| Parameter |
Value |
| Designation |
C/2007 Q3 (Siding Spring) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2009-10-07T06:29:51.262080Z |
| Orbit solution date (soln_date, UTC) |
2025-07-07T14:12:19Z |
| Obs used |
1341 |
| NEO |
- |
| M1 |
8.800 |
| K1 |
5.500 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2009-08-20.0000000 |
| e |
1.00023766 |
| q (au) |
2.251688 |
| a (au) |
-9474.438449 |
| i (deg) |
65.650492 |
| Ω (om, deg) |
149.412684 |
| ω (w, deg) |
2.092860 |
| M (ma, deg) |
-0.000052 |
Magnitude
Scatter + Global Linear
$$
M_a = (7.715 + 2.602\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
7.715 |
| n |
2.602 |
| gf |
1.000 |
| gb |
-0.644 |
| k |
0.990 |
| 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 |
| 2007-08-25 |
2009-03-15 |
+1.0261 |
-1.390 |
| 2009-03-15 |
2009-05-10 |
+22.4756 |
-12.601 |
| 2009-05-10 |
2009-10-03 |
-25.2024 |
+8.557 |
| 2009-10-10 |
2010-02-28 |
+8.7989 |
-3.980 |
| 2010-02-28 |
2010-06-04 |
+2.9606 |
-2.284 |
| 2010-06-04 |
2010-10-30 |
+3.8990 |
-2.293 |
| 2010-10-30 |
2011-09-25 |
+6.2804 |
-3.627 |
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 |
20:55:37.41 |
+08:39:13.2 |
HIP 103365 |
24.68 |
| 2026-05-12 12:00 |
20:55:37.02 |
+08:39:31.0 |
HIP 103365 |
24.48 |
| 2026-05-13 00:00 |
20:55:36.60 |
+08:39:48.6 |
HIP 103365 |
24.29 |
| 2026-05-13 12:00 |
20:55:36.16 |
+08:40:06.0 |
HIP 103365 |
24.10 |
| 2026-05-14 00:00 |
20:55:35.68 |
+08:40:23.4 |
HIP 103365 |
23.92 |
| 2026-05-14 12:00 |
20:55:35.18 |
+08:40:40.6 |
HIP 103365 |
23.75 |
| 2026-05-15 00:00 |
20:55:34.65 |
+08:40:57.6 |
HIP 103365 |
23.59 |
| 2026-05-15 12:00 |
20:55:34.10 |
+08:41:14.6 |
HIP 103365 |
23.44 |
| 2026-05-16 00:00 |
20:55:33.51 |
+08:41:31.3 |
HIP 103365 |
23.29 |
| 2026-05-16 12:00 |
20:55:32.90 |
+08:41:48.0 |
HIP 103365 |
23.16 |
| 2026-05-17 00:00 |
20:55:32.26 |
+08:42:04.5 |
HIP 103365 |
23.03 |
| 2026-05-17 12:00 |
20:55:31.59 |
+08:42:20.8 |
HIP 103365 |
22.92 |
| 2026-05-18 00:00 |
20:55:30.89 |
+08:42:37.0 |
HIP 103365 |
22.82 |
| 2026-05-18 12:00 |
20:55:30.17 |
+08:42:53.0 |
HIP 103365 |
22.72 |
| 2026-05-19 00:00 |
20:55:29.42 |
+08:43:08.9 |
HIP 103365 |
22.64 |
| 2026-05-19 12:00 |
20:55:28.64 |
+08:43:24.6 |
HIP 103365 |
22.56 |
| 2026-05-20 00:00 |
20:55:27.83 |
+08:43:40.2 |
HIP 103365 |
22.50 |
| 2026-05-20 12:00 |
20:55:27.00 |
+08:43:55.6 |
HIP 103365 |
22.45 |
| 2026-05-21 00:00 |
20:55:26.14 |
+08:44:10.9 |
HIP 103365 |
22.41 |
| 2026-05-21 12:00 |
20:55:25.25 |
+08:44:26.0 |
HIP 103365 |
22.38 |
| 2026-05-22 00:00 |
20:55:24.34 |
+08:44:41.0 |
HIP 103365 |
22.37 |
| 2026-05-22 12:00 |
20:55:23.40 |
+08:44:55.8 |
HIP 103365 |
22.36 |
| 2026-05-23 00:00 |
20:55:22.43 |
+08:45:10.4 |
HIP 103365 |
22.37 |
| 2026-05-23 12:00 |
20:55:21.43 |
+08:45:24.8 |
HIP 103365 |
22.39 |
| 2026-05-24 00:00 |
20:55:20.41 |
+08:45:39.1 |
HIP 103365 |
22.42 |
| 2026-05-24 12:00 |
20:55:19.36 |
+08:45:53.3 |
HIP 103365 |
22.46 |
| 2026-05-25 00:00 |
20:55:18.29 |
+08:46:07.2 |
HIP 103365 |
22.52 |
| 2026-05-25 12:00 |
20:55:17.19 |
+08:46:21.0 |
HIP 103365 |
22.58 |
| 2026-05-26 00:00 |
20:55:16.06 |
+08:46:34.7 |
HIP 103365 |
22.66 |
| 2026-05-26 12:00 |
20:55:14.91 |
+08:46:48.1 |
HIP 103365 |
22.76 |
| 2026-05-27 00:00 |
20:55:13.73 |
+08:47:01.4 |
HIP 103365 |
22.86 |
| 2026-05-27 12:00 |
20:55:12.52 |
+08:47:14.5 |
HIP 103365 |
22.98 |
| 2026-05-28 00:00 |
20:55:11.29 |
+08:47:27.5 |
HIP 103365 |
23.10 |
| 2026-05-28 12:00 |
20:55:10.03 |
+08:47:40.3 |
HIP 103365 |
23.24 |
| 2026-05-29 00:00 |
20:55:08.75 |
+08:47:52.8 |
HIP 103365 |
23.40 |
| 2026-05-29 12:00 |
20:55:07.44 |
+08:48:05.3 |
HIP 103365 |
23.56 |
| 2026-05-30 00:00 |
20:55:06.11 |
+08:48:17.5 |
HIP 103365 |
23.74 |
| 2026-05-30 12:00 |
20:55:04.75 |
+08:48:29.6 |
HIP 103365 |
23.93 |
| 2026-05-31 00:00 |
20:55:03.36 |
+08:48:41.5 |
HIP 103365 |
24.13 |
| 2026-05-31 12:00 |
20:55:01.96 |
+08:48:53.2 |
HIP 103365 |
24.34 |
| 2026-06-01 00:00 |
20:55:00.52 |
+08:49:04.7 |
HIP 103365 |
24.56 |
| 2026-06-01 12:00 |
20:54:59.06 |
+08:49:16.0 |
HIP 103365 |
24.80 |
| 2026-06-02 00:00 |
20:54:57.58 |
+08:49:27.2 |
HIP 103365 |
25.05 |