predict.txt

一个预测卫星方位俯仰的软件

       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.  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 groundstation 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.

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 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.

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 espe-
       cially valuable  to  spacecraft  designers  and  satellite
       groundstation  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
       L).

COMMAND LINE ARGUMENTS
       By default, PREDICT  reads  ground  station  location  and
       orbital  data  information from a pair of files located in
       the current working directory.   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 orbital data for more than 24
       satellites exists in predict.tle, then only the  first  24
       satellites are read by PREDICT.

       If  we  wish  to  run  PREDICT  using  data from alternate
       sources instead of these default files, the names of  such
       files  may  be  passed to PREDICT on the command line when
       the program is started. For example, if we  wish  to  read
       the  TLE  file  visual.tle  and  the  QTH file holiday.qth
       rather than the default files, we could start PREDICT  and
       pass  the names of these alternate files to the program in
       the following manner:

            predict -t visual.tle -q holiday.qth

       or

            predict -q holiday.qth -t visual.tle

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

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

            predict -t visual.tle

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

            predict -q bobs.qth

       reads  QTH  information  from bobs.qth and TLE information
       from the default predict.tle 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.  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-
       lows:

            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-
       lows:

            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.

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/pic-
       track.html>,  TAPR's EasyTrak Jr.  (currently under devel-
       opment), and Suding Associates  Incorporated's  Dish  Con-
       trollers         <http://www.ultimatecharger.com/Dish_Con-
       trollers.html>.  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 opera-
       tion, tracking data from PREDICT is directed to the speci-
       fied  serial  port  using the -a command line option.  For
       example:

            predict -a com1

       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 com1

       (Note:  The  DOS  version  of  PREDICT lacks a serial port
       driver that more likely than not will prevent PREDICT from
       successfully  sending  data  to  the  serial port tracking
       interfaces described here.)

ADDITIONAL OPTIONS
       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
       (N) and longitude (W)  of  the  satellite's  sub-satellite
       point at the time specified, the slant range to the satel-
       lite in kilometers with respect to  the  ground  station's
       location,  the orbit number, and the spacecraft's sunlight