Hi, I was checking NOAA18's APT transmission. I recorded it with some of my stations to test my orbit determination. Does anyone else ever checked or has further knowledge about how the NOAA sats control their clocks for the APT transmissions? [0] They seem very stable and the spikes in my graph are most likely just due to my script finding the SyncA[1] markers. For every spike there is a counter spike directly next compensating it. So the periods measured as diffs between the marker timestamps are plausible for me. I just expected more drift and a small slope due to the clock. I used Space-Track.org TLEs on the same day of recording. I used that to correct the propagation delay from my stations towards the known position in orbit based on the TLE. In this way I was able to determine the transmission time of each SyncA that I was able to receive and are graphed here[0]. My OrbitDeterminator finds this orbit/TLE 1 00000U OrbDet 22044.42720540 .00000000 00000-0 00000+0 0 08 2 00000 98.9781 114.8904 0013875 325.1502 152.9600 14.12701478 01 This is for one passage and almost all of the passage from ascending 18° until the descending 10° elevation. From Space-Tracks.org the closest TLE is this... 1 28654U 05018A 22044.47479952 .00000147 00000-0 10377-3 0 9991 2 28654 98.9643 114.9421 0013527 324.7524 35.2752 14.12687670862566 I know this is RF and not optical observations, nevertheless I am quite happy about my result from above matching so nicely. [0] https://twitter.com/andreashornig/status/1497691242200772619 [1] https://www.sigidwiki.com/wiki/Automatic_Picture_Transmission_(APT) Would be nice to understand more about what NOAA is doing on APT mode :). Andreas _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-lReceived on Sat Feb 26 2022 - 22:16:12 UTC
This archive was generated by hypermail 2.4.0 : Sat Feb 26 2022 - 22:17:58 UTC