| 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) |
| 2026-07-29 00:00 |
13:09:36.63 |
-01:28:50.5 |
HIP 64351 |
27.67 |
| 2026-07-29 12:00 |
13:09:38.29 |
-01:29:12.3 |
HIP 64351 |
27.21 |
| 2026-07-30 00:00 |
13:09:39.99 |
-01:29:34.4 |
HIP 64351 |
26.75 |
| 2026-07-30 12:00 |
13:09:41.73 |
-01:29:56.6 |
HIP 64351 |
26.28 |
| 2026-07-31 00:00 |
13:09:43.50 |
-01:30:19.0 |
HIP 64351 |
25.80 |
| 2026-07-31 12:00 |
13:09:45.31 |
-01:30:41.6 |
HIP 64351 |
25.32 |
| 2026-08-01 00:00 |
13:09:47.16 |
-01:31:04.4 |
HIP 64351 |
24.83 |
| 2026-08-01 12:00 |
13:09:49.04 |
-01:31:27.4 |
HIP 64351 |
24.34 |
| 2026-08-02 00:00 |
13:09:50.95 |
-01:31:50.6 |
HIP 64351 |
23.85 |
| 2026-08-02 12:00 |
13:09:52.90 |
-01:32:14.0 |
HIP 64351 |
23.35 |
| 2026-08-03 00:00 |
13:09:54.89 |
-01:32:37.5 |
HIP 64351 |
22.85 |
| 2026-08-03 12:00 |
13:09:56.92 |
-01:33:01.3 |
HIP 64351 |
22.35 |
| 2026-08-04 00:00 |
13:09:58.98 |
-01:33:25.2 |
HIP 64351 |
21.85 |
| 2026-08-04 12:00 |
13:10:01.07 |
-01:33:49.3 |
HIP 64351 |
21.34 |
| 2026-08-05 00:00 |
13:10:03.20 |
-01:34:13.5 |
HIP 64351 |
20.84 |
| 2026-08-05 12:00 |
13:10:05.36 |
-01:34:38.0 |
HIP 64351 |
20.34 |
| 2026-08-06 00:00 |
13:10:07.56 |
-01:35:02.6 |
HIP 64351 |
19.84 |
| 2026-08-06 12:00 |
13:10:09.80 |
-01:35:27.4 |
HIP 64351 |
19.34 |
| 2026-08-07 00:00 |
13:10:12.06 |
-01:35:52.4 |
HIP 64351 |
18.85 |
| 2026-08-07 12:00 |
13:10:14.37 |
-01:36:17.5 |
HIP 64351 |
18.36 |
| 2026-08-08 00:00 |
13:10:16.70 |
-01:36:42.9 |
HIP 64351 |
17.88 |
| 2026-08-08 12:00 |
13:10:19.07 |
-01:37:08.4 |
HIP 64351 |
17.41 |
| 2026-08-09 00:00 |
13:10:21.48 |
-01:37:34.0 |
HIP 64351 |
16.95 |
| 2026-08-09 12:00 |
13:10:23.92 |
-01:37:59.9 |
HIP 64351 |
16.51 |
| 2026-08-10 00:00 |
13:10:26.39 |
-01:38:25.9 |
HIP 64351 |
16.07 |
| 2026-08-10 12:00 |
13:10:28.90 |
-01:38:52.0 |
HIP 64351 |
15.66 |
| 2026-08-11 00:00 |
13:10:31.43 |
-01:39:18.3 |
HIP 64351 |
15.27 |
| 2026-08-11 12:00 |
13:10:34.01 |
-01:39:44.8 |
HIP 64351 |
14.90 |
| 2026-08-12 00:00 |
13:10:36.61 |
-01:40:11.5 |
HIP 64351 |
14.56 |
| 2026-08-12 12:00 |
13:10:39.25 |
-01:40:38.3 |
HIP 64351 |
14.25 |
| 2026-08-13 00:00 |
13:10:41.92 |
-01:41:05.2 |
HIP 64351 |
13.97 |
| 2026-08-13 12:00 |
13:10:44.62 |
-01:41:32.3 |
HIP 64351 |
13.73 |
| 2026-08-14 00:00 |
13:10:47.36 |
-01:41:59.6 |
HIP 64351 |
13.53 |
| 2026-08-14 12:00 |
13:10:50.12 |
-01:42:27.0 |
HIP 64351 |
13.37 |
| 2026-08-15 00:00 |
13:10:52.92 |
-01:42:54.6 |
HIP 64351 |
13.26 |
| 2026-08-15 12:00 |
13:10:55.75 |
-01:43:22.3 |
HIP 64351 |
13.21 |
| 2026-08-16 00:00 |
13:10:58.61 |
-01:43:50.2 |
HIP 64351 |
13.20 |
| 2026-08-16 12:00 |
13:11:01.50 |
-01:44:18.2 |
HIP 64351 |
13.24 |
| 2026-08-17 00:00 |
13:11:04.42 |
-01:44:46.3 |
HIP 64351 |
13.34 |
| 2026-08-17 12:00 |
13:11:07.38 |
-01:45:14.6 |
HIP 64351 |
13.50 |
| 2026-08-18 00:00 |
13:11:10.36 |
-01:45:43.0 |
HIP 64351 |
13.71 |
| 2026-08-18 12:00 |
13:11:13.37 |
-01:46:11.6 |
HIP 64351 |
13.97 |
| 2026-08-19 00:00 |
13:11:16.42 |
-01:46:40.3 |
HIP 64351 |
14.28 |