simulator 110 and/or the star sensor 120 via a communication medium, for example signal lines and/or BUS system and/or Ethernet and/or WLAN. Alternatively, the computing unit 140 can be outsourced to a cloud.

[0044] Using the system 100 according to the disclosure and the calibrated constellation simulator 110 according to the disclosure, an integrator/user can calibrate and/or test the star sensor 120 himself after mounting it on a spacecraft 130. No complex measurement technology is required for calibration and/or testing. By means of a calibrated star formation IRF of a star catalog of the star sensor, the system 100 uses the rotation Inv(Q.sub.STR) supplied by the star sensor from the BRF into the IRF and the fixed calibrated constellation simulator 110 rotation Q.sub.OSPS from the IRF into the ARF to make the star sensor 120 BRF visible (measurable) to the outside. The quaternion representation (quaternion metric with Q.sub.OSPS) or rotation matrices (classic rotation matrix A.sub.OSPS) can be used for the calculation. The system 100 uses the calibrated constellation simulator 110, whose 3-axis rotation is known between the output star formation IRF of the constellation simulator 110 and the position and/or location reference ARF of the fixed assembled alignment unit 113. The quaternion Q.sub.STR provided by the star sensor 120 describes the 3-axis rotation between the IRF and the BRF of the star sensor 120. The known 3-axis rotations STR and OSPS transfer the star sensor BRF to the ARF of the calibrated constellation simulator 110 through the following relationship:

[00003]$Q_{ARF}\left(\mathrm{BRF},\mathrm{IRF}\right)=\mathrm{Inv}\left(Q_{STR}?Q_{\mathrm{OSPS}}\right).$

[0045] The star sensor 120 BRF can be measured optically from the outside, e.g. by means of autocollimation, via the alignment unit 113 of the calibrated constellation simulator 110 through the transfer and application of the quaternion transformation. The required 3-axis rotation to the reference system of the SCRF spacecraft can be determined. For example, this can be determined by an integrator/user.

[0046] The constellation simulator 110 ARF has a fixed calibrated relationship to the IRF via the Q.sub.OSPS, which means that the calibrated constellation simulator 110 can be placed in any orientation relative to the star sensor 120. There must be no optical field clipping between the calibrated constellation simulator 110 and the star sensor 120. The calibrated constellation simulator 110 can be set up with any roll orientation (z axis). For alignment in the x-y axis without optical field trimming, a corresponding mounting device can be used. By means of the present disclosure, the constellation simulator 110 can be used as an alignment calibration standard for calibrating and/or testing star sensors 120 assembled on spacecraft 130.

[0047] FIG. 3 shows a flow chart of a method in accordance with one embodiment of the disclosure. In the embodiment shown, the method V comprises several method steps. In a first method step S1, a second rotation Q.sub.STR is detected, which results from a relative alignment reference BRF and a mechanical position and/or location reference MRF. The alignment reference BRF is a reference of a sensor optics 121 of the star sensor 120, and the mechanical position and/or location reference MRF is a reference of the star sensor 120 with respect to the spacecraft 130.

[0048] In a further method step S2, the alignment reference BRF is transferred to a position and/or location reference ARF of a calibrated constellation simulator 110 using the second rotation Q.sub.STR and a first fixed calibrated rotation Q.sub.OSPS.

[0049] In a further method step S3, a calibration S3 of the star sensor 120 is performed by determining at least one feature of an alignment unit 113 of the calibrated constellation simulator 110 by a detection unit 150 assembled on the spacecraft 130.

[0050] Furthermore, a readout of a fixed calibrated rotation Q.sub.OSPS can be provided, which results from a defined star formation IRF of a star catalog and a position and/or location reference ARF of an alignment unit 113 of a calibrated constellation simulator 110.

[0051] The order of the method steps, particularly as described in the illustrated embodiment, and/or partial aspects of the method steps, where appropriate, can also be changed and/or exchanged.

[0052] FIG. 4 shows a schematic diagram of a computing unit in accordance with one embodiment of the disclosure. In FIG. 4, reference numerals 140 denote the computing unit according to the disclosure for use in a calibrated constellation simulator 110. The computing unit 140 can be used to calibrate and/or test a star sensor 120 assembled on a spacecraft 130 (see FIG. 2). The computing unit 140 can be implemented as a computer, control apparatus or as a control unit in the system 100 (see FIG. 2). Alternatively, the computing unit 140 can be implemented in a cloud. The data is exchanged via data communication between the computing unit 140 in the cloud and the system 100 via a communication connection/data communication connection.

[0053] The computing unit 140 has a storage unit 141. In the storage unit 141, the method for calibrating and/or testing a star sensor 120 assembled on a spacecraft 130 using a calibrated constellation simulator 110 (see FIG. 2) can be stored as program code. The computing unit 140 further has a processor unit 143. The processor unit 143 is designed to carry out the method according to the disclosure and the method steps. The processor unit 143 is in data communication with the storage unit 141 via a communication interface 142. The communication interface 142 may comprise appropriate communication protocols and hardware implementation for communication. Further, the communication interface 142 is designed to provide data communication with the computing unit 140 and the system 100 (see FIG. 2) and the components of the system 100. In addition, the communication interface 142 may be designed for communication of the system 100 with the cloud.

[0054] The term may refers in particular to optional features of the disclosure. Accordingly, there are also developments and/or exemplary embodiments of the disclosure which additionally or alternatively have the respective feature or the respective features. From the feature combinations disclosed in herein, isolated features may also be singled out as required and, by resolving an optionally existing structural and/or functional relationship between the features in combination with other features, be used to delimit the subject matter of the claim. The order and/or number of method steps may be varied.

REFERENCE SIGNS

[0055] 100 system [0056] 110 calibrated constellation simulator [0057] 111 optical device of the calibrated constellation simulator [0058] 112 optics of the optical device [0059] 113 alignment unit [0060] 114 coherent light source [0061] 115 static constellation mask/static or dynamic display unit [0062] 120 star sensor [0063] 121 sensor optics [0064] 130 spacecraft [0065] 140 computing unit [0066] 141 storage unit [0067] 142 communication interface [0068] 143 processor unit [0069] 150 detection unit [0070] ARF position and/or location reference of the calibrated constellation simulator [0071] A.sub.OSPS rotation matrix [0072] BRF alignment reference [0073] IRF defined star formation [0074] MRF mechanical position and/or location reference of the star sensor [0075] Q.sub.OSPS first fixed calibrated rotation [0076] Q.sub.STR second rotation [0077] SCRF reference system of the spacecraft [0078] V method [0079] S1-S3 method steps