Cometsuite

Simulate cometary dust dynamics.

This is the maintained Python version. The unmaintained C++ version is also available.

Documentation is available at pycometsuite.readthedocs.io.

This code has been used in the following publications:

1. A Large Outburst, Coma Asymmetries, and the Color of Comet 243P/NEAT. Kelley, M. S. P., Protopapa, S., Bodewits, D. et al. 2025. The Planetary Science Journal 6, 185

2. Early Activity in Comet C/2014 UN271 Bernardinelli-Bernstein as Observed by TESS. Farnham, T. L., Kelley, M. S. P., and Bauer, J. M. 2021. The Planetary Science Journal 2, 236

Requirements

• Python 3
  • numpy
  • scipy
  • Cython
  • matplotlib
  • astropy
  • mskpy
  • spiceypy
• GNU Scientific Library and GSL CBLAS library

File formats

XYZ files are a saved particle simulation. The files consist of two parts: the header and the particle array. The header describes the simulation parameters and the particle array format.

Q: Could v2 be replaced with an ASDF format?

XYZ v1

v1 headers are valid YAML with the following keywords:

box: -1 comet: kernel: None name: C/2009 P1 r: - 199512618.6570191 - -186957807.98389882 - 149658240.7133305 v: - -23.28632377134447 - 10.860849832337532 - 13.85300854007757 cometsuite: 1.0.0 data: - d(radius) - d(graindensity) - d(beta) - d(age) - d[2](origin) - d[3](r_i) - d[3](v_ej) - d[3](r_f) date: '2011-09-11 00:00:00.000' header: 1.0 integrator: Kepler(GM=1.3274935144e+20) label: None nparticles: 10000000 pfunc: age: Uniform(x0=0, x1=31536000) composition: Geometric(rho0=1) density_scale: UnityScaler() radius: Log(x0=0, x1=3) speed: Delta(x0=0.1) speed_scale: SpeedRh(k=-0.5) * SpeedRadius(k=-0.5) vhat: Isotropic() save: - radius - graindensity - beta - age - origin - r_i - v_ej - r_f syndynes: false units: - micron - g/cm^3 - none - s - deg - km - km/s - km data: - d(radius) - d(graindensity) - d(beta) - d(age) - d[2](origin) - d[3](r_i) - d[3](v_ej) - d[3](r_f) units: - micron - g/cm^3 - none - s - deg - km - km/s - km ...

XYZ v0

Older versions of the file format can be read with cometsuite.xyzfiles.XYZFile0. The v0.x headers are key-value pairs, separated by a colon. Comments start with a "#" character in the first column:

```

CometSuite 0.9.5

Valid program names: syndynes, make comet, integratexyz

PROGRAM: syndynes

Parameters common to all programs.

COMET: encke KERNEL: encke.bsp JD: 2450643.5417 XYZFILE: output.xyz LABEL: PFUNC: TOL: 0.01 PLANETS: 511 PLANETLOOKUP: 0 CLOSEAPPROACHES: 1 BOX: -1 LTT: 0 SAVE: radius graindensity beta age origin ri vej r_f

Syndyne specific section.

BETA: 0.001 0.002 0.004 0.006 0.008 0.01 0.1 NDAYS: 200 STEPS: 31 ORBIT: 1

Make comet specific section.

NPARTICLES: 100000

data file description

UNITS: micron g/cm^3 none s deg km/s km km/s s km km/s s DATA: d(radius) d(graindensity) d(beta) d(age) d2 d3 d3 d3 d(ti) d3 d3 d(tf) ```

Acknowledgements

Two-body orbit propagation code is based on the universal variables approach in the SPICE Toolkit from the Navigation and Ancillary Information Facility (NAIF) at the NASA Jet Propulsion Laboratory.

The RADAU15 integrator of Everhart (1985), rewritten in C for the original C++ version of Cometsuite is included in this distribution. (Everhart 1985. in Dynamics of Comets: Their Origin and Evolution. A. Carusi and G. Valsecchi, eds. Astrophysics and Space Science Library 115 185).