| Parameter |
Value |
| Designation |
C/2007 K3 (Siding Spring) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2008-04-21T17:04:30.377280Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:31:08Z |
| Obs used |
94 |
| NEO |
- |
| M1 |
13.300 |
| K1 |
13.000 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2008-02-09.0000000 |
| e |
1.00124061 |
| q (au) |
2.050740 |
| a (au) |
-1653.004343 |
| i (deg) |
16.300560 |
| Ω (om, deg) |
263.252666 |
| ω (w, deg) |
23.593153 |
| M (ma, deg) |
-0.001066 |
Magnitude
Scatter + Global Linear
$$
M_a = (15.558 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
15.558 |
| n |
2.000 |
| gf |
0.992 |
| gb |
-0.528 |
| 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 |
| 2007-04-18 |
2007-07-18 |
-5.6572 |
+2.028 |
| 2008-06-09 |
2008-09-30 |
+25.5806 |
-9.587 |
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 |
05:11:18.83 |
+24:00:05.1 |
HIP 24283 |
20.04 |
| 2026-05-12 12:00 |
05:11:22.01 |
+24:00:07.7 |
HIP 24283 |
19.37 |
| 2026-05-13 00:00 |
05:11:25.21 |
+24:00:10.2 |
HIP 24283 |
18.70 |
| 2026-05-13 12:00 |
05:11:28.42 |
+24:00:12.8 |
HIP 24283 |
18.03 |
| 2026-05-14 00:00 |
05:11:31.65 |
+24:00:15.4 |
HIP 24283 |
17.36 |
| 2026-05-14 12:00 |
05:11:34.88 |
+24:00:18.0 |
HIP 24283 |
16.70 |
| 2026-05-15 00:00 |
05:11:38.13 |
+24:00:20.7 |
HIP 24283 |
16.04 |
| 2026-05-15 12:00 |
05:11:41.39 |
+24:00:23.3 |
HIP 24283 |
15.39 |
| 2026-05-16 00:00 |
05:11:44.66 |
+24:00:25.9 |
HIP 24283 |
14.74 |
| 2026-05-16 12:00 |
05:11:47.94 |
+24:00:28.6 |
HIP 24283 |
14.10 |
| 2026-05-17 00:00 |
05:11:51.23 |
+24:00:31.3 |
HIP 24283 |
13.47 |
| 2026-05-17 12:00 |
05:11:54.53 |
+24:00:34.0 |
HIP 24283 |
12.85 |
| 2026-05-18 00:00 |
05:11:57.84 |
+24:00:36.7 |
HIP 24283 |
12.25 |
| 2026-05-18 12:00 |
05:12:01.17 |
+24:00:39.5 |
HIP 24283 |
11.66 |
| 2026-05-19 00:00 |
05:12:04.50 |
+24:00:42.2 |
HIP 24283 |
11.09 |
| 2026-05-19 12:00 |
05:12:07.84 |
+24:00:44.9 |
HIP 24283 |
10.55 |
| 2026-05-20 00:00 |
05:12:11.19 |
+24:00:47.7 |
HIP 24283 |
10.03 |
| 2026-05-20 12:00 |
05:12:14.55 |
+24:00:50.5 |
HIP 24283 |
9.55 |
| 2026-05-21 00:00 |
05:12:17.92 |
+24:00:53.3 |
HIP 24283 |
9.10 |
| 2026-05-21 12:00 |
05:12:21.30 |
+24:00:56.1 |
HIP 24283 |
8.70 |
| 2026-05-22 00:00 |
05:12:24.68 |
+24:00:58.9 |
HIP 24283 |
8.35 |
| 2026-05-22 12:00 |
05:12:28.08 |
+24:01:01.7 |
HIP 24283 |
8.05 |
| 2026-05-23 00:00 |
05:12:31.48 |
+24:01:04.6 |
HIP 24283 |
7.83 |
| 2026-05-23 12:00 |
05:12:34.89 |
+24:01:07.4 |
HIP 24283 |
7.68 |
| 2026-05-24 00:00 |
05:12:38.30 |
+24:01:10.3 |
HIP 24283 |
7.60 |
| 2026-05-24 12:00 |
05:12:41.73 |
+24:01:13.2 |
HIP 24283 |
7.60 |
| 2026-05-25 00:00 |
05:12:45.16 |
+24:01:16.0 |
HIP 24283 |
7.69 |
| 2026-05-25 12:00 |
05:12:48.60 |
+24:01:18.9 |
HIP 24283 |
7.85 |
| 2026-05-26 00:00 |
05:12:52.04 |
+24:01:21.8 |
HIP 24283 |
8.09 |
| 2026-05-26 12:00 |
05:12:55.49 |
+24:01:24.7 |
HIP 24283 |
8.40 |
| 2026-05-27 00:00 |
05:12:58.95 |
+24:01:27.7 |
HIP 24283 |
8.76 |
| 2026-05-27 12:00 |
05:13:02.41 |
+24:01:30.6 |
HIP 24283 |
9.19 |
| 2026-05-28 00:00 |
05:13:05.88 |
+24:01:33.5 |
HIP 24283 |
9.66 |
| 2026-05-28 12:00 |
05:13:09.36 |
+24:01:36.5 |
HIP 24283 |
10.17 |
| 2026-05-29 00:00 |
05:13:12.84 |
+24:01:39.4 |
HIP 24283 |
10.71 |
| 2026-05-29 12:00 |
05:13:16.32 |
+24:01:42.4 |
HIP 24283 |
11.29 |
| 2026-05-30 00:00 |
05:13:19.82 |
+24:01:45.3 |
HIP 24283 |
11.89 |
| 2026-05-30 12:00 |
05:13:23.31 |
+24:01:48.3 |
HIP 24283 |
12.52 |
| 2026-05-31 00:00 |
05:13:26.81 |
+24:01:51.3 |
HIP 24283 |
13.17 |
| 2026-05-31 12:00 |
05:13:30.31 |
+24:01:54.3 |
HIP 24283 |
13.83 |
| 2026-06-01 00:00 |
05:13:33.82 |
+24:01:57.3 |
HIP 24283 |
14.51 |
| 2026-06-01 12:00 |
05:13:37.34 |
+24:02:00.3 |
HIP 24283 |
15.20 |
| 2026-06-02 00:00 |
05:13:40.85 |
+24:02:03.3 |
HIP 24283 |
15.90 |