| 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) |
| 2026-05-12 00:00 |
03:14:27.65 |
+17:03:09.4 |
HIP 14971 |
21.48 |
| 2026-05-12 12:00 |
03:15:16.25 |
+17:05:57.5 |
HIP 14971 |
32.61 |
| 2026-05-13 00:00 |
03:16:04.88 |
+17:08:44.9 |
HIP 15285 |
30.27 |
| 2026-05-13 12:00 |
03:16:53.55 |
+17:11:31.4 |
HIP 15285 |
23.29 |
| 2026-05-14 00:00 |
03:17:42.24 |
+17:14:17.2 |
HIP 15285 |
21.32 |
| 2026-05-14 12:00 |
03:18:30.96 |
+17:17:02.3 |
HIP 15519 |
24.75 |
| 2026-05-15 00:00 |
03:19:19.72 |
+17:19:46.5 |
HIP 15519 |
13.94 |
| 2026-05-15 12:00 |
03:20:08.50 |
+17:22:29.9 |
HIP 15519 |
7.87 |
| 2026-05-16 00:00 |
03:20:57.31 |
+17:25:12.6 |
HIP 15519 |
14.67 |
| 2026-05-16 12:00 |
03:21:46.14 |
+17:27:54.4 |
HIP 15683 |
14.02 |
| 2026-05-17 00:00 |
03:22:35.01 |
+17:30:35.5 |
HIP 15724 |
12.95 |
| 2026-05-17 12:00 |
03:23:23.89 |
+17:33:15.7 |
HIP 15854 |
12.02 |
| 2026-05-18 00:00 |
03:24:12.81 |
+17:35:55.1 |
HIP 15854 |
2.96 |
| 2026-05-18 12:00 |
03:25:01.75 |
+17:38:33.7 |
HIP 15954 |
8.09 |
| 2026-05-19 00:00 |
03:25:50.71 |
+17:41:11.5 |
HIP 15954 |
7.20 |
| 2026-05-19 12:00 |
03:26:39.69 |
+17:43:48.4 |
HIP 15954 |
18.00 |
| 2026-05-20 00:00 |
03:27:28.70 |
+17:46:24.5 |
HIP 15954 |
29.70 |
| 2026-05-20 12:00 |
03:28:17.73 |
+17:48:59.8 |
HIP 16152 |
38.99 |
| 2026-05-21 00:00 |
03:29:06.78 |
+17:51:34.2 |
HIP 16414 |
32.31 |
| 2026-05-21 12:00 |
03:29:55.86 |
+17:54:07.7 |
HIP 16414 |
20.40 |
| 2026-05-22 00:00 |
03:30:44.95 |
+17:56:40.4 |
HIP 16414 |
8.61 |
| 2026-05-22 12:00 |
03:31:34.06 |
+17:59:12.3 |
HIP 16414 |
4.24 |
| 2026-05-23 00:00 |
03:32:23.19 |
+18:01:43.2 |
HIP 16414 |
15.72 |
| 2026-05-23 12:00 |
03:33:12.34 |
+18:04:13.3 |
HIP 16613 |
12.76 |
| 2026-05-24 00:00 |
03:34:01.51 |
+18:06:42.6 |
HIP 16613 |
7.62 |
| 2026-05-24 12:00 |
03:34:50.70 |
+18:09:10.9 |
HIP 16613 |
15.45 |
| 2026-05-25 00:00 |
03:35:39.90 |
+18:11:38.4 |
HIP 16811 |
14.40 |
| 2026-05-25 12:00 |
03:36:29.12 |
+18:14:05.0 |
HIP 16811 |
7.76 |
| 2026-05-26 00:00 |
03:37:18.36 |
+18:16:30.7 |
HIP 16811 |
14.08 |
| 2026-05-26 12:00 |
03:38:07.62 |
+18:18:55.5 |
HIP 16944 |
9.99 |
| 2026-05-27 00:00 |
03:38:56.88 |
+18:21:19.4 |
HIP 17076 |
8.87 |
| 2026-05-27 12:00 |
03:39:46.17 |
+18:23:42.4 |
HIP 17076 |
3.07 |
| 2026-05-28 00:00 |
03:40:35.47 |
+18:26:04.6 |
HIP 17076 |
15.00 |
| 2026-05-28 12:00 |
03:41:24.78 |
+18:28:25.8 |
HIP 17282 |
18.34 |
| 2026-05-29 00:00 |
03:42:14.11 |
+18:30:46.1 |
HIP 17282 |
18.65 |
| 2026-05-29 12:00 |
03:43:03.45 |
+18:33:05.5 |
HIP 17421 |
24.22 |
| 2026-05-30 00:00 |
03:43:52.80 |
+18:35:24.0 |
HIP 17421 |
18.40 |
| 2026-05-30 12:00 |
03:44:42.17 |
+18:37:41.5 |
HIP 17586 |
19.04 |
| 2026-05-31 00:00 |
03:45:31.55 |
+18:39:58.2 |
HIP 17586 |
9.18 |
| 2026-05-31 12:00 |
03:46:20.94 |
+18:42:13.9 |
HIP 17586 |
9.49 |
| 2026-06-01 00:00 |
03:47:10.35 |
+18:44:28.7 |
HIP 17740 |
12.00 |
| 2026-06-01 12:00 |
03:47:59.76 |
+18:46:42.5 |
HIP 17740 |
6.94 |
| 2026-06-02 00:00 |
03:48:49.18 |
+18:48:55.5 |
HIP 17740 |
15.35 |