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GrandTour Voyager and Giotto Space Mission Simulator For IBM PC, XT, AT or compatible with 512K RAM, DOS 2.0 or higher, and CGA, EGA, or Hercules graphics GrandTour User Manual (Version 2.0) Copyright (C) 1990, 1991 by John D. Callahan P.O. Box 1281 LaCanada, CA 91012 Program and manual written by John D. Callahan CONTENTS 1 Introduction 2 Getting Started 2.1 Your Computer 2.2 Installing GrandTour 2.3 Control Files 2.4 Program Start Up 3 The Display 4 Running GrandTour 4.1 Field of View 4.2 Scene Complexity 4.3 Observer 4.4 Pointing 4.5 Time 4.6 Tips for Animation Appendix A.1 Interesting Facts About Voyager and Giotto A.2 Outer Solar System Data 1. Introduction GrandTour is a fascinating, state-of-the-art computer program which can simulate space as seen from the Voyager and Giotto spacecraft. In addition, GrandTour can generate scenes from arbitrary points in space or the Earth, with the spacecraft visible to the observer. The planet, moons, and rings of interest (or comet, nucleus, and tail), stars, the sun, and the spacecraft are all accurately drawn with wireframe representations. Hidden line removal is done for the body surfaces. For color EGA devices, stars are color coded according to spectral type. The motions of the bodies themselves are highly accurate, with errors no greater than 500 kilometers. Oblate bodies are given their true shape and it is possible to place landmarks on most of the bodies. Landmarks are fictitious and only designed to help visualize the bodies. For this reason, Titan and Uranus have no landmarks, because Voyager observed heavy, largely featureless atmospheres for them. The program was originally developed at the Jet Propulsion Laboratory (MIP program) to assist in the analysis of science and optical navigation data. It was under continual development for a 5 year period (1982 to 1987) and generated considerable interest among several groups at JPL. In addition, the program was filmed by the BBC as part of a NOVA documentary on the Voyager Uranus encounter, and by the Four Point Entertainment Company for a commercially available video on Halley's Comet (with William Shatner). The program was often demonstrated to technical groups within JPL and to visitors. Also, it played a critical role in obtaining a contract to develop Space Telescope solar system planning software (from Goddard Space Flight Center). Since the program was highly transportable, it ended up running on many computers -- from micros to minis. Computer animation at several frames per second is possible on fast machines. The program is interactive and user friendly with much flexibility and many options and features. 2. Getting Started 2.1 Your Computer GrandTour requires an IBM PC, XT, AT or compatible with 512K of RAM, DOS 2.0 or higher, and a CGA, EGA, or Hercules graphics board. Only one disk drive is required, and the program comes on two 5.25", 360K diskettes. Both diskettes are copyrighted. However, diskette #1 is shareware and may be copied without any restrictions. Diskette #2, on the other hand, may not be copied, and all copyright rights are reserved. IF YOU DO NOT HAVE DISKETTE #2, it may be ordered by sending $25 to John D. Callahan, P.O. Box 1281, LaCanada, CA 91012. The $25 charge includes postage and handling and any tax. If your computer has a math coprocessor, GrandTour will utilize it, and the program will run significantly faster. However, a coprocessor is not required. The program itself takes up 413K of RAM when loaded, so it is important not to have too many memory-resident programs (in addition to DOS) when GrandTour is run. GrandTour utilizes the high resolution B/W mode of the CGA. For the Hercules board, advantage is taken of its improved resolution, and scenes are noticeably sharper. Also, for those with a Hercules graphics card, it is important to make sure the card is in a graphics mode. Check the documentation which comes with your Hercules graphics card. GrandTour takes advantage of the capabilities of the EGA's high resolution color graphics. The board must have 128K of memory in order to run in the EGA mode. If your EGA has less than 128K, then you must use the CGA mode. On slower machines, it may take several seconds to generate one scene. However, on faster machines with math coprocessors, several frames per second can often be generated -- providing animation capability. Nevertheless, the amount of time required to calculate scenes will vary widely, and even on faster machines it may take several seconds to generate one difficult (for the computer) scene. This usually happens when the central body is quite large and there is some chance of seeing it in the field of view. 2.2 Installing GrandTour To install GrandTour, first back up your 360K diskettes. This may be done by copying all the files on the diskettes to other diskettes. The files are not in any special form -- such as compressed -- nor are they in any special subdirectories on the diskettes. The distribution diskettes should never be used to run the program. Diskette #1 contains the executable GrandTour program, grndtr.exe. Diskette #1 also contains mission data for Voyager 1 at Jupiter and Voyager 2 at Neptune. Diskette #2 contains mission data for Voyager 1 at Saturn, and Voyager 2 at Jupiter, Saturn, and Uranus, and Giotto at Halley's Comet. There are 3 duplicate files on the diskettes; these are milk.dat, lm.dat, and readme.doc. If you have a hard disk on your computer, then it is recommended that you make one directory (from which you plan to run GrandTour) and then copy all the files on the two diskettes into this directory. If you have only a disk drive or (drives) then make exact duplicate copies of the GrandTour diskettes. These will be the diskettes you will use to run the program. 2.3 Control Files For each of the seven missions there is a control file, shown below. Control file Mission Diskette v1j.ctr Voyager 1 at Jupiter #1 v1s.ctr Voyager 1 at Saturn #2 v2j.ctr Voyager 2 at Jupiter #2 v2s.ctr Voyager 2 at Saturn #2 v2u.ctr Voyager 2 at Uranus #2 v2n.ctr Voyager 2 at Neptune #1 gio.ctr Giotto at Halley's Comet #2 The control files contain instructions and reference other files needed by the GrandTour program. The control files are included along with the mission data on the appropriate diskette, as explained above. For example v1j.ctr is on Diskette #1 which contains mission data for Voyager 1 at Jupiter. 2.4 Program Start Up When GrandTour is run, the program will ask for the graphics board being used (CGA, EGA, or Hercules), and a control file. The default directory must contain the control file and mission data of the particular mission you wish to run. If you have copied all the data on the diskettes to one hard-disk directory, then make this directory the default. Now type grndtr at the DOS prompt and supply the desired control file when requested by the program. If you have two disk drives, then insert Diskette #1 into drive a: and Diskette #2 into drive b:. Then if you wish to run Voyager 1 at Jupiter or Voyager 2 at Neptune, make a: the default directory. Now type grndtr at the DOS prompt and supply the appropriate control file when requested. In order to run one of the other missions (Voyager 1 at Saturn, or Voyager 2 at Jupiter, Saturn, or Uranus, or Giotto) make b: the default directory. Now type a:grndtr at the DOS prompt and supply the appropriate control file when requested. If you have one disk drive, then make it the default and insert Diskette #1. Now type grndtr at the DOS prompt. When the program requests a control file, leave the diskette in if the mission you desire is Voyager 1 at Jupiter or Voyager 2 at Neptune. However, if you desire one of the other missions, replace Diskette #1 with Diskette #2 and then supply the appropriate control file. 3. The Display On the left hand part of the screen, you may bring up various help menus by using the function keys F2 through F7. The menus will be self explanatory when you run the program. The actual space scene (to the right of the help menus) is described below. The Universal (Greenwich mean) Time is in the upper left hand corner (UT=), followed by the distance to the observed body in kilometers (KM=), and the field of view in degrees (DEG=). In the lower left hand corner is given the right ascension and declination pointing (RA DEC=), followed by the phase angle of the observed body (PHASE=), and the observer latitude and longitude with respect to the observed body (LT LG=). If we were looking only at Uranus it would be labelled 7R1. The 7 stands for the 7th planet of the solar system, and the R1 means that Uranus is the closest body to us (which can be seen). Moons are similarly labelled. When observations are made from a point other than the spacecraft itself and the spacecraft is visible, it is labelled with SC. The sun is labelled SUN. Two field of view boxes are drawn. The smallest box is the narrow angle camera for Voyager (.424 degrees) and the larger box is the wide field camera (3.18 degrees). For Giotto the boxes are .1 and .25 degrees. A grid of 5 lines of longitude and the equator represents a body. The terminator is represented by an arc with short lines pointing in the sun direction and connected on the sun side. The sub-solar point (or where light from the sun first strikes a body) is represented by a small triangle. When rings are seen, they are unlike the other markings, because they can be seen behind the planet. However, their orientation can be inferred from the equator. If there were any landmarks drawn, they would be circles on the surface of the body, numbered 1 through 9. Suppose a 2.5 magnitude star were present in the scene. Then it would be labelled 25, for magnitude 2.5. Stars of greater magnitude are smaller in size. For example, if a star of 5.0 magnitude were visible, it would be smaller than the 2.5 star. Actually, the default star magnitude limit has been set at 4.0, because there would be many more stars visible if it were set at 5.0 (which is the limit for GrandTour). If the display were generated by a Hercules graphics card instead of CGA, it would be the same except for higher resolution. Also the body and star labels would be smaller. If the display were generated by an EGA graphics card, it would look similar to that generated by Hercules -- except in color. A color EGA display would have the field of view boxes in green, and the stars would be color coded according to spectral class: blue for O-B, light blue for A, white for F, yellow for G, pink for K, red for M, and green for unknown spectral class. Rings and landmarks would be yellow, and the terminator and sub-solar point would be in white. The planet and moons would also be color coded by the following scheme. The first moon is colored blue, the second is green, the third is light blue, the forth is red, the fifth is pink, the sixth is yellow, the seventh is white, the eighth is pale blue, the ninth is pale green, and the tenth is pale light blue. Finally, the planet assumes the color of the next non-existent moon, and the spacecraft (if visible) the color of the non-existent moon after that. In other words, if a planet has only 2 moons (Neptune), then it takes on the color of light blue, and the spacecraft (if visible) takes on the color of red. 4. Running GrandTour GrandTour is controlled by the primary keys of your keyboard. THE KEYBOARD MUST BE IN LOWER CASE; however, some letters need to be given as capitals (hold down the shift key for these). Typically, striking a single key will produce a result, which may involve changing the scene directly or asking you for more information. Sometimes you will hear a beep if the keyboard buffer overflows, but this causes no effect on the program. The program switches between graphics and text when it is necessary to print messages and instructions, or receive certain data from you. A message is printed if the key you have struck has no function, and the program is designed not to "bomb" if incorrect data is input (you are simply given a message and asked to continue). In addition to on-screen help menus (F2 through F7), help may be obtained while the program is operating by hitting F1. When this key is hit, the program goes into a help mode whereby an explanation is printed for the function of each key when it is hit. Also, keys grouped in specific subject areas will be shown. TO EXIT HELP, HIT F8. Since the exact ratio of horizontal to vertical dimensions will vary between different computers, the $ key is provided to allow you to adjust the screen dimensions. If the field of view boxes do not look square, then hit the $ key and input scale factors as instructed. The n key is an important key, and allows you to adjust the sensitivity, through 4 levels, of some of the keys. For instance making the c and v keys (zooming) more sensitive will cause larger changes in the field of view each time one of these keys is hit. Other keys affected by key n are e,r,d,f (pointing offsets), 3,4 (field twist), and 7,8 (external observer distance). These keys are explained below. The letter Z will give a summary of how the major parameters of the program are set, such as star magnitude limit, field orientation, observer position, etc. The letter A will give the right ascension and declination of the first 20 star (if any) plotted by the program. As you run GrandTour, you may wish to send scenes to your printer. For the CGA this is accomplished by running the DOS "graphics" program before running GrandTour, and then hitting the PrtSc key while GrandTour is operating. For the EGA and Hercules graphics boards, there are similar methods. Consult your computer documentation. In order to terminate operation of GrandTour, hit the letter y. After this letter is hit a message is printed asking you to input an s, carriage return. If you hit the y key by mistake you have only to hit carriage return (or another letter besides y and carriage return) to return to normal operation. A summary of the keys described above is given below. Major subject areas and the keys related to them are given in the following sections. $ - Adjust screen dimensions n - Adjust sensitivity of certain keys Z - Parameter status summary A - Display R.A. and Dec. of first 20 stars y - Terminate program execution 4.1 Field of View The field of view keys are shown below. The allowable limits on the field are quite large -- from 50 degrees to .000001 degrees. This will allow you to see constellations at large fields of view, and to also zoom in on small moons of planets, from the Earth in particular, with small fields of view. There is a small amount of distortion for very large fields. The Voyager narrow and wide angle cameras are .424 and 3.18 degrees respectively. For Giotto, there were two possible field dimensions for one camera: .1 and .25 degrees. The x key will cycle different fields depending on whether the mission is Voyager or Giotto. For Voyager the field of view was oriented based on a coordinate system which used a "roll reference star" and the Earth. This orientation is what is meant by "normal field orientation" (see key N below). c - Zoom the field in v - Zoom the field out ! - Print out the current field size (degrees), and optionally input any field size x - Cycle through a set of exact field sizes (.424 or .1, .848 or .2, 3.18 or .25, 15.0, 30.0, and 45.0 degrees) 3 - Rotate the field one way 4 - Rotate the field the opposite way as key 3 above 2 - Zero the effects of keys 3 and 4 above N - Sets either normal field orientation from the spacecraft (Voyager only) or North Celestial up 4.2 Scene Complexity The scene complexity keys are very valuable in order to speed up the calculations. The simpler the scene, the faster GrandTour can calculate and display it. For instance, the default star magnitude limit is 4.0. Eliminating all stars (key Q) will cause a significant speed up. On the contrary, increasing the star magnitude limit to 5.0 (stars dimmer than 5th magnitude are not available) will cause an even more significant slow down. a - Toggles grids on bodies on and off z - Toggles landmarks on bodies on and off w - Cycles through 3 levels of labelling -- none, around border, around border and on objects q - Input a star magnitude limit Q - Remove all stars & - Change resolution to draw bodies (5 levels) 4.3 Observer The initial observation point when GrandTour is executed is the spacecraft. However, observations may be made from the Earth or an external observer. For the external observer, the observation point is with respect to the central body (a planet for Voyager and the nucleus of Halley's Comet for Giotto). Think of the external observer as being tethered to the central body. In other words, if the distance of the external observer is changed -- keys 7 and 8 -- then this means that the distance of the external observer is being changed with respect to the central body -- no matter what body is actually being observed. The North pole (+90 degrees latitude) for bodies is defined in a similar way as that for the Earth. And Jupiter, Saturn, and Neptune are all oriented within the solar system very roughly like the Earth. However, Uranus "rolls" on its spin axis as it orbits the sun, and there is some controversy as to which pole should be defined as North. For GrandTour, the North pole of Uranus is defined such that it points towards the inner part of the solar system. Since the orientation of Halley's nucleus is uncertain, its North pole is defined as being normal to the orbit motion and roughly in the same direction as the Earth's pole. The Earth observation point means "in the vicinity of the Earth": neither the exact Earth's center nor a specific point on the Earth's surface is actually used. Also North Celestial is always up, and the horizon is not taken into account. Day or night is also not taken into account; however, if the sun is visible, it will be drawn. When key # is used there is sometimes a small discrepancy in the displayed angles on the screen (LT LG=). g - Observe from the spacecraft (default) 5 - Observe from the Earth 6 - Observe from any point in space, centered on the central body. Once key 6 is hit the keys below can be used: 9 - Observe from over the N. pole of the central body 0 - Observe from the equator of the central body 7 - Increase the distance to the central body 8 - Decrease the distance to the central body # - Observe from an adjustable central body longitude, latitude, and distance 4.4 Pointing When GrandTour is initially run, the default pointing is towards the central body. In order to change this to the 1st moon, simply hit key t once. Now to switch to the second moon, hit key t again, and so forth. When key = is hit nothing will happen until another key is hit. If this second key is 1, then the pointing will be changed to the 1st moon, and similarly for the other moons. If any key besides a "moon" key is hit after key =, then the pointing will be towards the central body. GrandTour will continue to track a body as time is run. If you desire to offset the pointing from the central body or moon, use keys d,f,r,e. If you desire to input an exact right ascension and declination, use key /. If you hit key / by mistake, then another / and carriage return must be input to return to normal operation. Key + will fix the current pointing in absolute right ascension and declination, and these angles will no longer be affected by time or any other keys. In other words, stars will now stay fixed and bodies will move. To return to the normal mode of operation (tracking a body) hit key + again. As with other keys, a message is printed explaining the procedure at the time + is hit. t - Cycles through the central body and any moons = - Hit this key and then the number of the moon you wish to point at. To point at the central body, hit any other / - Input an exact right ascension and declination d - Offset the pointing left f - Offset the pointing right r - Offset the pointing up e - Offset the pointing down h - Zero pointing offsets + - Fix or unfix the absolute right ascension and declination pointing 4.5 Time When GrandTour is run and a mission is input, a message will be given showing beginning and ending mission dates. It is impossible to run outside of these limits. If you try to, the program will stop at one of the limits and set the time step to zero. There are several keys which affect time, and once you are familiar with them you should have fine control over time. Key j will run the program and generate a new scene on your display. This will be done even if the time step is zero. Holding down key i will cause the time step to increase by one second each time a new frame is generated. Keys , and . will print instructions when hit (their functions are explained below). The s key is an important key because it prevents erasure of previous scenes. When it is hit, there will be no apparent change in the scene. However, when the next scene is generated (by any command) the previous scene will not be erased, and so forth. When you wish to return to normal operation, hit key s again. This will cause the entire display to be erased, leaving the last scene generated. The s key is included with the time keys because it is typically used to make a trace of the motion of bodies over time. u - Zero the time step j - Run GrandTour with the current time step i - Increase the time step by 1 second, and run o - Increase the time step by 10 seconds, and run p - Increase the time step by 100 seconds, and run [ - Increase the time step by 1000 seconds, and run k - Decrease the time step by 1 second, and run l - Decrease the time step by 10 seconds, and run ; - Decrease the time step by 100 seconds, and run ' - Decrease the time step by 1000 seconds, and run . - Input a calendar date, UT , - See time step, and optionally input any time step m - Change the sign of the current time step s - Toggles erase or no erase of previous scenes (makes a trace) 4.6 Tips For Animation Animation is best achieved by simplifying the scene as much as possible and then running GrandTour with the appropriate function. For instance, suppose you are centered on a planet and wish to zoom out in order to see where the moons are. This would be best achieved by first removing all the stars (key Q) and the grids (key a). Further, you may wish to remove the labelling (key w) and draw the bodies with less resolution (key &). After the scene is simplified, hold down the v key to zoom out, and stop when you can see the moons. Now you may wish to re-add some detail. As another example, suppose you observe a bright star about to pass behind a planet, and you wish to create an animation sequence as the star approaches the limb. To simplify the scene you could eliminate all stars dimmer than the one you are interested in (key q) and remove grids (key a). Before the sequence starts, you may wish to adjust the field of view in order to get an optimal size for the planet on your screen (keys c,v,x and !), or you could adjust the position of the planet on the screen by changing the pointing slightly (keys e,r,d,f). Now to start the animation sequence, choose a suitable time step (see the time keys above), and then hold down key j to create the animation. Animation sequences where previous scenes are not erased are often very interesting (key s). This also speeds up the calculations. Math coprocessors significantly speed up the operation of GrandTour, and therefore are important when animation is attempted. Appendix A.1 Interesting Facts About Voyager and Giotto The Voyager spacecraft each weigh one ton and were launched with Titan-Centaur boosters from Cape Canaveral in the summer of 1977. The first spacecraft launched was Voyager 2, because Voyager 1 would overtake it in flight. The mission was to take advantage of a rare alignment of the outer planets which occurs every 175 years and made it possible for Voyager 2 to encounter 4 different planets (Jupiter, Saturn, Uranus, and Neptune). Voyager 1 encountered Jupiter and Saturn and then continued on a path taking it out of the solar system. The gravity of one planet hurled the Voyagers on to the next. The spacecraft carried the most sophisticated cameras and scientific instruments ever flown into space. They returned spectacular photographs of the planets and invaluable scientific data. Never before had such high resolution photographs been made of the outer planets and their moons and rings. Our knowledge about a planet at least doubled every time a Voyager flew by it. Several new moons and rings, volcanos on Io, lightning on Jupiter, spoke features in the rings of Saturn, and many other discoveries are owed to the Voyager spacecraft. Voyager 1 Launch September 5, 1977 Jupiter March 5, 1979 Saturn November 12, 1980 Voyager 2 Launch August 20, 1977 Jupiter July 9, 1979 Saturn August 25, 1981 Uranus January 24, 1986 Neptune August 24, 1989 The European spacecraft Giotto flew by the famous Halley's Comet on March 13, 1986. The spacecraft travelled deep into the coma of the comet and passed within 1,000 kilometers of the nucleus. Like Voyager, Giotto made important discoveries. Before the Giotto flyby -- and that of the Soviet Vega 1 and 2 spacecraft, which passed within 10,000 kilometers of the nucleus -- it was thought that Halley's nucleus would be a "dirty snowball." It was thought that this "dirty snowball" had a reflectivity of 25%, and that it evaporated dust and gas uniformly from its surface. We now know that the nucleus is extremely dark, with a reflectivity of only 4% (similar to carbon black). Dust and gas are emitted from about half a dozen jets on the surface of the nucleus which account for about 10% of the total area. The nucleus itself is an irregularly shaped "potato" about 15 kilometers long, and it rotates and wobbles with a period of about 53 hours. Giotto also measured the composition of the coma, determining it to be 80% water and the rest mostly carbon dioxide. A.2 Outer Solar System Data Below is given a table containing information about the 4 outer planets and their moons which Voyager encountered. For the planets, the orbit period and distance are with respect to the sun. A planet's moons are grouped below it, and moon numbers are given in parentheses. For a tri-axial body, the radius given is representative. The rotation rates of the planets are: Jupiter and Saturn, 10 hours; Uranus and Neptune, 16 hours. Moons are typically locked in orbit and rotate at the same rate as they revolve. Body Radius (km) Orbit Orbit Period (days) Distance (km) Jupiter 71,398 4337.00 778,300,000 Amalthea (5) 100 .50 181,000 Io (1) 1,820 1.77 422,000 Europa (2) 1,570 3.55 671,000 Ganymede (3) 2,630 7.16 1,070,000 Callisto (4) 2,400 16.69 1,880,000 Saturn 60,000 10,760.00 1,427,000,000 Mimas (1) 200 .94 186,000 Enceladus (2) 250 1.37 238,000 Tethys (3) 520 1.89 295,000 Dione (4) 560 2.74 377,000 Rhea (5) 760 4.52 527,000 Titan (6) 2,580 15.95 1,220,000 Hyperion (7) 150 21.28 1,480,000 Iapetus (8) 720 79.33 3,560,000 Uranus 25,600 30,700.00 2,871,000,000 Miranda (5) 250 1.41 130,000 Ariel (1) 630 2.52 191,000 Umbriel (2) 590 4.14 260,000 Titania (3) 820 8.71 436,000 Oberon (4) 810 13.46 583,000 Neptune 24,300 60,200.00 4,497,100,000 Triton (1) 1,350 5.88 354,000 Nereid (2) 150 359.40 5,570,000 For Halley's Comet, the coma is approximately 50,000 kilometers in radius, and the nucleus measures 15 x 8 x 8 kilometers in radii. The orientation of the nucleus is uncertain, but it appears to rotate in 53 hours. The comet orbits the sun every 74 to 79 years in the opposite direction as the planets, and its orbit takes it from the very outer part of the solar system to the very inner part.