メタデータ

項目	値
Designation	C/2012 S1 (ISON)
Type	C
Perihelion (tp_cal, UTC)	2013-11-28T18:20:55.495680Z
Orbit solution date (soln_date, UTC)	2025-11-21T13:42:48Z
Obs used	6684
NEO	-
M1	10.400
K1	4.500
PC	-

オスキュレーティング軌道要素

項目	値
Epoch (epoch_cal, TDB)	2013-05-01.0000000
e	1.00000509
q (au)	0.012467
a (au)	-2446.893404
i (deg)	62.162896
Ω (om, deg)	295.686541
ω (w, deg)	345.541197
M (ma, deg)	-0.001724

等級

散乱 + 全体線形

$$ M_a = (11.695 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$

モデル定数

項目	値
H0	11.695
n	2.000
gf	1.000
gb	-0.791
k	0.951
δ90	10.000

パラメータ	記号	範囲	説明
太陽・地球距離が1 AUのときの絶対等級	H0	-5 to 20	彗星の固有の明るさ
測光スロープパラメータ	n	2 to 6	太陽距離に対する明るさ変化率
前方散乱非対称係数	gf	0.8 to 1	前方散乱の強さ
後方散乱非対称係数	gb	-1 to -0.5	後方散乱の強さ
分配係数	k	0.8 to 1	前方/後方散乱の寄与比
ダスト/ガス明るさ比	δ90	1 to 10	ダスト散乱とガス放射の相対寄与

参考: EPSC-DPS2025-160

残差 (区間線形)

$$\epsilon = a \log_{10} r_{\mathrm{au}} + b$$

開始日 (UTC)	終了日 (UTC)	a	b
2011-09-30	2013-11-13	+0.7784	-0.530
2013-11-13	2013-11-28	+7.8926	-0.124

log10 r = log10(太陽距離/AU)、Δ = 地球距離(AU)

天体暦

Date/Time (UTC)	RA (J2000)	Dec (J2000)	Nearest HIP	Dist from HIP (arcmin)
2026-03-26 00:00	07:17:07.44	+37:28:43.0	HIP 35225	14.32
2026-03-26 12:00	07:17:06.40	+37:28:29.9	HIP 35225	14.05
2026-03-27 00:00	07:17:05.39	+37:28:16.6	HIP 35225	13.79
2026-03-27 12:00	07:17:04.42	+37:28:03.3	HIP 35225	13.53
2026-03-28 00:00	07:17:03.50	+37:27:49.9	HIP 35225	13.27
2026-03-28 12:00	07:17:02.61	+37:27:36.5	HIP 35225	13.01
2026-03-29 00:00	07:17:01.77	+37:27:22.9	HIP 35225	12.76
2026-03-29 12:00	07:17:00.96	+37:27:09.3	HIP 35225	12.50
2026-03-30 00:00	07:17:00.20	+37:26:55.6	HIP 35225	12.25
2026-03-30 12:00	07:16:59.47	+37:26:41.9	HIP 35225	12.00
2026-03-31 00:00	07:16:58.79	+37:26:28.1	HIP 35225	11.75
2026-03-31 12:00	07:16:58.15	+37:26:14.2	HIP 35225	11.50
2026-04-01 00:00	07:16:57.55	+37:26:00.2	HIP 35225	11.25
2026-04-01 12:00	07:16:56.98	+37:25:46.2	HIP 35225	11.00
2026-04-02 00:00	07:16:56.46	+37:25:32.1	HIP 35225	10.76
2026-04-02 12:00	07:16:55.98	+37:25:18.0	HIP 35225	10.51
2026-04-03 00:00	07:16:55.54	+37:25:03.7	HIP 35225	10.26
2026-04-03 12:00	07:16:55.14	+37:24:49.5	HIP 35225	10.02
2026-04-04 00:00	07:16:54.78	+37:24:35.1	HIP 35225	9.77
2026-04-04 12:00	07:16:54.46	+37:24:20.7	HIP 35225	9.52
2026-04-05 00:00	07:16:54.17	+37:24:06.3	HIP 35225	9.28
2026-04-05 12:00	07:16:53.93	+37:23:51.8	HIP 35225	9.03
2026-04-06 00:00	07:16:53.73	+37:23:37.2	HIP 35225	8.79
2026-04-06 12:00	07:16:53.57	+37:23:22.6	HIP 35225	8.54
2026-04-07 00:00	07:16:53.45	+37:23:07.9	HIP 35225	8.30
2026-04-07 12:00	07:16:53.37	+37:22:53.2	HIP 35225	8.05
2026-04-08 00:00	07:16:53.33	+37:22:38.4	HIP 35225	7.80
2026-04-08 12:00	07:16:53.33	+37:22:23.6	HIP 35225	7.56
2026-04-09 00:00	07:16:53.37	+37:22:08.7	HIP 35225	7.31
2026-04-09 12:00	07:16:53.45	+37:21:53.8	HIP 35225	7.07
2026-04-10 00:00	07:16:53.57	+37:21:38.8	HIP 35225	6.82
2026-04-10 12:00	07:16:53.73	+37:21:23.8	HIP 35225	6.58
2026-04-11 00:00	07:16:53.93	+37:21:08.7	HIP 35225	6.34
2026-04-11 12:00	07:16:54.16	+37:20:53.6	HIP 35225	6.10
2026-04-12 00:00	07:16:54.44	+37:20:38.4	HIP 35225	5.86
2026-04-12 12:00	07:16:54.76	+37:20:23.2	HIP 35225	5.63
2026-04-13 00:00	07:16:55.12	+37:20:08.0	HIP 35225	5.39
2026-04-13 12:00	07:16:55.51	+37:19:52.7	HIP 35225	5.17
2026-04-14 00:00	07:16:55.95	+37:19:37.4	HIP 35225	4.94
2026-04-14 12:00	07:16:56.42	+37:19:22.0	HIP 35225	4.73
2026-04-15 00:00	07:16:56.94	+37:19:06.6	HIP 35225	4.52
2026-04-15 12:00	07:16:57.49	+37:18:51.2	HIP 35225	4.33
2026-04-16 00:00	07:16:58.08	+37:18:35.7	HIP 35225	4.14