18D/Perrine-Mrkos
| Parameter |
Value |
| Designation |
18D/Perrine-Mrkos |
| Type |
D |
| Perihelion (tp_cal, UTC) |
1968-11-01T13:00:40.325760Z |
| Orbit solution date (soln_date, UTC) |
2002-02-22T17:02:43Z |
| Obs used |
16 |
| NEO |
Yes |
| M1 |
11.500 |
| K1 |
20.000 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
1969-01-19.0000000 |
| e |
0.64258098 |
| q (au) |
1.272248 |
| a (au) |
3.559542 |
| i (deg) |
17.758983 |
| Ω (om, deg) |
240.875547 |
| ω (w, deg) |
166.050417 |
| M (ma, deg) |
11.514613 |
Magnitude
Scatter + Global Linear
$$
M_a = (12.123 + 4.437\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
12.123 |
| n |
4.437 |
| 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
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-02-03 00:00 |
10:24:52.63 |
-13:46:03.6 |
HIP 50923 |
29.82 |
| 2026-02-03 12:00 |
10:24:31.27 |
-13:45:14.0 |
HIP 50923 |
27.14 |
| 2026-02-04 00:00 |
10:24:09.77 |
-13:44:21.5 |
HIP 50874 |
25.16 |
| 2026-02-04 12:00 |
10:23:48.15 |
-13:43:26.3 |
HIP 50874 |
22.10 |
| 2026-02-05 00:00 |
10:23:26.41 |
-13:42:28.2 |
HIP 50874 |
19.96 |
| 2026-02-05 12:00 |
10:23:04.56 |
-13:41:27.4 |
HIP 50874 |
19.10 |
| 2026-02-06 00:00 |
10:22:42.59 |
-13:40:23.8 |
HIP 50787 |
17.60 |
| 2026-02-06 12:00 |
10:22:20.51 |
-13:39:17.4 |
HIP 50787 |
14.90 |
| 2026-02-07 00:00 |
10:21:58.34 |
-13:38:08.3 |
HIP 50787 |
13.89 |
| 2026-02-07 12:00 |
10:21:36.06 |
-13:36:56.4 |
HIP 50705 |
11.50 |
| 2026-02-08 00:00 |
10:21:13.69 |
-13:35:41.7 |
HIP 50705 |
11.50 |
| 2026-02-08 12:00 |
10:20:51.23 |
-13:34:24.4 |
HIP 50705 |
13.99 |
| 2026-02-09 00:00 |
10:20:28.68 |
-13:33:04.3 |
HIP 50705 |
17.99 |
| 2026-02-09 12:00 |
10:20:06.06 |
-13:31:41.5 |
HIP 50705 |
22.74 |
| 2026-02-10 00:00 |
10:19:43.36 |
-13:30:16.1 |
HIP 50476 |
22.77 |
| 2026-02-10 12:00 |
10:19:20.59 |
-13:28:47.9 |
HIP 50476 |
17.37 |
| 2026-02-11 00:00 |
10:18:57.76 |
-13:27:17.2 |
HIP 50476 |
12.23 |
| 2026-02-11 12:00 |
10:18:34.86 |
-13:25:43.7 |
HIP 50476 |
7.92 |
| 2026-02-12 00:00 |
10:18:11.91 |
-13:24:07.7 |
HIP 50476 |
6.52 |
| 2026-02-12 12:00 |
10:17:48.91 |
-13:22:29.1 |
HIP 50434 |
9.14 |
| 2026-02-13 00:00 |
10:17:25.86 |
-13:20:47.8 |
HIP 50434 |
12.40 |
| 2026-02-13 12:00 |
10:17:02.78 |
-13:19:04.1 |
HIP 50344 |
13.66 |
| 2026-02-14 00:00 |
10:16:39.65 |
-13:17:17.7 |
HIP 50344 |
11.46 |
| 2026-02-14 12:00 |
10:16:16.50 |
-13:15:28.9 |
HIP 50344 |
12.05 |
| 2026-02-15 00:00 |
10:15:53.32 |
-13:13:37.5 |
HIP 50344 |
15.12 |
| 2026-02-15 12:00 |
10:15:30.12 |
-13:11:43.7 |
HIP 50344 |
19.55 |
| 2026-02-16 00:00 |
10:15:06.91 |
-13:09:47.5 |
HIP 50344 |
24.63 |
| 2026-02-16 12:00 |
10:14:43.68 |
-13:07:48.8 |
HIP 50073 |
19.37 |
| 2026-02-17 00:00 |
10:14:20.45 |
-13:05:47.7 |
HIP 50073 |
13.94 |
| 2026-02-17 12:00 |
10:13:57.23 |
-13:03:44.2 |
HIP 50073 |
9.25 |
| 2026-02-18 00:00 |
10:13:34.00 |
-13:01:38.4 |
HIP 50073 |
7.07 |
| 2026-02-18 12:00 |
10:13:10.79 |
-12:59:30.3 |
HIP 50073 |
9.36 |
| 2026-02-19 00:00 |
10:12:47.59 |
-12:57:19.9 |
HIP 50073 |
14.11 |
| 2026-02-19 12:00 |
10:12:24.42 |
-12:55:07.3 |
HIP 50073 |
19.62 |
| 2026-02-20 00:00 |
10:12:01.27 |
-12:52:52.4 |
HIP 49853 |
18.09 |
| 2026-02-20 12:00 |
10:11:38.15 |
-12:50:35.3 |
HIP 49853 |
12.47 |
| 2026-02-21 00:00 |
10:11:15.07 |
-12:48:16.1 |
HIP 49853 |
7.62 |
| 2026-02-21 12:00 |
10:10:52.03 |
-12:45:54.8 |
HIP 49853 |
5.94 |
| 2026-02-22 00:00 |
10:10:29.03 |
-12:43:31.3 |
HIP 49809 |
7.81 |
| 2026-02-22 12:00 |
10:10:06.09 |
-12:41:05.8 |
HIP 49809 |
7.84 |
| 2026-02-23 00:00 |
10:09:43.20 |
-12:38:38.3 |
HIP 49809 |
11.70 |
| 2026-02-23 12:00 |
10:09:20.37 |
-12:36:08.8 |
HIP 49809 |
16.95 |
| 2026-02-24 00:00 |
10:08:57.61 |
-12:33:37.3 |
HIP 49809 |
22.64 |