| 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 |
0.997 |
| 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) |
| 2026-03-26 00:00 |
21:15:20.70 |
+61:01:09.3 |
HIP 105193 |
25.19 |
| 2026-03-26 12:00 |
21:15:23.66 |
+61:01:37.4 |
HIP 105193 |
24.68 |
| 2026-03-27 00:00 |
21:15:26.59 |
+61:02:05.7 |
HIP 105193 |
24.17 |
| 2026-03-27 12:00 |
21:15:29.49 |
+61:02:34.2 |
HIP 105193 |
23.67 |
| 2026-03-28 00:00 |
21:15:32.36 |
+61:03:02.8 |
HIP 105193 |
23.18 |
| 2026-03-28 12:00 |
21:15:35.20 |
+61:03:31.6 |
HIP 105193 |
22.69 |
| 2026-03-29 00:00 |
21:15:38.00 |
+61:04:00.6 |
HIP 105193 |
22.21 |
| 2026-03-29 12:00 |
21:15:40.78 |
+61:04:29.8 |
HIP 105193 |
21.74 |
| 2026-03-30 00:00 |
21:15:43.52 |
+61:04:59.1 |
HIP 105193 |
21.27 |
| 2026-03-30 12:00 |
21:15:46.23 |
+61:05:28.6 |
HIP 105193 |
20.82 |
| 2026-03-31 00:00 |
21:15:48.91 |
+61:05:58.2 |
HIP 105193 |
20.38 |
| 2026-03-31 12:00 |
21:15:51.56 |
+61:06:28.1 |
HIP 105193 |
19.95 |
| 2026-04-01 00:00 |
21:15:54.17 |
+61:06:58.0 |
HIP 105193 |
19.53 |
| 2026-04-01 12:00 |
21:15:56.75 |
+61:07:28.2 |
HIP 105193 |
19.12 |
| 2026-04-02 00:00 |
21:15:59.30 |
+61:07:58.5 |
HIP 105193 |
18.72 |
| 2026-04-02 12:00 |
21:16:01.81 |
+61:08:28.9 |
HIP 105193 |
18.34 |
| 2026-04-03 00:00 |
21:16:04.29 |
+61:08:59.5 |
HIP 105193 |
17.98 |
| 2026-04-03 12:00 |
21:16:06.74 |
+61:09:30.2 |
HIP 105193 |
17.63 |
| 2026-04-04 00:00 |
21:16:09.15 |
+61:10:01.1 |
HIP 105193 |
17.30 |
| 2026-04-04 12:00 |
21:16:11.53 |
+61:10:32.2 |
HIP 105193 |
16.99 |
| 2026-04-05 00:00 |
21:16:13.87 |
+61:11:03.4 |
HIP 105193 |
16.70 |
| 2026-04-05 12:00 |
21:16:16.18 |
+61:11:34.7 |
HIP 105193 |
16.42 |
| 2026-04-06 00:00 |
21:16:18.46 |
+61:12:06.1 |
HIP 105193 |
16.17 |
| 2026-04-06 12:00 |
21:16:20.70 |
+61:12:37.7 |
HIP 105193 |
15.94 |
| 2026-04-07 00:00 |
21:16:22.90 |
+61:13:09.5 |
HIP 105193 |
15.74 |
| 2026-04-07 12:00 |
21:16:25.07 |
+61:13:41.3 |
HIP 105193 |
15.56 |
| 2026-04-08 00:00 |
21:16:27.21 |
+61:14:13.3 |
HIP 105193 |
15.40 |
| 2026-04-08 12:00 |
21:16:29.31 |
+61:14:45.5 |
HIP 105193 |
15.28 |
| 2026-04-09 00:00 |
21:16:31.37 |
+61:15:17.7 |
HIP 105193 |
15.17 |
| 2026-04-09 12:00 |
21:16:33.40 |
+61:15:50.1 |
HIP 105193 |
15.10 |
| 2026-04-10 00:00 |
21:16:35.39 |
+61:16:22.6 |
HIP 105193 |
15.05 |
| 2026-04-10 12:00 |
21:16:37.34 |
+61:16:55.2 |
HIP 105193 |
15.03 |
| 2026-04-11 00:00 |
21:16:39.26 |
+61:17:27.9 |
HIP 105193 |
15.04 |
| 2026-04-11 12:00 |
21:16:41.14 |
+61:18:00.8 |
HIP 105193 |
15.08 |
| 2026-04-12 00:00 |
21:16:42.99 |
+61:18:33.8 |
HIP 105193 |
15.15 |
| 2026-04-12 12:00 |
21:16:44.79 |
+61:19:06.8 |
HIP 105193 |
15.24 |
| 2026-04-13 00:00 |
21:16:46.56 |
+61:19:40.0 |
HIP 105193 |
15.36 |
| 2026-04-13 12:00 |
21:16:48.30 |
+61:20:13.3 |
HIP 105193 |
15.51 |
| 2026-04-14 00:00 |
21:16:49.99 |
+61:20:46.7 |
HIP 105193 |
15.68 |
| 2026-04-14 12:00 |
21:16:51.65 |
+61:21:20.2 |
HIP 105193 |
15.88 |
| 2026-04-15 00:00 |
21:16:53.27 |
+61:21:53.8 |
HIP 105193 |
16.10 |
| 2026-04-15 12:00 |
21:16:54.85 |
+61:22:27.4 |
HIP 105193 |
16.35 |
| 2026-04-16 00:00 |
21:16:56.39 |
+61:23:01.2 |
HIP 105193 |
16.61 |