| 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) |
| 2026-03-26 00:00 |
13:07:07.62 |
+36:42:20.7 |
HIP 64083 |
18.94 |
| 2026-03-26 12:00 |
13:06:40.92 |
+36:43:04.3 |
HIP 64083 |
21.66 |
| 2026-03-27 00:00 |
13:06:14.20 |
+36:43:45.0 |
HIP 64083 |
25.29 |
| 2026-03-27 12:00 |
13:05:47.45 |
+36:44:22.8 |
HIP 63882 |
24.08 |
| 2026-03-28 00:00 |
13:05:20.68 |
+36:44:57.6 |
HIP 63817 |
22.10 |
| 2026-03-28 12:00 |
13:04:53.90 |
+36:45:29.6 |
HIP 63817 |
20.54 |
| 2026-03-29 00:00 |
13:04:27.11 |
+36:45:58.6 |
HIP 63701 |
16.77 |
| 2026-03-29 12:00 |
13:04:00.31 |
+36:46:24.6 |
HIP 63701 |
12.88 |
| 2026-03-30 00:00 |
13:03:33.51 |
+36:46:47.7 |
HIP 63701 |
10.37 |
| 2026-03-30 12:00 |
13:03:06.72 |
+36:47:07.9 |
HIP 63701 |
10.30 |
| 2026-03-31 00:00 |
13:02:39.93 |
+36:47:25.1 |
HIP 63701 |
12.72 |
| 2026-03-31 12:00 |
13:02:13.16 |
+36:47:39.4 |
HIP 63701 |
16.55 |
| 2026-04-01 00:00 |
13:01:46.40 |
+36:47:50.7 |
HIP 63701 |
21.04 |
| 2026-04-01 12:00 |
13:01:19.67 |
+36:47:59.0 |
HIP 63701 |
25.84 |
| 2026-04-02 00:00 |
13:00:52.96 |
+36:48:04.4 |
HIP 63701 |
30.80 |
| 2026-04-02 12:00 |
13:00:26.28 |
+36:48:06.8 |
HIP 63265 |
31.49 |
| 2026-04-03 00:00 |
12:59:59.64 |
+36:48:06.2 |
HIP 63265 |
26.21 |
| 2026-04-03 12:00 |
12:59:33.03 |
+36:48:02.7 |
HIP 63265 |
20.96 |
| 2026-04-04 00:00 |
12:59:06.47 |
+36:47:56.2 |
HIP 63265 |
15.76 |
| 2026-04-04 12:00 |
12:58:39.96 |
+36:47:46.8 |
HIP 63265 |
10.67 |
| 2026-04-05 00:00 |
12:58:13.50 |
+36:47:34.4 |
HIP 63265 |
5.95 |
| 2026-04-05 12:00 |
12:57:47.09 |
+36:47:19.0 |
HIP 63265 |
3.58 |
| 2026-04-06 00:00 |
12:57:20.74 |
+36:47:00.7 |
HIP 63265 |
6.77 |
| 2026-04-06 12:00 |
12:56:54.46 |
+36:46:39.4 |
HIP 63181 |
6.12 |
| 2026-04-07 00:00 |
12:56:28.25 |
+36:46:15.2 |
HIP 63181 |
6.11 |
| 2026-04-07 12:00 |
12:56:02.11 |
+36:45:48.0 |
HIP 63181 |
9.64 |
| 2026-04-08 00:00 |
12:55:36.05 |
+36:45:17.9 |
HIP 63004 |
13.15 |
| 2026-04-08 12:00 |
12:55:10.07 |
+36:44:44.9 |
HIP 63004 |
8.39 |
| 2026-04-09 00:00 |
12:54:44.18 |
+36:44:08.9 |
HIP 63004 |
4.72 |
| 2026-04-09 12:00 |
12:54:18.37 |
+36:43:30.0 |
HIP 63004 |
5.31 |
| 2026-04-10 00:00 |
12:53:52.66 |
+36:42:48.2 |
HIP 63004 |
9.37 |
| 2026-04-10 12:00 |
12:53:27.05 |
+36:42:03.5 |
HIP 63004 |
14.18 |
| 2026-04-11 00:00 |
12:53:01.54 |
+36:41:15.9 |
HIP 63004 |
19.16 |
| 2026-04-11 12:00 |
12:52:36.13 |
+36:40:25.4 |
HIP 63004 |
24.20 |
| 2026-04-12 00:00 |
12:52:10.83 |
+36:39:31.9 |
HIP 62648 |
26.85 |
| 2026-04-12 12:00 |
12:51:45.65 |
+36:38:35.7 |
HIP 62648 |
23.08 |
| 2026-04-13 00:00 |
12:51:20.58 |
+36:37:36.5 |
HIP 62648 |
19.96 |
| 2026-04-13 12:00 |
12:50:55.64 |
+36:36:34.5 |
HIP 62648 |
17.85 |
| 2026-04-14 00:00 |
12:50:30.82 |
+36:35:29.7 |
HIP 62648 |
17.11 |
| 2026-04-14 12:00 |
12:50:06.12 |
+36:34:22.0 |
HIP 62648 |
17.89 |
| 2026-04-15 00:00 |
12:49:41.56 |
+36:33:11.5 |
HIP 62504 |
19.21 |
| 2026-04-15 12:00 |
12:49:17.14 |
+36:31:58.1 |
HIP 62504 |
14.88 |
| 2026-04-16 00:00 |
12:48:52.85 |
+36:30:42.0 |
HIP 62504 |
11.17 |