Contents of the JUPSAT.DOC file
Documentation for JUPSAT.COM
This program calculates the positions of the four Galilean satellites (Io,
Europa, Ganymede and Callisto) orbiting Jupiter, and displays their
positions graphically on the screen. It has been written to run on CGA
machines or Hercules machines running the SIMCGA utility. It requires the
JUPITER.MNU data file in order for the user to have access to the pop-down
Other numerical data is also displayed. This is described below.
Both the users date abd time are required as input for the program. The
format of the date is "dd/mm/yyyy". The time entered is UT/GMT and is inthe
Both the date and time can be edited as they are entered. The ESC key can
be pressed to reset the date to "dd/mm/yyyy" or the time to "hh:mm".
The display is at its best on a monochrome monitor. This consists of four
distinct sections. Section one diplays the top-line menu.
Section two displays the Orbit scale, the type of instrument through which
the displayed view would be seen, the date and the time.
Section three is the graphics display window in which the satellite
positions are drawn in relation to Jupiter's disk. Compass directions,
related to the current view, are printed at the top left of the window. The
satellite and Jovian disks are drawn to scale, as are the satellites'
distances from Jupiter.
Section four contains the numerical information for each satellite, namely
its distance from Jupiter, as measured in Jupiter radii, and its angle from
Inferior Conjunction. Inferior Conjuntion occurs at zero (0) degrees, i.e.
when a satellite is directly behind Jupiter. The angles are measured
westward from this point, going to 90 degrees West, 180 degrees West (when
the satellite is immediately in front of Jupiter, to 270 degrees West and
finally back to zero.
A box with a thick border at the top left of section four contains the first
letter of each of the satellites' names. The sequence of these letters, read
from left to right, corresponds to the sequence of the satellites as they
appear in the display window. For example, suppose the box contained the
letter sequence EICG, then in the display window, the leftmost satellite
would be Europa, the next one in, Io, followed by Callisto, and lastly, the
TOP LINE MENU
This menu offers five options as described below. A bar highlights the
current option on the menu.
Orbit-Zoom: This option allows the user to set the magnification of the
display. When chosen, a pop-down menu appears on screen
listing the four Galilean satellites. Each name sets a
different magnification, by displaying everything within the
chosen satellites orbit, in the display window. The program
remembers which satellite orbit the user has chosen each time
the menu is called, by highlighting the current option with a
bar. The ESC key is used to escape back from the menu to the
Newcalc : This option allows the user to key in/edit a new date and/or
time. The ESC key is used to escape back to the top-line menu.
View : This allows the user to choose the type of instrument through
which he/she would normally observe the satellites. Altering
the view causes the graphics display, compass directions,
first letters and the numerical information to be
automatically updated. A pop-down menu offers the four
possible views with the most popular types of instrument.
Print : Sends a four-colour shaded hard copy of the screen to an Epson
compatible dot-matrix printer. The top-line menu is not
included as part of the screen dump. It is not necessary to
have previously run the GRAPHICS utility in order to get this
Exit : Returns the user to DOS.
MOVEMENT WITHIN MENUS
Moving between options in the top-line menu is achieved with the use of the
left and right cursor keys.
Movement within the pop-down menus is achieved by using the up and down
cursor keys. In addition, it is possible to move between the pop-down menus
with the left and right cursor keys.
In all cases the ENTER key is pressed to select the required option.
THE USE OF COLOUR CODING
Four colours are used throughout the display. These will appear as four
distinct shades on monochrome displays, and as four separate colours on
The colour shading applies particularly to the satellites as drawn in the
display window, their first letters and their numerical information. The
standard shadings are as follows: Black, Low Brightness (Green), Medium
Brightness (Red), and High Brightness (Brown).
Jupiter is always drawn in low brightness (Green). The satellites are drawn
in high brightness (Brown). Eclipsed satellites are not drawn.
The first letters and numerical information are normally printed in high
If, when using the Orbit-Zoom option, some satellites move out of the
display window, they will not be drawn. The corresponding first letters and
numerical information of any such satellite will then be printed in low
If a satellite is transiting, (passing in front of Jupiter's disk), then
it's corresponding first letter and numerical information will be printed in
medium brightness (Red).
Finally, if a satellite is being eclipsed by Jupiter, (behind Jupiter's
disk), it's corresponding first letter and numerical information are printed
in inverse high brightness (Black on Brown).