| Parameter |
Value |
| Designation |
C/1999 U4 (Catalina-Skiff) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2001-10-28T12:49:53.112000Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:30:02Z |
| Obs used |
847 |
| NEO |
- |
| M1 |
10.300 |
| K1 |
4.500 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2002-01-01.0000000 |
| e |
1.00756946 |
| q (au) |
4.915350 |
| a (au) |
-649.365763 |
| i (deg) |
51.925991 |
| Ω (om, deg) |
32.286666 |
| ω (w, deg) |
77.523394 |
| M (ma, deg) |
0.003840 |
Magnitude
Scatter + Global Linear
$$
M_a = (10.223 + 3.448\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
10.223 |
| n |
3.448 |
| gf |
0.972 |
| gb |
-0.814 |
| k |
0.800 |
| δ90 |
9.999 |
| 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 |
| 1999-09-18 |
2001-10-23 |
+6.1426 |
-5.783 |
| 2001-11-06 |
2004-04-11 |
+1.9350 |
-1.506 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-05-12 00:00 |
15:04:57.76 |
-48:17:41.9 |
HIP 73833 |
8.40 |
| 2026-05-12 12:00 |
15:04:53.90 |
-48:17:34.1 |
HIP 73833 |
8.61 |
| 2026-05-13 00:00 |
15:04:50.04 |
-48:17:26.1 |
HIP 73833 |
8.86 |
| 2026-05-13 12:00 |
15:04:46.18 |
-48:17:17.9 |
HIP 73833 |
9.15 |
| 2026-05-14 00:00 |
15:04:42.32 |
-48:17:09.5 |
HIP 73833 |
9.47 |
| 2026-05-14 12:00 |
15:04:38.47 |
-48:17:01.0 |
HIP 73833 |
9.83 |
| 2026-05-15 00:00 |
15:04:34.62 |
-48:16:52.2 |
HIP 73833 |
10.21 |
| 2026-05-15 12:00 |
15:04:30.78 |
-48:16:43.3 |
HIP 73833 |
10.62 |
| 2026-05-16 00:00 |
15:04:26.93 |
-48:16:34.2 |
HIP 73833 |
11.04 |
| 2026-05-16 12:00 |
15:04:23.10 |
-48:16:24.9 |
HIP 73833 |
11.49 |
| 2026-05-17 00:00 |
15:04:19.26 |
-48:16:15.5 |
HIP 73833 |
11.96 |
| 2026-05-17 12:00 |
15:04:15.44 |
-48:16:05.8 |
HIP 73833 |
12.44 |
| 2026-05-18 00:00 |
15:04:11.61 |
-48:15:56.0 |
HIP 73833 |
12.93 |
| 2026-05-18 12:00 |
15:04:07.80 |
-48:15:46.0 |
HIP 73833 |
13.44 |
| 2026-05-19 00:00 |
15:04:03.98 |
-48:15:35.9 |
HIP 73833 |
13.96 |
| 2026-05-19 12:00 |
15:04:00.18 |
-48:15:25.6 |
HIP 73833 |
14.48 |
| 2026-05-20 00:00 |
15:03:56.38 |
-48:15:15.1 |
HIP 73833 |
15.02 |
| 2026-05-20 12:00 |
15:03:52.59 |
-48:15:04.4 |
HIP 73833 |
15.56 |
| 2026-05-21 00:00 |
15:03:48.81 |
-48:14:53.5 |
HIP 73833 |
16.11 |
| 2026-05-21 12:00 |
15:03:45.03 |
-48:14:42.5 |
HIP 73833 |
16.67 |
| 2026-05-22 00:00 |
15:03:41.26 |
-48:14:31.3 |
HIP 73833 |
17.23 |
| 2026-05-22 12:00 |
15:03:37.50 |
-48:14:20.0 |
HIP 73742 |
17.67 |
| 2026-05-23 00:00 |
15:03:33.75 |
-48:14:08.5 |
HIP 73742 |
17.80 |
| 2026-05-23 12:00 |
15:03:30.01 |
-48:13:56.8 |
HIP 73742 |
17.94 |
| 2026-05-24 00:00 |
15:03:26.27 |
-48:13:45.0 |
HIP 73622 |
17.89 |
| 2026-05-24 12:00 |
15:03:22.55 |
-48:13:33.0 |
HIP 73622 |
17.54 |
| 2026-05-25 00:00 |
15:03:18.83 |
-48:13:20.9 |
HIP 73622 |
17.21 |
| 2026-05-25 12:00 |
15:03:15.13 |
-48:13:08.5 |
HIP 73622 |
16.89 |
| 2026-05-26 00:00 |
15:03:11.43 |
-48:12:56.1 |
HIP 73622 |
16.58 |
| 2026-05-26 12:00 |
15:03:07.75 |
-48:12:43.5 |
HIP 73622 |
16.30 |
| 2026-05-27 00:00 |
15:03:04.07 |
-48:12:30.7 |
HIP 73622 |
16.03 |
| 2026-05-27 12:00 |
15:03:00.41 |
-48:12:17.8 |
HIP 73622 |
15.79 |
| 2026-05-28 00:00 |
15:02:56.76 |
-48:12:04.7 |
HIP 73622 |
15.56 |
| 2026-05-28 12:00 |
15:02:53.12 |
-48:11:51.5 |
HIP 73622 |
15.36 |
| 2026-05-29 00:00 |
15:02:49.49 |
-48:11:38.1 |
HIP 73622 |
15.17 |
| 2026-05-29 12:00 |
15:02:45.87 |
-48:11:24.6 |
HIP 73622 |
15.02 |
| 2026-05-30 00:00 |
15:02:42.27 |
-48:11:10.9 |
HIP 73622 |
14.88 |
| 2026-05-30 12:00 |
15:02:38.68 |
-48:10:57.1 |
HIP 73622 |
14.77 |
| 2026-05-31 00:00 |
15:02:35.10 |
-48:10:43.1 |
HIP 73622 |
14.68 |
| 2026-05-31 12:00 |
15:02:31.54 |
-48:10:29.0 |
HIP 73622 |
14.62 |
| 2026-06-01 00:00 |
15:02:27.99 |
-48:10:14.8 |
HIP 73622 |
14.58 |
| 2026-06-01 12:00 |
15:02:24.45 |
-48:10:00.4 |
HIP 73622 |
14.57 |
| 2026-06-02 00:00 |
15:02:20.92 |
-48:09:45.9 |
HIP 73622 |
14.58 |