| Parameter |
Value |
| Designation |
C/1999 U1 (Ferris) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
1998-09-03T07:06:12.075840Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:30:02Z |
| Obs used |
208 |
| NEO |
- |
| M1 |
10.800 |
| K1 |
4.500 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
1999-11-14.0000000 |
| e |
1.00340647 |
| q (au) |
4.139123 |
| a (au) |
-1215.077481 |
| i (deg) |
105.745305 |
| Ω (om, deg) |
58.256738 |
| ω (w, deg) |
291.117936 |
| M (ma, deg) |
0.010162 |
Magnitude
Scatter + Global Linear
$$
M_a = (10.325 + 2.084\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
10.325 |
| n |
2.084 |
| gf |
0.999 |
| gb |
-0.920 |
| k |
0.999 |
| 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
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-09-20 00:00 |
20:59:29.28 |
+62:28:08.4 |
HIP 103385 |
20.87 |
| 2026-09-20 12:00 |
20:59:25.39 |
+62:27:40.2 |
HIP 103385 |
20.68 |
| 2026-09-21 00:00 |
20:59:21.53 |
+62:27:11.8 |
HIP 103385 |
20.50 |
| 2026-09-21 12:00 |
20:59:17.71 |
+62:26:43.3 |
HIP 103385 |
20.35 |
| 2026-09-22 00:00 |
20:59:13.92 |
+62:26:14.5 |
HIP 103385 |
20.22 |
| 2026-09-22 12:00 |
20:59:10.17 |
+62:25:45.5 |
HIP 103385 |
20.12 |
| 2026-09-23 00:00 |
20:59:06.45 |
+62:25:16.3 |
HIP 103385 |
20.05 |
| 2026-09-23 12:00 |
20:59:02.77 |
+62:24:46.9 |
HIP 103385 |
20.00 |
| 2026-09-24 00:00 |
20:58:59.12 |
+62:24:17.3 |
HIP 103385 |
19.97 |
| 2026-09-24 12:00 |
20:58:55.50 |
+62:23:47.5 |
HIP 103385 |
19.97 |
| 2026-09-25 00:00 |
20:58:51.92 |
+62:23:17.5 |
HIP 103385 |
20.00 |
| 2026-09-25 12:00 |
20:58:48.38 |
+62:22:47.4 |
HIP 103385 |
20.06 |
| 2026-09-26 00:00 |
20:58:44.87 |
+62:22:17.0 |
HIP 103385 |
20.14 |
| 2026-09-26 12:00 |
20:58:41.39 |
+62:21:46.4 |
HIP 103385 |
20.24 |
| 2026-09-27 00:00 |
20:58:37.96 |
+62:21:15.7 |
HIP 103385 |
20.37 |
| 2026-09-27 12:00 |
20:58:34.55 |
+62:20:44.7 |
HIP 103385 |
20.53 |
| 2026-09-28 00:00 |
20:58:31.19 |
+62:20:13.6 |
HIP 103385 |
20.70 |
| 2026-09-28 12:00 |
20:58:27.86 |
+62:19:42.3 |
HIP 103385 |
20.91 |
| 2026-09-29 00:00 |
20:58:24.57 |
+62:19:10.8 |
HIP 103385 |
21.13 |
| 2026-09-29 12:00 |
20:58:21.32 |
+62:18:39.1 |
HIP 103385 |
21.38 |
| 2026-09-30 00:00 |
20:58:18.10 |
+62:18:07.3 |
HIP 103276 |
21.57 |
| 2026-09-30 12:00 |
20:58:14.92 |
+62:17:35.3 |
HIP 103276 |
21.41 |
| 2026-10-01 00:00 |
20:58:11.78 |
+62:17:03.1 |
HIP 103276 |
21.28 |
| 2026-10-01 12:00 |
20:58:08.68 |
+62:16:30.8 |
HIP 103276 |
21.17 |
| 2026-10-02 00:00 |
20:58:05.61 |
+62:15:58.3 |
HIP 103276 |
21.08 |
| 2026-10-02 12:00 |
20:58:02.59 |
+62:15:25.6 |
HIP 103276 |
21.02 |
| 2026-10-03 00:00 |
20:57:59.60 |
+62:14:52.8 |
HIP 103276 |
20.98 |
| 2026-10-03 12:00 |
20:57:56.65 |
+62:14:19.8 |
HIP 103276 |
20.96 |
| 2026-10-04 00:00 |
20:57:53.74 |
+62:13:46.6 |
HIP 103276 |
20.98 |
| 2026-10-04 12:00 |
20:57:50.87 |
+62:13:13.3 |
HIP 103276 |
21.01 |
| 2026-10-05 00:00 |
20:57:48.04 |
+62:12:39.9 |
HIP 103276 |
21.08 |
| 2026-10-05 12:00 |
20:57:45.25 |
+62:12:06.3 |
HIP 103276 |
21.16 |
| 2026-10-06 00:00 |
20:57:42.49 |
+62:11:32.5 |
HIP 103276 |
21.27 |
| 2026-10-06 12:00 |
20:57:39.78 |
+62:10:58.6 |
HIP 103276 |
21.41 |
| 2026-10-07 00:00 |
20:57:37.11 |
+62:10:24.6 |
HIP 103276 |
21.57 |
| 2026-10-07 12:00 |
20:57:34.48 |
+62:09:50.4 |
HIP 103276 |
21.75 |
| 2026-10-08 00:00 |
20:57:31.89 |
+62:09:16.1 |
HIP 103276 |
21.95 |
| 2026-10-08 12:00 |
20:57:29.34 |
+62:08:41.7 |
HIP 103276 |
22.18 |
| 2026-10-09 00:00 |
20:57:26.84 |
+62:08:07.1 |
HIP 103276 |
22.42 |
| 2026-10-09 12:00 |
20:57:24.37 |
+62:07:32.4 |
HIP 103276 |
22.69 |
| 2026-10-10 00:00 |
20:57:21.94 |
+62:06:57.6 |
HIP 103276 |
22.97 |
| 2026-10-10 12:00 |
20:57:19.56 |
+62:06:22.7 |
HIP 103276 |
23.28 |
| 2026-10-11 00:00 |
20:57:17.22 |
+62:05:47.6 |
HIP 103276 |
23.60 |