Sapling uses LoRa, a chirp spread spectrum (CSS) radio modulation technique. The primary advantage is that you can decode signals with very low signal to noise (SNR), which means it works in noisy environments like cities and is capable of carrying low power signals all the way from low earth orbit. Read more about LoRa here: https://en.wikipedia.org/wiki/LoRa
Each sapling mission has slightly different telemetry formats, so we aim to provide and clearly differentiate the parameters and format for each. Let us know if something on this page is unclear or seems to be out of date!
| Sapling Sempervirens (did not deploy) | 437.4 MHz beacon every 30s |
|---|---|
| Sapling Giganteum (operational) | 437.4 MHz beacon every 60s |
| Sapling Magnifica (future mission) |
Frequency: 437.4MHz
Bandwidth (BW): 125KHz
Spreading Factor (SF): 7
Coding Rate (CR): 8
Low Data Rate Optimize (LDRO): On
In order to listen to a Sapling, you need to know where it is and when it will be overhead your position.
For ground stations that listen passively, this is not necessary (unless you want to listen to different satellites at different —in which case you need to know when to switch). A ground station with an antenna that tracks across the sky will need to point pretty close to Sapling—just how close depends on the gain (directionality) of the antenna.
Because LoRa works with very low SNR, you can listen to satetelites that are very close to the horizon. It might even be possible to listen to a satellite that is over the horizon (find reference)
We use TLEs from Celestrak to track the satellite for our ground stations.
Once satellites have been identified, you can find the TLEs here: https://celestrak.org/NORAD/elements/
Before and immediately after launch (while satellites are being commissioned) their TLEs are available here:
https://celestrak.org/NORAD/elements/supplemental/