Comet API Tools

This service computes the appropriate fluorescence efficiencies (g-factors) and/or Haser fractions needed to take a molecular flux measurement for a comet and derive a resulting production rate. Five optical/near-UV species are currently supported: OH, NH, CN, C2, C3.

We provide three comet flourescense "calculators" accessible via a REST interface:

g-factors

Return only the comet fluorescence efficiencies (L/N) from user-supplied heliocentric distance (r) and heliocentric velocity (v).

Haser Fraction

Return only the Haser fraction from user-supplied heliocentric velocity, geocentric distance, and aperture radius.

Compute Qs from Fluxes

Return all values in calculating production rates from params provided input r, Δ, v, aperture radius and fluxes. Return p, log p, area (cm2), L/N, M(p), log M(p), N(p), log N(p), xp, xd, H-frac, M(tot), log M(tot), Q, log Q.

g-factors

Number of molecules required to produce an observed emission flux for a particular molecular species. If flux has units of ergs/cm2/s, then the standard form of the fluorescence efficiency, luminosity per molecule, i.e. L/N, is needed (having units of ergs/s/molecule). This is what we provide here, both normalized to 1 AU, and again scaled by r^-2 to the heliocentric distance requested.

We, along with many researchers, use the generic term "g-factor" as a shorter form of "fluorescence efficiency"; note, however, that true g-factors are defined as having units of photons/s/molecule.

Endpoint

https://asteroid.lowell.edu/api/comet/calc/gfactor

Arguments

Value	Name	Units	Default
r	Heliocentric Distance	AU	1
v	Heliocentric Velocity	km/s	0

Return

extrapolated
Indicates if the spline solution was extrapolated at one or more points
raw
The raw, unformatted, response from the calculator
gfactors
- requested_AU
  - r
    Requested heliocentric distance (AU)
  - v
    Requested heliocentric velocity (km/s)
  - OH
    value of the 0-0 band centered near 3090 Angstroms varies with heliocentric velocity and whether or not the lambda-doublet ground state is quenched (unquenched values are given here); scaled by r^-2
  - NH
    value of the Δv=0 band sequence centered near 3360 Angstroms varies both with heliocentric velocity and with r (due to the strong change in the number of rotational levels populated with r). A 2-D table is scaled to 1 AU and double interpolated, then scaled by r^-2
  - CN
    value of the Δv=0 band sequence with a band head near 3885 Angstroms varies both with heliocentric velocity and with r (due to the strong change in the number of rotational levels populated with r). A 2-D table is scaled to 1 AU and double interpolated, then scaled by r^-2
  - C3
    single value for the C3 band complex which peaks near 4030 Angstroms and extends from 3300 to 4400 Anstroms; scaled by r^-2
  - C2
    Ssingle value for Δv=0 band sequence with a band head near 5160 Angstroms; scaled by r^-2
- one_AU
  Same as requested_AU but scaled to 1 AU

Example

https://asteroid.lowell.edu/api/comet/calc/gfactor?r=6&v=2

{
  "extrapolated": true,
  "gfactor": {
    "one_AU": {
      "C2": 4.5e-13,
      "C3": 1e-12,
      "CN": 3.33e-13,
      "NH": 7.78e-14,
      "OH": 1.76e-15,
      "r": 1,
      "v": 2.0
    },
    "requested_AU": {
      "C2": 1.25e-14,
      "C3": 2.78e-14,
      "CN": 9.25e-15,
      "NH": 2.16e-15,
      "OH": 4.89e-17,
      "r": 6.0,
      "v": 2.0
    }
  },
  "raw": [
    "",
    " Spline was extrapolated at one or more points!",
    "",
    " Spline was extrapolated at one or more points!",
    " 6.000   2.00",
    "  1.76E-15  7.78E-14  3.33E-13  1.00E-12  4.50E-13",
    "  4.89E-17  2.16E-15  9.25E-15  2.78E-14  1.25E-14",
    ""
  ]
}

Haser Fraction

Endpoint

https://asteroid.lowell.edu/api/comet/calc/haser

Arguments

Value	Name	Units	Default
r	Heliocentric Distance	AU	1
d	Geocentric Distance	AU	1
ap	Aperature Radius	arcsecond	30

Return

aperture
- r
  Heliocentric Distance (AU)
- delta
  Geocentric Distance (AU)
- aperture
  Aperature Radius (km)
- OH
- NH
- CN
- C3
  (km)
- C2
  (km)
raw
The raw, unformatted, response from the calculator
scalelength
- requested_AU
  - parent
    Parent Haser scalelength
    - OH
    - NH
    - CN
    - C2
    - C3
  - daughter
    Same as parent but for daughter Haser scalenlength
- one_AU
  Same as requested_AU but scaled to 1 AU

Example

https://asteroid.lowell.edu/api/comet/calc/haser?r=2&d=1.5&ap=10

{
  "aperture": {
    "C2": 0.00805,
    "C3": 0.0715,
    "CN": 0.00407,
    "NH": 0.00196,
    "OH": 0.00333,
    "aperture": 10.0,
    "delta": 1.5,
    "r": 2.0
  },
  "raw": [
    " 2.000   1.500     10.0",
    " 1.088E+04",
    "   24000.   50000.   13000.    2800.   22000.",
    "  160000.  150000.  210000.   27000.   66000.",
    "   96000.  200000.   52000.   11200.   88000.",
    "  640000.  600000.  840000.  108000.  264000.",
    "  3.33E-03  1.96E-03  4.07E-03  7.15E-02  8.05E-03",
    ""
  ],
  "scalelength": {
    "one_AU": {
      "daughter": {
        "C2": 66000.0,
        "C3": 27000.0,
        "CN": 210000.0,
        "NH": 150000.0,
        "OH": 160000.0
      },
      "parent": {
        "C2": 22000.0,
        "C3": 2800.0,
        "CN": 13000.0,
        "NH": 50000.0,
        "OH": 24000.0
      },
      "r": 1.0
    },
    "requested_AU": {
      "daughter": {
        "C2": 264000.0,
        "C3": 108000.0,
        "CN": 840000.0,
        "NH": 600000.0,
        "OH": 640000.0
      },
      "parent": {
        "C2": 88000.0,
        "C3": 11200.0,
        "CN": 52000.0,
        "NH": 200000.0,
        "OH": 96000.0
      },
      "r": 2.0
    }
  }
}

Compute Qs from Fluxes

Endpoint

https://asteroid.lowell.edu/api/comet/calc/ghq

Arguments

Field	Name	Units	Default
r	Heliocentric Discance	AU	1
d	Geocentric Distance	AU	1
v	Heliocentric Velocity	km/s	0
ap	Aperture Raduis	acrsec	1
oh	Flux - OH		0
nh	Flux - NH		0
cn	Flux - CN		0
c3	Flux - C₃		0
c2	Flux - C₂		0

Return

r
Heliocentric distance (AU)
delta
Geocentric distance (AU)
v
Heliocentric velocity (km/s)
aperture
Aperture radius (arcsecond)
rho
(km)
log_rho
log(rho)
area
Area (cm²)
flux
- OH
  (0-0)
- NH
  (delv=0)
- CN
  (delv=0)
- C3
  stuff
- C2
  (delv=0)
log_flux
Same as flux except for
gfactor
Same as flux except for
m_rho
Same as flux except for
log_m_rho
Same as flux except for
n_rho
Same as flux except for
log_n_rho
Same as flux except for
xp
Same as flux except for
xd
Same as flux except for
h_fraction
Same as flux except for
m_tot
Same as flux except for
log_m_tot
Same as flux except for
taud
Same as flux except for
q
Same as flux except for
log_q
Same as flux except for
q_div_q_oh
Same as flux except for

Example

https://asteroid.lowell.edu/api/comet/calc/haser?r=2&d=1.5&ap=10

{
  "aperture": 1.0,
  "area": 1.65e+16,
  "delta": 1.0,
  "flux": {
    "C2": 0.7,
    "C3": 1.0,
    "CN": 0.5,
    "NH": 0.0,
    "OH": 0.0
  },
  "gfactor": {
    "C2": 4.5e-13,
    "C3": 1e-12,
    "CN": 2.85e-13,
    "NH": 6.7e-14,
    "OH": 1.56e-15
  },
  "h_fraction": {
    "C2": 0.000811,
    "C3": 0.00944,
    "CN": 0.000416,
    "NH": 0.000186,
    "OH": 0.000327
  },
  "log_flux": {
    "C2": -0.15,
    "C3": 0.0,
    "CN": -0.3,
    "NH": 0.0,
    "OH": 0.0
  },
  "log_m_rho": {
    "C2": "inf",
    "C3": "inf",
    "CN": "inf",
    "NH": 0.0,
    "OH": 0.0
  },
  "log_m_tot": {
    "C2": "inf",
    "C3": "inf",
    "CN": "inf",
    "NH": 0.0,
    "OH": 0.0
  },
  "log_n_rho": {
    "C2": "inf",
    "C3": "inf",
    "CN": "inf",
    "NH": 0.0,
    "OH": 0.0
  },
  "log_q": {
    "C2": "inf",
    "C3": "inf",
    "CN": "inf",
    "NH": 0.0,
    "OH": 0.0
  },
  "log_rho": 2.86,
  "m_rho": {
    "C2": "inf",
    "C3": "inf",
    "CN": "inf",
    "NH": 0.0,
    "OH": 0.0
  },
  "m_tot": {
    "C2": "inf",
    "C3": "inf",
    "CN": "inf",
    "NH": 0.0,
    "OH": 0.0
  },
  "n_rho": {
    "C2": "inf",
    "C3": "inf",
    "CN": "inf",
    "NH": 0.0,
    "OH": 0.0
  },
  "q": {
    "C2": "inf",
    "C3": "inf",
    "CN": "inf",
    "NH": 0.0,
    "OH": 0.0
  },
  "q_div_q_oh": {
    "C2": "inf",
    "C3": "inf",
    "CN": "inf",
    "NH": "nan",
    "OH": "nan"
  },
  "r": 1.0,
  "rho": 725.0,
  "taud": {
    "C2": 66000.0,
    "C3": 27000.0,
    "CN": 210000.0,
    "NH": 150000.0,
    "OH": 160000.0
  },
  "v": 1.0,
  "xd": {
    "C2": 66000.0,
    "C3": 27000.0,
    "CN": 210000.0,
    "NH": 150000.0,
    "OH": 160000.0
  },
  "xp": {
    "C2": 22000.0,
    "C3": 2800.0,
    "CN": 13000.0,
    "NH": 50000.0,
    "OH": 24000.0
  }
}

Page Contents

Comet API Tools

g-factors

Endpoint

Arguments

Return

Example

Haser Fraction

Endpoint

Arguments

Return

Example

Compute Qs from Fluxes

Endpoint

Arguments

Return

Example