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README.DOC
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1992-01-02
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Satellite Orbital Prediction Program
Copyright (c) 1991 by Bill Penner, WB7DPF
Version 4.03
22 December 1991
INTRODUCTION
This program was written to be used to predict the position of a
satellite using either standard Keplerian orbital elements or a
position and velocity vector, such as the NASA M50 elements. This
program was based on the orbital predication calculations found the
orbit prediction program written by Dr. Thomas A. Clark, W3IWI,
however, since version 3.11 I have rewritten everything to slightly
improve accuracy, and to provide more information. I originally took
the Apple version by Dr. W. D. McCaa, K0RZ, rewrote it for the ATARI
800XL, adding a real time component, and then rewrote it for the ATARI
ST. This program is written in Megamax Laser C.
The program can be ran as either an application (normal program)
or an accessory. This program will run from either a floppy or hard
disk and will work on the ST, STE, MSTE, and the TT computers.
SETTING UP THE FILES
To run the program as a program, copy all data files to a
directory or subdirectory. The program does not need to be located in
the same directory as the data files and can be located in another
directory. I recommend that during initial use of the programs, the
data files and the program should be located in the same directory.
The default configuration expects the data file to be in the same
directory. If you wish to locate the data files separately, read the
section discussing configuration editing.
If you wish to run the program as an accessory, rename the
SAT403.PRG file to SAT403.ACC, and place the program on your root drive
(usually C: on hard drives or A: if you boot from floppy). For easiest
use, place the data files in the same directory as the accessory. If
you wish, you can place the data files in a subdirectory, however, you
will need to edit the program configuration.
STARTING THE PROGRAM
To run the program as an application, double click on the file.
To run the program as an accessory, simply boot the computer with the
accessory in the boot (root) drive as setup above.
When the program starts, if no configuration file (SATPRED.CNF) can
be found in the same directory, some defaults are assumed. The
defaults will attempt to locate a satellite data file called
BULLETIN.TXT in the same directory as the program or accessory, and
then a reference location data file called DEFAULT.SPL, also in the
same directory.
SETTING UP THE PROGRAM
To set up the program, once it is running, you will need to set up
the information about what time zone you are in. When the program is
run, you will automatically be shown a dialog box to set the time,
whether to ask for the time whenever the program is started, and if we
are currently in daylight savings. To adjust for daylight savings,
click on the daylight savings button (the box should become checked)
when daylight savings is in effect. The button, simply adds 1 hour
(easterly time) to the time offset internally when it is set. Next set
the "Ask time at boot" button. If you have a built in real time clock
or some other program for setting the time, turn off the check mark,
else when the program is started up, it will ask for the local time and
offset.
The next thing is to set up the location information. This file
tells the program where to center the map, what location to use for the
reference point for calculation of the azimuth (or bearing), the
satellite elevation relative to the horizon and the difference between
the computer clock time and UTC. To edit the location data, place the
mouse on the [Location] button, press the left button and hold it down.
While holding the button, drag the mouse to the Edit Station menu entry
which just appeared next to the Location button and then let go when
the mouse is above the [Edit Location Info] entry. You can also click
on the [Location] button and then click on the Edit Station entry. At
this point, a dialog box will appear. Fill in the location name (or
call sign) to indicate where the data is for, the latitude and
longitude for your location (in decimal degrees, i.e. 122.456) and then
the altitude in either feet or meters. You can configure the program
to use either US or metric units by clicking on the units value shown.
Next, set up the offset between UTC and local time. This value should
be set to 8 for the Pacific time zone or 5 for Eastern time zone for
example and then the WEST button should be darkened to indicate which
direction from UTC. When all of the parameters are correct, click on
the [Save] button
If everything started up ok, then you should be now able to click
on the [Real Time Tracking] button and the first satellite in the data
file will be shown on the screen showing where the satellite is located
and some parameters associated with the satellite.
PROGRAM DETAILS
The main intent of the program is two fold. The program is
intended to generate real time data for use in locating a satellite at
a specific time and to generate printed information over a specified
period of time. The program also provides utilities for loading,
merging, editing, sorting, purging, and saving satellite orbital data.
Nearly all program functions can be accessed from the main menu. The
uses of the main menu options are as follows.
[Satellite]
The [Satellite] button will bring up a pop-up menu. On this menu,
the satellite database can be loaded, saved, merged, edited, or enabled
for processing.
Satellite data can be saved in either ASCII or binary format.
When [Save Satellite] is selected, an alert box is displayed asking for
which mode to save the file in. ASCII format is to allow transferring
satellite data to other programs or computer types. The ASCII file
data is in the standard NASA 2 Line format. The binary format is
included mainly for speed. The ASCII file does take some time to load,
whereas the binary format can load nearly as fast as the screen can
redraw. When [Load Satellite] is selected, the file mode is not asked
as the program will automatically determine if the file is an ASCII or
binary file.
The [Edit Satellites] option is where the satellite orbital
parameters may be entered or edited. The time data can be entered in
either of two formats; year and decimal day, or MM/DD/YY HH:MM:SS.SSSS.
Either the use of semi-major axis (SMA) or mean motion (MM) may be
selected. This option is changed by clicking on the [MM] or [SMA]
button and selecting the desired mode on the pop-up menu. The units of
SMA can also be changed between meters and feet by clicking on the
[meters] or [feet] button and then select the desired units from the
pop-up menu. The option of entering a position and velocity vector can
be accomodated by clicking on the [Enter M-50 Parameters] button. This
will bring up a dialog box for the entry of these values. When
[Convert] is clicked, the orbital values of Inclination, RAAN,
Eccentricity, Arg of Perigee, Mean Anomal