| 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) |
| 2026-03-26 00:00 |
19:03:12.65 |
-09:27:12.1 |
HIP 93504 |
32.85 |
| 2026-03-26 12:00 |
19:03:22.32 |
-09:25:50.7 |
HIP 93504 |
32.33 |
| 2026-03-27 00:00 |
19:03:31.86 |
-09:24:29.1 |
HIP 93504 |
32.02 |
| 2026-03-27 12:00 |
19:03:41.26 |
-09:23:07.5 |
HIP 93504 |
31.91 |
| 2026-03-28 00:00 |
19:03:50.52 |
-09:21:45.9 |
HIP 93504 |
32.02 |
| 2026-03-28 12:00 |
19:03:59.65 |
-09:20:24.2 |
HIP 93504 |
32.32 |
| 2026-03-29 00:00 |
19:04:08.65 |
-09:19:02.4 |
HIP 93504 |
32.80 |
| 2026-03-29 12:00 |
19:04:17.50 |
-09:17:40.5 |
HIP 93780 |
33.27 |
| 2026-03-30 00:00 |
19:04:26.22 |
-09:16:18.7 |
HIP 93780 |
30.78 |
| 2026-03-30 12:00 |
19:04:34.80 |
-09:14:56.7 |
HIP 93780 |
28.33 |
| 2026-03-31 00:00 |
19:04:43.24 |
-09:13:34.8 |
HIP 93780 |
25.90 |
| 2026-03-31 12:00 |
19:04:51.55 |
-09:12:12.8 |
HIP 93780 |
23.52 |
| 2026-04-01 00:00 |
19:04:59.71 |
-09:10:50.7 |
HIP 93780 |
21.18 |
| 2026-04-01 12:00 |
19:05:07.73 |
-09:09:28.7 |
HIP 93780 |
18.88 |
| 2026-04-02 00:00 |
19:05:15.61 |
-09:08:06.6 |
HIP 93780 |
16.62 |
| 2026-04-02 12:00 |
19:05:23.35 |
-09:06:44.5 |
HIP 93780 |
14.43 |
| 2026-04-03 00:00 |
19:05:30.95 |
-09:05:22.4 |
HIP 93780 |
12.31 |
| 2026-04-03 12:00 |
19:05:38.40 |
-09:04:00.3 |
HIP 93780 |
10.30 |
| 2026-04-04 00:00 |
19:05:45.71 |
-09:02:38.3 |
HIP 93780 |
8.43 |
| 2026-04-04 12:00 |
19:05:52.88 |
-09:01:16.2 |
HIP 93780 |
6.82 |
| 2026-04-05 00:00 |
19:05:59.90 |
-08:59:54.1 |
HIP 93780 |
5.63 |
| 2026-04-05 12:00 |
19:06:06.77 |
-08:58:32.0 |
HIP 93780 |
5.15 |
| 2026-04-06 00:00 |
19:06:13.50 |
-08:57:10.0 |
HIP 93780 |
5.52 |
| 2026-04-06 12:00 |
19:06:20.09 |
-08:55:47.9 |
HIP 93780 |
6.57 |
| 2026-04-07 00:00 |
19:06:26.52 |
-08:54:26.0 |
HIP 93780 |
8.02 |
| 2026-04-07 12:00 |
19:06:32.81 |
-08:53:04.0 |
HIP 93780 |
9.68 |
| 2026-04-08 00:00 |
19:06:38.95 |
-08:51:42.1 |
HIP 93780 |
11.43 |
| 2026-04-08 12:00 |
19:06:44.94 |
-08:50:20.3 |
HIP 93780 |
13.23 |
| 2026-04-09 00:00 |
19:06:50.78 |
-08:48:58.4 |
HIP 93780 |
15.05 |
| 2026-04-09 12:00 |
19:06:56.47 |
-08:47:36.7 |
HIP 93780 |
16.87 |
| 2026-04-10 00:00 |
19:07:02.01 |
-08:46:15.0 |
HIP 93780 |
18.69 |
| 2026-04-10 12:00 |
19:07:07.40 |
-08:44:53.4 |
HIP 93780 |
20.49 |
| 2026-04-11 00:00 |
19:07:12.64 |
-08:43:31.9 |
HIP 93780 |
22.28 |
| 2026-04-11 12:00 |
19:07:17.72 |
-08:42:10.5 |
HIP 93780 |
24.05 |
| 2026-04-12 00:00 |
19:07:22.66 |
-08:40:49.1 |
HIP 93780 |
25.80 |
| 2026-04-12 12:00 |
19:07:27.43 |
-08:39:27.8 |
HIP 93780 |
27.52 |
| 2026-04-13 00:00 |
19:07:32.06 |
-08:38:06.7 |
HIP 93780 |
29.22 |
| 2026-04-13 12:00 |
19:07:36.53 |
-08:36:45.6 |
HIP 93780 |
30.90 |
| 2026-04-14 00:00 |
19:07:40.84 |
-08:35:24.7 |
HIP 93780 |
32.55 |
| 2026-04-14 12:00 |
19:07:45.00 |
-08:34:03.9 |
HIP 93780 |
34.17 |
| 2026-04-15 00:00 |
19:07:49.00 |
-08:32:43.2 |
HIP 93780 |
35.77 |
| 2026-04-15 12:00 |
19:07:52.85 |
-08:31:22.6 |
HIP 93780 |
37.35 |
| 2026-04-16 00:00 |
19:07:56.54 |
-08:30:02.2 |
HIP 93780 |
38.89 |