| Parameter |
Value |
| Designation |
361P/Spacewatch |
| Type |
P |
| Perihelion (tp_cal, UTC) |
2018-07-02T14:46:57.017280Z |
| Orbit solution date (soln_date, UTC) |
2023-02-13T23:14:08Z |
| Obs used |
381 |
| NEO |
- |
| M1 |
4.600 |
| K1 |
23.500 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2017-09-16.0000000 |
| e |
0.43788752 |
| q (au) |
2.780030 |
| a (au) |
4.945682 |
| i (deg) |
13.882834 |
| Ω (om, deg) |
203.277939 |
| ω (w, deg) |
219.242791 |
| M (ma, deg) |
334.047022 |
Magnitude
Scatter + Global Linear
$$
M_a = (7.723 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
7.723 |
| n |
6.000 |
| 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 |
| 2017-09-11 |
2018-01-27 |
+17.2864 |
-8.358 |
| 2018-08-25 |
2020-03-21 |
+2.3797 |
-1.430 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-06-01 00:00 |
19:02:13.61 |
-06:50:34.0 |
HIP 93441 |
28.45 |
| 2026-06-01 12:00 |
19:02:02.89 |
-06:49:53.5 |
HIP 93441 |
27.33 |
| 2026-06-02 00:00 |
19:01:52.05 |
-06:49:13.6 |
HIP 93441 |
26.47 |
| 2026-06-02 12:00 |
19:01:41.09 |
-06:48:34.5 |
HIP 93441 |
25.89 |
| 2026-06-03 00:00 |
19:01:29.99 |
-06:47:56.0 |
HIP 93441 |
25.62 |
| 2026-06-03 12:00 |
19:01:18.78 |
-06:47:18.3 |
HIP 93441 |
25.68 |
| 2026-06-04 00:00 |
19:01:07.44 |
-06:46:41.3 |
HIP 93441 |
26.09 |
| 2026-06-04 12:00 |
19:00:55.99 |
-06:46:04.9 |
HIP 93212 |
26.01 |
| 2026-06-05 00:00 |
19:00:44.41 |
-06:45:29.3 |
HIP 93212 |
23.31 |
| 2026-06-05 12:00 |
19:00:32.72 |
-06:44:54.5 |
HIP 93212 |
20.63 |
| 2026-06-06 00:00 |
19:00:20.91 |
-06:44:20.3 |
HIP 93212 |
18.02 |
| 2026-06-06 12:00 |
19:00:08.98 |
-06:43:46.9 |
HIP 93212 |
15.50 |
| 2026-06-07 00:00 |
18:59:56.94 |
-06:43:14.2 |
HIP 93212 |
13.17 |
| 2026-06-07 12:00 |
18:59:44.79 |
-06:42:42.3 |
HIP 93212 |
11.15 |
| 2026-06-08 00:00 |
18:59:32.52 |
-06:42:11.1 |
HIP 93212 |
9.68 |
| 2026-06-08 12:00 |
18:59:20.15 |
-06:41:40.7 |
HIP 93212 |
9.03 |
| 2026-06-09 00:00 |
18:59:07.67 |
-06:41:11.0 |
HIP 93212 |
9.42 |
| 2026-06-09 12:00 |
18:58:55.08 |
-06:40:42.0 |
HIP 93212 |
10.76 |
| 2026-06-10 00:00 |
18:58:42.39 |
-06:40:13.9 |
HIP 93212 |
12.76 |
| 2026-06-10 12:00 |
18:58:29.59 |
-06:39:46.5 |
HIP 93212 |
15.18 |
| 2026-06-11 00:00 |
18:58:16.70 |
-06:39:19.9 |
HIP 93212 |
17.86 |
| 2026-06-11 12:00 |
18:58:03.70 |
-06:38:54.0 |
HIP 93212 |
20.71 |
| 2026-06-12 00:00 |
18:57:50.60 |
-06:38:28.9 |
HIP 93212 |
23.68 |
| 2026-06-12 12:00 |
18:57:37.41 |
-06:38:04.6 |
HIP 93212 |
26.74 |
| 2026-06-13 00:00 |
18:57:24.12 |
-06:37:41.1 |
HIP 93212 |
29.87 |
| 2026-06-13 12:00 |
18:57:10.74 |
-06:37:18.4 |
HIP 93212 |
33.05 |
| 2026-06-14 00:00 |
18:56:57.27 |
-06:36:56.5 |
HIP 92868 |
31.09 |
| 2026-06-14 12:00 |
18:56:43.70 |
-06:36:35.3 |
HIP 92868 |
28.97 |
| 2026-06-15 00:00 |
18:56:30.05 |
-06:36:15.0 |
HIP 92868 |
27.08 |
| 2026-06-15 12:00 |
18:56:16.32 |
-06:35:55.4 |
HIP 92868 |
25.49 |
| 2026-06-16 00:00 |
18:56:02.50 |
-06:35:36.7 |
HIP 92868 |
24.26 |
| 2026-06-16 12:00 |
18:55:48.60 |
-06:35:18.8 |
HIP 92868 |
23.45 |
| 2026-06-17 00:00 |
18:55:34.62 |
-06:35:01.6 |
HIP 92868 |
23.13 |
| 2026-06-17 12:00 |
18:55:20.57 |
-06:34:45.3 |
HIP 92868 |
23.31 |
| 2026-06-18 00:00 |
18:55:06.43 |
-06:34:29.8 |
HIP 92868 |
24.00 |
| 2026-06-18 12:00 |
18:54:52.23 |
-06:34:15.1 |
HIP 92868 |
25.16 |
| 2026-06-19 00:00 |
18:54:37.95 |
-06:34:01.2 |
HIP 92868 |
26.74 |
| 2026-06-19 12:00 |
18:54:23.61 |
-06:33:48.1 |
HIP 92868 |
28.67 |
| 2026-06-20 00:00 |
18:54:09.20 |
-06:33:35.8 |
HIP 92868 |
30.89 |
| 2026-06-20 12:00 |
18:53:54.72 |
-06:33:24.3 |
HIP 92868 |
33.35 |
| 2026-06-21 00:00 |
18:53:40.18 |
-06:33:13.7 |
HIP 92601 |
34.87 |
| 2026-06-21 12:00 |
18:53:25.58 |
-06:33:03.8 |
HIP 92601 |
32.74 |
| 2026-06-22 00:00 |
18:53:10.93 |
-06:32:54.8 |
HIP 92517 |
30.66 |