Differences
This shows you the differences between two versions of the page.
Both sides previous revision Previous revision Next revision | Previous revision | ||
iridium:toolkit [2016/10/03 14:19] – ::1 | iridium:toolkit [2021/04/18 12:35] (current) – external edit 127.0.0.1 | ||
---|---|---|---|
Line 14: | Line 14: | ||
|1|UNIX timestamp in seconds when the recording started|i-1472473197-t1| The i- prefix and -t1 suffix a historical artefact...| | |1|UNIX timestamp in seconds when the recording started|i-1472473197-t1| The i- prefix and -t1 suffix a historical artefact...| | ||
|2|Time in milliseconds inside the recording|000001626| | | |2|Time in milliseconds inside the recording|000001626| | | ||
- | |3|Frequency in Herz|1627088000|Estimated center frequency| | + | |3|Frequency in Hertz|1627088000|Estimated center frequency| |
|4|Confidence in percent|97%|Confidence is estimated during demodulation by gr-iridium| | |4|Confidence in percent|97%|Confidence is estimated during demodulation by gr-iridium| | ||
|5|Signal level|0.009|Arbitrary scale| | |5|Signal level|0.009|Arbitrary scale| | ||
|6|Length in symbols|129|Excluding the 12 symbol sync word. One symbol equals two bits| | |6|Length in symbols|129|Excluding the 12 symbol sync word. One symbol equals two bits| | ||
|7|Direction|DL|DL or UL| | |7|Direction|DL|DL or UL| | ||
+ | |||
+ | |||
+ | ==== IRA: Ring Alert ==== | ||
+ | Ring alerts are sent periodically by the satellite to every spot beam. Every 90 ms a new ring alert gets sent to another spot beam. There are 48 spot beams, so every 4.32 s a ring alert is sent to the same spot beam. | ||
+ | |||
+ | Example: | ||
+ | < | ||
+ | |||
+ | ^Field Number^Content^Example^Comment^ | ||
+ | |8|Satellite number|sat: | ||
+ | |9|Spot beam number|beam: | ||
+ | |10|Satellite or spot beam position|pos=(+46.64/ | ||
+ | |11|Satellite or spot beam altitude|alt=791 |In km| | ||
+ | |12|Ring alert interval|RAI: | ||
+ | |13|Unknown|? | ||
+ | |14|Broadcast channel sub-band|bc_sb: | ||
+ | |15-|TMSI pages|PAGE(tmsi: | ||
+ | |||
+ | As there can be a different amount of pages, the size of a ring alert frame is not constant. | ||
+ | |||
+ | === Location Information === | ||
+ | The ring alert contains two different, alternating, | ||
+ | == SV Location == | ||
+ | Locations with a high altitude (e.g. > 100 km) can be treated as as the location of the SV (Space Vehicle). | ||
+ | |||
+ | == Spot Beam Location == | ||
+ | Locations with a low altitude (e.g. < 10 km) can be treated as the location where the SV thinks that the particular spot beam is hitting the earth’s surface. Note that this is not the location of a subscriber. | ||