Re: C/2012 X1 (Linear)

Tony Evans Sep 16, 2014

Puzzle more-or-less resolved. The non-grav parameters change significantly as the comet
progresses along its orbit but Find Orb tries to fit one set of values to cover the whole period.

The observations pre-perihelion make a good orbit with mean residuals 0.47”. The observations
post perihelion also make a good orbit with residual 0.39”. But put them all together and it does not work.

I see the MPC publishes 5 different orbits with different epochs and different non-grav parameters.

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/ony

> It depends on how the nongravitational parameters are computed.
 
> For example, without nongravitational parameter rms=0.810",
> using the MPC's nongravitational parameter we have rms=0.640",
> and with the JPL NASA's ngrv parameters we have rms=0.534".
 
> Computations were made using all 2311 observations of comet C/2012X1 and the OrbFit software.
 
> Best regards,
> Ireneusz Wlodarczyk



>> (C/2012 X1) I've been trying to make sense of the way Find Orb is handling the observations
>> of this comet. Since ~May this year the residuals are growing and growing and
>> non-gravitational does not seem to handle it. An ideas?


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/ony