| Parameter |
Value |
| Designation |
C/2017 O1 (ASASSN) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2017-10-14T18:50:39.171840Z |
| Orbit solution date (soln_date, UTC) |
2022-07-31T01:42:28Z |
| Obs used |
2877 |
| NEO |
- |
| M1 |
12.400 |
| K1 |
8.750 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2017-10-13.0000000 |
| e |
0.99642549 |
| q (au) |
1.498687 |
| a (au) |
419.270415 |
| i (deg) |
39.848413 |
| Ω (om, deg) |
25.809488 |
| ω (w, deg) |
20.907853 |
| M (ma, deg) |
359.999795 |
Magnitude
Scatter + Global Linear
$$
M_a = (12.630 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
12.630 |
| n |
2.000 |
| gf |
1.000 |
| gb |
-0.500 |
| k |
1.000 |
| 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 |
| 2017-07-20 |
2017-10-14 |
-12.1999 |
+1.263 |
| 2017-10-14 |
2019-03-12 |
+7.6667 |
-2.172 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-03-26 00:00 |
13:20:49.54 |
-01:57:09.5 |
HIP 65083 |
18.78 |
| 2026-03-26 12:00 |
13:20:44.69 |
-01:56:42.3 |
HIP 65083 |
17.99 |
| 2026-03-27 00:00 |
13:20:39.83 |
-01:56:15.1 |
HIP 65083 |
17.25 |
| 2026-03-27 12:00 |
13:20:34.96 |
-01:55:47.9 |
HIP 65083 |
16.58 |
| 2026-03-28 00:00 |
13:20:30.08 |
-01:55:20.8 |
HIP 65083 |
15.99 |
| 2026-03-28 12:00 |
13:20:25.18 |
-01:54:53.6 |
HIP 65083 |
15.48 |
| 2026-03-29 00:00 |
13:20:20.28 |
-01:54:26.5 |
HIP 65083 |
15.07 |
| 2026-03-29 12:00 |
13:20:15.36 |
-01:53:59.4 |
HIP 65083 |
14.77 |
| 2026-03-30 00:00 |
13:20:10.44 |
-01:53:32.3 |
HIP 65083 |
14.58 |
| 2026-03-30 12:00 |
13:20:05.51 |
-01:53:05.2 |
HIP 65083 |
14.50 |
| 2026-03-31 00:00 |
13:20:00.56 |
-01:52:38.2 |
HIP 65083 |
14.55 |
| 2026-03-31 12:00 |
13:19:55.61 |
-01:52:11.2 |
HIP 65083 |
14.72 |
| 2026-04-01 00:00 |
13:19:50.65 |
-01:51:44.2 |
HIP 65083 |
15.00 |
| 2026-04-01 12:00 |
13:19:45.68 |
-01:51:17.2 |
HIP 65083 |
15.39 |
| 2026-04-02 00:00 |
13:19:40.71 |
-01:50:50.3 |
HIP 65083 |
15.88 |
| 2026-04-02 12:00 |
13:19:35.73 |
-01:50:23.5 |
HIP 65083 |
16.47 |
| 2026-04-03 00:00 |
13:19:30.74 |
-01:49:56.6 |
HIP 65083 |
17.14 |
| 2026-04-03 12:00 |
13:19:25.74 |
-01:49:29.8 |
HIP 65083 |
17.89 |
| 2026-04-04 00:00 |
13:19:20.74 |
-01:49:03.1 |
HIP 65083 |
18.70 |
| 2026-04-04 12:00 |
13:19:15.74 |
-01:48:36.4 |
HIP 65083 |
19.57 |
| 2026-04-05 00:00 |
13:19:10.73 |
-01:48:09.8 |
HIP 65083 |
20.49 |
| 2026-04-05 12:00 |
13:19:05.71 |
-01:47:43.2 |
HIP 65083 |
21.45 |
| 2026-04-06 00:00 |
13:19:00.69 |
-01:47:16.7 |
HIP 65083 |
22.46 |
| 2026-04-06 12:00 |
13:18:55.67 |
-01:46:50.2 |
HIP 65083 |
23.49 |
| 2026-04-07 00:00 |
13:18:50.65 |
-01:46:23.8 |
HIP 65083 |
24.56 |
| 2026-04-07 12:00 |
13:18:45.62 |
-01:45:57.4 |
HIP 65083 |
25.65 |
| 2026-04-08 00:00 |
13:18:40.59 |
-01:45:31.2 |
HIP 65083 |
26.76 |
| 2026-04-08 12:00 |
13:18:35.56 |
-01:45:04.9 |
HIP 65083 |
27.90 |
| 2026-04-09 00:00 |
13:18:30.52 |
-01:44:38.8 |
HIP 65083 |
29.05 |
| 2026-04-09 12:00 |
13:18:25.49 |
-01:44:12.8 |
HIP 64968 |
29.23 |
| 2026-04-10 00:00 |
13:18:20.45 |
-01:43:46.8 |
HIP 64968 |
29.20 |
| 2026-04-10 12:00 |
13:18:15.42 |
-01:43:20.9 |
HIP 64968 |
29.23 |
| 2026-04-11 00:00 |
13:18:10.38 |
-01:42:55.0 |
HIP 64968 |
29.32 |
| 2026-04-11 12:00 |
13:18:05.35 |
-01:42:29.3 |
HIP 64968 |
29.47 |
| 2026-04-12 00:00 |
13:18:00.32 |
-01:42:03.7 |
HIP 64968 |
29.68 |
| 2026-04-12 12:00 |
13:17:55.29 |
-01:41:38.1 |
HIP 64769 |
28.90 |
| 2026-04-13 00:00 |
13:17:50.26 |
-01:41:12.6 |
HIP 64769 |
27.66 |
| 2026-04-13 12:00 |
13:17:45.23 |
-01:40:47.3 |
HIP 64769 |
26.43 |
| 2026-04-14 00:00 |
13:17:40.21 |
-01:40:22.0 |
HIP 64769 |
25.21 |
| 2026-04-14 12:00 |
13:17:35.19 |
-01:39:56.8 |
HIP 64769 |
24.00 |
| 2026-04-15 00:00 |
13:17:30.17 |
-01:39:31.8 |
HIP 64769 |
22.81 |
| 2026-04-15 12:00 |
13:17:25.16 |
-01:39:06.8 |
HIP 64769 |
21.64 |
| 2026-04-16 00:00 |
13:17:20.15 |
-01:38:42.0 |
HIP 64769 |
20.49 |