| Parameter |
Value |
| Designation |
487P/Siding Spring |
| Type |
P |
| Perihelion (tp_cal, UTC) |
2024-10-20T18:47:47.019840Z |
| Orbit solution date (soln_date, UTC) |
2025-09-30T13:39:51Z |
| Obs used |
1401 |
| NEO |
- |
| M1 |
12.600 |
| K1 |
12.000 |
| PC |
0.030 |
| Discovery observation (MPC, UTC) |
2024-07-05T08:27:27.360000Z |
| Discovery magnitude (MPC) |
19.10 V |
| Discovery observatory (MPC) |
I47 · Pierre Auger Observatory, Malargüe |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2022-08-22.0000000 |
| e |
0.64812734 |
| q (au) |
1.817415 |
| a (au) |
5.164980 |
| i (deg) |
39.365304 |
| Ω (om, deg) |
49.200900 |
| ω (w, deg) |
0.816323 |
| M (ma, deg) |
293.601469 |
Magnitude
Scatter + Global Linear
$$
M_a = (15.177 + 2.625\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
15.177 |
| n |
2.625 |
| gf |
1.000 |
| gb |
-0.640 |
| k |
0.800 |
| 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 |
| 2024-07-05 |
2024-10-17 |
+24.0739 |
-6.359 |
| 2024-10-22 |
2025-04-19 |
-0.5771 |
+0.059 |
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 |
13:10:46.68 |
+16:55:14.4 |
HIP 64226 |
14.71 |
| 2026-09-20 12:00 |
13:11:07.24 |
+16:51:57.1 |
HIP 64226 |
19.01 |
| 2026-09-21 00:00 |
13:11:27.82 |
+16:48:40.5 |
HIP 64226 |
24.02 |
| 2026-09-21 12:00 |
13:11:48.43 |
+16:45:24.6 |
HIP 64487 |
27.69 |
| 2026-09-22 00:00 |
13:12:09.05 |
+16:42:09.4 |
HIP 64487 |
22.01 |
| 2026-09-22 12:00 |
13:12:29.68 |
+16:38:54.9 |
HIP 64487 |
16.50 |
| 2026-09-23 00:00 |
13:12:50.34 |
+16:35:41.2 |
HIP 64487 |
11.41 |
| 2026-09-23 12:00 |
13:13:11.01 |
+16:32:28.2 |
HIP 64487 |
7.63 |
| 2026-09-24 00:00 |
13:13:31.70 |
+16:29:15.9 |
HIP 64487 |
7.50 |
| 2026-09-24 12:00 |
13:13:52.40 |
+16:26:04.3 |
HIP 64487 |
11.14 |
| 2026-09-25 00:00 |
13:14:13.12 |
+16:22:53.4 |
HIP 64487 |
16.18 |
| 2026-09-25 12:00 |
13:14:33.85 |
+16:19:43.3 |
HIP 64666 |
13.40 |
| 2026-09-26 00:00 |
13:14:54.60 |
+16:16:33.9 |
HIP 64666 |
7.54 |
| 2026-09-26 12:00 |
13:15:15.36 |
+16:13:25.3 |
HIP 64666 |
1.89 |
| 2026-09-27 00:00 |
13:15:36.13 |
+16:10:17.4 |
HIP 64666 |
4.45 |
| 2026-09-27 12:00 |
13:15:56.92 |
+16:07:10.2 |
HIP 64745 |
4.84 |
| 2026-09-28 00:00 |
13:16:17.71 |
+16:04:03.8 |
HIP 64745 |
2.04 |
| 2026-09-28 12:00 |
13:16:38.52 |
+16:00:58.1 |
HIP 64745 |
7.35 |
| 2026-09-29 00:00 |
13:16:59.34 |
+15:57:53.2 |
HIP 64745 |
13.16 |
| 2026-09-29 12:00 |
13:17:20.17 |
+15:54:49.0 |
HIP 64745 |
19.00 |
| 2026-09-30 00:00 |
13:17:41.00 |
+15:51:45.6 |
HIP 64745 |
24.86 |
| 2026-09-30 12:00 |
13:18:01.85 |
+15:48:42.9 |
HIP 64745 |
30.72 |
| 2026-10-01 00:00 |
13:18:22.70 |
+15:45:41.0 |
HIP 65061 |
28.28 |
| 2026-10-01 12:00 |
13:18:43.57 |
+15:42:39.8 |
HIP 65061 |
22.46 |
| 2026-10-02 00:00 |
13:19:04.44 |
+15:39:39.4 |
HIP 65061 |
16.68 |
| 2026-10-02 12:00 |
13:19:25.31 |
+15:36:39.8 |
HIP 65061 |
10.98 |
| 2026-10-03 00:00 |
13:19:46.20 |
+15:33:40.9 |
HIP 65061 |
5.59 |
| 2026-10-03 12:00 |
13:20:07.09 |
+15:30:42.8 |
HIP 65061 |
3.18 |
| 2026-10-04 00:00 |
13:20:27.98 |
+15:27:45.5 |
HIP 65080 |
1.19 |
| 2026-10-04 12:00 |
13:20:48.88 |
+15:24:49.0 |
HIP 65080 |
6.54 |
| 2026-10-05 00:00 |
13:21:09.78 |
+15:21:53.2 |
HIP 65080 |
12.33 |
| 2026-10-05 12:00 |
13:21:30.69 |
+15:18:58.3 |
HIP 65080 |
18.14 |
| 2026-10-06 00:00 |
13:21:51.60 |
+15:16:04.1 |
HIP 65300 |
16.52 |
| 2026-10-06 12:00 |
13:22:12.51 |
+15:13:10.7 |
HIP 65300 |
11.59 |
| 2026-10-07 00:00 |
13:22:33.42 |
+15:10:18.2 |
HIP 65300 |
7.96 |
| 2026-10-07 12:00 |
13:22:54.33 |
+15:07:26.4 |
HIP 65300 |
7.71 |
| 2026-10-08 00:00 |
13:23:15.24 |
+15:04:35.4 |
HIP 65300 |
11.08 |
| 2026-10-08 12:00 |
13:23:36.16 |
+15:01:45.3 |
HIP 65300 |
15.90 |
| 2026-10-09 00:00 |
13:23:57.07 |
+14:58:56.0 |
HIP 65427 |
12.24 |
| 2026-10-09 12:00 |
13:24:17.98 |
+14:56:07.5 |
HIP 65427 |
6.59 |
| 2026-10-10 00:00 |
13:24:38.88 |
+14:53:19.8 |
HIP 65427 |
1.97 |
| 2026-10-10 12:00 |
13:24:59.78 |
+14:50:32.9 |
HIP 65427 |
5.57 |
| 2026-10-11 00:00 |
13:25:20.68 |
+14:47:46.9 |
HIP 65427 |
11.16 |