| Parameter |
Value |
| Designation |
117P/Helin-Roman-Alu 1 |
| Type |
P |
| Perihelion (tp_cal, UTC) |
2014-03-27T04:27:16.583040Z |
| Orbit solution date (soln_date, UTC) |
2026-03-09T08:47:52Z |
| Obs used |
6500 |
| NEO |
- |
| M1 |
5.700 |
| K1 |
15.000 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2014-02-26.0000000 |
| e |
0.25383563 |
| q (au) |
3.056348 |
| a (au) |
4.096078 |
| i (deg) |
8.697534 |
| Ω (om, deg) |
58.898113 |
| ω (w, deg) |
222.686727 |
| M (ma, deg) |
356.530072 |
Magnitude
Scatter + Global Linear
$$
M_a = (4.689 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
4.689 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-0.922 |
| k |
1.000 |
| δ90 |
9.999 |
| 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
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-05-12 00:00 |
05:47:55.18 |
+27:46:27.1 |
HIP 27456 |
27.36 |
| 2026-05-12 12:00 |
05:48:21.64 |
+27:46:35.9 |
HIP 27456 |
25.50 |
| 2026-05-13 00:00 |
05:48:48.17 |
+27:46:44.6 |
HIP 27456 |
24.92 |
| 2026-05-13 12:00 |
05:49:14.76 |
+27:46:53.1 |
HIP 27613 |
21.45 |
| 2026-05-14 00:00 |
05:49:41.43 |
+27:47:01.5 |
HIP 27613 |
15.90 |
| 2026-05-14 12:00 |
05:50:08.16 |
+27:47:09.8 |
HIP 27613 |
10.70 |
| 2026-05-15 00:00 |
05:50:34.96 |
+27:47:17.9 |
HIP 27613 |
6.80 |
| 2026-05-15 12:00 |
05:51:01.82 |
+27:47:25.8 |
HIP 27613 |
6.96 |
| 2026-05-16 00:00 |
05:51:28.75 |
+27:47:33.6 |
HIP 27686 |
3.89 |
| 2026-05-16 12:00 |
05:51:55.74 |
+27:47:41.2 |
HIP 27686 |
4.45 |
| 2026-05-17 00:00 |
05:52:22.79 |
+27:47:48.6 |
HIP 27686 |
9.80 |
| 2026-05-17 12:00 |
05:52:49.91 |
+27:47:55.9 |
HIP 27830 |
12.99 |
| 2026-05-18 00:00 |
05:53:17.08 |
+27:48:03.0 |
HIP 27830 |
11.33 |
| 2026-05-18 12:00 |
05:53:44.32 |
+27:48:10.0 |
HIP 27830 |
12.67 |
| 2026-05-19 00:00 |
05:54:11.61 |
+27:48:16.8 |
HIP 27830 |
16.30 |
| 2026-05-19 12:00 |
05:54:38.97 |
+27:48:23.4 |
HIP 28033 |
14.61 |
| 2026-05-20 00:00 |
05:55:06.37 |
+27:48:29.8 |
HIP 28033 |
9.33 |
| 2026-05-20 12:00 |
05:55:33.84 |
+27:48:36.1 |
HIP 28033 |
5.84 |
| 2026-05-21 00:00 |
05:56:01.36 |
+27:48:42.2 |
HIP 28033 |
7.42 |
| 2026-05-21 12:00 |
05:56:28.93 |
+27:48:48.1 |
HIP 28033 |
12.26 |
| 2026-05-22 00:00 |
05:56:56.56 |
+27:48:53.8 |
HIP 28033 |
17.90 |
| 2026-05-22 12:00 |
05:57:24.24 |
+27:48:59.4 |
HIP 28033 |
23.78 |
| 2026-05-23 00:00 |
05:57:51.97 |
+27:49:04.7 |
HIP 28244 |
22.40 |
| 2026-05-23 12:00 |
05:58:19.76 |
+27:49:09.9 |
HIP 28327 |
18.49 |
| 2026-05-24 00:00 |
05:58:47.59 |
+27:49:14.9 |
HIP 28327 |
16.04 |
| 2026-05-24 12:00 |
05:59:15.47 |
+27:49:19.7 |
HIP 28327 |
15.77 |
| 2026-05-25 00:00 |
05:59:43.40 |
+27:49:24.4 |
HIP 28327 |
17.78 |
| 2026-05-25 12:00 |
06:00:11.38 |
+27:49:28.8 |
HIP 28416 |
18.12 |
| 2026-05-26 00:00 |
06:00:39.40 |
+27:49:33.1 |
HIP 28500 |
15.91 |
| 2026-05-26 12:00 |
06:01:07.47 |
+27:49:37.1 |
HIP 28500 |
15.36 |
| 2026-05-27 00:00 |
06:01:35.59 |
+27:49:41.0 |
HIP 28500 |
17.20 |
| 2026-05-27 12:00 |
06:02:03.74 |
+27:49:44.7 |
HIP 28500 |
20.82 |
| 2026-05-28 00:00 |
06:02:31.95 |
+27:49:48.2 |
HIP 28723 |
25.12 |
| 2026-05-28 12:00 |
06:03:00.19 |
+27:49:51.4 |
HIP 28723 |
20.63 |
| 2026-05-29 00:00 |
06:03:28.48 |
+27:49:54.5 |
HIP 28723 |
17.25 |
| 2026-05-29 12:00 |
06:03:56.81 |
+27:49:57.4 |
HIP 28723 |
15.75 |
| 2026-05-30 00:00 |
06:04:25.19 |
+27:50:00.1 |
HIP 28723 |
16.65 |
| 2026-05-30 12:00 |
06:04:53.60 |
+27:50:02.6 |
HIP 28920 |
19.11 |
| 2026-05-31 00:00 |
06:05:22.05 |
+27:50:04.9 |
HIP 28920 |
13.27 |
| 2026-05-31 12:00 |
06:05:50.54 |
+27:50:07.0 |
HIP 28920 |
8.14 |
| 2026-06-01 00:00 |
06:06:19.07 |
+27:50:08.8 |
HIP 28920 |
5.98 |
| 2026-06-01 12:00 |
06:06:47.64 |
+27:50:10.5 |
HIP 28920 |
9.22 |
| 2026-06-02 00:00 |
06:07:16.24 |
+27:50:12.0 |
HIP 29044 |
5.41 |