| Parameter |
Value |
| Designation |
C/2015 ER61 (PANSTARRS) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2017-05-09T22:39:09.815040Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:33:07Z |
| Obs used |
2826 |
| NEO |
- |
| M1 |
10.700 |
| K1 |
5.750 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2017-04-30.0000000 |
| e |
0.99727861 |
| q (au) |
1.042132 |
| a (au) |
382.940360 |
| i (deg) |
6.348649 |
| Ω (om, deg) |
235.221741 |
| ω (w, deg) |
68.192259 |
| M (ma, deg) |
359.998692 |
Magnitude
Scatter + Global Linear
$$
M_a = (6.320 + 4.711\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
6.320 |
| n |
4.711 |
| gf |
0.992 |
| gb |
-0.804 |
| k |
0.997 |
| δ90 |
9.979 |
| 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 |
| 2016-02-04 |
2017-05-08 |
-1.6782 |
-0.087 |
| 2017-05-13 |
2018-02-24 |
-0.6062 |
+0.657 |
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 |
06:27:28.52 |
+18:52:43.6 |
HIP 30773 |
8.11 |
| 2026-03-26 12:00 |
06:27:28.74 |
+18:52:49.0 |
HIP 30773 |
8.11 |
| 2026-03-27 00:00 |
06:27:29.00 |
+18:52:54.4 |
HIP 30773 |
8.10 |
| 2026-03-27 12:00 |
06:27:29.31 |
+18:52:59.7 |
HIP 30773 |
8.08 |
| 2026-03-28 00:00 |
06:27:29.67 |
+18:53:05.0 |
HIP 30773 |
8.05 |
| 2026-03-28 12:00 |
06:27:30.08 |
+18:53:10.2 |
HIP 30773 |
8.02 |
| 2026-03-29 00:00 |
06:27:30.53 |
+18:53:15.5 |
HIP 30773 |
7.98 |
| 2026-03-29 12:00 |
06:27:31.03 |
+18:53:20.6 |
HIP 30773 |
7.93 |
| 2026-03-30 00:00 |
06:27:31.57 |
+18:53:25.8 |
HIP 30773 |
7.87 |
| 2026-03-30 12:00 |
06:27:32.16 |
+18:53:30.9 |
HIP 30773 |
7.81 |
| 2026-03-31 00:00 |
06:27:32.80 |
+18:53:35.9 |
HIP 30773 |
7.74 |
| 2026-03-31 12:00 |
06:27:33.48 |
+18:53:40.9 |
HIP 30773 |
7.67 |
| 2026-04-01 00:00 |
06:27:34.21 |
+18:53:45.9 |
HIP 30773 |
7.59 |
| 2026-04-01 12:00 |
06:27:34.98 |
+18:53:50.9 |
HIP 30773 |
7.51 |
| 2026-04-02 00:00 |
06:27:35.80 |
+18:53:55.8 |
HIP 30773 |
7.42 |
| 2026-04-02 12:00 |
06:27:36.66 |
+18:54:00.6 |
HIP 30773 |
7.33 |
| 2026-04-03 00:00 |
06:27:37.57 |
+18:54:05.4 |
HIP 30773 |
7.24 |
| 2026-04-03 12:00 |
06:27:38.53 |
+18:54:10.2 |
HIP 30773 |
7.15 |
| 2026-04-04 00:00 |
06:27:39.53 |
+18:54:14.9 |
HIP 30773 |
7.05 |
| 2026-04-04 12:00 |
06:27:40.57 |
+18:54:19.6 |
HIP 30773 |
6.96 |
| 2026-04-05 00:00 |
06:27:41.66 |
+18:54:24.3 |
HIP 30773 |
6.87 |
| 2026-04-05 12:00 |
06:27:42.79 |
+18:54:28.9 |
HIP 30773 |
6.78 |
| 2026-04-06 00:00 |
06:27:43.97 |
+18:54:33.4 |
HIP 30773 |
6.69 |
| 2026-04-06 12:00 |
06:27:45.19 |
+18:54:38.0 |
HIP 30773 |
6.62 |
| 2026-04-07 00:00 |
06:27:46.46 |
+18:54:42.4 |
HIP 30773 |
6.55 |
| 2026-04-07 12:00 |
06:27:47.77 |
+18:54:46.9 |
HIP 30773 |
6.48 |
| 2026-04-08 00:00 |
06:27:49.12 |
+18:54:51.3 |
HIP 30773 |
6.43 |
| 2026-04-08 12:00 |
06:27:50.52 |
+18:54:55.6 |
HIP 30773 |
6.40 |
| 2026-04-09 00:00 |
06:27:51.96 |
+18:54:59.9 |
HIP 30773 |
6.37 |
| 2026-04-09 12:00 |
06:27:53.45 |
+18:55:04.1 |
HIP 30773 |
6.36 |
| 2026-04-10 00:00 |
06:27:54.98 |
+18:55:08.4 |
HIP 30773 |
6.38 |
| 2026-04-10 12:00 |
06:27:56.55 |
+18:55:12.5 |
HIP 30773 |
6.41 |
| 2026-04-11 00:00 |
06:27:58.17 |
+18:55:16.6 |
HIP 30773 |
6.46 |
| 2026-04-11 12:00 |
06:27:59.83 |
+18:55:20.7 |
HIP 30773 |
6.53 |
| 2026-04-12 00:00 |
06:28:01.53 |
+18:55:24.7 |
HIP 30773 |
6.63 |
| 2026-04-12 12:00 |
06:28:03.28 |
+18:55:28.7 |
HIP 30773 |
6.75 |
| 2026-04-13 00:00 |
06:28:05.07 |
+18:55:32.6 |
HIP 30773 |
6.90 |
| 2026-04-13 12:00 |
06:28:06.90 |
+18:55:36.5 |
HIP 30773 |
7.07 |
| 2026-04-14 00:00 |
06:28:08.77 |
+18:55:40.3 |
HIP 30773 |
7.27 |
| 2026-04-14 12:00 |
06:28:10.68 |
+18:55:44.1 |
HIP 30773 |
7.49 |
| 2026-04-15 00:00 |
06:28:12.64 |
+18:55:47.8 |
HIP 30773 |
7.73 |
| 2026-04-15 12:00 |
06:28:14.64 |
+18:55:51.5 |
HIP 30773 |
8.00 |
| 2026-04-16 00:00 |
06:28:16.68 |
+18:55:55.1 |
HIP 30773 |
8.29 |