| 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) |
| 2026-05-12 00:00 |
21:17:20.95 |
+61:53:21.9 |
HIP 105172 |
9.06 |
| 2026-05-12 12:00 |
21:17:20.31 |
+61:53:57.0 |
HIP 105172 |
9.51 |
| 2026-05-13 00:00 |
21:17:19.64 |
+61:54:32.0 |
HIP 105172 |
9.99 |
| 2026-05-13 12:00 |
21:17:18.92 |
+61:55:07.0 |
HIP 105172 |
10.47 |
| 2026-05-14 00:00 |
21:17:18.16 |
+61:55:41.9 |
HIP 105172 |
10.97 |
| 2026-05-14 12:00 |
21:17:17.36 |
+61:56:16.8 |
HIP 105172 |
11.48 |
| 2026-05-15 00:00 |
21:17:16.51 |
+61:56:51.7 |
HIP 105172 |
12.00 |
| 2026-05-15 12:00 |
21:17:15.63 |
+61:57:26.4 |
HIP 105172 |
12.53 |
| 2026-05-16 00:00 |
21:17:14.69 |
+61:58:01.1 |
HIP 105172 |
13.07 |
| 2026-05-16 12:00 |
21:17:13.72 |
+61:58:35.8 |
HIP 105172 |
13.61 |
| 2026-05-17 00:00 |
21:17:12.70 |
+61:59:10.4 |
HIP 105172 |
14.16 |
| 2026-05-17 12:00 |
21:17:11.65 |
+61:59:44.9 |
HIP 105257 |
14.66 |
| 2026-05-18 00:00 |
21:17:10.54 |
+62:00:19.4 |
HIP 105257 |
14.87 |
| 2026-05-18 12:00 |
21:17:09.40 |
+62:00:53.7 |
HIP 105257 |
15.11 |
| 2026-05-19 00:00 |
21:17:08.21 |
+62:01:28.1 |
HIP 105257 |
15.37 |
| 2026-05-19 12:00 |
21:17:06.98 |
+62:02:02.3 |
HIP 105257 |
15.66 |
| 2026-05-20 00:00 |
21:17:05.71 |
+62:02:36.4 |
HIP 105257 |
15.96 |
| 2026-05-20 12:00 |
21:17:04.40 |
+62:03:10.5 |
HIP 105257 |
16.29 |
| 2026-05-21 00:00 |
21:17:03.04 |
+62:03:44.5 |
HIP 105257 |
16.63 |
| 2026-05-21 12:00 |
21:17:01.64 |
+62:04:18.4 |
HIP 105257 |
16.99 |
| 2026-05-22 00:00 |
21:17:00.20 |
+62:04:52.1 |
HIP 105257 |
17.37 |
| 2026-05-22 12:00 |
21:16:58.72 |
+62:05:25.9 |
HIP 105257 |
17.76 |
| 2026-05-23 00:00 |
21:16:57.19 |
+62:05:59.5 |
HIP 105257 |
18.17 |
| 2026-05-23 12:00 |
21:16:55.63 |
+62:06:33.0 |
HIP 105257 |
18.59 |
| 2026-05-24 00:00 |
21:16:54.02 |
+62:07:06.4 |
HIP 105257 |
19.02 |
| 2026-05-24 12:00 |
21:16:52.37 |
+62:07:39.7 |
HIP 105257 |
19.46 |
| 2026-05-25 00:00 |
21:16:50.68 |
+62:08:12.9 |
HIP 105257 |
19.92 |
| 2026-05-25 12:00 |
21:16:48.94 |
+62:08:46.0 |
HIP 105257 |
20.38 |
| 2026-05-26 00:00 |
21:16:47.17 |
+62:09:19.0 |
HIP 105257 |
20.85 |
| 2026-05-26 12:00 |
21:16:45.35 |
+62:09:51.8 |
HIP 105257 |
21.34 |
| 2026-05-27 00:00 |
21:16:43.50 |
+62:10:24.6 |
HIP 104912 |
21.23 |
| 2026-05-27 12:00 |
21:16:41.60 |
+62:10:57.2 |
HIP 104912 |
20.65 |
| 2026-05-28 00:00 |
21:16:39.66 |
+62:11:29.7 |
HIP 104912 |
20.08 |
| 2026-05-28 12:00 |
21:16:37.68 |
+62:12:02.1 |
HIP 104912 |
19.50 |
| 2026-05-29 00:00 |
21:16:35.66 |
+62:12:34.4 |
HIP 104912 |
18.92 |
| 2026-05-29 12:00 |
21:16:33.59 |
+62:13:06.5 |
HIP 104912 |
18.34 |
| 2026-05-30 00:00 |
21:16:31.49 |
+62:13:38.6 |
HIP 104912 |
17.76 |
| 2026-05-30 12:00 |
21:16:29.35 |
+62:14:10.4 |
HIP 104912 |
17.18 |
| 2026-05-31 00:00 |
21:16:27.17 |
+62:14:42.2 |
HIP 104912 |
16.60 |
| 2026-05-31 12:00 |
21:16:24.94 |
+62:15:13.8 |
HIP 104912 |
16.02 |
| 2026-06-01 00:00 |
21:16:22.68 |
+62:15:45.3 |
HIP 104912 |
15.44 |
| 2026-06-01 12:00 |
21:16:20.37 |
+62:16:16.7 |
HIP 104912 |
14.86 |
| 2026-06-02 00:00 |
21:16:18.03 |
+62:16:47.9 |
HIP 104912 |
14.28 |