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AO-40: more successful ARCJET operations



Dear All,

The arc-jet thruster has been invoked on Orbit 296, MA 118-135,
which gave about 1 hour of thrusting gas only. 

The S2 TX is OFF from MA 100-180 to spare power for the ATOS. The gas
generator for the ammonia draws about 120 - 130 W of power when cycled on
by the thermostat. 

The IHU-2 is running and logging telemetry into a circular buffer and
and hold about 2.5 days worth of data. Downloaded telemetry from this 1h
burn indicated positive power budget and everything looks nominally. 

The thrust on orbit 296 started at MA 121.4 and lasted for 3618s. The
acceleration is guestimated to be 54E-6 m/s^2 , and the direction of
acceleration is towards alon 274, alat -2 (the current attitude).

Give or take the unknowns, the expected outcome of this was:

                     Before            After
  --------------------------------------------                   
  Epoch year            2001              2001    
  Epoch time       173.12145         173.16312    
  Inclination         5.2833         5.2833592    
  R.A.A.N          180.71591         180.70361    
  Eccentricity      0.815077         0.8150139    
  Arg perigee      288.69088         288.71333    
  Mean Anomaly         121.4         140.46836    
  Mean motion MM   1.2711484         1.2710861    
  Revolution             296               296
  SMA                36003.6         36004.773
      
  Perigee height     279.754          282.2427    <<<  +2.5 km
  Apogee height    58971.166         58971.024    
  --------------------------------------------

So the perigee was raised by this 1h burn by about +2.5 km, but only a
thrust rate of 50% was used. 

Since everything went so well, the computer onboard AO-40 was commanded
to initiate 2h "burns" starting around apogee on orbit 297 for the next
three orbits. 

The first 2-hour burn stopped at Orbit 297 MA 142, which is 2001 Jun 23
0154 utc. Again, all telemetry is looking good and we may soon expand to
4h "burns" and possibly increase the thrust level as well. 

While we haven't yet seen the latest NORAD data, some effects of the
changing orbit should be soon noticeable. 

Indeed, we all are very happy with the successful results of the ATOS
(Arcjet Thruster on OSCAR Satellite) so far.

Some more information about the ATOS system is available here:

http://www.irs.uni-stuttgart.de/RESEARCH/EL_PROP/PROJ/e_atos.html


best 73s
 Peter DB2OS for the AO-40 team

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