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PREDICT(1)			KD2BD Software			    PREDICT(1)

       predict - Track and predict passes of satellites	in Earth orbit.

       predict	[-u  tle_update_source]	 [-t  tlefile]	[-q  qthfile]  [-a se-
       rial_port] [-a1 serial_port]  [-n  network_port]	 [-f  sat_name	start-
       ing_date/time  ending_date/time]	 [-dp sat_name starting_date/time end-
       ing_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 pro-
       gram 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.

       PREDICT tracks and predicts passes of satellites	based on the geograph-
       ical location of	the ground station, the	current	date and time as  pro-
       vided  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 nor-
       mally  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  de-
       grees  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.ce-,, and

       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	satel-
       lite 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 noth-
       ing and hitting simply the ENTER	key when prompted to enter the	start-
       ing date	and time.

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


       Entering	 the  time is optional.	 If it is omitted, midnight (00:00:00)
       is assumed.  Once complete, orbital calculations	are started  and  pre-
       diction 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  or-
       bital  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	satel-
       lite name are replaced by the underscore	(_) symbol. The	 logging  fea-
       ture  may  be toggled on	and off	at any time by pressing	the or hitting
       the ESCape key will also	close the log file. The	log file will  be  ap-
       pended  with  additional	information if additional predictions are con-
       ducted 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  op-
       tion  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	start-
       ing  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.

       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 sat-
       ellites 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 dis-
       played.	The current date and time is displayed along with  the	satel-
       lite'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 sta-
       tion,  the  amount  of Doppler shift experienced	on uplink and downlink
       frequencies, path loss, propagation delay, and echo times are also dis-
       played.	The expected time of LOS is also provided.

       Uplink and downlink frequencies are held	in PREDICT's transponder data-
       base 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 sta-
       tion TX frequency will be displayed by PREDICT.

       Obviously, an accurate system clock and up-to-date orbital data are re-
       quired 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	satel-
       lite'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

       are  made at intervals that are a function of how quickly the satellite
       is moving across	the sky. Announcements can occur as frequently as  ev-
       ery  50 seconds for satellites in low earth orbits such as the Interna-
       tional 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 an-
       nouncements are made. Alarms and	special	announcements  are  made  when
       the  satellite being tracked enters into	or out of eclipse. Regular an-
       nouncements 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 posi-
       tions of	the Sun	and Moon. Tracking data	for  the  satellites  is  dis-
       played in two columns of	12 satellites each. The	name, azimuth heading,
       elevation, sub-satellite	point latitude (in degrees North)  and	longi-
       tude  (in  degrees  West)  positions are	provided, along	with the slant
       range distance between the satellite and	the ground station (in kilome-

       A letter	displayed to the right of the slant range indicates the	satel-
       lite's sunlight and eclipse conditions. If the satellite	is  experienc-
       ing  an	eclipse	period,	an N is	displayed. If the satellite is in sun-
       light and the ground station is under the cover of  darkness,  a	 V  is
       displayed to indicate the possibility that the satellite	is visible un-
       der the current conditions. If the satellite is in sunlight while  con-
       ditions	at the ground station do not allow the satellite to be seen, a
       D is displayed.	Satellites in range of the  ground  station  are  dis-
       played  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.  Pre-
       dictions	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.

       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  informa-
       tion  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 illu-
       mination	predictions may	be logged to a file in the  same  manner  that
       orbital predictions may be logged (by pressing L).

       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  az-
       imuth  and elevation headings, the right	ascension, declination,	Green-
       wich 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  ex-
       perienced in Moonbounce communications is minimal.  The normalized dis-
       tance 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 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

       By  default, PREDICT reads ground station location and orbital data in-
       formation from a	pair of	files located in the user's home directory un-
       der  a  hidden subdirectory named .predict. Ground station location in-
       formation is held in a file named predict.qth, while orbital  data  in-
       formation 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


	    predict -q beach_house.qth -t visual.tle

       If the files specified are not located in the  current  working	direc-
       tory,  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  de-
       fault ~/.predict/predict.tle location.

       It  is also possible to update PREDICT's	satellite orbital database us-
       ing another command line	option that updates the	database from  a  NASA
       two-line	 element data set. PREDICT then	quietly	exits without display-
       ing 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	Keple-
       rian  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  or-
       bital database via the Internet:

	  wget -qr	-O amateur.txt
	  wget -qr -O visual.txt
	  wget -qr	-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	kepup-
       date),  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

       PREDICT	is compatible with serial port antenna rotator interfaces con-
       forming to  the	EasyComm  2  protocol  standard.   This	 includes  the
       PIC/TRACK interface developed by	Vicenzo	Mezzalira, IW3FOL <http://dig->, TAPR's EasyTrak  Jr.   (currently
       under  development),  and  Suding  Associates  Incorporated's Dish Con-
       trollers	 <>.   The
       FODTRACK	 rotator  interface is supported through the use of Luc	Lange-
       hegermann's (LX1GT) fodtrack utility written for	and included with PRE-

       Using  any of these hardware interfaces,	PREDICT	can automatically con-
       trol the	position of AZ/EL antenna rotators, and	 keep  antennas	 accu-
       rately  pointed toward a	satellite being	tracked	by PREDICT.  In	opera-
       tion, 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 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 sat-
       ellite 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 time-

       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	speci-
       fied,  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 res-
       olution.	 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


	    predict -f 25544 977446390 977446400 -o datafile

       Note that referencing a satellite by its	object number rather  than  by
       its name	is the preferred practice when the name	is especially long.

       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

	    predict -f ISS +10m

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

       The -p option allows orbital predictions	for a single pass to be	gener-
       ated 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,  the	space-
       craft's	sunlight  visibility  information, and,	if the satellite is in
       range, 100 MHz-normalized downlink Doppler shift	information.

       For example:

       1589489403 Thu 14May20 20:50:03	 20   65  209	45   57	  1766	 38901
       * 74.989726

       The  output  isn't  annotated, but then again, it's meant to be read by
       other software.

       The Unix	"date" command can be used to determine	the Unix time if  only
       a human-readable	date and time string are known.

       For example:

	    date -d "Oct 12 2020 12:00:00 EDT" +%s

       returns a value of 1602518400 seconds for Unix time.  Any time zone un-
       derstood	by the "date" command can be used.  The	"date" commmand	can be
       combined	in a call to PREDICT by	enclosing its invocation within	a pair
       of grave	quotes (` `) as	follows:

	    predict -p ISS `date -d "Oct 12 2020 16:00:00 UTC" +%s`

       The -dp option produces a quick orbital prediction for the next pass of
       a  specified satellite, including 100 MHz downlink Doppler shift	infor-
       mation, in CSV format.  For example:

	    predict -dp	ISS


       1525500165,Sat 05May18 06:02:45,701.256856
       1525500169,Sat 05May18 06:02:49,678.755942
       1525500172,Sat 05May18 06:02:52,656.033048
       1525500176,Sat 05May18 06:02:56,633.093151
       1525500179,Sat 05May18 06:02:59,609.940999
       1525500183,Sat 05May18 06:03:03,586.582443
       1525500186,Sat 05May18 06:03:06,563.022553
       <... output trimmed ...>
       1525500367,Sat 05May18 06:06:07,-733.663728
       1525500370,Sat 05May18 06:06:10,-755.793182
       1525500374,Sat 05May18 06:06:14,-777.690366
       1525500377,Sat 05May18 06:06:17,-799.351435
       1525500381,Sat 05May18 06:06:21,-820.773340
       1525500384,Sat 05May18 06:06:24,-841.952820
       1525500388,Sat 05May18 06:06:28,-862.887147

       where the Unix time is followed by the UTC date/time and	100 MHz	 down-
       link-referenced Doppler shift.  The satellite name or object number can
       be followed by a	starting date/time and ending date/time	much like  the
       -f option.

       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 ma-
       chines provided the clients are connected to the	server through a func-
       tioning 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 sat-
       ellites in the program's	database may be	accessed  by  client  applica-
       tions.  When in Single-Satellite	Tracking mode, only live tracking data
       for the single satellite	being tracked may be accessed.	Either	track-
       ing mode	may be ended at	any time.  When	this is	done, PREDICT will re-
       turn the	last calculated	satellite tracking data	until the  program  is
       again  put into a real-time tracking mode.  This	allows the user	to re-
       turn 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 argu-
       ments 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  re-
       lease of	PREDICT, and may be found under	the predict/clients directory.

       One  of	the  most frequently asked questions is	how satellites in PRE-
       DICT'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  sat-
       ellite.	 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  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 electroni-
       cally in	this format.

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

	       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 re-
       mote 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 ac-
       quires 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.

       Point in	a satellite's orbit when the satellite is at its farthest dis-
       tance from the earth's surface.

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

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 de-

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	calcu-
       lates  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 posi-
       tioned  below  the local	horizon, and radio communication with a	satel-
       lite in such a position is not possible 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 communications 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.  Or-
       bital 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 an-
       tennas  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  dis-
       tance 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 in-
       terface 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 lo-
       cated 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			  14 May 2020			    PREDICT(1)


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