Modeling of Ground Based Space Surveillance System Based on MAS Method. Xue Chen 1,a, Li Zhi 2

Transcription

1 Applied Mechanics and Materials Online: ISSN: , Vols , pp doi: / Trans Tech Publications, Switzerland Modeling of Ground Based Space Surveillance System Based on MAS Method Xue Chen 1,a, Li Zhi Equipment Academy. Beijing, China a xuechen_006@ 163.com Keywords: Ground based Space Surveillance System; MAS modeling; UML Abstract. Introducing the operational principle and basic composition of ground based space surveillance system (GBSSS) [1]. Expound the steps of modeling by MAS method. After analysed how does GBSSS work, we build the simulation model of GBSSS. Lastly, we are using UML to give a structure of core simulation software based on MAS model of GBSSS and REPAST HPC, and descript how to achieve it. Introduction The complexity of space environment has already impacted on normal human space activities. So, the space situation awareness (SSA) has become more and more important. There are two means, ground base and space base, as the approaches to SSA. Because of many restrictions, such as power, technology, maintenance costs, space based space surveillance system can t play a major role. Currently, we still need GBSSS to complete the tasks which are searching, catching, discrimination and catalogue of orbit objects, and orbit determination etc. However, the prime cost of ground based space surveillance net (SSN) [2] is high and the construction is a very complex work, and if not simulate the whole process, it will be easy to cause a lot of wastes. In addition, GBSSS of other countries could make a big threaten to our space vehicles if we don t simulate the situation of GBSSS. So, we must establish a GBSSS simulation model to dispose of these problems above. MAS modeling method, which regard every unit in the system as an that can make a special effect, reflects active situation that the system runs, and we can achieve the target of researching complex systems by communicating between s interactively. This method gives expression to the uncertainty and emergence of complex systems beautifully. So, we decide to establish GBSSS model by MAS method. Components, and rule properties of simulation system Components of simulation system. GBSSS is composed of ground based radar system, photoelectricity telescope system, orbit objects data bases, and control center. Specific equipment can be divided into general survey type devices and precision tracking type devices. NAVSPASUR system is mainly general survey radar to the U.S., and the precision tracking devices comprise AN/FPS-85 phase array radar, MILLSTONE and HAYSTACK parabolic radar etc. These devices constitute the whole space surveillance net (SSN). Rule properties. Rule properties of GBSSS equipment. (1) General properties. GBSSS stations have 5 general properties below: the geographical position, observation area, maximum and minimum elevation angle, maximum and minimum azimuth angle, maximum and minimum detecting range. (2) Special properties It has many special properties to radar devices, which come from Radar Equation. The specific contents show as table 1 below. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-05/03/16,17:20:11)

2 2756 Vehicle, Mechatronics and Information Technologies II Table 1 Special properties of radar device [3] Properties Implication Properties Implication Pt Transmitter Peak Power T e Noise temperature Gt Transmitter Antenna Gains f Signal bandwidth Ar Effective area of radar receiver Antenna Working frequency S / N Signal to noise ratio L Loss factor Special property of photoelectricity telescope is mainly the minimum snr threshold T SN. The rule properties of Obit objects The general properties of Obit objects are consist of position vector, velocity vector, which are volumes under J2000 coordinate system, RCS characteristic, apparent magnitude, geometric characteristic. Among them, apparent magnitude is an active variable quantity and that is a function which relate to the phase angle of orbit object and the range between object and station. RCS characteristic is affected by the size and surface material of objects and radar s working frequency. Here, we give the empirical value of RCS of normal obit objects as simulation RCS volume, just for convenience. MAS modeling Steps[4] When establishing a GBSSS model, we must follow some steps below. (1) Analyse any concrete characteristics of objects modeled. (2) We will establish an interactive model of s to ensure the structure of each s after analyzing. (3) On the basis of the functions and working principle of the entities which constitute GBSSS, we begin to establish the physical model of s. It will be divided two parts, the first is to have attribute sets, which contain all the properties of every in the GBSSS scenario, such as the unique ID to every, the name, and other special properties of s; The second step is to finish the action sets, which consist of the behaviors of s and some reaction of s under the influence of outer environment. Running of orbit objects around the earth and the detection by ground based devices are all belong to the scope. MAS modeling of GBSSS Establish s interactive model [5]. As the steps of part 3 presented, after analyzing the structure of the GBSSS, we start to Establish s interactive model. Interactive model is shown as figure 1. Orbit Object s General survey radar Survey and catalogue Data and Data processing control center Identifying and tracing Inducting before tracing Generating tracing plan Data processing Inducting before tracing Observing minutely and identifying Tracing radar Data processing Generating tracing plan Photoelectricity telescope Figure 1 GBSSS interactive model with orbit objects Now, I will introduce the specific interaction process between GBSSS s and object s. General survey radar s start to search orbit objects s firstly, and transmit initial orbital determination information to data and control center. Then, data and control center generates a tracing plan and control tracing radar s and photoelectricity telescope s to observe minutely and identify orbit objects. This time, general survey radar s provides inducting to the two kinds of devices before tracing. At last, the data acquired by radar s and telescope s will be transmitted to the DC center to have farther process.

3 Applied Mechanics and Materials Vols Establish physical model (1) Physical model of station ID: the unique mark of station ; Name: The name of station, the uniform class is station. Attribution set: Table 2 Properties of station Properties Geographical position Detecting range Other properties Action set: Action The judgement of visibility Noting data The latitude, longitude, elevation of Station located The area that is divided by maximum and minimum elevation angle, maximum and minimum azimuth angle, maximum and minimum detecting range Radar: P t, T e, G t, f, A r,, S / N, L ;photoelectricity telescope : T SN Table 3 The action of station The visibility of orbit objects is judged by many constraints, the properties of objects must be satisfied with geometry visible(objects is in the area of detecting range), apparent magnitude visible(the volume must be less than the maximum), RCS visible(the snr must beyond minimum). If the objects fulfill all the condition above, note its ID and count the number of objects. (2) Physical model of orbit objects ID: the unique mark of orbit objects ; Name: the name of orbit objects, the uniform class is onorbittarget. Attribution set: Table 4 Properties of orbit objects Properties position vector, velocity vector Orbit parameter Action set Action Running along orbit Note the transit time Position coordinate and velocity vector under J2000,it consists of x, y, z, vx, vy, vz,6 components totally. The volume will be updated constantly. The orbit parameter will be updated constantly. when objects runs,it contains semimajor axis, eccentricity, inclination, argument of perigee, RAAN, true anomaly. Table 5 The action of orbit objects Using SGP4 model to update the position coordinate of objects in one time step. When objects pass through the detecting area, we will note the arc of orbit track. This parameter is expressed by transit time. Using UML to establish GBSSS MAS model framework On the base of GBSSS MAS model, we intend to structure the MAS simulation model by Unified Modeling Language (UML) [6]. The logical class diagram of orbit object is shown as figure 2. Members variable come from attribute sets of onorbittarget class basically. Here we don t make a redundant introduction. The titles behind red labels are member functions. OrbitTarget() is constructor that is responsible for initializing members variable; ~OrbitTarget() is used to delete objects when it has been disappeared. Advance() is the track pre push program, and it supply updated orbit data to variable ele. get_pv() and get_ele() can output and show pv and ele volume. step() is to control the simulation time step size. The last 4 functions are used to calculate the range from some station to the object, the detected arc and probability respectively. Record() is to note all of calculation results.

4 2758 Vehicle, Mechatronics and Information Technologies II Figure2 The logical class diagram of orbit object Figure 3 is radar station class diagram. It is similar with object class diagram. Excepting position and address variable, it has constraints variable to show a piece of area as observing district. Judge_and_Record() function is used to judge the objects weather be satisfied with geometry visible and RCS visible. Telescope station work in the similar principle, and just the function Judge_and_Record() judge objects through geometry visible model, not RCS model. The logical class diagram of telescope station is shown as Figure 4. Figure 3 The radar station class diagram Figure 4 The telescope station class diagram UML logical class diagrams exhibit interactive relation between GBSSS and orbit objects perfectly, and it can be transformed as executable program easily. Summary After analysing GBSSS structure and working principle deeply, and introducing the general process of MAS modeling method, we establish the GBSSS interactive model and physical model. Facts proved that MAS can exhibit the kind of interactive relation between GBSSS and orbit objects flexibility. More importantly, it has performed system s uncertainty and emergence of GBSSS. In this sight, MAS is the best mean to model GBSSS. At the end of this paper, we give some UML class diagrams to establish a framework of MAS simulation model, which can make a convenient description to the last program. References [1] McCall G H.Space surveillance[r].vandenberg: Air Force Space Command,2001. [2] Liu Zhonggui. Design of space objects surveillance system[d]. Nanjing Univercity, [3] Zhang Guangyi, Wang Dechun. Space surveillance detecting phased array radar [M]. Beijing: Publishing House of science. [4] Ang Yang. A Networked Multi- Combat. Model: Emergence Explained. New South Wales, Australia, 2006: [5] Liu Yong. Researching of MAS theory and application [D].Chongqing University, [6] Wendy Boggs, Michael Boggs. UML and Rational Rose2002 [M]. Beijing: Publishing House of Electronics Industry, 2002.

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