NAME¶
seesat5 - provides satellite visibility information.
DESCRIPTION¶
This man page explains the commands used by seesat5 to produce and control the
satellites that will be analysed and the output criterion. These commands are
valid for use in SEESAT5.INI, in the command line, and from the seesat5
prompt.
SELECTION COMMANDS¶
- MAXELEV <number>
- This selects data where the calculated elevation is less or
equal to the entered value.
means that only elevation values of 70 or less will be selected. Only
satellites that are at 70 or less degrees in elevation will be selected.
- MINELEV <number>
- This selects data where the calculated elevation is greater
or equal to the entered value.
means that only elevation values of 15 or more will be selected. Only
satellites that get to 15 or more degrees in elevation will be selected.
- MINPHASE <number>
- This selects data where the calculated phase angle (the
angle between the sun and the satellite as seen by the observer), is
greater or equal the entered value.
- MINRANGE and MAXRANGE <number>
- This selects data where the range of the satellite is
within these limits. The number denotes either miles or kilometers
depending upon whether you set the MILES or KILOMETERS option. If the
satellite never gets between the MINRANGE and MAXRANGE values at your
location, then no data is printed for it. The default values for MINRANGE
and MAXRANGE is zero and 65535 respectively.
- SET and RESET
- These commands are used to set and reset conditions and
options. They are as follows :
|
SET SHOWTLE |
|
SET SHOWNORAD |
|
etc. |
is is useful when you want to see all the data using the ALL command. If you
don't reset the selection conditions, the program does not print any lines
because the conditions are not satisfied. The values for SHOWTLE, VISMAG,
SUNELEVSAT, SUNELEVOBS, MINELEV, MINRANGE, MAXRANGE and SHOWAGE can be
reset.
- SET KILOMETERS | MILES
- This varient of SET determines whether distances are to be
printed in MILES or KILOMETERS. Various people can only visualize distance
in one or the other of these units.
- SHOWAGE
- When this option is SET, the age (in days) of the element
is displayed. This is the age of the element at the time for which the
satellite data is printed. Also note that this value is UTC relative. For
example, if you do a whole weeks run with the same satellite elements and
the satellite is visible every day, then the TleAge value will be 1 day
greater in each days printout.
- SHOWNORAD
- Show the satellite NORAD number on the printout.
- SHOWTLE
- Controles the printing of the Keplerian elements when a
LOAD or NEXT is done. When SET, Keplerian elements are printed. When
RESET, they are not
- SUNELEVOBS <number>
- This selects data where the calculated SUN's elevation at
the observers location is less or equal the entered value.
means select data when the sun is at or below the horizon. This will let you
filter out satellite's that pass over in daylight.
- SUNELEVSAT <number>
- This selects data where the calculated SUN's elevation at
the satellite is greater or equal than the entered value.
means that only positive SUN values will be selected. This lets you select
data when the sun is shining on the satellite.
- VISMAG <number>
- This selects data where the MAGNITUDE is less or equal to
the supplied value.
means the calculated magnitude must be less than or equal to 1.0. This lets
you select bright satellites only.
GENERAL COMMANDS¶
- ALL
- Toggles between normal mode (predictions below horizon
suppressed) and a mode which displays all predictions.
- APPENDSDF
- This command requires a file name parameter. This is the
same as the OPENSDF command except the file is opened for extend. If the
file named does not exist, it will be created.
- BLOCK
- This command is used to customize the skyline that you view
from. It has the format BLOCK begin-azimuth end-azimuth elevation. The
azimuth values are integers between 0 and 359 and the elevation 0 and 90
degrees. You can use this to accurately define your view of the sky. You
can enter up to 30 block commands, each one defines a block from a
starting azimuth, ending azimuth and an elevation. If a satellite never
gets out from behind the blocks you define then its data will not be
printed. If at any time (be careful with time steps here), the satellite
is visible, then its data is printed and the data where it is behind a
block will be printed with a particular time you will not be able to see
the satellite although it is above the horizon. The MINELEV command is a
more simplified version of BLOCK and only useful in an open field where
the "mist line" at the horizon is uniform. BLOCK provides a
better solution for "city dwellers" where buildings tend to
block only some areas of the sky.
- CENTER
- Followed by a time, this command determins the time to
center the data run, usually used in conjuction with SPAN.
- Comments
- If you want to put comments inside your SEESAT5.INI file,
just type in a forward slash (/) anywhere you want. When the slash is at
the start of a line the entire line is treated as a comment. When it is in
the middle of a line, everthing after the slash up to the end of the line
is treated as a comment.
- CMDLINE
- This command is reserved for use in SEESAT5.INI. When
seesat5 encounters this command it executes the commands found on the
command line as though they were located in the init file where the
cmdline command is located. The main use of this command is to impliment
the "go label" command. Typically the init file begins with
setup commands that set the viewing location as well as some general
filter criterion. Following this with cmdline, followed by as many blocks
of instructions as you like, each one beginning with a unique label,
allows a runtime choice of which block to execute.
- DBS and DBS#
- To select satellites you want to run predictions on. You
can maintain the list inside the seesat.bat file, together with comments.
You may load the satellite either by name or by Norad Satellite Number.
|
DBS "HST ARRAY" / Last seen 2/3/94, dim, blinks |
|
DBS HST / Last seen with shuttle |
|
DBS "OKEAN 1" / Fast |
|
DBS MIR / Must see soon |
|
DBS 23028 / SEDS 2 |
|
DBS# 16609 / Its MIR again |
After selecting your favorite satellites, run the prediction using the
RUNDBS command.
RUNDBS is like RUNTIME but just runs satellites in your database. You can
still do RUNALL or RUNTIME any time to run all the satellites loaded with
your last OPEN.
If you want to select another set of DBS satellites, you can either OPEN a
new TLE file (that resets all the DBS entries to false), or more
efficiently (if you want to keep the current TLE file open), use the RESET
DBS command.
- EX <filename>
- Execute a batch file of commands. Any SEESAT command may
appear in a batch file. Multiple commands per line are allowed, just as if
you were entering the command line manually. EX itself may be in a batch
file. If encountered, it will close the current batch file and begin
executing the specified file. Control will not return to the preceding
file. I.e., you can chain batch files but not nest them.
- EXIT
- Exit from seesat5.
- GO or GOTO
- Requires a label name to go to, and starts processing
there. The GOTO command is probably going to be most useful from the
command line to let you jump into a particular SEESAT5.INI file section of
your choice. Obviously, any commands following the GOTO will not be
processed. When you specify a GOTO command, the program begins searching
the SEESAT5.INI file from the beginning and looks for the LABEL
<labelname> line. If one is not found, the message END OF BATCH FILE
is displayed and the program goes into keyboard command mode. If you have
duplicate labels, the first one will be processed. No checking is done to
prevent you from making the program loop continously, so be careful. Also,
if you use EX'ed files, the GOTO will only goto labels in the current file
that is open.
- HELP
- Displays a help screen.
- HEIGHT <number>
- Number, specifies, in kilometers, the height of the viewing
location. Errors incurred from incorrect values for height have little
propogation into the satellite location prediction. As a result, if you
don't know your height, it may safely be left 0.
- INDEX
- Lists the satellites in the currently open file. If there
is more than one screenful, it will pause with a "more>"
prompt. At this prompt you may either press RETURN to continue the
listing, or enter a command (or commands) just as you would at the normal
command prompt. In that case, the listing is aborted and your commands are
executed.
- LABEL
- This command requires a parameter that is a label that you
want to GOTO later. The maximum label length is 30 characters and it must
be the FIRST command on the line. More commands are allowed after the
label name if you want, but I found it more readable to have the command
on a single line.
Use labels to keep my run parameters for different situations in a single
SEESAT5.INI file and select which ones to process using the GOTO command.
- LAT <number>
- The number, in degrees, specifies the latitude of the
viewing location. Southern latitudes are declaired with a negative number.
Precision in this location is critical. A .14 degree error in location,
approximately 10 miles will cause a 1 degree error in the satellite
position.
- LENGTH <integer>
- Sets maximum number of characters the OPEN command will
consider significant in the satellite name when building the index. The
LENGTH command must therefore be issued before OPEN, to have any effect.
Any number from 1 - 22 is allowed. Default is 22, and may be left alone
unless you're using a file such as Molczan's N2L series. In that case,
you'll want to reduce LENGTH to 15 to prevent SEESAT from using the extra
data as part of the satellite name. LENGTH is set to 22 if you enter a
number larger than 22.
- LINEFEED
- This command as added for predictions done on a machine
where a typical run takes hours. Starting the run with the output
redirected to the printer serves two purposes:
1. |
to print out the data, and |
2. |
to serve as an alarm. |
How does this serve as an alarm? With a dot matrix printer the machine can
be left to run. While other work gets done the machine chuggs along.
Eventually, the program finds a satellite that can be seen. When the
printer starts clacking away after the long silence you know that there is
new data available. So that you can come to the printer and tear off the
new data without interfering with potential new printing this command
prints a selected number of linefeeds after the satellite listing.
- LOAD <name>
- Loads the named satellite from the file you opened with the
OPEN command. If the name has spaces, begin the name with quotes.
- LOAD# <number>
- This is just like the original LOAD command except you must
supply the Norad Satellite number. This is most usefull when you have TLE
files from different sources and the satellite names are not consistent.
- LON <number>
- The number, in degrees, specifies the longitude of the
viewing location. Western longitudes are specified with a negative number.
As with latitude a relatively small error of .14 degrees will cause a 1
degree error in the satellite location.
- MAG <number>
- For entering the absolute magnitude of a satellite. It will
be adjusted for range and illumination angle to generate the
"mag" value in the prediction table. Absolute magnitude is its
magnitude at 1000 km and 50% illuminated (i.e., 90 degree phase angle).
Absolute magnitude input can be automatic during loading of the elements
from the file. If the first line of the element set (the satellite name
line) is longer than 32 characters, SEESAT assumes it's a Molczan format
line, and reads the magnitude. You can use the MAG command to override the
value if necessary.
- MAGBIAS <number>
- Bias to be applied to SEESAT's computed magnitude before
display. A negative sign is allowed. The default is zero. If your absolute
magnitudes assume a different range and/or illumination than 1000 km and
50%, the MAGBIAS command will bring your scale into coincidence with
SEESAT's. If r and k are your assumed standard conditions (in km and
percent, respectively), set MAGBIAS to:
|
2.5 * log10 ((1000/r)^2 * k/50) |
For example, if your absolute magnitude is for 1000 km range and 100%
illuminated, enter:
- MERIDIAN
- The satellite longitudes in the prediction table may be
computed with respect to either Greenwich or your local meridian. MERIDIAN
toggles this mode, and informs you of the current mode. Default is
Greenwich.
- MOON <date time>
- Print the azimuth & elevation of the moon at the given
time. Percentage of illumination is also given.
- NEXT
- Loads the next satellite from the current open element
file.
- NOMINAL <date time> / ACTUAL <date time>
- These commands adjust the epoch and RAAN of the currently
loaded elements for the difference between the nominal and actual launch
times. They are useful for correcting a prelaunch element set.
|
EXAMPLE: |
|
NOMINAL 19 1851 ACTUAL 1918 |
tells SEESAT that the currently loaded elements assume a launch on the 19th
at 1851, but the launch actually occurred at 1918. You can't use NOMINAL
or ACTUAL by itself! If you use one, you must also use the other or you'll
get crazy results. The order of the commands does not matter, and they
don't have to be on the same line. Just be sure that both commands have
been given before starting a prediction run. The entered values are
remembered. So you may, for example, use NOMINAL just once, then
experiment with different ACTUAL values. Loading an element set (even
reloading the same one) disables the effect of NOMINAL and ACTUAL. Their
values are still remembered, however, so you may re-enable the adjustment
by giving one or both commands. The NOMINAL and ACTUAL arguments may be
for any time zone, as seesat5 cares only about their time difference.
- NULL
- This command is useful if you want to specify year, month
day and time for the start/stop/span commands but don't want to do the RUN
command automatically. It can save specifying repeated information on
every line of your parameters.
|
Example : |
|
open my.tle span 720 null |
|
start 1993 oct 01 1900 runall |
|
start 1993 oct 02 1900 runall |
|
exit |
- OFFSET <time>
- Applies an offset to the epoch of the satellite elements,
thereby making the satellite come early or late in the predictions. Useful
for putting a satellite ahead of or behind schedule, to evaluate the
resulting track drift with respect to the stars. Also can be used to
adjust for any discrepancy noted between predicted and actual times of
passes. A negative sign is allowed on <time>. A negative
<time> will make the effective epoch EARLIER, and make the satellite
come EARLIER in your predictions. If OFFSET is nonzero, an advisory of its
value is printed at the top of each prediction table. OFFSET is reset to
zero when an element set is loaded.
- OPEN <filename>
- Opens the orbital element file. If an element file is
already open, that file will be closed first.OPEN builds an index of the
satellites in the file, using linked blocks in RAM. Each block holds 50
satellites. Storage is requested as needed at run time, so the size of the
element file is limited only by available memory. Assuming your system
uses 4-byte longs and 2-byte pointers, each 50-satellite block uses 1352
bytes.The index only contains the name of the satellite and its location
in the file. The elements are not read from the disk until you issue the
LOAD or NEXT command.
- OPENSDF
- This command requires a file name parameter that will open
a STANDARD DELIMITED FILE with that name. The file format is as follows:
|
1st. record |
|
"satellite","date","time", ... |
|
|
|
2nd. record thru EOF |
|
satellite name |
|
date |
|
time |
|
: |
|
: |
- ORBITMINS
- This a value that has a default of 60 minutes. This is used
in the RUNTIME mode to determine how long to keep a satellites above
horizon values in memory before they are deemed un-useable. The way the
RUNTIME mode works is that it does a prediction for a satellite. If that
satellite is above the horizon at a particular time, that time is saved in
memory. When the satellites other attributes (elevation, magnitude etc)
are checked and they pass the conditions, the stored time values are used
to start printing the prediction run. If the satellite never satisfied the
selection conditions, then after 60 minutes has passed, the stored time
values are reset. This prevents misleading prediction data being printed.
- PARA <date time>
- Print the parallactic angle at the predicted position of
the satellite for the given time. Parallactic angle is the direction of
celestial north, as seen in a binocular field of view. E.g., 0 = straight
up, 90 = 3 o'clock. This command allows you to examine your star atlas
plot and visualize the star field orientation you'll see when you go
outside.
- PRECESS <date time>
- Controls the correction of Right Ascension and declination
for precession. PRECESS sets the final epoch. The epoch of the elements is
always used as the initial epoch. For 1950.0 or 2000.0 coordinates,
respectively:
|
PRECESS 1950 JAN 0 2210 |
|
PRECESS 2000 JAN 1 1200 |
These are Greenwich times, so, strictly speaking, the PRECESS command should
be given before setting ZONE. But for all practical purposes it doesn't
matter. Precession is so slow there will be virtually no error even if you
miss by a full year. Over several decades, though, it will build up to a
significant level. For example, if your atlas is 1950.0 and you neglect
the PRECESS command, an error of up to 42 arc minutes can occur in your
plot of a satellite's track. This is perhaps four or five times worse than
SEESAT's prediction accuracy under good conditions! The PRECESS value
remains until you change it or exit SEESAT. Default setting is 2000.0 at
program startup.
- PREDICT
- This will run the current parameters and conditions for
each satellite in the TLE file, and display results whenever a satellites
data passes the selection conditions. It then increments the time by 1
minute and re-runs the prediction again. This will continue forever or
until a key is pressed.
The START command must be done first to setup the date and time at which the
prediction starts. This is the raw data generator for the realtime
graphical display and also gives you in time order, the satellites you may
be able to see.
- PRINT?
- If the last prediction run resulted in a line of data being
printed, execute the command to the right of PRINT?. Otherwise, skip it.
There must be at least one command after PRINT?.
- PRINTLIMIT
- This command is used to limit the number lines printed per
satellite prediction when running in the RUNTIME mode. The reason you may
want limit the lines printed is because of very slow moving or stationery
satellites. The RUNTIME mode normally prints prediction data until the
satellite dips below the horizon. Of course, some satellites never dip
below the horizon so end up with either a lot of prediction data or the
program just keeps printing the data forever. I had coded a default value
for the printlimit of 60 lines. This default is fine for most regular
runs, but for some special purpose runs you may want to change it.
- RET
- If encountered in a batch file, returns control to user. If
entered manually, resumes execution of the batch file.
- REPEAT
- Jump back to beginning of command line.
- REPORT
- This command is used to suppress printing of lines that
come from the SEESAT5.INI file. It requires a 0 or 1 as a parameter. The
default is to suppress (value 0). If you want to see all command lines and
messages printed, set the report option to 1. Messages like
"complete; nn satellites found" are suppressed. More message may
be suppressed by this command in the furure. This just helps to 'clean'
the output to just the interesting satellite data.
- RUN
- Begin a prediction run, using the current time parameters.
The START, STOP, CENTER, SPAN, or STEP command automatically begins a run
if it is at the end of the command line. That is the normal way to get a
run. The RUN command is convenient if, for example, you load a new element
set and want a run without changing time parameters.
- RUNALL
- This command is almost a combination of OPEN, NEXT, RUN and
REPEAT. It takes no parameter values or filenames. It will reposition the
current TLE files pointer to BOF, read thru each two line element set, do
the RUN command on it and repeat until all elements in the file have been
read. The difference between this command and the commands it replaces, is
that it carries on processing the next input command after all two line
elements have been processed. The NEXT RUN REPEAT commands unfortunately
stops the entire run as soon as it reaches the end of the elements file. I
use this to generate a list of all satellites that I can see each day for
the whole of the month!
|
Example : |
|
open my.tle |
|
start 1993 oct 01 1900 span 720 runall |
|
: |
|
start 1993 oct 18 1900 span 720 runall |
|
: |
|
start 1993 oct 31 1900 span 720 runall |
|
exit |
- RUNDBS
- Like RUNTIME but only runs the satellites in your database.
You can still do RUNALL or RUNTIME any time to run all the satellites
loaded with your last OPEN.
- RUNTIME
- This runs prediction in time order. This produces the exact
same output data as the RUN command except it is in time order. It does
however take a little longer to run. The processing involved in this
command is to run through every satellite looking for a satellite that is
above the horizon at a particalur instance. The instances starts at the
start time and continues until the stop time is exceeded with an increment
of the step.
When a satellite is found that is above the horizon and it also satifies the
selection conditions, its data is printed until it dips below the horizon.
At that time the printing stops and the next satellite in the input TLE
file is processed.
For Geo Stationary satellites the parameter PRINTLIMIT comes into play. This
allows you to stop the printing of data when a certain number of lines
have been printed. If this command was not present, the data print would
print forever if a geo-stationary satellite ever passed all the selection
conditions.
- SDFCLOSE
- This command requires NO parameter, it just closes the last
opened SDF file.
- SKIP
- Skip the command to the immediate right of SKIP. To be used
following PRINT?, to reverse the test. There must be at least one command
after SKIP.
- SPAN
- Followed by a time in minutes, this command determins the
length of the data run. When used with the CENTER command the time
value is centered on this time.
- START
- Defines the start time for the run. Requires a date and a
time as parameters.
- STEP <time>
- Controls size of time steps in the prediction run in
minutes. A run begins automatically if STEP is the last command on the
line.
- STOP
- Defines the stop time for the run. If only a time is
specified, the start date will be used. Accepts a date and a time as
parameters.
- STOPDAY (and STARTDAY)
- These commands require an integer and a time. The integer
is when you want to stop (start) the prediction in number of days from
today, followed by a time that you want to stop (start). Just for
consistency, the TODAY command can now also be specified as STARTDAY.
- SUMMARY
- This command will show a selected summary data about the
last TLE file that you OPENed. At present it shows the satellites that
have the earliest and latest epoch dates.
- SUN <date time>
- Print the azimuth & elevation of the sun at the given
time.
- TODAY
- This commands automatically sets up todays date as the
default START date. The command must be followed by a number indicating
how many days you want to add to the system date as the START value. This
number may be zero or an integer number of days.
|
Example : |
|
OPEN NASA.TLE |
|
TODAY +0 1700 STOP 2300 RUNALL |
|
TODAY +1 0400 STOP 0800 RUNALL |
gives tonight and tomorrow mornings satellite viewing data. This command was
implemented because it saves changing SEESAT5.INI every day to run nightly
and morning predictions. You can set up the similar parameters as the
example above, depending on when you do your regular/daily prediction run.
- ZONE <time>
- Set timezone to that at the viewing location in UTC. A
negative sign is permitted. E.g., for Pacific Standard Time:
The ZONE value need not be an integral number of hours, e.g., Newfoundland
standard time is 3h 30m behind UTC:
Default ZONE at program startup is Greenwich time.
ORBITAL ELEMENT ENTRY¶
The following commands are used for entering orbital elements when no tle file
is available for the satellite in question.
- AOP <number>
- Number represents the argument of the perigee.
- B <number>
- Number represent the BSTAR value.
- E <number>
- Number specifies the eccentricity of the orbit
- EPOCH <epoch>
- Manually enter epoch of the orbital elements. Must be in
NORAD format: YYDDD.DDD... (use any number of decimal places). Unused
digits in the integer part of day number must be padded with spaces or
zeros. If spaces are used for padding, the number must be enclosed in
quotes.
|
EXAMPLE: |
|
EPOCH 91003.52029891 or |
|
EPOCH "91 3.52029891" |
- I <number>
- The number stands for the inclination of the orbit.
- MA <number>
- This number specifies the mean anomaly.
- MM <number>
- Mean motion is determined by the value of number.
- MMDOT <number>
- This number represents the first derivative of the mean
motion. Note: this value is not used in the SPG4 model used by seesat5 and
is only retained for compatability with the older SPG model
- MMDOTDOT <number>
- The second derivative of the mean motion is specified by
this number. Note: this value is not used in the SPG4 model used by
seesat5 and is only retained for compatibility with the older SPG model.
- NAME <satellite name>
- Satellite name will appear in the printout for the current
element data being loaded by the above commands.
- RAAN <number>
- This number specifies the right ascension of the ascending
node.
SEE ALSO¶
seesat5(1),
SEESAT5.INI(5),
tle(5),
cr(1)
BUGS¶
Many of the above commands "do not work well with others" so some
unexpected behavior may result at times. Please report any suspected bugs to
Dale Scheetz <dwarf@polaris.net>.