Sunday, September 15, 2013
Comet C/2012 S1 ISON in Celestia
I can't believe this, but it seems that I have not previously posted a Celestia file for comet C/2012 S1 ISON. I remedy this oversight now.
Unfortunately, comet C/2012 S1 ISON has a hyperbolic orbit, and Celestia doesn't like those. The comet's orbit and name won't turn up when you turn on the comet attributes, or when you select the comet by clicking on it. As usual, copy the code below and save as it as a text file 2012S1.ssc in the Celestia extras folder.
Class "comet" # Just copying the data for Halley
Radius 5 # best guess at maximum semi-axis
MeshCenter [ -0.338 1.303 0.230 ]
# Data from latest JPL Horizons orbit as of 15 Sep 2013
# Comet has a hyperbolic orbit, so Celestia will not show an orbit track
Epoch 2456625.280420214468 # 2013-Nov-28.78042021 TT
Period 165849.9873 # (q/(e-1))^1.5 hyperbolic orbit
SemiMajorAxis -3018.632859 #Hyperbolic orbit
# Again, this data is copied straight from the ssc files for Halleys’ Comet
# chaotic rotation, imperfectly defined:
# this version from "The New Solar System", 4th Edition; Eds.
# JK Beatty, CC Petersen, A Chaikin
Period 170 # 7.1 day axial rotation period
PrecessionPeriod 3457004.12 # 3.7 day precession period