| Parameter |
Value |
| Designation |
C/1987 W1 (Ichimura) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
1988-01-10T02:29:58.758720Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:29:36Z |
| Obs used |
48 |
| NEO |
- |
| M1 |
8.900 |
| K1 |
10.000 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
1987-11-28.0000000 |
| e |
0.99999939 |
| q (au) |
0.199518 |
| a (au) |
327902.551553 |
| i (deg) |
41.620500 |
| Ω (om, deg) |
226.527901 |
| ω (w, deg) |
329.292632 |
| M (ma, deg) |
360.000000 |
Magnitude
Scatter + Global Linear
$$
M_a = (10.506 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
10.506 |
| n |
2.000 |
| gf |
0.800 |
| gb |
-1.000 |
| k |
0.843 |
| δ90 |
1.000 |
| 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) |
| 2026-09-20 00:00 |
00:23:21.11 |
+28:43:54.0 |
HIP 1690 |
30.20 |
| 2026-09-20 12:00 |
00:23:19.20 |
+28:43:45.9 |
HIP 1690 |
29.85 |
| 2026-09-21 00:00 |
00:23:17.28 |
+28:43:37.7 |
HIP 1690 |
29.51 |
| 2026-09-21 12:00 |
00:23:15.36 |
+28:43:29.4 |
HIP 1690 |
29.17 |
| 2026-09-22 00:00 |
00:23:13.44 |
+28:43:21.0 |
HIP 1690 |
28.83 |
| 2026-09-22 12:00 |
00:23:11.52 |
+28:43:12.4 |
HIP 1690 |
28.50 |
| 2026-09-23 00:00 |
00:23:09.60 |
+28:43:03.7 |
HIP 1690 |
28.17 |
| 2026-09-23 12:00 |
00:23:07.67 |
+28:42:54.9 |
HIP 1690 |
27.84 |
| 2026-09-24 00:00 |
00:23:05.74 |
+28:42:46.0 |
HIP 1690 |
27.52 |
| 2026-09-24 12:00 |
00:23:03.81 |
+28:42:37.0 |
HIP 1690 |
27.20 |
| 2026-09-25 00:00 |
00:23:01.88 |
+28:42:27.9 |
HIP 1690 |
26.88 |
| 2026-09-25 12:00 |
00:22:59.95 |
+28:42:18.6 |
HIP 1690 |
26.57 |
| 2026-09-26 00:00 |
00:22:58.02 |
+28:42:09.3 |
HIP 1690 |
26.27 |
| 2026-09-26 12:00 |
00:22:56.09 |
+28:41:59.8 |
HIP 1690 |
25.96 |
| 2026-09-27 00:00 |
00:22:54.15 |
+28:41:50.2 |
HIP 1690 |
25.67 |
| 2026-09-27 12:00 |
00:22:52.21 |
+28:41:40.5 |
HIP 1690 |
25.38 |
| 2026-09-28 00:00 |
00:22:50.28 |
+28:41:30.7 |
HIP 1690 |
25.09 |
| 2026-09-28 12:00 |
00:22:48.34 |
+28:41:20.7 |
HIP 1690 |
24.82 |
| 2026-09-29 00:00 |
00:22:46.40 |
+28:41:10.7 |
HIP 1690 |
24.54 |
| 2026-09-29 12:00 |
00:22:44.47 |
+28:41:00.6 |
HIP 1690 |
24.28 |
| 2026-09-30 00:00 |
00:22:42.53 |
+28:40:50.3 |
HIP 1690 |
24.02 |
| 2026-09-30 12:00 |
00:22:40.59 |
+28:40:40.0 |
HIP 1690 |
23.77 |
| 2026-10-01 00:00 |
00:22:38.66 |
+28:40:29.5 |
HIP 1690 |
23.52 |
| 2026-10-01 12:00 |
00:22:36.72 |
+28:40:18.9 |
HIP 1690 |
23.28 |
| 2026-10-02 00:00 |
00:22:34.79 |
+28:40:08.2 |
HIP 1690 |
23.05 |
| 2026-10-02 12:00 |
00:22:32.85 |
+28:39:57.5 |
HIP 1690 |
22.83 |
| 2026-10-03 00:00 |
00:22:30.92 |
+28:39:46.6 |
HIP 1690 |
22.62 |
| 2026-10-03 12:00 |
00:22:28.98 |
+28:39:35.6 |
HIP 1690 |
22.41 |
| 2026-10-04 00:00 |
00:22:27.05 |
+28:39:24.5 |
HIP 1690 |
22.22 |
| 2026-10-04 12:00 |
00:22:25.12 |
+28:39:13.3 |
HIP 1690 |
22.03 |
| 2026-10-05 00:00 |
00:22:23.19 |
+28:39:02.0 |
HIP 1690 |
21.86 |
| 2026-10-05 12:00 |
00:22:21.26 |
+28:38:50.6 |
HIP 1690 |
21.69 |
| 2026-10-06 00:00 |
00:22:19.34 |
+28:38:39.1 |
HIP 1690 |
21.53 |
| 2026-10-06 12:00 |
00:22:17.42 |
+28:38:27.5 |
HIP 1690 |
21.39 |
| 2026-10-07 00:00 |
00:22:15.49 |
+28:38:15.8 |
HIP 1690 |
21.25 |
| 2026-10-07 12:00 |
00:22:13.58 |
+28:38:04.0 |
HIP 1690 |
21.13 |
| 2026-10-08 00:00 |
00:22:11.66 |
+28:37:52.1 |
HIP 1704 |
20.90 |
| 2026-10-08 12:00 |
00:22:09.74 |
+28:37:40.2 |
HIP 1704 |
20.53 |
| 2026-10-09 00:00 |
00:22:07.83 |
+28:37:28.1 |
HIP 1704 |
20.15 |
| 2026-10-09 12:00 |
00:22:05.92 |
+28:37:15.9 |
HIP 1704 |
19.78 |
| 2026-10-10 00:00 |
00:22:04.02 |
+28:37:03.6 |
HIP 1704 |
19.41 |
| 2026-10-10 12:00 |
00:22:02.12 |
+28:36:51.3 |
HIP 1704 |
19.05 |
| 2026-10-11 00:00 |
00:22:00.22 |
+28:36:38.8 |
HIP 1704 |
18.69 |