| 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 |
+11.4698 |
-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) |
| 2026-03-26 00:00 |
11:07:02.39 |
+02:18:09.0 |
HIP 54281 |
12.99 |
| 2026-03-26 12:00 |
11:06:46.21 |
+02:20:31.4 |
HIP 54281 |
8.32 |
| 2026-03-27 00:00 |
11:06:30.11 |
+02:22:53.4 |
HIP 54281 |
3.72 |
| 2026-03-27 12:00 |
11:06:14.11 |
+02:25:14.9 |
HIP 54281 |
1.40 |
| 2026-03-28 00:00 |
11:05:58.19 |
+02:27:36.1 |
HIP 54281 |
5.74 |
| 2026-03-28 12:00 |
11:05:42.37 |
+02:29:56.8 |
HIP 54220 |
8.22 |
| 2026-03-29 00:00 |
11:05:26.64 |
+02:32:17.0 |
HIP 54220 |
10.83 |
| 2026-03-29 12:00 |
11:05:11.01 |
+02:34:36.8 |
HIP 54220 |
14.42 |
| 2026-03-30 00:00 |
11:04:55.48 |
+02:36:56.0 |
HIP 54220 |
18.42 |
| 2026-03-30 12:00 |
11:04:40.05 |
+02:39:14.8 |
HIP 54220 |
22.60 |
| 2026-03-31 00:00 |
11:04:24.73 |
+02:41:33.0 |
HIP 54220 |
26.85 |
| 2026-03-31 12:00 |
11:04:09.51 |
+02:43:50.7 |
HIP 54117 |
26.22 |
| 2026-04-01 00:00 |
11:03:54.40 |
+02:46:07.8 |
HIP 54117 |
24.81 |
| 2026-04-01 12:00 |
11:03:39.40 |
+02:48:24.3 |
HIP 54117 |
24.14 |
| 2026-04-02 00:00 |
11:03:24.51 |
+02:50:40.2 |
HIP 54117 |
24.24 |
| 2026-04-02 12:00 |
11:03:09.74 |
+02:52:55.5 |
HIP 54117 |
25.09 |
| 2026-04-03 00:00 |
11:02:55.08 |
+02:55:10.2 |
HIP 54117 |
26.60 |
| 2026-04-03 12:00 |
11:02:40.54 |
+02:57:24.3 |
HIP 54117 |
28.67 |
| 2026-04-04 00:00 |
11:02:26.12 |
+02:59:37.7 |
HIP 53804 |
28.43 |
| 2026-04-04 12:00 |
11:02:11.82 |
+03:01:50.4 |
HIP 53804 |
25.09 |
| 2026-04-05 00:00 |
11:01:57.65 |
+03:04:02.5 |
HIP 53804 |
22.08 |
| 2026-04-05 12:00 |
11:01:43.60 |
+03:06:13.9 |
HIP 53804 |
19.52 |
| 2026-04-06 00:00 |
11:01:29.68 |
+03:08:24.5 |
HIP 53804 |
17.59 |
| 2026-04-06 12:00 |
11:01:15.89 |
+03:10:34.4 |
HIP 53804 |
16.49 |
| 2026-04-07 00:00 |
11:01:02.23 |
+03:12:43.6 |
HIP 53804 |
16.36 |
| 2026-04-07 12:00 |
11:00:48.71 |
+03:14:52.0 |
HIP 53804 |
17.20 |
| 2026-04-08 00:00 |
11:00:35.32 |
+03:16:59.7 |
HIP 53804 |
18.86 |
| 2026-04-08 12:00 |
11:00:22.07 |
+03:19:06.5 |
HIP 53807 |
18.17 |
| 2026-04-09 00:00 |
11:00:08.95 |
+03:21:12.6 |
HIP 53807 |
17.00 |
| 2026-04-09 12:00 |
10:59:55.98 |
+03:23:17.8 |
HIP 53807 |
16.66 |
| 2026-04-10 00:00 |
10:59:43.15 |
+03:25:22.3 |
HIP 53807 |
17.18 |
| 2026-04-10 12:00 |
10:59:30.46 |
+03:27:25.9 |
HIP 53807 |
18.47 |
| 2026-04-11 00:00 |
10:59:17.92 |
+03:29:28.6 |
HIP 53807 |
20.36 |
| 2026-04-11 12:00 |
10:59:05.52 |
+03:31:30.5 |
HIP 53807 |
22.67 |
| 2026-04-12 00:00 |
10:58:53.28 |
+03:33:31.5 |
HIP 53807 |
25.29 |
| 2026-04-12 12:00 |
10:58:41.18 |
+03:35:31.6 |
HIP 53807 |
28.10 |
| 2026-04-13 00:00 |
10:58:29.24 |
+03:37:30.9 |
HIP 53512 |
26.96 |
| 2026-04-13 12:00 |
10:58:17.45 |
+03:39:29.2 |
HIP 53512 |
25.19 |
| 2026-04-14 00:00 |
10:58:05.81 |
+03:41:26.5 |
HIP 53512 |
23.84 |
| 2026-04-14 12:00 |
10:57:54.34 |
+03:43:23.0 |
HIP 53512 |
22.97 |
| 2026-04-15 00:00 |
10:57:43.02 |
+03:45:18.5 |
HIP 53512 |
22.61 |
| 2026-04-15 12:00 |
10:57:31.86 |
+03:47:13.0 |
HIP 53512 |
22.77 |
| 2026-04-16 00:00 |
10:57:20.86 |
+03:49:06.6 |
HIP 53512 |
23.42 |