| Parameter |
Value |
| Designation |
128P/Shoemaker-Holt 1 |
| Type |
P |
| Perihelion (tp_cal, UTC) |
2017-01-10T18:32:09.657600Z |
| Orbit solution date (soln_date, UTC) |
2026-03-09T08:49:55Z |
| Obs used |
847 |
| NEO |
- |
| M1 |
7.300 |
| K1 |
19.500 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2016-02-17.0000000 |
| e |
0.32145501 |
| q (au) |
3.055732 |
| a (au) |
4.503359 |
| i (deg) |
4.363922 |
| Ω (om, deg) |
214.293861 |
| ω (w, deg) |
210.579379 |
| M (ma, deg) |
326.092601 |
Magnitude
Scatter + Global Linear
$$
M_a = (10.427 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
10.427 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-0.905 |
| 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) |
| 2026-03-26 00:00 |
02:01:35.16 |
+11:56:51.7 |
HIP 9490 |
15.91 |
| 2026-03-26 12:00 |
02:02:19.04 |
+12:00:24.6 |
HIP 9490 |
10.95 |
| 2026-03-27 00:00 |
02:03:03.00 |
+12:03:57.4 |
HIP 9490 |
15.57 |
| 2026-03-27 12:00 |
02:03:47.02 |
+12:07:29.9 |
HIP 9490 |
24.93 |
| 2026-03-28 00:00 |
02:04:31.12 |
+12:11:02.3 |
HIP 9764 |
14.83 |
| 2026-03-28 12:00 |
02:05:15.27 |
+12:14:34.6 |
HIP 9764 |
5.98 |
| 2026-03-29 00:00 |
02:05:59.50 |
+12:18:06.6 |
HIP 9764 |
10.48 |
| 2026-03-29 12:00 |
02:06:43.79 |
+12:21:38.4 |
HIP 9764 |
21.04 |
| 2026-03-30 00:00 |
02:07:28.15 |
+12:25:10.0 |
HIP 9764 |
32.18 |
| 2026-03-30 12:00 |
02:08:12.57 |
+12:28:41.4 |
HIP 10106 |
28.17 |
| 2026-03-31 00:00 |
02:08:57.05 |
+12:32:12.6 |
HIP 10106 |
19.85 |
| 2026-03-31 12:00 |
02:09:41.60 |
+12:35:43.6 |
HIP 10106 |
15.97 |
| 2026-04-01 00:00 |
02:10:26.22 |
+12:39:14.3 |
HIP 10106 |
19.43 |
| 2026-04-01 12:00 |
02:11:10.90 |
+12:42:44.8 |
HIP 10197 |
23.24 |
| 2026-04-02 00:00 |
02:11:55.64 |
+12:46:15.0 |
HIP 10329 |
23.63 |
| 2026-04-02 12:00 |
02:12:40.45 |
+12:49:45.0 |
HIP 10329 |
14.45 |
| 2026-04-03 00:00 |
02:13:25.32 |
+12:53:14.7 |
HIP 10329 |
11.08 |
| 2026-04-03 12:00 |
02:14:10.25 |
+12:56:44.2 |
HIP 10329 |
17.34 |
| 2026-04-04 00:00 |
02:14:55.24 |
+13:00:13.3 |
HIP 10476 |
17.72 |
| 2026-04-04 12:00 |
02:15:40.30 |
+13:03:42.2 |
HIP 10476 |
23.02 |
| 2026-04-05 00:00 |
02:16:25.42 |
+13:07:10.8 |
HIP 10730 |
30.74 |
| 2026-04-05 12:00 |
02:17:10.60 |
+13:10:39.2 |
HIP 10730 |
20.26 |
| 2026-04-06 00:00 |
02:17:55.84 |
+13:14:07.2 |
HIP 10730 |
11.92 |
| 2026-04-06 12:00 |
02:18:41.14 |
+13:17:34.9 |
HIP 10730 |
11.85 |
| 2026-04-07 00:00 |
02:19:26.51 |
+13:21:02.3 |
HIP 10730 |
20.15 |
| 2026-04-07 12:00 |
02:20:11.93 |
+13:24:29.3 |
HIP 10921 |
17.06 |
| 2026-04-08 00:00 |
02:20:57.42 |
+13:27:56.1 |
HIP 10921 |
13.06 |
| 2026-04-08 12:00 |
02:21:42.96 |
+13:31:22.5 |
HIP 10921 |
17.84 |
| 2026-04-09 00:00 |
02:22:28.56 |
+13:34:48.6 |
HIP 11042 |
24.28 |
| 2026-04-09 12:00 |
02:23:14.22 |
+13:38:14.3 |
HIP 11259 |
24.71 |
| 2026-04-10 00:00 |
02:23:59.94 |
+13:41:39.6 |
HIP 11259 |
14.02 |
| 2026-04-10 12:00 |
02:24:45.72 |
+13:45:04.6 |
HIP 11259 |
7.27 |
| 2026-04-11 00:00 |
02:25:31.56 |
+13:48:29.3 |
HIP 11259 |
13.41 |
| 2026-04-11 12:00 |
02:26:17.45 |
+13:51:53.5 |
HIP 11422 |
16.22 |
| 2026-04-12 00:00 |
02:27:03.40 |
+13:55:17.4 |
HIP 11422 |
4.74 |
| 2026-04-12 12:00 |
02:27:49.41 |
+13:58:40.9 |
HIP 11422 |
7.35 |
| 2026-04-13 00:00 |
02:28:35.48 |
+14:02:04.0 |
HIP 11522 |
9.47 |
| 2026-04-13 12:00 |
02:29:21.60 |
+14:05:26.7 |
HIP 11522 |
17.23 |
| 2026-04-14 00:00 |
02:30:07.77 |
+14:08:48.9 |
HIP 11672 |
9.41 |
| 2026-04-14 12:00 |
02:30:54.01 |
+14:12:10.8 |
HIP 11672 |
5.92 |
| 2026-04-15 00:00 |
02:31:40.29 |
+14:15:32.2 |
HIP 11672 |
15.99 |
| 2026-04-15 12:00 |
02:32:26.63 |
+14:18:53.2 |
HIP 11672 |
27.40 |
| 2026-04-16 00:00 |
02:33:13.03 |
+14:22:13.8 |
HIP 12025 |
29.14 |