| Parameter |
Value |
| Designation |
C/2015 F4 (Jacques) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2015-08-10T20:42:31.959360Z |
| Orbit solution date (soln_date, UTC) |
2022-06-07T21:44:08Z |
| Obs used |
2837 |
| NEO |
- |
| M1 |
11.300 |
| K1 |
9.500 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2015-08-22.0000000 |
| e |
0.98587145 |
| q (au) |
1.643925 |
| a (au) |
116.354874 |
| i (deg) |
48.704931 |
| Ω (om, deg) |
285.958058 |
| ω (w, deg) |
36.346505 |
| M (ma, deg) |
0.008746 |
Magnitude
Scatter + Global Linear
$$
M_a = (13.073 + 3.298\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
13.073 |
| n |
3.298 |
| gf |
1.000 |
| gb |
-0.617 |
| 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 |
| 2015-03-27 |
2015-08-10 |
-1.7959 |
+0.136 |
| 2015-08-10 |
2015-10-17 |
+11.1365 |
-2.891 |
| 2015-10-17 |
2016-11-06 |
-3.6108 |
+1.480 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-09-20 00:00 |
07:37:46.32 |
+15:02:03.0 |
HIP 37066 |
13.94 |
| 2026-09-20 12:00 |
07:37:48.37 |
+15:01:47.5 |
HIP 37066 |
14.18 |
| 2026-09-21 00:00 |
07:37:50.40 |
+15:01:32.1 |
HIP 37066 |
14.43 |
| 2026-09-21 12:00 |
07:37:52.39 |
+15:01:16.7 |
HIP 37066 |
14.68 |
| 2026-09-22 00:00 |
07:37:54.34 |
+15:01:01.3 |
HIP 37066 |
14.95 |
| 2026-09-22 12:00 |
07:37:56.26 |
+15:00:46.0 |
HIP 37066 |
15.22 |
| 2026-09-23 00:00 |
07:37:58.14 |
+15:00:30.8 |
HIP 37066 |
15.50 |
| 2026-09-23 12:00 |
07:38:00.00 |
+15:00:15.6 |
HIP 37066 |
15.79 |
| 2026-09-24 00:00 |
07:38:01.80 |
+15:00:00.5 |
HIP 37066 |
16.08 |
| 2026-09-24 12:00 |
07:38:03.58 |
+14:59:45.4 |
HIP 37066 |
16.37 |
| 2026-09-25 00:00 |
07:38:05.32 |
+14:59:30.4 |
HIP 37066 |
16.66 |
| 2026-09-25 12:00 |
07:38:07.02 |
+14:59:15.4 |
HIP 37066 |
16.96 |
| 2026-09-26 00:00 |
07:38:08.69 |
+14:59:00.5 |
HIP 37066 |
17.25 |
| 2026-09-26 12:00 |
07:38:10.33 |
+14:58:45.7 |
HIP 37066 |
17.55 |
| 2026-09-27 00:00 |
07:38:11.92 |
+14:58:30.9 |
HIP 37066 |
17.84 |
| 2026-09-27 12:00 |
07:38:13.48 |
+14:58:16.2 |
HIP 37066 |
18.14 |
| 2026-09-28 00:00 |
07:38:15.00 |
+14:58:01.5 |
HIP 37066 |
18.43 |
| 2026-09-28 12:00 |
07:38:16.49 |
+14:57:46.9 |
HIP 37066 |
18.71 |
| 2026-09-29 00:00 |
07:38:17.94 |
+14:57:32.4 |
HIP 37066 |
19.00 |
| 2026-09-29 12:00 |
07:38:19.35 |
+14:57:17.9 |
HIP 37066 |
19.28 |
| 2026-09-30 00:00 |
07:38:20.73 |
+14:57:03.5 |
HIP 37066 |
19.56 |
| 2026-09-30 12:00 |
07:38:22.06 |
+14:56:49.1 |
HIP 37066 |
19.83 |
| 2026-10-01 00:00 |
07:38:23.37 |
+14:56:34.9 |
HIP 37066 |
20.10 |
| 2026-10-01 12:00 |
07:38:24.63 |
+14:56:20.7 |
HIP 37066 |
20.37 |
| 2026-10-02 00:00 |
07:38:25.85 |
+14:56:06.5 |
HIP 37066 |
20.63 |
| 2026-10-02 12:00 |
07:38:27.04 |
+14:55:52.4 |
HIP 37066 |
20.88 |
| 2026-10-03 00:00 |
07:38:28.19 |
+14:55:38.4 |
HIP 37066 |
21.13 |
| 2026-10-03 12:00 |
07:38:29.30 |
+14:55:24.5 |
HIP 37066 |
21.38 |
| 2026-10-04 00:00 |
07:38:30.37 |
+14:55:10.6 |
HIP 37066 |
21.61 |
| 2026-10-04 12:00 |
07:38:31.41 |
+14:54:56.8 |
HIP 37066 |
21.85 |
| 2026-10-05 00:00 |
07:38:32.40 |
+14:54:43.1 |
HIP 37066 |
22.07 |
| 2026-10-05 12:00 |
07:38:33.36 |
+14:54:29.5 |
HIP 37066 |
22.29 |
| 2026-10-06 00:00 |
07:38:34.28 |
+14:54:15.9 |
HIP 37066 |
22.50 |
| 2026-10-06 12:00 |
07:38:35.16 |
+14:54:02.4 |
HIP 37066 |
22.70 |
| 2026-10-07 00:00 |
07:38:36.00 |
+14:53:49.0 |
HIP 37066 |
22.90 |
| 2026-10-07 12:00 |
07:38:36.80 |
+14:53:35.6 |
HIP 37066 |
23.09 |
| 2026-10-08 00:00 |
07:38:37.56 |
+14:53:22.4 |
HIP 37066 |
23.28 |
| 2026-10-08 12:00 |
07:38:38.29 |
+14:53:09.2 |
HIP 37066 |
23.45 |
| 2026-10-09 00:00 |
07:38:38.97 |
+14:52:56.1 |
HIP 37066 |
23.62 |
| 2026-10-09 12:00 |
07:38:39.61 |
+14:52:43.1 |
HIP 37066 |
23.78 |
| 2026-10-10 00:00 |
07:38:40.22 |
+14:52:30.1 |
HIP 37066 |
23.93 |
| 2026-10-10 12:00 |
07:38:40.78 |
+14:52:17.3 |
HIP 37066 |
24.08 |
| 2026-10-11 00:00 |
07:38:41.31 |
+14:52:04.5 |
HIP 37066 |
24.21 |