| 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) |
| 2026-05-12 00:00 |
19:07:26.76 |
-07:26:08.2 |
HIP 93936 |
3.52 |
| 2026-05-12 12:00 |
19:07:21.90 |
-07:25:04.0 |
HIP 93936 |
4.12 |
| 2026-05-13 00:00 |
19:07:16.88 |
-07:24:00.3 |
HIP 93936 |
5.22 |
| 2026-05-13 12:00 |
19:07:11.70 |
-07:22:57.1 |
HIP 93936 |
6.58 |
| 2026-05-14 00:00 |
19:07:06.36 |
-07:21:54.4 |
HIP 93936 |
8.09 |
| 2026-05-14 12:00 |
19:07:00.86 |
-07:20:52.2 |
HIP 93936 |
9.69 |
| 2026-05-15 00:00 |
19:06:55.20 |
-07:19:50.5 |
HIP 93936 |
11.36 |
| 2026-05-15 12:00 |
19:06:49.39 |
-07:18:49.3 |
HIP 93936 |
13.09 |
| 2026-05-16 00:00 |
19:06:43.41 |
-07:17:48.6 |
HIP 93936 |
14.85 |
| 2026-05-16 12:00 |
19:06:37.28 |
-07:16:48.4 |
HIP 93936 |
16.65 |
| 2026-05-17 00:00 |
19:06:30.99 |
-07:15:48.8 |
HIP 93936 |
18.49 |
| 2026-05-17 12:00 |
19:06:24.55 |
-07:14:49.7 |
HIP 93936 |
20.36 |
| 2026-05-18 00:00 |
19:06:17.95 |
-07:13:51.2 |
HIP 93724 |
20.03 |
| 2026-05-18 12:00 |
19:06:11.20 |
-07:12:53.2 |
HIP 93724 |
18.16 |
| 2026-05-19 00:00 |
19:06:04.29 |
-07:11:55.7 |
HIP 93724 |
16.28 |
| 2026-05-19 12:00 |
19:05:57.23 |
-07:10:58.8 |
HIP 93724 |
14.38 |
| 2026-05-20 00:00 |
19:05:50.02 |
-07:10:02.5 |
HIP 93724 |
12.47 |
| 2026-05-20 12:00 |
19:05:42.65 |
-07:09:06.8 |
HIP 93724 |
10.57 |
| 2026-05-21 00:00 |
19:05:35.14 |
-07:08:11.6 |
HIP 93724 |
8.69 |
| 2026-05-21 12:00 |
19:05:27.47 |
-07:07:17.0 |
HIP 93724 |
6.89 |
| 2026-05-22 00:00 |
19:05:19.66 |
-07:06:23.0 |
HIP 93724 |
5.29 |
| 2026-05-22 12:00 |
19:05:11.70 |
-07:05:29.6 |
HIP 93724 |
4.17 |
| 2026-05-23 00:00 |
19:05:03.59 |
-07:04:36.8 |
HIP 93724 |
3.99 |
| 2026-05-23 12:00 |
19:04:55.34 |
-07:03:44.6 |
HIP 93724 |
4.92 |
| 2026-05-24 00:00 |
19:04:46.94 |
-07:02:53.0 |
HIP 93724 |
6.51 |
| 2026-05-24 12:00 |
19:04:38.40 |
-07:02:02.0 |
HIP 93724 |
8.43 |
| 2026-05-25 00:00 |
19:04:29.71 |
-07:01:11.6 |
HIP 93724 |
10.51 |
| 2026-05-25 12:00 |
19:04:20.88 |
-07:00:21.9 |
HIP 93724 |
12.70 |
| 2026-05-26 00:00 |
19:04:11.91 |
-06:59:32.8 |
HIP 93724 |
14.95 |
| 2026-05-26 12:00 |
19:04:02.80 |
-06:58:44.3 |
HIP 93724 |
17.26 |
| 2026-05-27 00:00 |
19:03:53.55 |
-06:57:56.4 |
HIP 93724 |
19.61 |
| 2026-05-27 12:00 |
19:03:44.16 |
-06:57:09.2 |
HIP 93724 |
22.01 |
| 2026-05-28 00:00 |
19:03:34.64 |
-06:56:22.7 |
HIP 93724 |
24.44 |
| 2026-05-28 12:00 |
19:03:24.98 |
-06:55:36.8 |
HIP 93724 |
26.90 |
| 2026-05-29 00:00 |
19:03:15.18 |
-06:54:51.5 |
HIP 93724 |
29.40 |
| 2026-05-29 12:00 |
19:03:05.25 |
-06:54:06.9 |
HIP 93724 |
31.93 |
| 2026-05-30 00:00 |
19:02:55.18 |
-06:53:23.0 |
HIP 93724 |
34.50 |
| 2026-05-30 12:00 |
19:02:44.98 |
-06:52:39.7 |
HIP 93441 |
32.93 |
| 2026-05-31 00:00 |
19:02:34.66 |
-06:51:57.1 |
HIP 93441 |
31.28 |
| 2026-05-31 12:00 |
19:02:24.20 |
-06:51:15.2 |
HIP 93441 |
29.77 |
| 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 |