| Parameter |
Value |
| Designation |
C/2021 D2 (ZTF) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2022-02-03T23:30:34.882560Z |
| Orbit solution date (soln_date, UTC) |
2026-01-13T08:12:19Z |
| Obs used |
654 |
| NEO |
- |
| M1 |
13.300 |
| K1 |
4.500 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2021-11-09.0000000 |
| e |
1.00133730 |
| q (au) |
2.946303 |
| a (au) |
-2203.174195 |
| i (deg) |
83.831242 |
| Ω (om, deg) |
305.677385 |
| ω (w, deg) |
125.029250 |
| M (ma, deg) |
-0.000829 |
Magnitude
Scatter + Global Linear
$$
M_a = (15.473 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
15.473 |
| n |
2.000 |
| gf |
1.000 |
| gb |
-0.788 |
| 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 |
| 2021-02-19 |
2021-05-22 |
+15.6409 |
-9.727 |
| 2021-05-22 |
2021-08-10 |
-4.4730 |
+2.199 |
| 2021-08-10 |
2022-02-03 |
+4.5999 |
-2.464 |
| 2022-02-21 |
2023-04-22 |
+12.0730 |
-5.101 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-06-01 00:00 |
07:30:44.76 |
-44:19:57.0 |
HIP 36592 |
17.35 |
| 2026-06-01 12:00 |
07:30:53.85 |
-44:19:09.9 |
HIP 36592 |
15.89 |
| 2026-06-02 00:00 |
07:31:02.99 |
-44:18:23.7 |
HIP 36592 |
14.51 |
| 2026-06-02 12:00 |
07:31:12.18 |
-44:17:38.4 |
HIP 36592 |
13.25 |
| 2026-06-03 00:00 |
07:31:21.43 |
-44:16:53.9 |
HIP 36592 |
12.15 |
| 2026-06-03 12:00 |
07:31:30.74 |
-44:16:10.2 |
HIP 36592 |
11.24 |
| 2026-06-04 00:00 |
07:31:40.09 |
-44:15:27.5 |
HIP 36592 |
10.59 |
| 2026-06-04 12:00 |
07:31:49.50 |
-44:14:45.5 |
HIP 36592 |
10.25 |
| 2026-06-05 00:00 |
07:31:58.97 |
-44:14:04.5 |
HIP 36592 |
10.24 |
| 2026-06-05 12:00 |
07:32:08.48 |
-44:13:24.3 |
HIP 36592 |
10.57 |
| 2026-06-06 00:00 |
07:32:18.05 |
-44:12:44.9 |
HIP 36592 |
11.21 |
| 2026-06-06 12:00 |
07:32:27.67 |
-44:12:06.5 |
HIP 36592 |
12.11 |
| 2026-06-07 00:00 |
07:32:37.33 |
-44:11:28.9 |
HIP 36592 |
13.23 |
| 2026-06-07 12:00 |
07:32:47.05 |
-44:10:52.2 |
HIP 36592 |
14.51 |
| 2026-06-08 00:00 |
07:32:56.81 |
-44:10:16.4 |
HIP 36592 |
15.92 |
| 2026-06-08 12:00 |
07:33:06.63 |
-44:09:41.4 |
HIP 36592 |
17.42 |
| 2026-06-09 00:00 |
07:33:16.49 |
-44:09:07.3 |
HIP 36592 |
19.00 |
| 2026-06-09 12:00 |
07:33:26.40 |
-44:08:34.2 |
HIP 36875 |
17.74 |
| 2026-06-10 00:00 |
07:33:36.35 |
-44:08:01.9 |
HIP 36875 |
16.56 |
| 2026-06-10 12:00 |
07:33:46.35 |
-44:07:30.5 |
HIP 36875 |
15.49 |
| 2026-06-11 00:00 |
07:33:56.40 |
-44:07:00.0 |
HIP 36875 |
14.56 |
| 2026-06-11 12:00 |
07:34:06.48 |
-44:06:30.4 |
HIP 36875 |
13.81 |
| 2026-06-12 00:00 |
07:34:16.62 |
-44:06:01.6 |
HIP 36875 |
13.27 |
| 2026-06-12 12:00 |
07:34:26.79 |
-44:05:33.8 |
HIP 36875 |
12.96 |
| 2026-06-13 00:00 |
07:34:37.01 |
-44:05:06.9 |
HIP 36875 |
12.90 |
| 2026-06-13 12:00 |
07:34:47.27 |
-44:04:40.9 |
HIP 36875 |
13.10 |
| 2026-06-14 00:00 |
07:34:57.57 |
-44:04:15.9 |
HIP 36875 |
13.55 |
| 2026-06-14 12:00 |
07:35:07.91 |
-44:03:51.7 |
HIP 36875 |
14.23 |
| 2026-06-15 00:00 |
07:35:18.29 |
-44:03:28.4 |
HIP 36875 |
15.11 |
| 2026-06-15 12:00 |
07:35:28.71 |
-44:03:06.1 |
HIP 36875 |
16.15 |
| 2026-06-16 00:00 |
07:35:39.17 |
-44:02:44.7 |
HIP 36875 |
17.32 |
| 2026-06-16 12:00 |
07:35:49.66 |
-44:02:24.2 |
HIP 36875 |
18.61 |
| 2026-06-17 00:00 |
07:36:00.20 |
-44:02:04.6 |
HIP 36875 |
20.00 |
| 2026-06-17 12:00 |
07:36:10.76 |
-44:01:45.9 |
HIP 36875 |
21.46 |
| 2026-06-18 00:00 |
07:36:21.36 |
-44:01:28.2 |
HIP 36875 |
22.98 |
| 2026-06-18 12:00 |
07:36:32.00 |
-44:01:11.3 |
HIP 36875 |
24.55 |
| 2026-06-19 00:00 |
07:36:42.67 |
-44:00:55.5 |
HIP 36875 |
26.16 |
| 2026-06-19 12:00 |
07:36:53.37 |
-44:00:40.5 |
HIP 37148 |
25.35 |
| 2026-06-20 00:00 |
07:37:04.11 |
-44:00:26.4 |
HIP 37148 |
24.26 |
| 2026-06-20 12:00 |
07:37:14.88 |
-44:00:13.3 |
HIP 37148 |
23.30 |
| 2026-06-21 00:00 |
07:37:25.68 |
-44:00:01.1 |
HIP 37148 |
22.47 |
| 2026-06-21 12:00 |
07:37:36.50 |
-43:59:49.9 |
HIP 37148 |
21.81 |
| 2026-06-22 00:00 |
07:37:47.36 |
-43:59:39.5 |
HIP 37148 |
21.32 |