2021-10-03, 02:38 PM
(This post was last modified: 2021-10-03, 02:43 PM by bigmasterdrago.)
Too many years ago to even count, I used "Dance of the Planets". Whenever you added any new comet or asteroid, You had to always make sure to do it at the epoch date. I had no idea why back then. It was rather well refined for the date of the software and the machines we ran it on. Today, stand alone software can easily take a rock with an epoch date back 5 or more years ago and generate an ephemeris that is the same as the ones generated at Horizons. They match in current dates. Rocks generally have no non-gravs, so it work well. Comets not so much. Processors are so fast today that the software makes a new set of elements at each step b4 calculating the next step. I'm fairly sure that is what Horizons does also.
As for 2014 TM, I asked about the uncertainty of locating it on amastro and got this answer from Brian Skiff at Lowell Observatory:
…it has only the 1-day arc from 2014, so this is an object that won’t get re(dis)covered except by chance some time downstream. The actual ephemeris uncertainty is ± 360 degrees (at least!). If it was actually near Earth on the one night (and not an artificial satellite, and not simply a bad detection), picking up such an object even one _week_ downstream would have been difficult, much less seven years away.
\Brian
The observation is simply a straight line!
I think it works very similarly to the stand alone software I've used for over 14 years. The initial conditions, integration, and final results are all done using 3D position and velocity vectors. They're only converted to osculating elements for the convenience of the user, who would much rather see osculating elements than 3D position and velocity vectors.
As for 2014 TM, I asked about the uncertainty of locating it on amastro and got this answer from Brian Skiff at Lowell Observatory:
…it has only the 1-day arc from 2014, so this is an object that won’t get re(dis)covered except by chance some time downstream. The actual ephemeris uncertainty is ± 360 degrees (at least!). If it was actually near Earth on the one night (and not an artificial satellite, and not simply a bad detection), picking up such an object even one _week_ downstream would have been difficult, much less seven years away.
\Brian
The observation is simply a straight line!
I think it works very similarly to the stand alone software I've used for over 14 years. The initial conditions, integration, and final results are all done using 3D position and velocity vectors. They're only converted to osculating elements for the convenience of the user, who would much rather see osculating elements than 3D position and velocity vectors.