WWW.AO27.NET

2023/April/19

Control has been recovered!

OS-27 has been uploaded.  Checkout is on going and we should have a schedule up soon if 
everything checks out.

Current Uplink Center Freq  : 145.850 MHz
Current Downlink Center Freq: 436.797 MHz 


- Michael, N3UC
- AO-27 Control Operator

2020/Sept/21


As of  Sept 21, AO-27 is now running a TOPR schedule as follows:

Orbit Epoch:      1600708166
Orbital Period:   6045.0

State     Mode    Duration of Mode (seconds)       State End (seconds)
  1         0              0                           529        
  2         4            300                           740         
  3         0              0                          2230       
  4         2             20                          2250       
  5         4            240                          2490       
  6         0              0                           n/a


- Bridget, N1XAU
Sept 21, 2020


The Epoch for the times are the time of the Ascending Node. This defines when State 1 starts.  The End Seconds is when that state will end and the next on begins.

NOTE:  In this example the end of a mode corresponds to the end of a state.  This is not required.

We have a concept of States and Modes.  States are just a part of the orbit, (see the TEPR state descriptions from N1UC)  And we have TX Modes.

Modes:
0 = Off
1 = AFSK Telemetry High Power
2 = AFSK Telemetry Low Power
3 = Reserved
4 = Analogue Repeater
5 = Frequency Reference One
6 = Frequency Reference Two
7 = 9600 Baud GMSK Telemetry

So for the example above:
Starting at the Ascending node,  Off for 440 seconds,  Then on Repeater for 240 seconds, then off 1550 seconds, then TLM for 20 seconds, then Repeater on for 240 seconds,  then off until the next orbit.

The Time of the Ascending node is computed onboard open loop.  It is currently using 1590347040 as the Epoch and 6045.0 seconds for the orbital period.  
This is updated every time we send a new time to the satellite based on the latest orbital elements.

To Calculate the current orbital time,  take (CurrentTime-OrbitEpoch) mod OrbitalPeriod. 
N.B.  OrbitalPeriod is not 86400 / meanMotion.  It is the time from one ascending node to next ascending node.

Currently there is no check for eclipse.   The eclipse is only over the south pole right now.  So the bird is on both Morning and Evening passes.


- Michael Wyrick,  N3UC
- AO-27 Control Operator