| Parameter |
Value |
| Designation |
C/2020 R4 (ATLAS) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2021-03-01T22:27:03.700800Z |
| Orbit solution date (soln_date, UTC) |
2022-06-06T17:33:25Z |
| Obs used |
2399 |
| NEO |
- |
| M1 |
12.800 |
| K1 |
11.750 |
| PC |
0.030 |
| Discovery observation (MPC, UTC) |
2020-09-12T11:53:38.889600Z |
| Discovery magnitude (MPC) |
19.71 o |
| Discovery observatory (MPC) |
T08 · ATLAS-MLO, Mauna Loa |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2021-03-13.0000000 |
| e |
0.98936453 |
| q (au) |
1.028587 |
| a (au) |
96.712911 |
| i (deg) |
164.463346 |
| Ω (om, deg) |
323.272439 |
| ω (w, deg) |
46.707930 |
| M (ma, deg) |
0.011466 |
Magnitude
Scatter + Global Linear
$$
M_a = (12.395 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
12.395 |
| n |
6.000 |
| gf |
0.999 |
| gb |
-0.526 |
| 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 |
| 2020-08-29 |
2020-11-08 |
-9.0126 |
+3.872 |
| 2020-11-08 |
2020-12-10 |
+15.0380 |
-3.885 |
| 2020-12-10 |
2021-02-27 |
+6.3925 |
-2.570 |
| 2021-03-04 |
2021-04-25 |
+19.4111 |
-2.321 |
| 2021-04-25 |
2021-06-04 |
+1.2854 |
-0.645 |
| 2021-06-04 |
2022-03-01 |
-6.4189 |
+0.769 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-07-29 00:00 |
08:26:25.89 |
+14:27:23.1 |
HIP 41421 |
23.12 |
| 2026-07-29 12:00 |
08:26:32.10 |
+14:26:58.3 |
HIP 41421 |
23.11 |
| 2026-07-30 00:00 |
08:26:38.30 |
+14:26:33.4 |
HIP 41421 |
23.21 |
| 2026-07-30 12:00 |
08:26:44.50 |
+14:26:08.5 |
HIP 41421 |
23.41 |
| 2026-07-31 00:00 |
08:26:50.69 |
+14:25:43.5 |
HIP 41421 |
23.71 |
| 2026-07-31 12:00 |
08:26:56.87 |
+14:25:18.4 |
HIP 41421 |
24.11 |
| 2026-08-01 00:00 |
08:27:03.06 |
+14:24:53.3 |
HIP 41421 |
24.61 |
| 2026-08-01 12:00 |
08:27:09.23 |
+14:24:28.1 |
HIP 41578 |
24.40 |
| 2026-08-02 00:00 |
08:27:15.40 |
+14:24:02.8 |
HIP 41578 |
22.89 |
| 2026-08-02 12:00 |
08:27:21.56 |
+14:23:37.5 |
HIP 41578 |
21.39 |
| 2026-08-03 00:00 |
08:27:27.72 |
+14:23:12.1 |
HIP 41578 |
19.90 |
| 2026-08-03 12:00 |
08:27:33.86 |
+14:22:46.7 |
HIP 41578 |
18.41 |
| 2026-08-04 00:00 |
08:27:40.00 |
+14:22:21.3 |
HIP 41578 |
16.95 |
| 2026-08-04 12:00 |
08:27:46.13 |
+14:21:55.7 |
HIP 41578 |
15.49 |
| 2026-08-05 00:00 |
08:27:52.26 |
+14:21:30.2 |
HIP 41578 |
14.06 |
| 2026-08-05 12:00 |
08:27:58.37 |
+14:21:04.5 |
HIP 41578 |
12.65 |
| 2026-08-06 00:00 |
08:28:04.48 |
+14:20:38.9 |
HIP 41578 |
11.29 |
| 2026-08-06 12:00 |
08:28:10.57 |
+14:20:13.1 |
HIP 41578 |
9.97 |
| 2026-08-07 00:00 |
08:28:16.66 |
+14:19:47.4 |
HIP 41578 |
8.72 |
| 2026-08-07 12:00 |
08:28:22.73 |
+14:19:21.6 |
HIP 41578 |
7.59 |
| 2026-08-08 00:00 |
08:28:28.79 |
+14:18:55.7 |
HIP 41578 |
6.61 |
| 2026-08-08 12:00 |
08:28:34.84 |
+14:18:29.8 |
HIP 41578 |
5.88 |
| 2026-08-09 00:00 |
08:28:40.88 |
+14:18:03.9 |
HIP 41578 |
5.48 |
| 2026-08-09 12:00 |
08:28:46.91 |
+14:17:37.9 |
HIP 41578 |
5.49 |
| 2026-08-10 00:00 |
08:28:52.92 |
+14:17:11.9 |
HIP 41578 |
5.91 |
| 2026-08-10 12:00 |
08:28:58.92 |
+14:16:45.9 |
HIP 41578 |
6.65 |
| 2026-08-11 00:00 |
08:29:04.91 |
+14:16:19.8 |
HIP 41578 |
7.63 |
| 2026-08-11 12:00 |
08:29:10.89 |
+14:15:53.7 |
HIP 41578 |
8.75 |
| 2026-08-12 00:00 |
08:29:16.84 |
+14:15:27.5 |
HIP 41578 |
9.97 |
| 2026-08-12 12:00 |
08:29:22.79 |
+14:15:01.4 |
HIP 41578 |
11.26 |
| 2026-08-13 00:00 |
08:29:28.72 |
+14:14:35.2 |
HIP 41578 |
12.60 |
| 2026-08-13 12:00 |
08:29:34.63 |
+14:14:09.0 |
HIP 41578 |
13.96 |
| 2026-08-14 00:00 |
08:29:40.52 |
+14:13:42.8 |
HIP 41578 |
15.35 |
| 2026-08-14 12:00 |
08:29:46.40 |
+14:13:16.5 |
HIP 41578 |
16.75 |
| 2026-08-15 00:00 |
08:29:52.27 |
+14:12:50.3 |
HIP 41578 |
18.16 |
| 2026-08-15 12:00 |
08:29:58.11 |
+14:12:24.0 |
HIP 41749 |
18.22 |
| 2026-08-16 00:00 |
08:30:03.94 |
+14:11:57.7 |
HIP 41749 |
17.65 |
| 2026-08-16 12:00 |
08:30:09.74 |
+14:11:31.4 |
HIP 41749 |
17.18 |
| 2026-08-17 00:00 |
08:30:15.53 |
+14:11:05.1 |
HIP 41749 |
16.83 |
| 2026-08-17 12:00 |
08:30:21.30 |
+14:10:38.7 |
HIP 41749 |
16.61 |
| 2026-08-18 00:00 |
08:30:27.05 |
+14:10:12.4 |
HIP 41749 |
16.52 |
| 2026-08-18 12:00 |
08:30:32.78 |
+14:09:46.1 |
HIP 41749 |
16.56 |
| 2026-08-19 00:00 |
08:30:38.49 |
+14:09:19.7 |
HIP 41749 |
16.72 |