C/1999 U4 (Catalina-Skiff)
| 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) |
| 2026-02-03 00:00 |
15:12:18.12 |
-47:42:48.3 |
HIP 74252 |
19.11 |
| 2026-02-03 12:00 |
15:12:18.72 |
-47:43:12.8 |
HIP 74252 |
19.33 |
| 2026-02-04 00:00 |
15:12:19.29 |
-47:43:37.2 |
HIP 74252 |
19.56 |
| 2026-02-04 12:00 |
15:12:19.83 |
-47:44:01.5 |
HIP 74252 |
19.79 |
| 2026-02-05 00:00 |
15:12:20.33 |
-47:44:25.7 |
HIP 74252 |
20.02 |
| 2026-02-05 12:00 |
15:12:20.79 |
-47:44:49.9 |
HIP 74252 |
20.25 |
| 2026-02-06 00:00 |
15:12:21.22 |
-47:45:14.0 |
HIP 74252 |
20.48 |
| 2026-02-06 12:00 |
15:12:21.62 |
-47:45:38.1 |
HIP 74252 |
20.71 |
| 2026-02-07 00:00 |
15:12:21.98 |
-47:46:02.1 |
HIP 74252 |
20.94 |
| 2026-02-07 12:00 |
15:12:22.31 |
-47:46:26.0 |
HIP 74252 |
21.17 |
| 2026-02-08 00:00 |
15:12:22.61 |
-47:46:49.9 |
HIP 74252 |
21.40 |
| 2026-02-08 12:00 |
15:12:22.86 |
-47:47:13.7 |
HIP 74252 |
21.62 |
| 2026-02-09 00:00 |
15:12:23.09 |
-47:47:37.4 |
HIP 74252 |
21.85 |
| 2026-02-09 12:00 |
15:12:23.28 |
-47:48:01.1 |
HIP 74252 |
22.08 |
| 2026-02-10 00:00 |
15:12:23.43 |
-47:48:24.6 |
HIP 74252 |
22.30 |
| 2026-02-10 12:00 |
15:12:23.55 |
-47:48:48.1 |
HIP 74252 |
22.52 |
| 2026-02-11 00:00 |
15:12:23.64 |
-47:49:11.5 |
HIP 74252 |
22.75 |
| 2026-02-11 12:00 |
15:12:23.69 |
-47:49:34.8 |
HIP 74252 |
22.97 |
| 2026-02-12 00:00 |
15:12:23.70 |
-47:49:58.1 |
HIP 74252 |
23.19 |
| 2026-02-12 12:00 |
15:12:23.68 |
-47:50:21.2 |
HIP 74418 |
22.81 |
| 2026-02-13 00:00 |
15:12:23.63 |
-47:50:44.3 |
HIP 74418 |
22.43 |
| 2026-02-13 12:00 |
15:12:23.54 |
-47:51:07.3 |
HIP 74418 |
22.05 |
| 2026-02-14 00:00 |
15:12:23.41 |
-47:51:30.2 |
HIP 74418 |
21.67 |
| 2026-02-14 12:00 |
15:12:23.25 |
-47:51:53.0 |
HIP 74418 |
21.29 |
| 2026-02-15 00:00 |
15:12:23.06 |
-47:52:15.7 |
HIP 74418 |
20.92 |
| 2026-02-15 12:00 |
15:12:22.83 |
-47:52:38.3 |
HIP 74418 |
20.54 |
| 2026-02-16 00:00 |
15:12:22.56 |
-47:53:00.9 |
HIP 74418 |
20.17 |
| 2026-02-16 12:00 |
15:12:22.26 |
-47:53:23.3 |
HIP 74418 |
19.80 |
| 2026-02-17 00:00 |
15:12:21.93 |
-47:53:45.6 |
HIP 74418 |
19.44 |
| 2026-02-17 12:00 |
15:12:21.56 |
-47:54:07.8 |
HIP 74418 |
19.07 |
| 2026-02-18 00:00 |
15:12:21.15 |
-47:54:29.9 |
HIP 74418 |
18.71 |
| 2026-02-18 12:00 |
15:12:20.71 |
-47:54:52.0 |
HIP 74418 |
18.35 |
| 2026-02-19 00:00 |
15:12:20.24 |
-47:55:13.9 |
HIP 74418 |
18.00 |
| 2026-02-19 12:00 |
15:12:19.73 |
-47:55:35.7 |
HIP 74418 |
17.64 |
| 2026-02-20 00:00 |
15:12:19.19 |
-47:55:57.4 |
HIP 74418 |
17.29 |
| 2026-02-20 12:00 |
15:12:18.61 |
-47:56:18.9 |
HIP 74418 |
16.95 |
| 2026-02-21 00:00 |
15:12:17.99 |
-47:56:40.4 |
HIP 74418 |
16.61 |
| 2026-02-21 12:00 |
15:12:17.34 |
-47:57:01.8 |
HIP 74418 |
16.27 |
| 2026-02-22 00:00 |
15:12:16.66 |
-47:57:23.0 |
HIP 74418 |
15.94 |
| 2026-02-22 12:00 |
15:12:15.94 |
-47:57:44.1 |
HIP 74418 |
15.61 |
| 2026-02-23 00:00 |
15:12:15.19 |
-47:58:05.1 |
HIP 74418 |
15.28 |
| 2026-02-23 12:00 |
15:12:14.40 |
-47:58:26.0 |
HIP 74418 |
14.97 |
| 2026-02-24 00:00 |
15:12:13.58 |
-47:58:46.8 |
HIP 74418 |
14.65 |