| 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
$$
M_a = (10.099 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
10.099 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-0.925 |
| 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) |
| 2026-09-20 00:00 |
06:31:50.64 |
+20:11:57.5 |
HIP 31140 |
17.00 |
| 2026-09-20 12:00 |
06:32:22.10 |
+20:10:48.6 |
HIP 31140 |
16.56 |
| 2026-09-21 00:00 |
06:32:53.36 |
+20:09:39.3 |
HIP 31140 |
19.24 |
| 2026-09-21 12:00 |
06:33:24.41 |
+20:08:29.7 |
HIP 31249 |
17.98 |
| 2026-09-22 00:00 |
06:33:55.24 |
+20:07:19.6 |
HIP 31249 |
19.04 |
| 2026-09-22 12:00 |
06:34:25.86 |
+20:06:09.2 |
HIP 31249 |
22.53 |
| 2026-09-23 00:00 |
06:34:56.26 |
+20:04:58.3 |
HIP 31249 |
27.51 |
| 2026-09-23 12:00 |
06:35:26.45 |
+20:03:47.1 |
HIP 31626 |
29.77 |
| 2026-09-24 00:00 |
06:35:56.41 |
+20:02:35.6 |
HIP 31626 |
23.78 |
| 2026-09-24 12:00 |
06:36:26.16 |
+20:01:23.7 |
HIP 31680 |
18.48 |
| 2026-09-25 00:00 |
06:36:55.69 |
+20:00:11.4 |
HIP 31680 |
12.37 |
| 2026-09-25 12:00 |
06:37:24.99 |
+19:58:58.9 |
HIP 31680 |
7.98 |
| 2026-09-26 00:00 |
06:37:54.07 |
+19:57:45.9 |
HIP 31680 |
8.48 |
| 2026-09-26 12:00 |
06:38:22.92 |
+19:56:32.7 |
HIP 31680 |
13.25 |
| 2026-09-27 00:00 |
06:38:51.55 |
+19:55:19.2 |
HIP 31680 |
19.30 |
| 2026-09-27 12:00 |
06:39:19.94 |
+19:54:05.3 |
HIP 31896 |
17.66 |
| 2026-09-28 00:00 |
06:39:48.11 |
+19:52:51.2 |
HIP 31896 |
13.78 |
| 2026-09-28 12:00 |
06:40:16.04 |
+19:51:36.8 |
HIP 31896 |
12.57 |
| 2026-09-29 00:00 |
06:40:43.74 |
+19:50:22.1 |
HIP 32016 |
11.30 |
| 2026-09-29 12:00 |
06:41:11.21 |
+19:49:07.2 |
HIP 32016 |
9.09 |
| 2026-09-30 00:00 |
06:41:38.43 |
+19:47:52.0 |
HIP 32016 |
11.11 |
| 2026-09-30 12:00 |
06:42:05.42 |
+19:46:36.5 |
HIP 32016 |
15.75 |
| 2026-10-01 00:00 |
06:42:32.17 |
+19:45:20.8 |
HIP 32016 |
21.33 |
| 2026-10-01 12:00 |
06:42:58.67 |
+19:44:04.9 |
HIP 32016 |
27.23 |
| 2026-10-02 00:00 |
06:43:24.93 |
+19:42:48.8 |
HIP 32324 |
23.45 |
| 2026-10-02 12:00 |
06:43:50.95 |
+19:41:32.5 |
HIP 32324 |
17.55 |
| 2026-10-03 00:00 |
06:44:16.71 |
+19:40:16.0 |
HIP 32324 |
12.05 |
| 2026-10-03 12:00 |
06:44:42.23 |
+19:38:59.2 |
HIP 32324 |
7.72 |
| 2026-10-04 00:00 |
06:45:07.49 |
+19:37:42.4 |
HIP 32324 |
7.00 |
| 2026-10-04 12:00 |
06:45:32.50 |
+19:36:25.3 |
HIP 32324 |
10.55 |
| 2026-10-05 00:00 |
06:45:57.25 |
+19:35:08.1 |
HIP 32324 |
15.64 |
| 2026-10-05 12:00 |
06:46:21.74 |
+19:33:50.7 |
HIP 32324 |
21.13 |
| 2026-10-06 00:00 |
06:46:45.98 |
+19:32:33.2 |
HIP 32324 |
26.75 |
| 2026-10-06 12:00 |
06:47:09.95 |
+19:31:15.6 |
HIP 32324 |
32.38 |
| 2026-10-07 00:00 |
06:47:33.66 |
+19:29:57.9 |
HIP 32554 |
33.45 |
| 2026-10-07 12:00 |
06:47:57.11 |
+19:28:40.1 |
HIP 32727 |
30.11 |
| 2026-10-08 00:00 |
06:48:20.28 |
+19:27:22.2 |
HIP 32727 |
25.12 |
| 2026-10-08 12:00 |
06:48:43.19 |
+19:26:04.2 |
HIP 32727 |
20.49 |
| 2026-10-09 00:00 |
06:49:05.83 |
+19:24:46.1 |
HIP 32727 |
16.49 |
| 2026-10-09 12:00 |
06:49:28.19 |
+19:23:28.0 |
HIP 32727 |
13.58 |
| 2026-10-10 00:00 |
06:49:50.28 |
+19:22:09.8 |
HIP 32824 |
10.98 |
| 2026-10-10 12:00 |
06:50:12.10 |
+19:20:51.6 |
HIP 32824 |
5.79 |
| 2026-10-11 00:00 |
06:50:33.63 |
+19:19:33.3 |
HIP 32824 |
1.68 |