
			*******************************
			*  PREDICT Version 2 For DOS  *
			* First Time Use Instructions *
			*******************************

PREDICT tracks and predicts passes of satellites based on the geographical
location of the ground station, the current date and time as provided by the
computer system's clock, and Keplerian orbital data for the satellites of
interest to the ground station.  First time users should supply PREDICT with
their geographical location by selecting option [G] from the program's main
menu) the first time the program is run.  Latitude is entered in decimal
degrees north.  Latitudes south of the equator are entered as negative
numbers.  Longitude is entered as decimal degrees west.  Eastern longitudes
may be entered as negative numbers.  Station altitude is entered as the
number of meters the ground station is located above sea level. This
parameter is not very critical.  If unsure, make a realistic guess or
simply enter 0.  The UTC hour offset represents how many hours the PC's
clock/calendar is relative to Universal Time. 

Users of PREDICT need Keplerian orbital data for the satellites they wish
to track that is preferably no older than one month.  The orbital data
supplied with the program are liable to be quite old, and so must be brought
up to date if accurate results are to be expected.  This may be accomplished
by selecting option [E] from PREDICT's main menu and manually entering
Keplerian data for each satellite in the program's database, or by selecting
option [U] and specifying a file containing recent 2-line Keplerian element
data sets that correspond to the satellites in the program's database.
Keplerian orbital data is available from a variety of sources, including
http://www.celestrak.com/ and http://www.amsat.org/


* Program Operation *
=====================
The operation of PREDICT is uncomplicated by design.  The start-up screen
of the program lists the program's main functions.  Several tracking and
orbital prediction modes are available, as well as several utilities to
manage the program's orbital database.


* Predicting Satellite Passes *
===============================
Orbital predictions are useful for determining in advance when a satellite
is expected to come within range of a ground station.  They can also be
used to look back to previous passes to help to confirm or identify past
observations.

PREDICT includes two orbital prediction modes to predict any pass above a
ground station (main menu option [P]), or list only those passes that might
be visible to a ground station through optical means (main menu option [V]).
In either mode, the user is asked to select a satellite of interest from a
menu, and then asked to enter the date and time (in UTC) at which prediction
calculations should start.

The current date and time may be selected by default by entering nothing and
hitting simply the ENTER key when prompted to enter the starting date and
time.

Otherwise, the starting date and time should be entered in the form:

        DDMonYY HH:MM:SS

Entering the hour, minute, and seconds is optional.  If it is omitted, then
00:00:00 is assumed.  After the date is entered, orbital calculations are
started and prediction information is displayed on the screen.

The date and time in UTC, along with the satellite's elevation above ground,
azimuth heading, modulo 256 orbital phase, sub-satellite point latitude and
longitude, slant range between the ground station and the satellite, and the
satellite's orbit number are all displayed.  An asterisk (*) displayed to
the right of the orbit number means the satellite is in sunlight at the
date and time listed on the line.  A plus symbol (+) means the satellite
is in sunlight while the ground station is under the cover of darkness at
the time and date listed.  Under good viewing conditions, large satellites
such as the International Space Station, and the US Space Shuttles are
visible to the naked eye.  If no symbol appears to the right of the orbit
number, then the satellite is in the Earth's shadow at the time and date
listed, and is not receiving any illumination from the sun.

Pressing the ENTER key, the 'Y' key, or the space bar advances the orbital
predictions to a screen listing the next available passes.  Pressing the 'L'
key allows the currently displayed screen plus any subsequent screens to be
logged to a text file in your current working directory. The name given to
this file is the name of the satellite plus a ".txt" extension.  Any slashes
or spaces appearing in the satellite name are replaced by the underscore (_)
symbol.  The logging feature may be toggled on and off at any time by
pressing the 'L' key.  Exiting the orbital prediction mode by pressing 'N'
or hitting the ESCape key will also close the log file.  The log file will
be appended with additional information if additional predictions are
conducted for the same satellite with the logging feature turned on.

Selecting [V] from PREDICT's main menu will permit a ground station to only
predict passes for satellites that are potentially visible through optical
means.  Since all other passes are filtered out in this mode, and since
some satellites may never arrive over a ground station when optical viewing
conditions are possible, the program provides the option of breaking out of
visual orbital prediction mode by pressing the [ESC]ape key as calculations
are made.  A prompt is displayed at the bottom of the screen to alert the
user of this option.

In either orbital prediction mode, predictions will not be attempted for
satellites that can never rise above the ground station's horizon, or for
satellites in geostationary orbits.  If a satellite is in range at the
starting date and time specified, PREDICT will adjust the starting date back
in time until the point of AOS so that the prediction screen displays the
first pass in its entirety from start to finish.


* Single Satellite Tracking Mode *
==================================
In addition to predicting satellite passes, PREDICT allows satellites to
be tracked singly in real-time using PREDICT's Single Satellite Tracking
Mode (main menu option [T]), or simultaneously as a group of 24 using
the program's Multi-Satellite Tracking Mode (main menu option [M]). The
positions of the Sun and Moon are also displayed when tracking satellites
in real-time.

Selecting option [T] from PREDICT's main menu places the program in Single
Satellite Tracking Mode.  The user will be prompted to select the satellite
of interest, after which a screen will appear and display tracking positions
for the satellite selected.

In Single Satellite Tracking Mode, the current date and time are displayed
along with the satellite's sub-satellite point, its orbital altitude in both
kilometers and statute miles, the slant range distance between the ground
station and the satellite in both kilometers and statute miles, the current
azimuth and elevation headings toward the satellite, the orbital velocity of
the satellite in both kilometers per hour and statute miles per hour, the
footprint of the satellite in both kilometers and statute miles, the orbital
phase of the satellite in both modulo 256 and 360, as well as the current
orbit number.  Additionally, if the satellite is currently in range of the
ground station, the amount of Doppler shift experienced by the ground
station receiving downlinks at 146 MHz and 435 MHz are displayed, as well as
the one-way path loss for these frequencies.  The predicted time of LOS as
well as sunlight and visibility information is also displayed at the bottom
of the screen.  If the satellite is not in range, then the Doppler shift and
path loss calculations are not performed, and the next predicted AOS date
and time is shown at the bottom of the screen.


* Multi-Satellite Tracking Mode *
=================================
Selecting [M] from PREDICT's main menu places the program in a real-time
multi-satellite tracking mode.  In this mode, all 24 satellites in the
program's database are tracked simultaneously along with the positions of
the Sun and Moon.  Tracking data for the satellites is displayed in two
columns of 12 satellites each.  The name, azimuth heading, elevation,
sub-satellite point latitude (in degrees North) and longitude (in degrees
West) positions are provided, along with the slant range (in kilometers),
and the slant range distance between the satellite and the ground station
(also in kilometers).

A letter displayed to the right of the slant range indicates the satellite's
sunlight and eclipse conditions.  If the satellite is experiencing an
eclipse period, an N is displayed.  If the satellite is in sunlight and
the ground station is under the cover of darkness, a V is displayed to
indicate the possibility that the satellite is visible under the current
conditions.  If the satellite is in sunlight while conditions at the ground
station do not allow the satellite to be seen, a D is displayed.  Satellites
in range of the ground station are displayed in BOLD lettering.  The AOS
dates and times for the next three satellites predicted to come into range
are displayed on the bottom of the screen between the tracking coordinates
of the Sun and Moon.  Predictions are not made for satellites in
geostationary orbits or for satellites so low in inclination and/or
altitude that they can never rise above the horizon of the ground station.


* Command Line Arguments *
==========================
By default, PREDICT reads ground station location and orbital data
information from the predict.qth and predict.tle files located in the
current working directory.  If we wish to run PREDICT using data from
alternate sources instead of these default files, the names of such files
may be passed to PREDICT on the command line when the program is started.
For example, if we wish to read the TLE file "visual.tle" and the QTH file
"holiday.qth" rather than the default files, we could start PREDICT and
pass the names of these alternate files to the program in the following
manner:

        predict -t visual.tle -q holiday.qth

or

        predict -q holiday.qth -t visual.tle

If the files specified are not located in the current working directory,
then their relative or absolute paths should also be specified along with
their names (predict -t c:\download\visual.tle).

It is also possible to specify only one alternate file while using the
default for the other. For example,

        predict -t visual.tle

reads QTH information from the default predict.qth file in the current
working directory, and TLE information from visual.tle, while

        predict -q bobs.qth

reads QTH information from "bobs.qth" and TLE information from the default
predict.tle file.


* "Quiet" Orbital Database Updates *
====================================
It is also possible to update PREDICT's satellite orbital database using
another command line option that updates the database from a NASA two-line
element data set.  PREDICT then quietly exits without displaying anything
to the screen, thereby eliminating the need for entering the program and
selecting the appropriate menu options.  This option is invoked using the
-u command line switch as follows:

        predict -u orbs248.tle

This example updates PREDICT's default orbital database with the Keplerian
elements found in the file "orbs248.tle".  If an alternate datafile requires
updating, it may also be specified on the command line using the -t switch
as follows:

        predict -t oscar.tle -u amateur.txt

This example updates the "oscar.tle" orbital database with the two-line
element data contained in "amateur.txt".

These options permit the automatic update of PREDICT's orbital data files
using Keplerian orbital data obtained through automatic means such as FTP
or Pacsat satellite download.


* Neat Tricks *
===============
In addition to tracking and predicting passes of satellites, PREDICT may
also be used to generate a NASA two-line Keplerian element data set from
data entered via keyboard.  For example, let's say you're listening to Space
Shuttle audio re-broadcasts via WA3NAN and Keplerian elements for the Space
Shuttle's orbit are given by the announcer.  The orbital data provided by
WA3NAN in verbal form may be manually entered into PREDICT's orbital
database using option [E] of the program's main menu (Keyboard Edit of
Orbital Database).  The orbital data for the Space Shuttle in NASA two-line
element form can then be found in your orbital database file, and may
imported to any other satellite tracking program that accepts two-line
element files or distributed to others electronically.


* Glossary of Terms *
=====================
   * AOS: Acquisition of Signal - the time at which a ground station first
     acquires radio signals from a satellite.  PREDICT defines AOS as the
     time when the satellite being tracked comes within +/- 0.03 degress of
     the local horizon, although it may have to rise higher than this before
     signals are first heard.

   * Apogee: Point in a satellite's orbit when the satellite is at its
     farthest distance from the earth's surface.

   * Anomalistic Period: A satellite orbital parameter specifying the time
     between successive perigees.

   * Ascending Node: Point in a satellite's orbit when its sub-satellite
     point crosses the equator moving south to north.

   * Azimuth: The compass direction measured clockwise from true north.
     North = 0 degrees, East = 90 degrees, South = 180 degrees, and West =
     270 degrees.

   * Descending Node: Point in a satellite's orbit when its sub-satellite
     point crosses the equator moving north to south.

   * Doppler Shift: The motion of a satellite in its orbit around the earth,
     and in many cases the rotational motion of the earth itself, causes
     radio signals generated by satellites to be received on Earth at
     frequencies slightly different than those upon which they were
     transmitted.  PREDICT calculates what effect these motions have upon
     the reception of satellites transmitting on the 146 MHz and 435 MHz
     Amateur Radio bands.

   * Elevation: The angle between the local horizon and the position of
     the satellite.  A satellite that appears directly above a particular
     location is said to be located at an elevation of 90 degrees.  A
     satellite located on the horizon of a particular location is said to
     be located at an elevation of 0 degrees.  A satellite with an elevation
     of less than zero is positioned below the local horizon, and radio
     communication with a satellite in such a position is not possible
     under normal circumstances.

   * Footprint: Diameter of the Earth's surface visible from a satellite.
     The higher the satellite's orbital altitude, the greater the footprint,
     and the wider the satellite's communications coverage.

   * LOS: Loss of Signal - the time at which a ground station loses radio
     contact with a satellite.  PREDICT defines LOS as the time when the
     satellite being tracked comes within +/- 0.03 degress of the local
     horizon.

   * Orbital Phase: An orbital "clock" that describes a satellite's orbital
     position with respect to perigee. Orbital Phase may be modulo 256, or
     modulo 360, and is sometimes referred to as mean anomaly when speaking
     of amateur radio satellites in elliptical orbits, such as the Phase 3
     satellites.  Orbital phase is zero at perigee.

   * Path Loss: The apparent attenuation a radio signal undergoes as it
     travels a given distance.  This attenuation is the result of the
     dispersion radio waves experience as they propagate between transmitter
     and receiver using antennas of finite gain.  Free space path loss is
     technically an oxymoron since free space is loss free.

   * Perigee: Point in a satellite's orbit when the satellite is at its
     closest distance to the earth's surface.

   * Nodal Period: A satellite orbital parameter specifying the time between
     successive ascending nodes.

   * Slant Range: The straight line distance between the ground station and
     the satellite at a given time.

   * Sub Satellite Point: The latitude and longitude specifying the location
     on the Earth that is directly below the satellite.

  ------------------------------------------------------------------------

John A. Magliacane, KD2BD
