| 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) |
| 2026-07-29 00:00 |
10:41:58.62 |
-06:05:01.5 |
HIP 52388 |
17.96 |
| 2026-07-29 12:00 |
10:42:24.26 |
-06:06:42.0 |
HIP 52388 |
17.97 |
| 2026-07-30 00:00 |
10:42:49.92 |
-06:08:23.4 |
HIP 52492 |
16.30 |
| 2026-07-30 12:00 |
10:43:15.62 |
-06:10:05.5 |
HIP 52492 |
10.91 |
| 2026-07-31 00:00 |
10:43:41.35 |
-06:11:48.4 |
HIP 52492 |
7.75 |
| 2026-07-31 12:00 |
10:44:07.10 |
-06:13:32.0 |
HIP 52492 |
9.43 |
| 2026-08-01 00:00 |
10:44:32.89 |
-06:15:16.4 |
HIP 52492 |
14.36 |
| 2026-08-01 12:00 |
10:44:58.70 |
-06:17:01.6 |
HIP 52654 |
18.78 |
| 2026-08-02 00:00 |
10:45:24.54 |
-06:18:47.6 |
HIP 52654 |
12.63 |
| 2026-08-02 12:00 |
10:45:50.40 |
-06:20:34.3 |
HIP 52654 |
7.41 |
| 2026-08-03 00:00 |
10:46:16.29 |
-06:22:21.7 |
HIP 52654 |
6.25 |
| 2026-08-03 12:00 |
10:46:42.21 |
-06:24:09.9 |
HIP 52654 |
10.60 |
| 2026-08-04 00:00 |
10:47:08.15 |
-06:25:58.8 |
HIP 52654 |
16.59 |
| 2026-08-04 12:00 |
10:47:34.12 |
-06:27:48.5 |
HIP 52654 |
22.98 |
| 2026-08-05 00:00 |
10:48:00.11 |
-06:29:38.9 |
HIP 52933 |
28.14 |
| 2026-08-05 12:00 |
10:48:26.12 |
-06:31:30.0 |
HIP 52933 |
21.95 |
| 2026-08-06 00:00 |
10:48:52.16 |
-06:33:21.9 |
HIP 52933 |
16.16 |
| 2026-08-06 12:00 |
10:49:18.22 |
-06:35:14.4 |
HIP 52933 |
11.45 |
| 2026-08-07 00:00 |
10:49:44.30 |
-06:37:07.7 |
HIP 52933 |
9.57 |
| 2026-08-07 12:00 |
10:50:10.41 |
-06:39:01.7 |
HIP 52995 |
4.55 |
| 2026-08-08 00:00 |
10:50:36.53 |
-06:40:56.4 |
HIP 52995 |
2.23 |
| 2026-08-08 12:00 |
10:51:02.68 |
-06:42:51.8 |
HIP 52995 |
8.99 |
| 2026-08-09 00:00 |
10:51:28.84 |
-06:44:47.9 |
HIP 52995 |
15.77 |
| 2026-08-09 12:00 |
10:51:55.03 |
-06:46:44.7 |
HIP 53196 |
13.65 |
| 2026-08-10 00:00 |
10:52:21.23 |
-06:48:42.2 |
HIP 53196 |
6.94 |
| 2026-08-10 12:00 |
10:52:47.45 |
-06:50:40.3 |
HIP 53196 |
1.44 |
| 2026-08-11 00:00 |
10:53:13.69 |
-06:52:39.2 |
HIP 53196 |
6.97 |
| 2026-08-11 12:00 |
10:53:39.95 |
-06:54:38.7 |
HIP 53309 |
13.44 |
| 2026-08-12 00:00 |
10:54:06.22 |
-06:56:38.8 |
HIP 53309 |
12.95 |
| 2026-08-12 12:00 |
10:54:32.51 |
-06:58:39.7 |
HIP 53406 |
12.69 |
| 2026-08-13 00:00 |
10:54:58.81 |
-07:00:41.2 |
HIP 53406 |
6.84 |
| 2026-08-13 12:00 |
10:55:25.13 |
-07:02:43.3 |
HIP 53406 |
5.10 |
| 2026-08-14 00:00 |
10:55:51.46 |
-07:04:46.1 |
HIP 53406 |
9.96 |
| 2026-08-14 12:00 |
10:56:17.80 |
-07:06:49.5 |
HIP 53406 |
16.32 |
| 2026-08-15 00:00 |
10:56:44.16 |
-07:08:53.6 |
HIP 53406 |
22.97 |
| 2026-08-15 12:00 |
10:57:10.53 |
-07:10:58.3 |
HIP 53645 |
21.13 |
| 2026-08-16 00:00 |
10:57:36.91 |
-07:13:03.6 |
HIP 53645 |
16.37 |
| 2026-08-16 12:00 |
10:58:03.30 |
-07:15:09.5 |
HIP 53645 |
13.56 |
| 2026-08-17 00:00 |
10:58:29.70 |
-07:17:16.0 |
HIP 53645 |
13.96 |
| 2026-08-17 12:00 |
10:58:56.11 |
-07:19:23.1 |
HIP 53645 |
17.34 |
| 2026-08-18 00:00 |
10:59:22.52 |
-07:21:30.9 |
HIP 53738 |
14.16 |
| 2026-08-18 12:00 |
10:59:48.95 |
-07:23:39.2 |
HIP 53738 |
10.96 |
| 2026-08-19 00:00 |
11:00:15.38 |
-07:25:48.1 |
HIP 53738 |
11.61 |