| Parameter |
Value |
| Designation |
205P/Giacobini |
| Type |
P |
| Perihelion (tp_cal, UTC) |
2015-05-14T00:01:56.562240Z |
| Orbit solution date (soln_date, UTC) |
2023-07-20T15:02:32Z |
| Obs used |
564 |
| NEO |
- |
| M1 |
14.000 |
| K1 |
9.750 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2014-02-19.0000000 |
| e |
0.56693106 |
| q (au) |
1.536180 |
| a (au) |
3.547195 |
| i (deg) |
15.287237 |
| Ω (om, deg) |
179.624626 |
| ω (w, deg) |
154.256561 |
| M (ma, deg) |
293.759426 |
Magnitude
Scatter + Global Linear
$$
M_a = (14.018 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
14.018 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-0.635 |
| 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 |
| 2021-05-14 |
2021-11-14 |
+11.4692 |
-2.714 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-09-25 00:00 |
12:03:38.09 |
-00:07:07.3 |
HIP 58908 |
18.62 |
| 2026-09-25 12:00 |
12:04:02.92 |
-00:09:21.0 |
HIP 58908 |
12.02 |
| 2026-09-26 00:00 |
12:04:27.76 |
-00:11:34.7 |
HIP 58908 |
5.43 |
| 2026-09-26 12:00 |
12:04:52.62 |
-00:13:48.4 |
HIP 58908 |
1.20 |
| 2026-09-27 00:00 |
12:05:17.49 |
-00:16:02.2 |
HIP 58908 |
7.79 |
| 2026-09-27 12:00 |
12:05:42.36 |
-00:18:16.0 |
HIP 58908 |
14.39 |
| 2026-09-28 00:00 |
12:06:07.25 |
-00:20:29.9 |
HIP 58908 |
21.00 |
| 2026-09-28 12:00 |
12:06:32.15 |
-00:22:43.8 |
HIP 59102 |
17.99 |
| 2026-09-29 00:00 |
12:06:57.05 |
-00:24:57.6 |
HIP 59102 |
13.33 |
| 2026-09-29 12:00 |
12:07:21.97 |
-00:27:11.5 |
HIP 59102 |
10.93 |
| 2026-09-30 00:00 |
12:07:46.89 |
-00:29:25.5 |
HIP 59198 |
8.98 |
| 2026-09-30 12:00 |
12:08:11.82 |
-00:31:39.4 |
HIP 59198 |
3.85 |
| 2026-10-01 00:00 |
12:08:36.76 |
-00:33:53.3 |
HIP 59198 |
6.06 |
| 2026-10-01 12:00 |
12:09:01.71 |
-00:36:07.3 |
HIP 59208 |
10.96 |
| 2026-10-02 00:00 |
12:09:26.66 |
-00:38:21.2 |
HIP 59208 |
16.91 |
| 2026-10-02 12:00 |
12:09:51.62 |
-00:40:35.1 |
HIP 59208 |
23.23 |
| 2026-10-03 00:00 |
12:10:16.58 |
-00:42:49.0 |
HIP 59476 |
28.43 |
| 2026-10-03 12:00 |
12:10:41.55 |
-00:45:02.9 |
HIP 59476 |
24.55 |
| 2026-10-04 00:00 |
12:11:06.52 |
-00:47:16.7 |
HIP 59476 |
22.03 |
| 2026-10-04 12:00 |
12:11:31.50 |
-00:49:30.5 |
HIP 59491 |
18.03 |
| 2026-10-05 00:00 |
12:11:56.48 |
-00:51:44.3 |
HIP 59491 |
14.19 |
| 2026-10-05 12:00 |
12:12:21.46 |
-00:53:58.0 |
HIP 59491 |
12.87 |
| 2026-10-06 00:00 |
12:12:46.44 |
-00:56:11.7 |
HIP 59491 |
14.76 |
| 2026-10-06 12:00 |
12:13:11.43 |
-00:58:25.4 |
HIP 59518 |
16.90 |
| 2026-10-07 00:00 |
12:13:36.41 |
-01:00:38.9 |
HIP 59621 |
13.57 |
| 2026-10-07 12:00 |
12:14:01.40 |
-01:02:52.4 |
HIP 59621 |
12.97 |
| 2026-10-08 00:00 |
12:14:26.38 |
-01:05:05.9 |
HIP 59621 |
15.50 |
| 2026-10-08 12:00 |
12:14:51.36 |
-01:07:19.2 |
HIP 59732 |
12.46 |
| 2026-10-09 00:00 |
12:15:16.35 |
-01:09:32.5 |
HIP 59732 |
10.85 |
| 2026-10-09 12:00 |
12:15:41.33 |
-01:11:45.7 |
HIP 59732 |
12.95 |
| 2026-10-10 00:00 |
12:16:06.30 |
-01:13:58.8 |
HIP 59732 |
17.49 |
| 2026-10-10 12:00 |
12:16:31.27 |
-01:16:11.8 |
HIP 59732 |
23.05 |
| 2026-10-11 00:00 |
12:16:56.24 |
-01:18:24.7 |
HIP 59732 |
29.07 |
| 2026-10-11 12:00 |
12:17:21.20 |
-01:20:37.4 |
HIP 59979 |
30.63 |
| 2026-10-12 00:00 |
12:17:46.16 |
-01:22:50.1 |
HIP 59979 |
26.92 |
| 2026-10-12 12:00 |
12:18:11.11 |
-01:25:02.6 |
HIP 59979 |
24.48 |
| 2026-10-13 00:00 |
12:18:36.05 |
-01:27:15.0 |
HIP 59979 |
23.68 |
| 2026-10-13 12:00 |
12:19:00.98 |
-01:29:27.3 |
HIP 59979 |
24.70 |
| 2026-10-14 00:00 |
12:19:25.91 |
-01:31:39.4 |
HIP 59979 |
27.32 |
| 2026-10-14 12:00 |
12:19:50.83 |
-01:33:51.3 |
HIP 60077 |
30.54 |
| 2026-10-15 00:00 |
12:20:15.73 |
-01:36:03.1 |
HIP 60077 |
31.40 |
| 2026-10-15 12:00 |
12:20:40.63 |
-01:38:14.8 |
HIP 60077 |
33.55 |
| 2026-10-16 00:00 |
12:21:05.52 |
-01:40:26.3 |
HIP 60410 |
34.58 |