Satellite Tracking

indi-allsky tracks visual satellite passes overhead in real time, determining which spacecraft and orbital objects are within the camera field of view and rendering their positional metadata as text overlays.

---

1. TLE Orbital Data Synchronization

Satellite orbital ephemerides are retrieved automatically from CelesTrak:

• Catalog: 100+ Brightest Visual Satellites (GROUP=visual), including the International Space Station (ISS), CSS Tiangong, Hubble Space Telescope (HST), and prominent rocket bodies.
• Storage: Stored in the database table tledata (IndiAllSkyDbTleDataTable).
• Refresh Frequency: Polled every 24 hours. If CelesTrak returns rate-limit or network errors, an exponential backoff schedule delays subsequent requests.

---

2. Ephemeris & Visibility Calculation

When processing an image frame:

1. indi-allsky propagates satellite orbits using the SGP4 orbital model paired with the observatory's latitude, longitude, and elevation.
2. The system checks if any satellite has an altitude above the local horizon threshold.
3. If an object is visible, its coordinates and photometric properties are exposed as image annotation tokens.

---

3. Image Overlay Variables

Satellite telemetry tokens can be embedded into custom image label templates under Configuration → Image Overlays → Image Labels:

Token Variable	Type	Description	Example Output
{satellite.title}	String	Name of the visible satellite.	ISS (ZARYA)
{satellite.alt}	Float	Angular altitude above the local horizon (degrees).	42.5
{satellite.az}	Float	Azimuth bearing (degrees clockwise from North).	215.3
{satellite.dir}	String	Cardinal compass direction from the observer.	SW
{satellite.mag}	Float	Estimated visual magnitude ($m_v$).	-2.1
{satellite.elevation}	Float	Orbital altitude (elevation) above sea level in kilometers.	418.2
{satellite.range}	Float	Slant range distance from the observer to the spacecraft (km).	612.4
{satellite.range_velocity}	Float	Radial velocity relative to the observer (km/s).	-6.8
{satellite.latitude}	Float	Sub-satellite geocentric latitude.	28.52
{satellite.longitude}	Float	Sub-satellite geocentric longitude.	-80.68

Sample Overlay Template

Satellite: {satellite.title} | Alt: {satellite.alt:.1f}° | Az: {satellite.az:.1f}° ({satellite.dir}) | Mag: {satellite.mag:.1f}