The disclosure relates to a method for re-entry prediction of an artificial space object and, more particularly, to a method for re-entry prediction of an uncontrolled artificial space object by using a drag scale factor estimation (DSFE) method.
The re-entry of an uncontrolled artificial space object of 1 ton or more is highly likely to cause damage to the ground. Therefore, the domestic response manual for a crash and collision of an artificial space object specifies that a crisis alert for the re-entry status of the space object is issued when an artificial space object reaches an altitude of 250 km or less. Accordingly, it is very important to provide accurate re-entry prediction information quickly in order to predict the re-entry status and risk of damage by artificial space objects.
Particularly, when artificial space objects fall and reach an altitude of 250 km, the artificial space objects begin the re-entry process into the atmosphere within about one month, and at the re-entry of an artificial space object with a weight of 1 ton or more, fragments of about 10 to 40% of the artificial space object reach the earth's surface. Particularly, the re-entry of an uncontrolled artificial space object is difficult to predict, which results in loss of lives and assets on the ground. Therefore, to prepare for the re-entry risk of space objects, a technique of predicting the re-entry risk of space objects is necessary to minimize such risk.
A method for re-entry prediction of an uncontrolled artificial space object in the related art is configured to predict a re-entry time point by using the simplified general perturbations 4 (SGP4) orbit propagator using two-line elements (TLE). However, when comparing the predicted re-entry time point with actual re-entry estimation time point and place, the prediction accuracy is very low, whereby there is a problem of not being applied to the re-entry status of the actual space object.
In order to solve the above problems, the disclosure provides a method for re-entry prediction of an uncontrolled artificial space object which is configured to accurately predict an expected time point and place of a re-entry of the space object by using a drag scale factor estimation (DSFE) method.
In order to achieve the above object, an embodiment of the disclosure provides a method for re-entry prediction of an uncontrolled artificial space object, the method includes: calculating an average semi-major axis and an argument of latitude by inputting two-line elements (TLE) or osculating elements of the artificial space object at two different time points; calculating an average semi-major axis, an argument of latitude, and an atmospheric drag at a second time point of the two different time points by performing orbital propagation with a Cowell's high-precision orbital propagator using numerical integration up to the second time point, the orbital propagation being performed by applying an initial drag scale factor, which is an arbitrary constant, to orbit information at the first time point; estimating an optimum drag scale factor while changing the drag scale factor until error becomes smaller than an arbitrary convergence value by comparing the predicted average semi-major axis or the argument of latitude with a preset average semi-major axis or a preset argument of latitude at the second time point; and predicting time and place of re-entry of the artificial space object into the atmosphere by performing orbit prediction with the Cowell's high-precision orbital propagator using numerical integration from the second time point to a re-entry time point and being applied with the estimated drag scale factor.
The two-line elements (TLE) may be converted into the osculating elements and an average orbit may be calculated in a true-of-date (TOD) coordinate system.
The convergence value may be a position error arbitrarily determined by a user.
As described above, according to the disclosure, the atmospheric re-entry time and place of an uncontrolled artificial space object can be precisely predicted by using the DSFE method.
The above and other objects, features and other advantages of the disclosure will be more clearly understood from the following detailed description when taken in conjunction with the accompanying drawings, in which:
Hereinafter, exemplary embodiments of the disclosure will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the disclosure pertains for the convenience of the person skilled in the art to which the disclosure pertains. The disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.
Hereinafter, a system and method for re-entry prediction of an uncontrolled artificial space object according to embodiments of the disclosure will be described.
Referring to
The SSN radar 100 and the OWL-Net 200 may obtain orbit information by observing the re-entry artificial space object. Here, the orbit information of the re-entry artificial space object may be two-line elements (TLE) observed by the SSN radar 100, or osculating elements observed by the OWL-Net 200.
The server 300 may include a communication interface 310 to communicate with the SSN radar 100 and the OWL-Net 200 for receiving the orbit information of a re-entry artificial space object, wherein the communication interface 310 may be a software or hardware interface; the processor 320 for predicting re-entry of the artificial space object by using the orbit information received through the communication interface 310, wherein the processor 320 may be a hardware processor and/or software processor; and the storage unit 330 for storing various information, data, programs, etc. related to the operation of the artificial space object re-entry prediction system, wherein the storage unit 330 is a non-transitory storage medium.
Referring to
Here, the initial orbital elements may be osculating elements observed by OWL-Net 200, or two-line elements (TLE) observed by SSN radar 100. Where the orbital elements are the two-line elements, the two-line elements are converted into osculating elements and the osculating elements may be used to calculate an average orbit in a True of Date (TOD) coordinate system. The average semi-major axes and the arguments of latitude are calculated by the processor 320 in the server 300.
Next, at step S110, S210, or S310, orbit propagation is performed up to the second time point t2 by applying an initial Drag Scale factor Dsf
argument of latitude
and atmospheric drag
according to the orbital element
at the second time point t2 predicted by a Cowell's high-precision orbital propagator using numerical integration, wherein Cd is a drag coefficient, A is a cross-sectional area, m is the mass, p is a degree of tightness, {right arrow over (v)}a is a velocity vector, and va is a velocity vector size.
The Cowell's high-precision orbital propagator is an algorithm to obtain the position and velocity of an artificial space object at an arbitrary time based on the consideration of all perturbing forces such as earth's gravitational field, atmospheric influence, attraction of sun and moon, solar radiation pressure, etc. that affect artificial space objects. Since this technique is widely known in the field, detailed description will be omitted.
Next, when the error of a comparative value of average semi-major axes of
or argument of latitude value
estimated by reflecting the drag scale factor Dsf from the first time point t1 to the second time point t2 with the initially input average semi-major axis SMAt2 or initially input argument of latitude value AOLt
Next, orbit prediction is performed by applying an optimized drag scale factor Dsf, through the Cowell's high-precision orbital propagator using numerical integration from the second time point t2 to a re-entry time point. Thus, the accuracy of prediction of re-entry time and place within 100 km altitude is improved, and atmospheric re-entry time and place (latitude, longitude, and altitude) of an uncontrolled artificial space object are predicted at step S150, S250, or S350.
While the disclosure has been particularly shown and described with reference to exemplary embodiments thereof, the scope of rights of the disclosure is not limited thereto and various modifications and improvements of those skilled in the art using the basic concept of the disclosure defined in the following claims are also within the scope of the disclosure.
Number | Date | Country | Kind |
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10-2018-0063148 | Jun 2018 | KR | national |
This application is a continuation-in-part application of co-pending U.S. application Ser. No. 16/146,157, filed Sep. 28, 2018, the disclosure of which is incorporated herein by reference. The present application claims priority to Korean Patent Application No. 10-2018-0063148, filed Jun. 10, 2018, the entire contents of which is incorporated herein for all purposes by this reference.
Number | Date | Country | |
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Parent | 16146157 | Sep 2018 | US |
Child | 18350740 | US |