Provided by: predict_2.2.3-4_amd64 bug

NAME

       predict - Track and predict passes of satellites in Earth orbit

SYNOPSIS

       predict   [-u   tle_update_source]   [-t  tlefile]  [-q  qthfile]  [-a  serial_port]  [-a1
       serial_port] [-n  network_port]  [-f  sat_name  starting_date/time  ending_date/time]  [-p
       sat_name starting_date/time] [-o output_file] [-s] [-east] [-west] [-north] [-south]

DESCRIPTION

       PREDICT  is  a  multi-user satellite tracking and orbital prediction program written under
       the Linux operating system by John A. Magliacane, KD2BD. PREDICT is free software. You can
       redistribute  it  and/or  modify  it  under the terms of the GNU General Public License as
       published by the Free Software Foundation, either version 2 of the License  or  any  later
       version.

       PREDICT  is  distributed  in  the  hope  that it will be useful, but WITHOUT ANY WARRANTY,
       without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR  PURPOSE.
       See the GNU General Public License for more details.

FIRST TIME USE

       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 of PREDICT are provided default ground station location and orbital data information
       files.  These  files are managed by the program, and are normally located in a user's home
       directory under a hidden subdirectory named .predict. First time users will be prompted to
       supply PREDICT with their geographical location (the same as selecting option [G] from the
       program's main menu) the first time the program is run. Latitude is normally expressed  in
       degrees north with latitudes south of the equator expressed in negative degrees. Longitude
       is normally expressed in degrees  west  with  eastern  longitudes  expressed  in  negative
       degrees.  This  behavior  can  be  modified  by  passing the -east or -south commmand line
       switches to PREDICT.

       Latitudes and longitudes may be either entered in decimal degrees, or in degrees, minutes,
       seconds  (DMS)  format.   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.

       Users of PREDICT need Keplerian orbital data for the satellites they wish to track that is
       preferably no older than one month. The default orbital data supplied with the program  is
       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/,
       http://www.space-track.org/, and http://www.amsat.org/.

PROGRAM OPERATION

       The  start-up  screen of PREDICT 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 time is optional.  If it is omitted, midnight (00:00:00)  is  assumed.   Once
       complete,  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.   If  spacecraft  attitude  parameters  (ALAT,  ALON) are included in PREDICT's
       transponder database file, then spacecraft antenna squint angles are displayed instead  of
       orbit numbers in the orbital prediction output.

       An  asterisk  (*)  displayed  to  the  right of the orbit number or squint angle 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 (ISS), the US Space Shuttles, and Hubble Space Telescope, and
       the Upper Atmosphere Research Satellite (UARS) are visible to the naked eye. If no  symbol
       appears to the right of each line, 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 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,  a  wealth  of  information  related  to tracking a
       spacecraft and communicating through its transponder is displayed.  The current  date  and
       time  is 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 modulo 256 orbital phase of  the  satellite,  the  eclipse  depth,  the
       spacecraft  antenna  squint  angle, and orbital model in use, as well as the current orbit
       number are also displayed.  The date and time for the next AOS is also provided.

       Additionally, if the satellite is currently in range of the ground station, the amount  of
       Doppler  shift  experienced  on  uplink  and  downlink frequencies, path loss, propagation
       delay, and echo times are also displayed.  The expected time of LOS is also provided.

       Uplink and downlink frequencies are held in PREDICT's transponder database file predict.db
       located under $HOME/.predict.  A default file is provided with PREDICT.

       Transponders  may  be selected by pressing the SPACE BAR.  The passband of the transponder
       may be tuned in 1 kHz increments by pressing the < and > keys.  100 Hz tuning is  possible
       using the , and . keys.  (These are simply the < and > keys without the SHIFT key.)

       If  no  transponder information is available, the data displayed on the tracking screen is
       abbreviated.

       The features available  in  the  Single  Satellite  Tracking  Mode  make  it  possible  to
       accurately  determine  the proper uplink frequency to yield a given downlink frequency, or
       vice versa.  For example, if one wishes to communicate with a station heard  on  435.85200
       MHz  via  FO-29,  then  435.85200  MHz can be selected via the keyboard as an RX frequency
       using the tuning keys while tracking  FO-29,  and  the  corresponding  ground  station  TX
       frequency will be displayed by PREDICT.

       Obviously,  an accurate system clock and up-to-date orbital data are required for the best
       tuning accuracy.

       If a sound card is present on your machine and  the  Single  Satellite  Tracking  Mode  is
       invoked  with  an  uppercase  'T'  rather than a lowercase 't', PREDICT will make periodic
       voice  announcements  stating  the  satellite's   tracking   coordinates   in   real-time.
       Announcements such as:

       "This  is  PREDICT.   Satellite  is  at  fifty  six degrees azimuth and forty five degrees
       elevation, and is approaching.  Satellite is currently visible."

       are made at intervals that are a function of how quickly the satellite  is  moving  across
       the  sky.  Announcements can occur as frequently as every 50 seconds for satellites in low
       earth orbits such as the International Space Station (370 km), or as infrequently as every
       8  minutes  for  satellites in very high orbits, such as the AMC-6 geostationary satellite
       (35780 km). Voice announcements are  performed  as  background  processes  so  as  not  to
       interfere  with  tracking  calculations  as the announcements are made. Alarms and special
       announcements are made when the satellite being tracked enters into  or  out  of  eclipse.
       Regular  announcements  can be forced by pressing the 'T' key in Single Satellite Tracking
       Mode.

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 distance between the satellite and the
       ground station (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.

SOLAR ILLUMINATION PREDICTIONS

       Selecting [S] from PREDICT's main menu will allow solar  illumination  predictions  to  be
       made.  These predictions indicate how much sunlight a particular satellite will receive in
       a 24 hour period.  This information is especially valuable  to  spacecraft  designers  and
       satellite  ground station controllers who must monitor spacecraft power budgets or thermal
       conditions on-board their spacecraft due to sunlight and eclipse periods.  It can even  be
       used  to predict the optimum times for astronauts to perform extra-vehicular activities in
       space. Solar illumination predictions may be logged to a file  in  the  same  manner  that
       orbital predictions may be logged (by pressing L).

SOLAR AND LUNAR ORBITAL PREDICTIONS

       In addition to making orbital predictions of spacecraft, PREDICT can also predict transits
       of  the Sun and the Moon.  Lunar predictions are initiated by selecting [L] from PREDICT's
       Main Menu.  Solar predictions are selected through Main Menu option [O].

       When  making  solar  and lunar orbital predictions, PREDICT provides azimuth and elevation
       headings, the right ascension, declination, Greenwich Hour Angle (GHA),  radial  velocity,
       and  normalized distance (range) to the Sun or Moon.  Declination and Greenwich Hour Angle
       correspond to the latitude and longitude of the object's  sub-satellite  point  above  the
       Earth's surface.  The radial velocity corresponds to the speed and direction the object is
       traveling toward (+) or away (-) from the ground station, and is expressed in  meters  per
       second.   When  the  radial  distance  of the Moon is close to zero, the amount of Doppler
       shift experienced in  Moonbounce  communications  is  minimal.   The  normalized  distance
       corresponds  to  the  object's  actual  distance to the ground station divided its average
       distance.  In practice, the normalized distance can range from about 0.945  to  1.055  for
       the Moon, and about 0.983 to 1.017 for the Sun.

       Note  that the effects of atmospherics are ignored in determining the elevation angles for
       the Sun and Moon. Furthermore, the data provided by PREDICT corresponds  to  the  object's
       center,  and  not the upper or lower limb, as is sometimes done when predicting the rising
       and setting times of these celestial objects.

OPERATION UNDER THE X-WINDOW SYSTEM

       PREDICT may be run under the X-Window System by invoking it through  the  xpredict  script
       contained  with  this software. xpredict can invoke rxvt, xterm, Eterm, gnome-terminal, or
       kvt, and display PREDICT in a virtual terminal window.  xpredict should be edited for best
       results.   In many cases, holding down the SHIFT key while pressing the plus (+) and minus
       (-) keys allows PREDICT's window to be re-sized when started under xpredict.

COMMAND LINE ARGUMENTS

       By default, PREDICT reads ground station location and orbital data information from a pair
       of  files located in the user's home directory under a hidden subdirectory named .predict.
       Ground station location information is held in a file  named  predict.qth,  while  orbital
       data information for 24 satellites is held in a file named predict.tle.

       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 beach_house.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 beach_house.qth

       or

            predict -q beach_house.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
       /home/kd2bd/orbs/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/predict.qth  location,   and   TLE
       information from visual.tle, while

            predict -q bobs.qth

       reads   QTH   information   from   bobs.qth   and   TLE   information   from  the  default
       ~/.predict/predict.tle location.

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. PREDICT may be updated from a list of files as well:

            predict -u amateur.tle visual.tle weather.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.tle

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

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

       For example, the following script can be used to update PREDICT's orbital database via the
       Internet:

          #!/bin/sh
          wget -qr www.celestrak.com/NORAD/elements/amateur.txt -O amateur.txt
          wget -qr www.celestrak.com/NORAD/elements/visual.txt -O visual.txt
          wget -qr www.celestrak.com/NORAD/elements/weather.txt -O weather.txt
          /usr/local/bin/predict -u amateur.txt visual.txt weather.txt

       To truly automate the process of updating your orbital database, save the  above  commands
       to  a  file in your home directory (such as kepupdate), and add the following line to your
       crontab (type crontab -e to edit your crontab):

            0 2 * * * kepupdate

       and PREDICT will automatically update its database every day at 2:00 AM.

AUTOMATIC ANTENNA TRACKING

       PREDICT is compatible with serial  port  antenna  rotator  interfaces  conforming  to  the
       EasyComm  2 protocol standard.  This includes the PIC/TRACK interface developed by Vicenzo
       Mezzalira, IW3FOL  <http://digilander.iol.it/iw3fol/pictrack.html>,  TAPR's  EasyTrak  Jr.
       (currently  under  development),  and  Suding  Associates  Incorporated's Dish Controllers
       <http://www.ultimatecharger.com/Dish_Controllers.html>.  The FODTRACK rotator interface is
       supported through the use of Luc Langehegermann's (LX1GT) fodtrack utility written for and
       included with PREDICT.

       Using any of these hardware interfaces, PREDICT can automatically control the position  of
       AZ/EL  antenna  rotators,  and  keep  antennas accurately pointed toward a satellite being
       tracked by PREDICT.  In operation, tracking data from PREDICT is directed to the specified
       serial port using the -a command line option.  For example:

            predict -a /dev/ttyS0

       will  send  AZ/EL  tracking  data  to the first serial port when the program is tracking a
       satellite in the Single Satellite Tracking Mode.  The data sent to the serial port  is  of
       the  form:  AZ241.0  EL26.0  using  9600  baud, 8-data bits, 1-stop bit, no parity, and no
       handshaking.  Data is sent to the interface if the azimuth or elevation headings change by
       one  degree  or more.  For interfaces requiring keepalive updates at least once per second
       whether the AZ/EL headings have changed or not (such as the ones by SAI), the  -a1  option
       may be used:

            predict -a1 /dev/ttyS0

ADDITIONAL OPTIONS

       The  -f  command-line  option,  when  followed  by  a  satellite name or object number and
       starting date/time, allows PREDICT to respond with satellite positional information.  This
       feature  allows PREDICT to be invoked within other applications that need to determine the
       location of a satellite at a particular point in time, such as the location of where a CCD
       camera image was taken by a Pacsat satellite based on its timestamp.

       The  information  produced  includes  the  date/time in Unix format (the number of seconds
       since midnight UTC on January 1, 1970), the date/time in ASCII (UTC), the elevation of the
       satellite  in  degrees,  the  azimuth  heading of the satellite, the orbital phase (modulo
       256), the latitude and longitude of  the  satellite's  sub-satellite  point  at  the  time
       specified,  the  slant  range  to  the  satellite in kilometers with respect to the ground
       station's  location,  the  orbit  number,  and  the   spacecraft's   sunlight   visibility
       information.

       The  date/time  must  be specified in Unix format (number of seconds since midnight UTC on
       January 1, 1970).  If no starting or ending time is specified, the  current  date/time  is
       assumed  and  a  single  line  of  output  is produced.  If a starting and ending time are
       specified, a list of coordinates beginning at the starting time/date and ending  with  the
       ending  time/date  will  be  returned by the program with a one second resolution.  If the
       letter m is appended to the ending time/date, then the data returned by the  program  will
       have  a  one  minute resolution.  The -o option allows the program to write the calculated
       data to an output file rather than directing it to the standard output device if desired.

       The proper syntax for this option is as follows:

            predict -f ISS 977446390 977446400 -o datafile

       A list of coordinates starting at the current date/time and ending 10 seconds later may be
       produced by the following command:

            predict -f ISS +10

       If  a  list  of  coordinates specifying the position of the satellite every minute for the
       next 10 minutes is desired, the following command may be used:

            predict -f ISS +10m

       If a satellite name contains spaces, then the entire name must be enclosed by "quotes".

       The -p option allows orbital predictions for a single pass to be generated by PREDICT  via
       the command-line.  For example:

            predict -p OSCAR-11 1003536767

       starts  predictions  for  the OSCAR-11 satellite at a Unix time of 1003536767 (Sat 20Oct01
       00:12:47 UTC).  If the starting date/time is omitted, the current date/time is used.  If a
       pass  is  already in progress at the starting date/time specified, orbital predictions are
       moved back to the beginning of AOS of the current pass, and data for the entire pass  from
       AOS to LOS is provided.

       When  either  the  -f or -p options are used, PREDICT produces an output consisting of the
       date/time in Unix format, the date and time in ASCII (UTC), the elevation of the satellite
       in  degrees,  the azimuth of the satellite in degrees, the orbital phase (modulo 256), the
       latitude (N) and longitude (W) of the satellite's sub-satellite point, the slant range  to
       the  satellite (in kilometers), the orbit number, and the spacecraft's sunlight visibility
       information.  For example: 1003611710 Sat 20Oct01 21:01:50   11    6  164   51   72   1389
       16669  *  The  output  isn't  annotated,  but  then  again, it's meant to be read by other
       software.

SERVER MODE

       PREDICT's network socket interface allows the program to operate as a  server  capable  of
       providing  tracking  data  and  other  information  to  client  applications using the UDP
       protocol.  It is even possible to have the PREDICT server and client applications  running
       on  separate  machines  provided  the  clients  are  connected  to  the  server  through a
       functioning network connection.

       The -s switch is used to start PREDICT in server mode:

            predict -s

       By default, PREDICT uses socket port 1210  for  communicating  with  client  applications.
       Therefore, the following line needs to be added to the end your /etc/services file:

            predict   1210/udp

       The  port  number (1210) can be changed to something else if desired.  There is no need to
       recompile the program if it is changed.  To run more  than  one  instance  of  PREDICT  in
       server  mode  on  a  single  host,  an  alternate port must be specified when invoking the
       additional instances of PREDICT.  This can be accomplished by using the -n switch:

            predict -n 1211 -t other_tle_file -s

       When invoked in server mode, PREDICT immediately enters Multi-Satellite Tracking Mode, and
       makes live tracking data available to clients.  Clients may poll PREDICT for tracking data
       when the program is running in either the Multi-Satellite  or  Single  Satellite  Tracking
       Mode.   When  in Multi-Satellite Tracking mode, tracking data for any of the 24 satellites
       in the program's database may  be  accessed  by  client  applications.   When  in  Single-
       Satellite  Tracking  mode,  only live tracking data for the single satellite being tracked
       may be accessed.  Either tracking mode may be ended at  any  time.   When  this  is  done,
       PREDICT will return the last calculated satellite tracking data until the program is again
       put into a real-time tracking mode.  This allows the user to return to the main menu,  and
       use  other  features  of  the  program  without sending potentially harmful data to client
       applications.

       The best way to write a client application is to use the  demonstration  program  (demo.c)
       included  in  this distribution of PREDICT as a guide.  The sample program has comments to
       explain how each component operates.  It is useful to pipe  the  output  of  this  program
       through less to easily browse through the data returned (demo | less).

       In  operation,  a  character  array is filled with the command and arguments to be sent to
       PREDICT.  A socket connection is then opened, the request is sent, a response is received,
       and the socket connection is closed.  The command and arguments are in ASCII text format.

       Several excellent network client applications are included in this release of PREDICT, and
       may be found under the predict/clients directory.

ADDING SATELLITES

       One of the most frequently asked questions is how satellites in PREDICT's orbital database
       may  be  added,  modified,  or replaced.  As it turns out, there are several ways in which
       this can be done.  Probably the easiest is to manually  edit  your  ~/.predict/predict.tle
       file,  and  replace  an  existing satellite's entry with 2-line Keplerian data for the new
       satellite.  If this method is chosen, however, just make sure to include ONLY the two line
       data, and nothing else.

       Another  way is to is select the Keyboard Edit option from the program's Main Menu, select
       a satellite you wish to replace.  Edit the name  and  object  number  (replacing  the  old
       information  with  the new information).  Just hit ENTER, and accept all the other orbital
       parameters shown.  Get back to PREDICT's Main Menu.  Select Auto Update,  and  then  enter
       the  filename containing the 2-line element data for your favorite new satellite.  The new
       satellite data should be detected by PREDICT, and the orbital data for the  old  satellite
       will be overwritten by the new data.

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.

       It  is  also  possible to run PREDICT as a background process and direct its display to an
       unused virtual console by using the following command:

               predict < /dev/tty8 > /dev/tty8 &

       Switching to virtual console number 8 (ALT-F8 in text  mode)  will  allow  PREDICT  to  be
       controlled  and  displayed  even  after  you've logged out.  This is especially handy when
       running PREDICT in server mode on a remote machine.

GLOSSARY OF TERMS

       The following terms are frequently used in association with satellite  communications  and
       space technology:

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  degrees  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
       degrees 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.

ADDITIONAL INFORMATION

       Detailed  information  on the operation of PREDICT's UDP socket-based interface as well as
       sample  code  for  writing  your   own   client   applications   is   available   in   the
       predict/clients/samples  subdirectory.   The latest news is available through the official
       PREDICT software web page located at: <http://www.qsl.net/kd2bd/predict.html>.

FILES

       ~/.predict/predict.tle
              Default database of orbital data

       ~/.predict/predict.db
              Satellite transponder database file

       ~/.predict/predict.qth
              Default ground station location information

SEE ALSO

       predict-g1yhh(1)

AUTHORS

       PREDICT was written by John A. Magliacane, KD2BD  <kd2bd@amsat.org>.   The  socket  server
       code  was  contributed  by  Ivan Galysh, KD4HBO <galysh@juno.nrl.navy.mil>.  The PIC/TRACK
       serial port antenna rotator controller code was contributed by Vittorio  Benvenuti,  I3VFJ
       <benscosm@iol.it>.   SGP4/SDP4  code  was derived from Pacsal routines written by Dr. T.S.
       Kelso, and converted to 'C'  by  Neoklis  Kyriazis,  5B4AZ.   See  the  CREDITS  file  for
       additional information.