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Interactive System for Computation of Spacecraft Orientation Parameters of Control
INTERACTIVE SYSTEM FOR COMPUTATION OF SPACECRAFT ORIENTATION PARAMETERS OF CONTROL R. K. Kazakova The Keldysh Institute of Applied Mathematics, the USSR Academy of Sciences, Moscow, USSR
Abstract. This report considers the interactive system for computation of the optimal variant of spacecraft orientation alterations during the manoeuvres and performance of scientific experiments in space. The system consis~s of blocks, which computate the turns of spacecraft and its apparatus on given angles or matching the aparatus' axes with given directions in space. Interactive means based on graphical display facilitate the change of quality criterion during the choice of an optimal solution. The system is orientated on its usage in the process of spacecraft flight Keywords. Interactive system, orientation characteristics, light pen, light buttons, limb, terminator. INTRODUCTION The necessity of solving the following problems exists during the manoeuvres of spacecraft and performance of scientific experiments connected with its definite orientation in space: - computation of characteristics of the spacecraft's location in space according to a given position of orientational sensors; - computation of needed location of orientational sensors for realization of the spacecraft's given position in spacel - control of the correct work conditions for the orientational system during the manoeuvre concerning the variation of the spacecraft's orientation.
The comprehension and large scale of orientational system capabilities of contemporary spacecrafts reguire special set of computer programma for their solution. Such programma should consist of rather exact models of inertial, optical and ratio apparatus of orientational system and also in particular cases should contain models of gyro and reactive engines, which we call executive force. Each of this sensors and devices have definite position in the spacecraft and is characterized by the location of axis, by their fields of vision and sensitivity of transducers, possible turns of elements, and permissible consequence of operations. It is rather difficult to foresee all possible cases of interaction of above-mentioned modules, so refers to all possible values of orienta-
359
360
R. K. Kazakova
tional system's parameteres during -computation of directions to additiothe design of the spacecraft and lanal sat of celestial bodies; ter during its flight. In other words, - computation of vision (taking into the required set of computational consideration the visible angular dimethods for solving various problems, mensions) of celestial bodies in giwhich appeared during the performance ven field of vision and with the given of a spaceflight, is more complicated axes of sighting; than any complex automatical program- computation of characteristics of ming system. angles alteration between the directions to the given celestial bodies Sooner or later close character of with time of flight, such programming complex will come - computation of an~les between a giin contradiction with the extension ven directions, requirements of possible sphere of the problems solved. A system which consists of sufficiently complete set of elementary operations to compute the spacecraft's orientation parameters and interactive means which allow to form the necessary set of operations in order to obtain a desired result just through the ~roblem solution is an alternative to the fixed set of the automatic programming systems.
- computation of axes orientation of the coordinate system, connected with the spacecraft, for known direction of vectors, given in this coordinate system. - computation of the given vector position after its turn in space, - performance of widenedoparations of vector algebra.
The above-mentioned functions are realized in the system with the help of There is a complete set of such primodules of "operation of language mitive operations to compute orientation characteristics which was checked for the computation of spacecraft orientation" and "the programm for by the solution of various problems. The sufficient list of them was perfor- computing the directions of the spacecraft in space" (see Fig. I). med in the report by Kazakova (I97I). The present report is aimed to discribe the second part of the above system - the interactive means for the control of computations of orientation parameters and the system of parameters computation as a whole. THE STRUCTURE OF THE SYSTEM
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The first module provides the performance of actions and comprehensive operations in terms of vector algebra, with the following algebra objects: vectors, directions and coordinate systems. The second module provides the performance of actions and operations in terms of names of directions and axes of spacecraft and celestial bodies. In general the consequence of addres-
ses to modules pointed out depends on results of operations and is determined during computation. The ability to modify the order of computations directly during the process of their performance is provided by means of dynamic control of works. There is the following method of dynamic control of works in the described system. All programm modules of package of applied programm are translated and loaded together with the main programme The access to them is realized by addresses from the main programm after the consumer indicates the corresponding light button on the screen of display. The light button is defined as any arbitrary object (latter, word, point or line), which is shining on the screen of display and is stored in the computer as definite structure of data. The indication of light pen to a light button causes reset state in the computer, that can be processed by programmapparatus means so that the address in computer storage is specified as a result of this actions, and according to this address the indicated light button is stored. According to this information we can determine the number of indicated light button (if their numbers are correct). Representation of light buttons of display screen is performed by a special
361
programm (Lazutin, 1972) , addressing to which is made from a main programm, written in terms of ~ORTRAN. This programm provides representation of mentioned formal parameters of certain part of storage, called "display buffer". It contains the desired light buttons until the user indicates necessary button by light pen. In this case the programm stores the number of indicated button and finishes its activity turning control to the basic programm. The basic programm, so called "the light buttons operating programm", provides causing (according to mentioned number) of subroutine 0r a number of subroutines out of the package in order to perform the operdtion according to light button distinguished by the user. When this programm ends the control again turned to the subroutine of lighting out, also informing about point of display buffer's domain which contains the needed set of light buttons. So the interactive system of calling and executing of translated FORTRAN-programma is organized as it has shown before. To realize this system it is necessary to provide the storage for needed light buttons in the display buffer and also to have a certain part of basic programm for light button. The problem of dynamic exchange of data between programma is more complecated. In the described system the "COMMON"-operation of FORTRAN is used to organize such informational field. Every operation from applied package has its own part of data in the informational field (they may coincied for different programma). This part of storage contains internal and external arreas of given operation. The analysis of
362
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calculational processes in the system of calculation of spacecraft's orientation shows that data handled may be classified in the following way: - standart data at which we aware constructing system,
in standart part of I:lemory or is transformed from standart part of memory to the indicated point of information field,or in this programm there exist input and addressing to following programms of the given regime.
- data which have standart format and standart application, but whose concrete values we obtain during solving the problem, - data whose format and type of application are not defined apriory. Standart data are stored in lists of tables with fixed format. There are specialized fields in the informational field for data with standart format. There is a special access to the working fields for scalar values, vectors and ~atrixes which are connected with interactive operations upon them to operate with apriory indefined data. There are two ways at transfering of data, autowatical and manual. Automatical method realized by concordance of external and internal arrears of applied programma in the inforlliational field or by special transfering of data with main programme Manual method is necessary to use the capability of transformating of data while constructing. It was realized by sensors of light buttons which is similar to the discribed. The light buttons corresponds to every element of informational field (single, variable or massive). A set of such light buttons is selected into special table which is lighted on display screen (see Fig. 2). Due to the corresponding programm of processing the light buttons according to the regime of data work the object of information field is stored
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There are 3 regimes of data processin~ input, output and dynamic data control. Each of these regimes is realized as a special programm of processing light buttons of information field. The first regime (see Fig. 3) provides input from every indicated by li&bt pen installation in the mentioned part of memory. The keeboard of light buttons on the display screen is one of the variants of input.
363
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The second regime provides output from a standart domain of memory on any exterior installation indicated by a light button and on the display screen too (Fig. 4).
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This regime stipulates the correction to locate suitably the obtained time D,ynamic data processing provides the data on the screen (Kazakova, 1976) performance of the simpliest operatioos as well as to add the points of trawith scalars and vectors and transjectories for the moment of time giportation of data. The performance of ven in the regime "data input". these operations is made in the stanIMAGE OF THE ORIENTATION dart memory domain, and exchange of standart data region with information SPACECRAFT CHARACTERISTICS field is provided by buttons of The spacecraft location is described information field. by the radius-vector of the coordinaDuring ballistic projection (or desig- te system origin, connected with this ning) the possibility of determinaspacecraft. Position of the spacecraft tion of motion's characteristics in and its sensors in space is described any moment of time during the flight by the set of three-dimensioned vecof projecting spacecraft Or celestial tors and matrix of transforming the body is of great importance.So in the connected coordinate system into the system the method of access of data absolute system of coordinates. While is realized which is additional to men- calCUlating it may be necessary to tioned above and is based on utilizasee the mutual position of the spacetion of dots,by which the trajectory craft, its sensors and celestial boof constructing object and orbits of dies. Here two points of view may be celestial bodies are represented. To used: each point of this sort we establish I. External - when all vector set is the correspondence of set of coordirepresented under any angle of appr~ nate and velocity components for a given moment of time in the memory. 2. Internal - when some part of In order to input data concerning surrounding space is represented F IG.Y.
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.-
-- -
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.
364
R. K. Kazakova
which is visible along the selected line of sighting taking into consideration the field of view of the given sensors. External point of view allows to see a mutual position of sensor axes of the spacecraft. Internal point of view - what part of space gets into the field of view of the chosen sensor. Modern facilities of computer graphics permit to receive comparatively easy the orientation characteristic image according to the internal point of view. For this purpose a special modul has been specified in this system. This modul provides:
tion in form of the print of planetgraphic latitude and longitUde of the indicated point.
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- image of field of vision on the display screen or grafplotter; - image of the scale of the degree net in this field of vision with the standart step, - survey of all directions known in the system and image of visible object positions in form of a point in the sensor's field of vision. In addition the angular diuension of such objects is less, than a step of display's discretenessi - definition and image of the disc parts, limb and terminator, visible in the sensor's field of vision. The example of this displayed image is shown in Fig. 6. It may be composed the impression about dynamic of the relative motion of spacecraft and celestial body visible in sensor's field of vision by surveying image on the display screen during successive time moments. It can be noted that points of limb, disc and terminator visible on the display screen are the light buttons. The indication to this point excites the reac-
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Indication to the point in the planetary disc by the light pen offers the possibility to the user to get the print planetgraphic latitude and longitude of this planet point. There is a possibility to place the lighting point on the visible disc part according to the given planetgraphic latitude and longitude. Indication to the point celestial body by the light pen excites the reaction in form printing the body name and its characteristics (absolute coordinate and others). Image of the orientation characteristics from the external point of view is less Visually (see Fig. 7), YKAII-1TE BEKTOP
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365
Interactive System for Computation of Spacecraft
However, it can be benefit as means of access to the characteristics of any directions and the axes of the spacecraft sensors. This imagination is an external perspective projection on the display screen of unit vectors of all directions fixed with the spacecraft. The center of projection where abserver's eye disposes, direction of sighting line and scale can change itself with the help of the light buttons (see Fig. 6). This allows to consider i~age unit vectors of directions from the different points of view, to receive imagination about mutual disposition of vectors. Each vector on the display is connected with the data file characterizing the vector direction in fixed and absolute coordinate systems in the memory of the disign system. As an absolute coordinate system we can take any coordinate system from some sufficiently full set by the light pen. Each vector on the display screen plays a part of light button. The indication to the vector by the light pen excites the print and addresses the orientation characteristics of this vector to standart cells of memory. There is a possibility of realization to draw a picture from a direction which is normal to two indicated vectors or from the direction of intersection line of two planes which are defined by four indicated vectors. It is also possible to obtain characteristics of their mutual orientation (angele between them etc) by indicating to two vectors. The bUilding of reference point with indication to the names and basic values of orientation is produced by a consumer with the help of teletype write or light pen.
CONCLUSION The utilization of described interactive system gives large possibilities to determine characteristics for control of the spacecraft orientation during its flight. The author wishes to express her sincere appreciation for the encouragement and invaluable guidance extended by Platonov A.K. during the preparation of this paper. REFERENCES KaS8KOBa, P.K., nna~oHOB A.K. (1971). l1ShlK ,l(JIH orUlcaH~fl Bpaa(eH~fi I;OCMH'leCKOro 8rrnapa Ta. f1perrp~HT ~mM AB CCCP, 59, ~ocKBa, 34 CTp.
Kazakova, R.K. (I976). Computation of spacecraft motion characteristics. In E.Gottzein (ed.), Preprints of the VII !FAC Symposium on Automatic Control in Space, Vol. 2, VDljVDE Gesellschaft Meft - and Regelungstechnik, 624-643. ]aSYT~H, ~.M.
(1972).
JpraH~3aU~fl
pa60TbI co cneTOBblM rrepoM lIa H3b1Ke ~OPTPAH-il o.di.l SDS-910. IIperrpHHT ~mu AB CCCP, 64,~iocKBa, 40 CTp.
Abstract. This report considers the interactive system for computation of the optimal variant of spacecraft orientation alterations during the manoeuvres and performance of scientific experiments in space. The system consis~s of blocks, which computate the turns of spacecraft and its apparatus on given angles or matching the aparatus' axes with given directions in space. Interactive means based on graphical display facilitate the change of quality criterion during the choice of an optimal solution. The system is orientated on its usage in the process of spacecraft flight Keywords. Interactive system, orientation characteristics, light pen, light buttons, limb, terminator. INTRODUCTION The necessity of solving the following problems exists during the manoeuvres of spacecraft and performance of scientific experiments connected with its definite orientation in space: - computation of characteristics of the spacecraft's location in space according to a given position of orientational sensors; - computation of needed location of orientational sensors for realization of the spacecraft's given position in spacel - control of the correct work conditions for the orientational system during the manoeuvre concerning the variation of the spacecraft's orientation.
The comprehension and large scale of orientational system capabilities of contemporary spacecrafts reguire special set of computer programma for their solution. Such programma should consist of rather exact models of inertial, optical and ratio apparatus of orientational system and also in particular cases should contain models of gyro and reactive engines, which we call executive force. Each of this sensors and devices have definite position in the spacecraft and is characterized by the location of axis, by their fields of vision and sensitivity of transducers, possible turns of elements, and permissible consequence of operations. It is rather difficult to foresee all possible cases of interaction of above-mentioned modules, so refers to all possible values of orienta-
359
360
R. K. Kazakova
tional system's parameteres during -computation of directions to additiothe design of the spacecraft and lanal sat of celestial bodies; ter during its flight. In other words, - computation of vision (taking into the required set of computational consideration the visible angular dimethods for solving various problems, mensions) of celestial bodies in giwhich appeared during the performance ven field of vision and with the given of a spaceflight, is more complicated axes of sighting; than any complex automatical program- computation of characteristics of ming system. angles alteration between the directions to the given celestial bodies Sooner or later close character of with time of flight, such programming complex will come - computation of an~les between a giin contradiction with the extension ven directions, requirements of possible sphere of the problems solved. A system which consists of sufficiently complete set of elementary operations to compute the spacecraft's orientation parameters and interactive means which allow to form the necessary set of operations in order to obtain a desired result just through the ~roblem solution is an alternative to the fixed set of the automatic programming systems.
- computation of axes orientation of the coordinate system, connected with the spacecraft, for known direction of vectors, given in this coordinate system. - computation of the given vector position after its turn in space, - performance of widenedoparations of vector algebra.
The above-mentioned functions are realized in the system with the help of There is a complete set of such primodules of "operation of language mitive operations to compute orientation characteristics which was checked for the computation of spacecraft orientation" and "the programm for by the solution of various problems. The sufficient list of them was perfor- computing the directions of the spacecraft in space" (see Fig. I). med in the report by Kazakova (I97I). The present report is aimed to discribe the second part of the above system - the interactive means for the control of computations of orientation parameters and the system of parameters computation as a whole. THE STRUCTURE OF THE SYSTEM
'.-'Pf' S;',AMIC
II L:Ot'.iPO_ JAT;:'
I I
"qOGR~"'S
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IQ. COMPUiAT I'J"-l
The structure of the system is shown in Fig. I. For a given moment of time the system should provide the following things: - computation of directions to standart set of celestial bodies;
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T
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S 'S~E"
"lCIlITIES ORIENTATION
or
SPACECRACT CONTROL'
Interactive System for Computation of Spacecraft
The first module provides the performance of actions and comprehensive operations in terms of vector algebra, with the following algebra objects: vectors, directions and coordinate systems. The second module provides the performance of actions and operations in terms of names of directions and axes of spacecraft and celestial bodies. In general the consequence of addres-
ses to modules pointed out depends on results of operations and is determined during computation. The ability to modify the order of computations directly during the process of their performance is provided by means of dynamic control of works. There is the following method of dynamic control of works in the described system. All programm modules of package of applied programm are translated and loaded together with the main programme The access to them is realized by addresses from the main programm after the consumer indicates the corresponding light button on the screen of display. The light button is defined as any arbitrary object (latter, word, point or line), which is shining on the screen of display and is stored in the computer as definite structure of data. The indication of light pen to a light button causes reset state in the computer, that can be processed by programmapparatus means so that the address in computer storage is specified as a result of this actions, and according to this address the indicated light button is stored. According to this information we can determine the number of indicated light button (if their numbers are correct). Representation of light buttons of display screen is performed by a special
361
programm (Lazutin, 1972) , addressing to which is made from a main programm, written in terms of ~ORTRAN. This programm provides representation of mentioned formal parameters of certain part of storage, called "display buffer". It contains the desired light buttons until the user indicates necessary button by light pen. In this case the programm stores the number of indicated button and finishes its activity turning control to the basic programm. The basic programm, so called "the light buttons operating programm", provides causing (according to mentioned number) of subroutine 0r a number of subroutines out of the package in order to perform the operdtion according to light button distinguished by the user. When this programm ends the control again turned to the subroutine of lighting out, also informing about point of display buffer's domain which contains the needed set of light buttons. So the interactive system of calling and executing of translated FORTRAN-programma is organized as it has shown before. To realize this system it is necessary to provide the storage for needed light buttons in the display buffer and also to have a certain part of basic programm for light button. The problem of dynamic exchange of data between programma is more complecated. In the described system the "COMMON"-operation of FORTRAN is used to organize such informational field. Every operation from applied package has its own part of data in the informational field (they may coincied for different programma). This part of storage contains internal and external arreas of given operation. The analysis of
362
R. K. Kazakova
calculational processes in the system of calculation of spacecraft's orientation shows that data handled may be classified in the following way: - standart data at which we aware constructing system,
in standart part of I:lemory or is transformed from standart part of memory to the indicated point of information field,or in this programm there exist input and addressing to following programms of the given regime.
- data which have standart format and standart application, but whose concrete values we obtain during solving the problem, - data whose format and type of application are not defined apriory. Standart data are stored in lists of tables with fixed format. There are specialized fields in the informational field for data with standart format. There is a special access to the working fields for scalar values, vectors and ~atrixes which are connected with interactive operations upon them to operate with apriory indefined data. There are two ways at transfering of data, autowatical and manual. Automatical method realized by concordance of external and internal arrears of applied programma in the inforlliational field or by special transfering of data with main programme Manual method is necessary to use the capability of transformating of data while constructing. It was realized by sensors of light buttons which is similar to the discribed. The light buttons corresponds to every element of informational field (single, variable or massive). A set of such light buttons is selected into special table which is lighted on display screen (see Fig. 2). Due to the corresponding programm of processing the light buttons according to the regime of data work the object of information field is stored
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There are 3 regimes of data processin~ input, output and dynamic data control. Each of these regimes is realized as a special programm of processing light buttons of information field. The first regime (see Fig. 3) provides input from every indicated by li&bt pen installation in the mentioned part of memory. The keeboard of light buttons on the display screen is one of the variants of input.
363
Interactive System for Computation of Spacecraft
The second regime provides output from a standart domain of memory on any exterior installation indicated by a light button and on the display screen too (Fig. 4).
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This regime stipulates the correction to locate suitably the obtained time D,ynamic data processing provides the data on the screen (Kazakova, 1976) performance of the simpliest operatioos as well as to add the points of trawith scalars and vectors and transjectories for the moment of time giportation of data. The performance of ven in the regime "data input". these operations is made in the stanIMAGE OF THE ORIENTATION dart memory domain, and exchange of standart data region with information SPACECRAFT CHARACTERISTICS field is provided by buttons of The spacecraft location is described information field. by the radius-vector of the coordinaDuring ballistic projection (or desig- te system origin, connected with this ning) the possibility of determinaspacecraft. Position of the spacecraft tion of motion's characteristics in and its sensors in space is described any moment of time during the flight by the set of three-dimensioned vecof projecting spacecraft Or celestial tors and matrix of transforming the body is of great importance.So in the connected coordinate system into the system the method of access of data absolute system of coordinates. While is realized which is additional to men- calCUlating it may be necessary to tioned above and is based on utilizasee the mutual position of the spacetion of dots,by which the trajectory craft, its sensors and celestial boof constructing object and orbits of dies. Here two points of view may be celestial bodies are represented. To used: each point of this sort we establish I. External - when all vector set is the correspondence of set of coordirepresented under any angle of appr~ nate and velocity components for a given moment of time in the memory. 2. Internal - when some part of In order to input data concerning surrounding space is represented F IG.Y.
SCHEME or DATA OUTPUT.
.-
-- -
II
.
364
R. K. Kazakova
which is visible along the selected line of sighting taking into consideration the field of view of the given sensors. External point of view allows to see a mutual position of sensor axes of the spacecraft. Internal point of view - what part of space gets into the field of view of the chosen sensor. Modern facilities of computer graphics permit to receive comparatively easy the orientation characteristic image according to the internal point of view. For this purpose a special modul has been specified in this system. This modul provides:
tion in form of the print of planetgraphic latitude and longitUde of the indicated point.
I
. .
. . .
. . .
I.JEHA DEnEHI-151=
- image of field of vision on the display screen or grafplotter; - image of the scale of the degree net in this field of vision with the standart step, - survey of all directions known in the system and image of visible object positions in form of a point in the sensor's field of vision. In addition the angular diuension of such objects is less, than a step of display's discretenessi - definition and image of the disc parts, limb and terminator, visible in the sensor's field of vision. The example of this displayed image is shown in Fig. 6. It may be composed the impression about dynamic of the relative motion of spacecraft and celestial body visible in sensor's field of vision by surveying image on the display screen during successive time moments. It can be noted that points of limb, disc and terminator visible on the display screen are the light buttons. The indication to this point excites the reac-
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Indication to the point in the planetary disc by the light pen offers the possibility to the user to get the print planetgraphic latitude and longitude of this planet point. There is a possibility to place the lighting point on the visible disc part according to the given planetgraphic latitude and longitude. Indication to the point celestial body by the light pen excites the reaction in form printing the body name and its characteristics (absolute coordinate and others). Image of the orientation characteristics from the external point of view is less Visually (see Fig. 7), YKAII-1TE BEKTOP
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365
Interactive System for Computation of Spacecraft
However, it can be benefit as means of access to the characteristics of any directions and the axes of the spacecraft sensors. This imagination is an external perspective projection on the display screen of unit vectors of all directions fixed with the spacecraft. The center of projection where abserver's eye disposes, direction of sighting line and scale can change itself with the help of the light buttons (see Fig. 6). This allows to consider i~age unit vectors of directions from the different points of view, to receive imagination about mutual disposition of vectors. Each vector on the display is connected with the data file characterizing the vector direction in fixed and absolute coordinate systems in the memory of the disign system. As an absolute coordinate system we can take any coordinate system from some sufficiently full set by the light pen. Each vector on the display screen plays a part of light button. The indication to the vector by the light pen excites the print and addresses the orientation characteristics of this vector to standart cells of memory. There is a possibility of realization to draw a picture from a direction which is normal to two indicated vectors or from the direction of intersection line of two planes which are defined by four indicated vectors. It is also possible to obtain characteristics of their mutual orientation (angele between them etc) by indicating to two vectors. The bUilding of reference point with indication to the names and basic values of orientation is produced by a consumer with the help of teletype write or light pen.
CONCLUSION The utilization of described interactive system gives large possibilities to determine characteristics for control of the spacecraft orientation during its flight. The author wishes to express her sincere appreciation for the encouragement and invaluable guidance extended by Platonov A.K. during the preparation of this paper. REFERENCES KaS8KOBa, P.K., nna~oHOB A.K. (1971). l1ShlK ,l(JIH orUlcaH~fl Bpaa(eH~fi I;OCMH'leCKOro 8rrnapa Ta. f1perrp~HT ~mM AB CCCP, 59, ~ocKBa, 34 CTp.
Kazakova, R.K. (I976). Computation of spacecraft motion characteristics. In E.Gottzein (ed.), Preprints of the VII !FAC Symposium on Automatic Control in Space, Vol. 2, VDljVDE Gesellschaft Meft - and Regelungstechnik, 624-643. ]aSYT~H, ~.M.
(1972).
JpraH~3aU~fl
pa60TbI co cneTOBblM rrepoM lIa H3b1Ke ~OPTPAH-il o.di.l SDS-910. IIperrpHHT ~mu AB CCCP, 64,~iocKBa, 40 CTp.