| Parameter |
Value |
| Designation |
90P/Gehrels 1 |
| Type |
P |
| Perihelion (tp_cal, UTC) |
2017-06-19T06:36:36.149760Z |
| Orbit solution date (soln_date, UTC) |
2022-05-24T23:57:55Z |
| Obs used |
577 |
| NEO |
- |
| M1 |
7.000 |
| K1 |
18.000 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2017-02-16.0000000 |
| e |
0.50979286 |
| q (au) |
2.974897 |
| a (au) |
6.068654 |
| i (deg) |
9.635376 |
| Ω (om, deg) |
13.251828 |
| ω (w, deg) |
29.270027 |
| M (ma, deg) |
351.872780 |
Magnitude
Scatter + Global Linear
$$
M_a = (8.608 + 4.725\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
8.608 |
| n |
4.725 |
| gf |
1.000 |
| gb |
-0.828 |
| 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 |
| 2016-08-27 |
2017-01-18 |
+56.4715 |
-28.048 |
| 2017-07-30 |
2018-04-15 |
-5.8039 |
+3.002 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-09-20 00:00 |
15:16:05.33 |
-24:53:31.5 |
HIP 74860 |
25.05 |
| 2026-09-20 12:00 |
15:16:16.39 |
-24:54:00.0 |
HIP 74860 |
22.50 |
| 2026-09-21 00:00 |
15:16:27.53 |
-24:54:28.8 |
HIP 74860 |
19.93 |
| 2026-09-21 12:00 |
15:16:38.75 |
-24:54:58.0 |
HIP 74860 |
17.34 |
| 2026-09-22 00:00 |
15:16:50.05 |
-24:55:27.5 |
HIP 74860 |
14.74 |
| 2026-09-22 12:00 |
15:17:01.43 |
-24:55:57.4 |
HIP 74860 |
12.11 |
| 2026-09-23 00:00 |
15:17:12.88 |
-24:56:27.7 |
HIP 74860 |
9.47 |
| 2026-09-23 12:00 |
15:17:24.41 |
-24:56:58.3 |
HIP 74860 |
6.82 |
| 2026-09-24 00:00 |
15:17:36.02 |
-24:57:29.2 |
HIP 74860 |
4.16 |
| 2026-09-24 12:00 |
15:17:47.70 |
-24:58:00.5 |
HIP 74860 |
1.55 |
| 2026-09-25 00:00 |
15:17:59.46 |
-24:58:32.2 |
HIP 74860 |
1.46 |
| 2026-09-25 12:00 |
15:18:11.30 |
-24:59:04.2 |
HIP 74860 |
4.09 |
| 2026-09-26 00:00 |
15:18:23.21 |
-24:59:36.5 |
HIP 74923 |
3.29 |
| 2026-09-26 12:00 |
15:18:35.19 |
-25:00:09.2 |
HIP 74923 |
0.56 |
| 2026-09-27 00:00 |
15:18:47.25 |
-25:00:42.2 |
HIP 74923 |
2.29 |
| 2026-09-27 12:00 |
15:18:59.38 |
-25:01:15.5 |
HIP 74923 |
5.09 |
| 2026-09-28 00:00 |
15:19:11.58 |
-25:01:49.1 |
HIP 74923 |
7.90 |
| 2026-09-28 12:00 |
15:19:23.86 |
-25:02:23.1 |
HIP 74923 |
10.74 |
| 2026-09-29 00:00 |
15:19:36.20 |
-25:02:57.4 |
HIP 74923 |
13.60 |
| 2026-09-29 12:00 |
15:19:48.62 |
-25:03:32.1 |
HIP 74923 |
16.47 |
| 2026-09-30 00:00 |
15:20:01.11 |
-25:04:07.0 |
HIP 74923 |
19.35 |
| 2026-09-30 12:00 |
15:20:13.67 |
-25:04:42.3 |
HIP 74923 |
22.26 |
| 2026-10-01 00:00 |
15:20:26.29 |
-25:05:17.9 |
HIP 74923 |
25.18 |
| 2026-10-01 12:00 |
15:20:38.99 |
-25:05:53.8 |
HIP 74923 |
28.11 |
| 2026-10-02 00:00 |
15:20:51.76 |
-25:06:30.1 |
HIP 75227 |
29.30 |
| 2026-10-02 12:00 |
15:21:04.59 |
-25:07:06.6 |
HIP 75227 |
26.90 |
| 2026-10-03 00:00 |
15:21:17.49 |
-25:07:43.4 |
HIP 75227 |
24.60 |
| 2026-10-03 12:00 |
15:21:30.46 |
-25:08:20.6 |
HIP 75227 |
22.46 |
| 2026-10-04 00:00 |
15:21:43.50 |
-25:08:58.1 |
HIP 75227 |
20.52 |
| 2026-10-04 12:00 |
15:21:56.60 |
-25:09:35.8 |
HIP 75227 |
18.86 |
| 2026-10-05 00:00 |
15:22:09.77 |
-25:10:13.9 |
HIP 75227 |
17.55 |
| 2026-10-05 12:00 |
15:22:23.00 |
-25:10:52.2 |
HIP 75227 |
16.70 |
| 2026-10-06 00:00 |
15:22:36.30 |
-25:11:30.9 |
HIP 75227 |
16.39 |
| 2026-10-06 12:00 |
15:22:49.67 |
-25:12:09.8 |
HIP 75227 |
16.64 |
| 2026-10-07 00:00 |
15:23:03.09 |
-25:12:49.1 |
HIP 75227 |
17.45 |
| 2026-10-07 12:00 |
15:23:16.58 |
-25:13:28.6 |
HIP 75227 |
18.75 |
| 2026-10-08 00:00 |
15:23:30.13 |
-25:14:08.4 |
HIP 75227 |
20.46 |
| 2026-10-08 12:00 |
15:23:43.75 |
-25:14:48.5 |
HIP 75227 |
22.48 |
| 2026-10-09 00:00 |
15:23:57.42 |
-25:15:28.9 |
HIP 75403 |
23.94 |
| 2026-10-09 12:00 |
15:24:11.16 |
-25:16:09.5 |
HIP 75403 |
23.96 |
| 2026-10-10 00:00 |
15:24:24.95 |
-25:16:50.4 |
HIP 75433 |
23.40 |
| 2026-10-10 12:00 |
15:24:38.81 |
-25:17:31.6 |
HIP 75433 |
22.49 |
| 2026-10-11 00:00 |
15:24:52.72 |
-25:18:13.1 |
HIP 75433 |
22.01 |