                              
                              
                              
                                GrandTour
                              
                         Voyager and Giotto Space
                             Mission Simulator
				    
                          GrandTour User Manual
                              (Version 3.1)
                              
          Copyright (C) 1990, 1991, 1997, 2001 by John D. Callahan
                            johndcal@mail.com
                          8601 Sunland Blvd. #44
                           Sun Valley, CA 91352
                       
                              
                        Program and manual written
                           by John D. Callahan

                                                            
                              
                                 CONTENTS


1    Introduction                                        

2    Getting Started                                        
     2.1  Your Computer                                
     2.2  Installing GrandTour and Executing
     2.3  Windows Users

3    The Display                                            

4    Running GrandTour                                     
     4.1  Field of View                                
     4.2  Scene Complexity                                  
     4.3  Observer                                     
     4.4  Pointing                                     
     4.5  Time                                         

     Appendix                                          
     A.1  Interesting Facts About Voyager and Giotto        
     A.2  Outer Solar System Data                      

                                                            
                              
                             1. Introduction
                              
                              
     GrandTour is a 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. 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 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. Computer animation at many 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 only requires an IBM PC compatible with 512K of RAM, 1M of
hard drive, DOS 2.0 or higher, and EGA graphics. If your computer has a
math coprocessor, GrandTour will utilize it, and the program will run
significantly faster. However, a coprocessor is not required.

     On modern PCs, many frames per second can usually 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 time to generate one difficult (for the computer) scene. This usually
happens when the scene is complicated and the central body is quite large
and there is some chance of seeing it in the field of view. The user may
simplify the scene by removing landmarks, labelling, etc.
     
     
2.2 Installing GrandTour and Executing
     
     To install GrandTour, first extract the distribution file,
grandt31.zip, and keep all the files in one directory. Name this directory
anything you wish. Now execute the GrandTour program, gt.exe, and follow
the directions the program gives you. The program runs under DOS but is
designed to run conveniently from Windows operating systems running on top
of DOS (see next section).


2.3 Windows Users

     For Windows users it will be convenient to associate icons with
gt.exe, readme.txt, and manual.txt, and a text reader with readme.txt and
manual.txt.  Then one has only to click on the icons to execute the
program, gt.exe, or read the support documentation, readme.txt and
manual.txt. For instruction on how to do this, read your Windows
documentation.



                              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).

     The field of view boxes are in green, and the stars are 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 are yellow, and the terminator and sub-solar point are
in white. The planet and moons are 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 nonexistent moon, and the spacecraft (if visible) the color of the
nonexistent 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.

     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

     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. For continuous running,
hold the key j down. 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)

IMPORTANT NOTE: Each mission spans a short period around encounter. When
the start and stop times are reached, the time step is set to zero.

                                 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, volcanoes 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.