C/2012 S1 (ISON)
Metadata
| Parameter | Value |
|---|---|
| Designation | C/2012 S1 (ISON) |
| Type | C |
| Perihelion (tp_cal, UTC) | 2013-11-28T18:20:55.495680Z |
| Orbit solution date (soln_date, UTC) | 2025-11-21T13:42:48Z |
| Obs used | 6684 |
| NEO | - |
| M1 | 10.400 |
| K1 | 4.500 |
| PC | - |
Osculating Elements
| Parameter | Value |
|---|---|
| Epoch (epoch_cal, TDB) | 2013-05-01.0000000 |
| e | 1.00000509 |
| q (au) | 0.012467 |
| a (au) | -2446.893404 |
| i (deg) | 62.162896 |
| Ω (om, deg) | 295.686541 |
| ω (w, deg) | 345.541197 |
| M (ma, deg) | -0.001724 |
Magnitude
Scatter + Global Linear
$$ M_a = (11.695 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 11.695 |
| n | 2.000 |
| gf | 1.000 |
| gb | -0.791 |
| k | 0.951 |
| δ90 | 10.000 |
| Parameter | Symbol | Range | Description |
|---|---|---|---|
| Absolute magnitude at 1 AU from Sun and Earth | H0 | -5 to 20 | Intrinsic brightness of the comet |
| Photometric slope parameter | n | 2 to 6 | Rate of brightness change with heliocentric distance |
| Forward scattering asymmetry factor | gf |
0.8 to 1 | Degree of forward scattering |
| Backward scattering asymmetry factor | gb |
-1 to -0.5 | Degree of backward scattering |
| Partitioning coefficient | k | 0.8 to 1 | Ratio between forward/backward scattering contributions |
| Dust-to-gas brightness ratio | δ90 | 1 to 10 | Relative contribution of dust scattering to gas emission |
Reference: EPSC-DPS2025-160
Residuals (Piecewise)
$$\epsilon = a \log_{10} r_{\mathrm{au}} + b$$
| Start (UTC) | End (UTC) | a | b |
|---|---|---|---|
| 2011-09-30 | 2013-11-13 | +0.7784 | -0.530 |
| 2013-11-13 | 2013-11-28 | +7.8926 | -0.124 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) | RA (J2000) | Dec (J2000) | Nearest HIP | Dist from HIP (arcmin) |
|---|---|---|---|---|
| 2026-06-01 00:00 | 07:20:18.49 | +36:54:47.3 | HIP 35477 | 18.13 |
| 2026-06-01 12:00 | 07:20:21.97 | +36:54:33.1 | HIP 35477 | 18.39 |
| 2026-06-02 00:00 | 07:20:25.47 | +36:54:18.9 | HIP 35477 | 18.68 |
| 2026-06-02 12:00 | 07:20:29.00 | +36:54:04.8 | HIP 35477 | 19.00 |
| 2026-06-03 00:00 | 07:20:32.55 | +36:53:50.7 | HIP 35477 | 19.34 |
| 2026-06-03 12:00 | 07:20:36.11 | +36:53:36.7 | HIP 35710 | 19.07 |
| 2026-06-04 00:00 | 07:20:39.70 | +36:53:22.8 | HIP 35710 | 18.32 |
| 2026-06-04 12:00 | 07:20:43.30 | +36:53:08.9 | HIP 35710 | 17.57 |
| 2026-06-05 00:00 | 07:20:46.93 | +36:52:55.1 | HIP 35710 | 16.82 |
| 2026-06-05 12:00 | 07:20:50.58 | +36:52:41.3 | HIP 35710 | 16.06 |
| 2026-06-06 00:00 | 07:20:54.24 | +36:52:27.6 | HIP 35710 | 15.30 |
| 2026-06-06 12:00 | 07:20:57.92 | +36:52:13.9 | HIP 35710 | 14.54 |
| 2026-06-07 00:00 | 07:21:01.63 | +36:52:00.3 | HIP 35710 | 13.78 |
| 2026-06-07 12:00 | 07:21:05.35 | +36:51:46.8 | HIP 35710 | 13.02 |
| 2026-06-08 00:00 | 07:21:09.09 | +36:51:33.3 | HIP 35710 | 12.25 |
| 2026-06-08 12:00 | 07:21:12.84 | +36:51:19.9 | HIP 35710 | 11.49 |
| 2026-06-09 00:00 | 07:21:16.62 | +36:51:06.6 | HIP 35710 | 10.72 |
| 2026-06-09 12:00 | 07:21:20.41 | +36:50:53.3 | HIP 35710 | 9.96 |
| 2026-06-10 00:00 | 07:21:24.22 | +36:50:40.1 | HIP 35710 | 9.20 |
| 2026-06-10 12:00 | 07:21:28.04 | +36:50:27.0 | HIP 35710 | 8.44 |
| 2026-06-11 00:00 | 07:21:31.89 | +36:50:13.9 | HIP 35710 | 7.69 |
| 2026-06-11 12:00 | 07:21:35.75 | +36:50:00.9 | HIP 35710 | 6.95 |
| 2026-06-12 00:00 | 07:21:39.62 | +36:49:48.0 | HIP 35710 | 6.22 |
| 2026-06-12 12:00 | 07:21:43.51 | +36:49:35.1 | HIP 35710 | 5.51 |
| 2026-06-13 00:00 | 07:21:47.42 | +36:49:22.3 | HIP 35710 | 4.82 |
| 2026-06-13 12:00 | 07:21:51.34 | +36:49:09.5 | HIP 35710 | 4.19 |
| 2026-06-14 00:00 | 07:21:55.28 | +36:48:56.9 | HIP 35710 | 3.63 |
| 2026-06-14 12:00 | 07:21:59.23 | +36:48:44.3 | HIP 35710 | 3.18 |
| 2026-06-15 00:00 | 07:22:03.20 | +36:48:31.8 | HIP 35710 | 2.89 |
| 2026-06-15 12:00 | 07:22:07.18 | +36:48:19.3 | HIP 35710 | 2.83 |
| 2026-06-16 00:00 | 07:22:11.18 | +36:48:07.0 | HIP 35710 | 3.01 |
| 2026-06-16 12:00 | 07:22:15.19 | +36:47:54.7 | HIP 35710 | 3.38 |
| 2026-06-17 00:00 | 07:22:19.21 | +36:47:42.5 | HIP 35710 | 3.90 |
| 2026-06-17 12:00 | 07:22:23.25 | +36:47:30.3 | HIP 35710 | 4.52 |
| 2026-06-18 00:00 | 07:22:27.29 | +36:47:18.3 | HIP 35710 | 5.20 |
| 2026-06-18 12:00 | 07:22:31.35 | +36:47:06.3 | HIP 35710 | 5.92 |
| 2026-06-19 00:00 | 07:22:35.43 | +36:46:54.4 | HIP 35710 | 6.68 |
| 2026-06-19 12:00 | 07:22:39.51 | +36:46:42.5 | HIP 35710 | 7.45 |
| 2026-06-20 00:00 | 07:22:43.61 | +36:46:30.8 | HIP 35710 | 8.24 |
| 2026-06-20 12:00 | 07:22:47.72 | +36:46:19.1 | HIP 35710 | 9.04 |
| 2026-06-21 00:00 | 07:22:51.84 | +36:46:07.5 | HIP 35710 | 9.85 |
| 2026-06-21 12:00 | 07:22:55.96 | +36:45:56.0 | HIP 35710 | 10.67 |
| 2026-06-22 00:00 | 07:23:00.10 | +36:45:44.6 | HIP 35710 | 11.50 |