| Parameter |
Value |
| Designation |
C/2020 U3 (Rankin) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2021-02-05T23:23:23.781120Z |
| Orbit solution date (soln_date, UTC) |
2023-04-24T19:06:41Z |
| Obs used |
178 |
| NEO |
- |
| M1 |
9.700 |
| K1 |
22.000 |
| PC |
- |
| Discovery observation (MPC, UTC) |
2020-10-22T03:37:43.852800Z |
| Discovery magnitude (MPC) |
20.14 G |
| Discovery observatory (MPC) |
G96 · Mt. Lemmon Survey |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2020-11-22.0000000 |
| e |
0.96479330 |
| q (au) |
2.276177 |
| a (au) |
64.651799 |
| i (deg) |
30.176991 |
| Ω (om, deg) |
282.679092 |
| ω (w, deg) |
124.262013 |
| M (ma, deg) |
359.855954 |
Magnitude
Scatter + Global Linear
$$
M_a = (11.589 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
11.589 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-0.500 |
| k |
1.000 |
| 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 |
| 2020-07-21 |
2021-02-05 |
+3.5360 |
-1.291 |
| 2021-02-07 |
2021-10-31 |
+2.0235 |
-1.913 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-03-26 00:00 |
11:06:26.00 |
-29:01:03.0 |
HIP 54282 |
3.99 |
| 2026-03-26 12:00 |
11:06:18.54 |
-29:00:08.4 |
HIP 54282 |
4.27 |
| 2026-03-27 00:00 |
11:06:11.11 |
-28:59:13.3 |
HIP 54282 |
5.25 |
| 2026-03-27 12:00 |
11:06:03.72 |
-28:58:17.7 |
HIP 54282 |
6.63 |
| 2026-03-28 00:00 |
11:05:56.36 |
-28:57:21.6 |
HIP 54282 |
8.20 |
| 2026-03-28 12:00 |
11:05:49.04 |
-28:56:25.1 |
HIP 54282 |
9.88 |
| 2026-03-29 00:00 |
11:05:41.75 |
-28:55:28.1 |
HIP 54282 |
11.61 |
| 2026-03-29 12:00 |
11:05:34.50 |
-28:54:30.7 |
HIP 54282 |
13.37 |
| 2026-03-30 00:00 |
11:05:27.29 |
-28:53:32.9 |
HIP 54282 |
15.16 |
| 2026-03-30 12:00 |
11:05:20.11 |
-28:52:34.6 |
HIP 54282 |
16.96 |
| 2026-03-31 00:00 |
11:05:12.98 |
-28:51:35.9 |
HIP 54282 |
18.77 |
| 2026-03-31 12:00 |
11:05:05.88 |
-28:50:36.8 |
HIP 54282 |
20.58 |
| 2026-04-01 00:00 |
11:04:58.83 |
-28:49:37.2 |
HIP 54282 |
22.39 |
| 2026-04-01 12:00 |
11:04:51.81 |
-28:48:37.3 |
HIP 54311 |
23.98 |
| 2026-04-02 00:00 |
11:04:44.84 |
-28:47:36.9 |
HIP 54004 |
25.01 |
| 2026-04-02 12:00 |
11:04:37.91 |
-28:46:36.2 |
HIP 54004 |
23.36 |
| 2026-04-03 00:00 |
11:04:31.02 |
-28:45:35.0 |
HIP 54004 |
21.74 |
| 2026-04-03 12:00 |
11:04:24.18 |
-28:44:33.5 |
HIP 54004 |
20.17 |
| 2026-04-04 00:00 |
11:04:17.38 |
-28:43:31.6 |
HIP 54004 |
18.66 |
| 2026-04-04 12:00 |
11:04:10.62 |
-28:42:29.4 |
HIP 54004 |
17.21 |
| 2026-04-05 00:00 |
11:04:03.91 |
-28:41:26.8 |
HIP 54004 |
15.84 |
| 2026-04-05 12:00 |
11:03:57.24 |
-28:40:23.8 |
HIP 54004 |
14.58 |
| 2026-04-06 00:00 |
11:03:50.63 |
-28:39:20.5 |
HIP 54004 |
13.46 |
| 2026-04-06 12:00 |
11:03:44.06 |
-28:38:16.8 |
HIP 54004 |
12.50 |
| 2026-04-07 00:00 |
11:03:37.53 |
-28:37:12.8 |
HIP 54004 |
11.75 |
| 2026-04-07 12:00 |
11:03:31.06 |
-28:36:08.5 |
HIP 54004 |
11.25 |
| 2026-04-08 00:00 |
11:03:24.63 |
-28:35:03.9 |
HIP 54004 |
11.03 |
| 2026-04-08 12:00 |
11:03:18.25 |
-28:33:58.9 |
HIP 54004 |
11.10 |
| 2026-04-09 00:00 |
11:03:11.92 |
-28:32:53.6 |
HIP 54004 |
11.46 |
| 2026-04-09 12:00 |
11:03:05.65 |
-28:31:48.1 |
HIP 54004 |
12.07 |
| 2026-04-10 00:00 |
11:02:59.42 |
-28:30:42.2 |
HIP 54004 |
12.90 |
| 2026-04-10 12:00 |
11:02:53.25 |
-28:29:36.1 |
HIP 54004 |
13.91 |
| 2026-04-11 00:00 |
11:02:47.13 |
-28:28:29.7 |
HIP 54004 |
15.06 |
| 2026-04-11 12:00 |
11:02:41.06 |
-28:27:23.0 |
HIP 54004 |
16.31 |
| 2026-04-12 00:00 |
11:02:35.04 |
-28:26:16.0 |
HIP 54004 |
17.65 |
| 2026-04-12 12:00 |
11:02:29.08 |
-28:25:08.8 |
HIP 54004 |
19.06 |
| 2026-04-13 00:00 |
11:02:23.17 |
-28:24:01.4 |
HIP 54004 |
20.51 |
| 2026-04-13 12:00 |
11:02:17.32 |
-28:22:53.7 |
HIP 54004 |
22.00 |
| 2026-04-14 00:00 |
11:02:11.52 |
-28:21:45.8 |
HIP 54004 |
23.52 |
| 2026-04-14 12:00 |
11:02:05.78 |
-28:20:37.6 |
HIP 54004 |
25.06 |
| 2026-04-15 00:00 |
11:02:00.10 |
-28:19:29.2 |
HIP 54004 |
26.62 |
| 2026-04-15 12:00 |
11:01:54.47 |
-28:18:20.7 |
HIP 54004 |
28.19 |
| 2026-04-16 00:00 |
11:01:48.90 |
-28:17:11.9 |
HIP 54004 |
29.77 |