| Parameter |
Value |
| Designation |
38P/Stephan-Oterma |
| Type |
P |
| Perihelion (tp_cal, UTC) |
2018-11-10T23:41:26.018880Z |
| Orbit solution date (soln_date, UTC) |
2024-12-04T09:13:02Z |
| Obs used |
3293 |
| NEO |
- |
| M1 |
11.600 |
| K1 |
9.500 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2018-05-28.0000000 |
| e |
0.85928734 |
| q (au) |
1.588509 |
| a (au) |
11.289028 |
| i (deg) |
18.352950 |
| Ω (om, deg) |
78.000299 |
| ω (w, deg) |
359.588512 |
| M (ma, deg) |
355.660875 |
Magnitude
Scatter + Global Linear
$$
M_a = (10.352 + 4.047\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
10.352 |
| n |
4.047 |
| gf |
1.000 |
| gb |
-1.000 |
| 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
Residuals (Piecewise)
$$\epsilon = a \log_{10} r_{\mathrm{au}} + b$$
| Start (UTC) |
End (UTC) |
a |
b |
| 2017-06-24 |
2018-11-10 |
+2.7675 |
-1.692 |
| 2018-11-11 |
2020-05-21 |
+1.0409 |
-0.769 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-05-12 00:00 |
15:54:32.46 |
-13:32:28.8 |
HIP 77904 |
8.53 |
| 2026-05-12 12:00 |
15:54:25.25 |
-13:32:08.5 |
HIP 77904 |
9.21 |
| 2026-05-13 00:00 |
15:54:18.03 |
-13:31:48.2 |
HIP 77904 |
10.17 |
| 2026-05-13 12:00 |
15:54:10.80 |
-13:31:28.0 |
HIP 77904 |
11.33 |
| 2026-05-14 00:00 |
15:54:03.55 |
-13:31:07.9 |
HIP 77812 |
10.55 |
| 2026-05-14 12:00 |
15:53:56.30 |
-13:30:47.9 |
HIP 77812 |
8.83 |
| 2026-05-15 00:00 |
15:53:49.04 |
-13:30:27.9 |
HIP 77812 |
7.15 |
| 2026-05-15 12:00 |
15:53:41.77 |
-13:30:08.1 |
HIP 77812 |
5.53 |
| 2026-05-16 00:00 |
15:53:34.50 |
-13:29:48.3 |
HIP 77812 |
4.07 |
| 2026-05-16 12:00 |
15:53:27.21 |
-13:29:28.6 |
HIP 77812 |
3.00 |
| 2026-05-17 00:00 |
15:53:19.93 |
-13:29:09.0 |
HIP 77812 |
2.81 |
| 2026-05-17 12:00 |
15:53:12.64 |
-13:28:49.5 |
HIP 77812 |
3.65 |
| 2026-05-18 00:00 |
15:53:05.34 |
-13:28:30.1 |
HIP 77812 |
5.02 |
| 2026-05-18 12:00 |
15:52:58.04 |
-13:28:10.8 |
HIP 77812 |
6.60 |
| 2026-05-19 00:00 |
15:52:50.74 |
-13:27:51.6 |
HIP 77812 |
8.27 |
| 2026-05-19 12:00 |
15:52:43.44 |
-13:27:32.5 |
HIP 77812 |
9.99 |
| 2026-05-20 00:00 |
15:52:36.14 |
-13:27:13.5 |
HIP 77812 |
11.73 |
| 2026-05-20 12:00 |
15:52:28.84 |
-13:26:54.6 |
HIP 77812 |
13.49 |
| 2026-05-21 00:00 |
15:52:21.54 |
-13:26:35.8 |
HIP 77812 |
15.26 |
| 2026-05-21 12:00 |
15:52:14.24 |
-13:26:17.1 |
HIP 77812 |
17.03 |
| 2026-05-22 00:00 |
15:52:06.94 |
-13:25:58.6 |
HIP 77812 |
18.81 |
| 2026-05-22 12:00 |
15:51:59.64 |
-13:25:40.1 |
HIP 77609 |
19.57 |
| 2026-05-23 00:00 |
15:51:52.35 |
-13:25:21.8 |
HIP 77609 |
17.78 |
| 2026-05-23 12:00 |
15:51:45.06 |
-13:25:03.6 |
HIP 77609 |
15.99 |
| 2026-05-24 00:00 |
15:51:37.78 |
-13:24:45.5 |
HIP 77609 |
14.20 |
| 2026-05-24 12:00 |
15:51:30.50 |
-13:24:27.5 |
HIP 77609 |
12.41 |
| 2026-05-25 00:00 |
15:51:23.23 |
-13:24:09.7 |
HIP 77609 |
10.63 |
| 2026-05-25 12:00 |
15:51:15.97 |
-13:23:52.0 |
HIP 77609 |
8.86 |
| 2026-05-26 00:00 |
15:51:08.71 |
-13:23:34.4 |
HIP 77609 |
7.09 |
| 2026-05-26 12:00 |
15:51:01.46 |
-13:23:16.9 |
HIP 77609 |
5.34 |
| 2026-05-27 00:00 |
15:50:54.22 |
-13:22:59.6 |
HIP 77609 |
3.64 |
| 2026-05-27 12:00 |
15:50:46.99 |
-13:22:42.4 |
HIP 77609 |
2.07 |
| 2026-05-28 00:00 |
15:50:39.77 |
-13:22:25.3 |
HIP 77609 |
1.29 |
| 2026-05-28 12:00 |
15:50:32.56 |
-13:22:08.4 |
HIP 77609 |
2.32 |
| 2026-05-29 00:00 |
15:50:25.36 |
-13:21:51.6 |
HIP 77609 |
3.92 |
| 2026-05-29 12:00 |
15:50:18.17 |
-13:21:35.0 |
HIP 77609 |
5.62 |
| 2026-05-30 00:00 |
15:50:11.00 |
-13:21:18.5 |
HIP 77609 |
7.35 |
| 2026-05-30 12:00 |
15:50:03.84 |
-13:21:02.1 |
HIP 77609 |
9.09 |
| 2026-05-31 00:00 |
15:49:56.69 |
-13:20:45.9 |
HIP 77609 |
10.84 |
| 2026-05-31 12:00 |
15:49:49.56 |
-13:20:29.8 |
HIP 77609 |
12.58 |
| 2026-06-01 00:00 |
15:49:42.44 |
-13:20:13.9 |
HIP 77609 |
14.32 |
| 2026-06-01 12:00 |
15:49:35.34 |
-13:19:58.1 |
HIP 77609 |
16.06 |
| 2026-06-02 00:00 |
15:49:28.26 |
-13:19:42.5 |
HIP 77609 |
17.80 |