| 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) |
| 2026-07-29 00:00 |
21:08:20.21 |
+62:52:05.8 |
HIP 104475 |
12.18 |
| 2026-07-29 12:00 |
21:08:14.83 |
+62:52:08.3 |
HIP 104475 |
12.73 |
| 2026-07-30 00:00 |
21:08:09.43 |
+62:52:10.5 |
HIP 104280 |
12.74 |
| 2026-07-30 12:00 |
21:08:04.03 |
+62:52:12.4 |
HIP 104280 |
12.53 |
| 2026-07-31 00:00 |
21:07:58.62 |
+62:52:14.0 |
HIP 104280 |
12.35 |
| 2026-07-31 12:00 |
21:07:53.21 |
+62:52:15.2 |
HIP 104280 |
12.20 |
| 2026-08-01 00:00 |
21:07:47.79 |
+62:52:16.2 |
HIP 104280 |
12.08 |
| 2026-08-01 12:00 |
21:07:42.37 |
+62:52:16.8 |
HIP 104146 |
11.99 |
| 2026-08-02 00:00 |
21:07:36.94 |
+62:52:17.1 |
HIP 104146 |
11.39 |
| 2026-08-02 12:00 |
21:07:31.51 |
+62:52:17.1 |
HIP 104146 |
10.80 |
| 2026-08-03 00:00 |
21:07:26.07 |
+62:52:16.7 |
HIP 104146 |
10.21 |
| 2026-08-03 12:00 |
21:07:20.63 |
+62:52:16.1 |
HIP 104146 |
9.62 |
| 2026-08-04 00:00 |
21:07:15.19 |
+62:52:15.1 |
HIP 104146 |
9.04 |
| 2026-08-04 12:00 |
21:07:09.75 |
+62:52:13.8 |
HIP 104146 |
8.47 |
| 2026-08-05 00:00 |
21:07:04.30 |
+62:52:12.2 |
HIP 104146 |
7.90 |
| 2026-08-05 12:00 |
21:06:58.85 |
+62:52:10.3 |
HIP 104146 |
7.35 |
| 2026-08-06 00:00 |
21:06:53.40 |
+62:52:08.1 |
HIP 104146 |
6.81 |
| 2026-08-06 12:00 |
21:06:47.95 |
+62:52:05.5 |
HIP 104146 |
6.29 |
| 2026-08-07 00:00 |
21:06:42.50 |
+62:52:02.6 |
HIP 104146 |
5.79 |
| 2026-08-07 12:00 |
21:06:37.05 |
+62:51:59.4 |
HIP 104146 |
5.32 |
| 2026-08-08 00:00 |
21:06:31.60 |
+62:51:55.9 |
HIP 104146 |
4.89 |
| 2026-08-08 12:00 |
21:06:26.15 |
+62:51:52.0 |
HIP 104146 |
4.51 |
| 2026-08-09 00:00 |
21:06:20.70 |
+62:51:47.9 |
HIP 104146 |
4.20 |
| 2026-08-09 12:00 |
21:06:15.25 |
+62:51:43.4 |
HIP 104146 |
3.96 |
| 2026-08-10 00:00 |
21:06:09.80 |
+62:51:38.6 |
HIP 104146 |
3.82 |
| 2026-08-10 12:00 |
21:06:04.36 |
+62:51:33.5 |
HIP 104146 |
3.78 |
| 2026-08-11 00:00 |
21:05:58.92 |
+62:51:28.0 |
HIP 104146 |
3.85 |
| 2026-08-11 12:00 |
21:05:53.48 |
+62:51:22.3 |
HIP 104146 |
4.02 |
| 2026-08-12 00:00 |
21:05:48.05 |
+62:51:16.2 |
HIP 104146 |
4.28 |
| 2026-08-12 12:00 |
21:05:42.62 |
+62:51:09.8 |
HIP 104146 |
4.62 |
| 2026-08-13 00:00 |
21:05:37.19 |
+62:51:03.0 |
HIP 104146 |
5.02 |
| 2026-08-13 12:00 |
21:05:31.77 |
+62:50:56.0 |
HIP 104146 |
5.47 |
| 2026-08-14 00:00 |
21:05:26.36 |
+62:50:48.6 |
HIP 104146 |
5.95 |
| 2026-08-14 12:00 |
21:05:20.95 |
+62:50:41.0 |
HIP 104146 |
6.46 |
| 2026-08-15 00:00 |
21:05:15.55 |
+62:50:33.0 |
HIP 104146 |
6.99 |
| 2026-08-15 12:00 |
21:05:10.16 |
+62:50:24.7 |
HIP 104146 |
7.54 |
| 2026-08-16 00:00 |
21:05:04.77 |
+62:50:16.0 |
HIP 104146 |
8.11 |
| 2026-08-16 12:00 |
21:04:59.39 |
+62:50:07.1 |
HIP 104146 |
8.69 |
| 2026-08-17 00:00 |
21:04:54.02 |
+62:49:57.9 |
HIP 104146 |
9.27 |
| 2026-08-17 12:00 |
21:04:48.66 |
+62:49:48.3 |
HIP 104146 |
9.87 |
| 2026-08-18 00:00 |
21:04:43.31 |
+62:49:38.4 |
HIP 104146 |
10.47 |
| 2026-08-18 12:00 |
21:04:37.96 |
+62:49:28.2 |
HIP 104146 |
11.07 |
| 2026-08-19 00:00 |
21:04:32.63 |
+62:49:17.7 |
HIP 104146 |
11.68 |