| 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
$$
M_a = (10.431 + 3.907\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
10.431 |
| n |
3.907 |
| gf |
1.000 |
| gb |
-0.500 |
| 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 |
+2.8190 |
-1.701 |
| 2018-11-11 |
2020-05-21 |
+1.0455 |
-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) |
| 2026-09-20 00:00 |
15:42:23.79 |
-13:46:41.8 |
HIP 76983 |
17.44 |
| 2026-09-20 12:00 |
15:42:28.17 |
-13:47:09.6 |
HIP 76983 |
17.15 |
| 2026-09-21 00:00 |
15:42:32.61 |
-13:47:37.5 |
HIP 76983 |
16.94 |
| 2026-09-21 12:00 |
15:42:37.09 |
-13:48:05.5 |
HIP 76983 |
16.80 |
| 2026-09-22 00:00 |
15:42:41.62 |
-13:48:33.6 |
HIP 76983 |
16.73 |
| 2026-09-22 12:00 |
15:42:46.20 |
-13:49:01.8 |
HIP 76983 |
16.75 |
| 2026-09-23 00:00 |
15:42:50.83 |
-13:49:30.1 |
HIP 76983 |
16.86 |
| 2026-09-23 12:00 |
15:42:55.50 |
-13:49:58.4 |
HIP 76983 |
17.05 |
| 2026-09-24 00:00 |
15:43:00.22 |
-13:50:26.9 |
HIP 76983 |
17.33 |
| 2026-09-24 12:00 |
15:43:04.99 |
-13:50:55.5 |
HIP 76983 |
17.69 |
| 2026-09-25 00:00 |
15:43:09.81 |
-13:51:24.1 |
HIP 76983 |
18.13 |
| 2026-09-25 12:00 |
15:43:14.68 |
-13:51:52.8 |
HIP 76983 |
18.65 |
| 2026-09-26 00:00 |
15:43:19.59 |
-13:52:21.6 |
HIP 76983 |
19.24 |
| 2026-09-26 12:00 |
15:43:24.54 |
-13:52:50.5 |
HIP 76983 |
19.90 |
| 2026-09-27 00:00 |
15:43:29.55 |
-13:53:19.4 |
HIP 76983 |
20.63 |
| 2026-09-27 12:00 |
15:43:34.59 |
-13:53:48.5 |
HIP 76983 |
21.42 |
| 2026-09-28 00:00 |
15:43:39.69 |
-13:54:17.6 |
HIP 76983 |
22.26 |
| 2026-09-28 12:00 |
15:43:44.83 |
-13:54:46.8 |
HIP 76983 |
23.15 |
| 2026-09-29 00:00 |
15:43:50.01 |
-13:55:16.0 |
HIP 76983 |
24.09 |
| 2026-09-29 12:00 |
15:43:55.24 |
-13:55:45.3 |
HIP 76983 |
25.07 |
| 2026-09-30 00:00 |
15:44:00.51 |
-13:56:14.7 |
HIP 76983 |
26.09 |
| 2026-09-30 12:00 |
15:44:05.82 |
-13:56:44.2 |
HIP 77154 |
25.85 |
| 2026-10-01 00:00 |
15:44:11.18 |
-13:57:13.7 |
HIP 77154 |
24.68 |
| 2026-10-01 12:00 |
15:44:16.58 |
-13:57:43.3 |
HIP 77154 |
23.52 |
| 2026-10-02 00:00 |
15:44:22.03 |
-13:58:13.0 |
HIP 77154 |
22.38 |
| 2026-10-02 12:00 |
15:44:27.51 |
-13:58:42.7 |
HIP 77154 |
21.27 |
| 2026-10-03 00:00 |
15:44:33.04 |
-13:59:12.5 |
HIP 77154 |
20.20 |
| 2026-10-03 12:00 |
15:44:38.62 |
-13:59:42.3 |
HIP 77154 |
19.17 |
| 2026-10-04 00:00 |
15:44:44.23 |
-14:00:12.2 |
HIP 77154 |
18.18 |
| 2026-10-04 12:00 |
15:44:49.89 |
-14:00:42.2 |
HIP 77154 |
17.26 |
| 2026-10-05 00:00 |
15:44:55.58 |
-14:01:12.2 |
HIP 77154 |
16.42 |
| 2026-10-05 12:00 |
15:45:01.32 |
-14:01:42.3 |
HIP 77154 |
15.66 |
| 2026-10-06 00:00 |
15:45:07.10 |
-14:02:12.4 |
HIP 77154 |
15.01 |
| 2026-10-06 12:00 |
15:45:12.91 |
-14:02:42.5 |
HIP 77154 |
14.49 |
| 2026-10-07 00:00 |
15:45:18.77 |
-14:03:12.7 |
HIP 77154 |
14.10 |
| 2026-10-07 12:00 |
15:45:24.67 |
-14:03:43.0 |
HIP 77154 |
13.87 |
| 2026-10-08 00:00 |
15:45:30.61 |
-14:04:13.2 |
HIP 77154 |
13.81 |
| 2026-10-08 12:00 |
15:45:36.58 |
-14:04:43.6 |
HIP 77154 |
13.91 |
| 2026-10-09 00:00 |
15:45:42.60 |
-14:05:13.9 |
HIP 77270 |
13.51 |
| 2026-10-09 12:00 |
15:45:48.65 |
-14:05:44.3 |
HIP 77270 |
12.39 |
| 2026-10-10 00:00 |
15:45:54.74 |
-14:06:14.8 |
HIP 77270 |
11.38 |
| 2026-10-10 12:00 |
15:46:00.86 |
-14:06:45.2 |
HIP 77270 |
10.49 |
| 2026-10-11 00:00 |
15:46:07.03 |
-14:07:15.7 |
HIP 77270 |
9.78 |