| 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 |
1.000 |
| gb |
-0.814 |
| k |
0.800 |
| 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
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) |
| 2026-09-20 00:00 |
14:59:59.30 |
-47:09:11.8 |
HIP 73556 |
20.00 |
| 2026-09-20 12:00 |
15:00:01.88 |
-47:09:05.5 |
HIP 73556 |
19.56 |
| 2026-09-21 00:00 |
15:00:04.48 |
-47:08:59.4 |
HIP 73556 |
19.12 |
| 2026-09-21 12:00 |
15:00:07.11 |
-47:08:53.4 |
HIP 73556 |
18.68 |
| 2026-09-22 00:00 |
15:00:09.75 |
-47:08:47.7 |
HIP 73556 |
18.23 |
| 2026-09-22 12:00 |
15:00:12.43 |
-47:08:42.1 |
HIP 73556 |
17.78 |
| 2026-09-23 00:00 |
15:00:15.12 |
-47:08:36.6 |
HIP 73556 |
17.32 |
| 2026-09-23 12:00 |
15:00:17.84 |
-47:08:31.4 |
HIP 73556 |
16.87 |
| 2026-09-24 00:00 |
15:00:20.58 |
-47:08:26.3 |
HIP 73556 |
16.40 |
| 2026-09-24 12:00 |
15:00:23.34 |
-47:08:21.4 |
HIP 73556 |
15.94 |
| 2026-09-25 00:00 |
15:00:26.12 |
-47:08:16.7 |
HIP 73556 |
15.47 |
| 2026-09-25 12:00 |
15:00:28.93 |
-47:08:12.2 |
HIP 73556 |
15.00 |
| 2026-09-26 00:00 |
15:00:31.76 |
-47:08:07.8 |
HIP 73556 |
14.53 |
| 2026-09-26 12:00 |
15:00:34.61 |
-47:08:03.6 |
HIP 73556 |
14.05 |
| 2026-09-27 00:00 |
15:00:37.48 |
-47:07:59.6 |
HIP 73556 |
13.57 |
| 2026-09-27 12:00 |
15:00:40.37 |
-47:07:55.8 |
HIP 73556 |
13.08 |
| 2026-09-28 00:00 |
15:00:43.28 |
-47:07:52.1 |
HIP 73556 |
12.60 |
| 2026-09-28 12:00 |
15:00:46.22 |
-47:07:48.6 |
HIP 73556 |
12.11 |
| 2026-09-29 00:00 |
15:00:49.17 |
-47:07:45.3 |
HIP 73556 |
11.62 |
| 2026-09-29 12:00 |
15:00:52.15 |
-47:07:42.2 |
HIP 73556 |
11.12 |
| 2026-09-30 00:00 |
15:00:55.14 |
-47:07:39.3 |
HIP 73556 |
10.62 |
| 2026-09-30 12:00 |
15:00:58.16 |
-47:07:36.5 |
HIP 73556 |
10.12 |
| 2026-10-01 00:00 |
15:01:01.20 |
-47:07:33.9 |
HIP 73556 |
9.62 |
| 2026-10-01 12:00 |
15:01:04.25 |
-47:07:31.5 |
HIP 73556 |
9.12 |
| 2026-10-02 00:00 |
15:01:07.33 |
-47:07:29.3 |
HIP 73556 |
8.61 |
| 2026-10-02 12:00 |
15:01:10.42 |
-47:07:27.3 |
HIP 73556 |
8.10 |
| 2026-10-03 00:00 |
15:01:13.54 |
-47:07:25.4 |
HIP 73556 |
7.59 |
| 2026-10-03 12:00 |
15:01:16.67 |
-47:07:23.7 |
HIP 73556 |
7.08 |
| 2026-10-04 00:00 |
15:01:19.82 |
-47:07:22.2 |
HIP 73556 |
6.57 |
| 2026-10-04 12:00 |
15:01:22.99 |
-47:07:20.9 |
HIP 73556 |
6.06 |
| 2026-10-05 00:00 |
15:01:26.18 |
-47:07:19.8 |
HIP 73556 |
5.56 |
| 2026-10-05 12:00 |
15:01:29.39 |
-47:07:18.8 |
HIP 73556 |
5.05 |
| 2026-10-06 00:00 |
15:01:32.62 |
-47:07:18.1 |
HIP 73556 |
4.55 |
| 2026-10-06 12:00 |
15:01:35.86 |
-47:07:17.5 |
HIP 73556 |
4.06 |
| 2026-10-07 00:00 |
15:01:39.12 |
-47:07:17.1 |
HIP 73556 |
3.59 |
| 2026-10-07 12:00 |
15:01:42.40 |
-47:07:16.9 |
HIP 73556 |
3.13 |
| 2026-10-08 00:00 |
15:01:45.70 |
-47:07:16.8 |
HIP 73556 |
2.71 |
| 2026-10-08 12:00 |
15:01:49.01 |
-47:07:17.0 |
HIP 73556 |
2.34 |
| 2026-10-09 00:00 |
15:01:52.34 |
-47:07:17.3 |
HIP 73556 |
2.06 |
| 2026-10-09 12:00 |
15:01:55.69 |
-47:07:17.9 |
HIP 73556 |
1.91 |
| 2026-10-10 00:00 |
15:01:59.05 |
-47:07:18.6 |
HIP 73556 |
1.92 |
| 2026-10-10 12:00 |
15:02:02.43 |
-47:07:19.5 |
HIP 73556 |
2.09 |
| 2026-10-11 00:00 |
15:02:05.83 |
-47:07:20.5 |
HIP 73556 |
2.39 |