Using Predict

PREDICT(1)                KD2BD Software               PREDICT(1)

       predict  - Track and predict passes of satellites in Earth

       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]

       PREDICT is a multi-user  satellite  tracking  and  orbital
       prediction  program written under the Linux operating sys-
       tem by John A. Magliacane, KD2BD. PREDICT  is  free  soft-
       ware.  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 war-
       POSE. See the GNU General Public License for more details.

       PREDICT tracks and predicts passes of satellites based  on
       the  geographical location of the ground station, the cur-
       rent 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  PRE-
       DICT  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 pro-
       gram 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 satel-
       lites in the program's database.  Keplerian  orbital  data
       is   available   from  a  variety  of  sources,  including,,

       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.

       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 pre-
       vious  passes to help to confirm or identify past observa-

       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

       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 calcula-
       tions are started and prediction information is  displayed
       on the screen.

       The  date and time in UTC, along with the satellite's ele-
       vation 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 space-
       craft attitude parameters (ALAT,  ALON)  are  included  in
       PREDICT's   transponder  database  file,  then  spacecraft
       antenna squint angles are displayed instead of orbit  num-
       bers 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 Shut-
       tles, 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

       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 direc-
       tory. 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 under-
       score  (_)  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 pre-
       dictions 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  pro-
       vides the option of breaking out of visual orbital predic-
       tion 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 geostation-
       ary  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 pre-
       diction screen displays the first  pass  in  its  entirety
       from start to finish.

       In addition to predicting satellite passes, PREDICT allows
       satellites to be tracked in real-time using PREDICT's Sin-
       gle  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 posi-
       tions 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 experi-
       enced on uplink and downlink frequencies, path loss, prop-
       agation  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 dis-
       played 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 dis-
       played 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 coor-
       dinates in real-time. Announcements such as:

       "This  is  PREDICT.   Satellite  is  at  fifty six degrees
       azimuth and forty five degrees elevation, and is approach-
       ing.  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 satel-
       lites 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 announce-
       ments can be forced by pressing  the  'T'  key  in  Single
       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 head-
       ing,  elevation,  sub-satellite point latitude (in degrees
       North) and longitude (in degrees West) positions are  pro-
       vided,  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  indi-
       cates  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  sun-
       light  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 letter-
       ing. 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 geo-
       stationary orbits or for satellites so low in  inclination
       and/or altitude that they can never rise above the horizon
       of the ground station.

       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 espe-
       cially valuable  to  spacecraft  designers  and  satellite
       ground  station  controllers  who  must monitor spacecraft
       power budgets or thermal conditions on-board their  space-
       craft due to sunlight and eclipse periods.  It can even be
       used to predict the optimum times for astronauts  to  per-
       form  extra-vehicular activities in space. Solar illumina-
       tion predictions may be logged to a file in the same  man-
       ner  that  orbital  predictions may be logged (by pressing

       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 ascen-
       sion, 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 cor-
       responds  to the speed and direction the object is travel-
       ing 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.

       PREDICT  may  be run under the X-Window System by invoking
       it through the xpredict script contained with  this  soft-
       ware. xpredict can invoke rxvt, xterm, Eterm, gnome-termi-
       nal, 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.

       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 pre-

       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


            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/pre-
       dict.qth location, and TLE  information  from  visual.tle,

            predict -q bobs.qth

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

       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.  PRE-
       DICT then quietly exits without displaying anything to the
       screen, thereby eliminating the need for entering the pro-
       gram  and  selecting  the  appropriate  menu options. This
       option is invoked using the -u command line switch as fol-

            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  fol-

            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:

          wget  -qr
       -O amateur.txt
          wget -qr -O
          wget  -qr
       -O weather.txt
          /usr/local/bin/predict    -u   amateur.txt   visual.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.

       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  <
       track.html>, TAPR's EasyTrak Jr.  (currently under  devel-
       opment),  and  Suding  Associates Incorporated's Dish Con-
       trollers         <
       trollers.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 auto-
       matically 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

       The  -f  command-line option, when followed by a satellite
       name or object number and starting date/time, allows  PRE-
       DICT  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 loca-
       tion  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 Jan-
       uary 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

       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  pro-
       duced.   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 follow-
       ing 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

            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  pro-
       duces  an  output consisting of the date/time in Unix for-
       mat, 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.

       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  pro-
       vided  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  communicat-
       ing  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 PRE-
       DICT.  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  distribu-
       tion  of  PREDICT as a guide.  The sample program has com-
       ments to explain how each component operates.  It is  use-
       ful  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 com-
       mand 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.

       One of the most frequently asked questions is  how  satel-
       lites  in  PREDICT's  orbital database may be added, modi-
       fied, 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 Keple-
       rian data for the new satellite.  If this method  is  cho-
       sen,  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.

       In  addition  to  tracking and predicting passes of satel-
       lites, PREDICT may also be used to generate  a  NASA  two-
       line Keplerian element data set from data entered via key-
       board. For example, let's say you're  listening  to  Space
       Shuttle  audio re-broadcasts via WA3NAN and Keplerian ele-
       ments 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 (Key-
       board 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.

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

       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  sig-
       nals are first heard.

       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.

       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.

       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 com-
       munication with a satellite in such a position is not pos-
       sible under normal circumstances.

       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  communica-
       tions coverage.

       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.

       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.

       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  pre-
       dict/clients/samples  subdirectory.   The  latest  news is
       available through the official PREDICT software  web  page
       located at: <>.

              Default database of orbital data

              Satellite transponder database file

              Default ground station location information

       PREDICT   was   written   by  John  A.  Magliacane,  KD2BD
       <>.  The socket server code was contributed
       by  Ivan  Galysh,  KD4HBO <>.  The
       PIC/TRACK serial port antenna rotator controller code  was
       contributed    by    Vittorio   Benvenuti,   I3VFJ   <ben->.  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.

KD2BD Software             15 May 2006                 PREDICT(1)