Calculate Comet Production Rates from Fluxes

This service calculates production rates for a comet.

Provided measured fluxes for the appropriate molecular emission bands, one can derive the production rates associated with these fluxes in a straight-forward series of calculations. Needed input: r in AU, Δ in AU, heliocentric velocity, v, in km/s, aperture radius in arcsec.

  1. Extract L/N (g-factors): Interpolated from look-up tables scaled to 1 AU; then scale by r-2.
  2. Compute the number of molecules within the observing aperture: M(ρ) = 2.812E27 * Δ * Δ * Flux / L/N , where the constant term is 4 * pi * AU-to-cm squared unit conversion.
  3. Compute the column density within the observing aperture: N(ρ) = M(ρ) / Area of aperture projected to the comet [Note: column density is a near-useless quantity and is not used for subsequent calculations.]
  4. Compute Haser-fraction (what fraction of the total coma is within the observing aperture): Look-up table of Haser parent and daughter scalelengths, and parent and daughter r-dependencies. Then use these values, plus r, Δ, and aperture radius in a Haser model calculation.
  5. Compute M(total): Extrapolate to the total number of molecules in the entire coma by taking M(ρ) and dividing by the Haser fraction.
  6. Compute daughter lifetime: Extract from look-up table for 1 AU and scale by r2.
  7. Compute production rate (Q): Divide total number of molecules from step 5, by daughter lifetimes from step 6. This yields the destruction rate which, for static equilibrium, must be equal to the production rate.

Note: For convenience, the logarithm for many of the previous values is also calculated.

R (AU) Delta (AU) V (km/s) Aperture Radius (")
Rho (km) log(Rho) Area (cm2)
OH(0-0) NH(delv=0) CN(delv=0) C3 C2(delv=0)