svarog-ctl

Svarog-ctl is a command-line driven automated satellite tracking software that uses rotctld to control antenna rotator to track satellites fly overs.

Status

The software is functional, but still in relatively early development. It can calculate the passes based on either specified TLE data, or download data from Celestrak if sat name or Norad ID is specified, then it can connect to rotctld and send commands to move the rotator.

Setup

svarog-ctl requires a configured rotctld daemon running. Make sure your actual rotator hardware is supported by rotctld. For testing purposes, rotctld can be started with a dummy rotator: rotctld -m 1 -t 4533

Usage

To predict a satellite fly-over (pass), several pieces of information are required. First, observer's coordinates have to be specified (see --lat, --lon and optionally also --alt parameters). The second essential parameter is to when to start the prediction (--time). If time is not specified, current time stamp is used.

Also, svarog-ctl needs to know which sat to track. The orbit is determined using the TLE format. There are two ways to provide this. First is to specify the two TLE lines explicitly. Let's check KRAKSAT pass over Gdansk. The TLE available for KRAKSAT are:

1 44427U 98067QM  21192.54020985  .00022355  00000-0  19763-3 0  9995
2 44427  51.6376 177.8799 0003618 359.5888  93.1405 15.68562202115256

Gdansk is located at 53.35N 18.53E. We can use the following command to order the svarog_ctl to follow the next pass after 18:44 on July 14th:

./svarog_ctl.py --lat 53.35 --lon 18.53 --time "2021-07-14 18:44:00" \
--tle1 "1 44427U 98067QM  21192.54020985  .00022355  00000-0  19763-3 0  9995" \
--tle2 "2 44427  51.6376 177.8799 0003618 359.5888  93.1405 15.68562202115256"

Alternatively, svarog-ctl can download TLE data from Celestrak.org website. See the config.yml.template for direct link.

If you need to provide additional or alternative sources, see TLE_SOURCES in https://github.com/gut-space/svarog-ctl/blob/master/svarog_ctl/orbitdb.py#L21 This mode of operation requires Internet access. The downloaded data is cached for 7 days until it's refreshed.

If the sat is in the Celestrak database, it can be referenced using either its name (--sat) or its NORAD ID (--satid).

python ./svarog_ctl.py --lat 53.5 --lon 18.5 --sat "NOAA 18"

python ./svarog_ctl.py --lat 53.5 --lon 18.5 --satid 25338

To be able to connect to rotctld, you also need to specify hostname (--host) and port (--port).

By default, svarog-ctl prints everything using UTC timezone, but --local switch will make it use local timezone instead.

For debugging purposes, svarog-ctl can be told to not wait till the next sat pass actually starts, but pretent the sat is starting its flyover right now (--now). That is obviously useful for testing purposes only.

Python Usage

The rotator controller can also be easily controlled from Python. It requires the rotctld daemon to be running. Here's example code:

from svarog_ctl import rotctld

# Let's assume the rotcltd is listening on loopback on port 4533.
ctl = rotctld.Rotctld("127.0.0.1", 4533, 1)
ctl.connect()

# Let's see what kind of capabilities the rotctld reported for this rotator
print(ctl.capabilities())

# Let's check the current position.
print(ctl.get_pos())

# Ok, let's move it around.
ctl.set_pos(123.0, 45.0)