Periodic SOHO Comets

1. P/1999 J6 = 2004 V9 = 2010 H3 (SOHO) = 2015/09/26

The first periodic SOHO comet was identified by Brian Marsden in 2004 December when C/1999 J6 had returned as C/2004 V9. Brian wrote on MPEC 2004-X73:

     Although the orbits computed for the SOHO comets that are members of
sungrazing groups other than Kreutz have hitherto necessarily been assumed to
be parabolic, the low orbital inclinations and the indicated associations with
meteor streams suggest that the members of the Marsden and Kracht groups, at
least, are of short period (which still means that  e  is no smaller than
0.98).  If so, it might now be the case that individual members can be
recognized at more than one perihelion passage.  Furthermore, the implied
success in having at least one member survive perihelion passage would provide
an obvious mechanism for the continued maintenance of these comet groups.

     It is eminently possible that C/2004 V9 is in fact identical with
C/1999 J6 (cf. MPEC 2000-F30).  To demonstrate this, the following represents
a tentative linkage of the observations.  Since there is a well-known
inconsistency between the C3 and C2 observations, only the latter (i.e.,
those of the 1999 comet made on May 11.46257 UT and earlier and those of the
2004 comet on Nov. 8.35423 and earlier) have been used, the resulting
residuals being very comparable to those of the individual parabolic
solutions.  It should also be noted that the object would have passed only
0.0091 AU from the moon and 0.0087 AU from the earth on 1999 June 12.22 and
12.31 UT, respectively:

Epoch 1999 May 22.0 TT = JDT 2451320.5
T 1999 May 11.58356 TT                                  MPC
q   0.0491317            (2000.0)            P               Q
n   0.17952782     Peri.   22.21043     -0.20252199     -0.87330037
a   3.1120618      Node    81.80049     +0.81764025     -0.39980558
e   0.9842125      Incl.   26.59424     +0.53893345     +0.27839172
P   5.49

Epoch 2004 Nov. 11.0 TT = JDT 2453320.5
T 2004 Nov. 8.56075 TT                                  MPC
q   0.0490617            (2000.0)            P               Q
n   0.17940682     Peri.   22.31612     -0.20213975     -0.87355162
a   3.1134609      Node    81.67998     +0.81732637     -0.39954766
e   0.9842421      Incl.   26.58223     +0.53955270     +0.27797346
P   5.49

This identification was correct, the comet returned in 2010 April (MPEC 2010-H37). But the return was 11.6 days earlier than expected from the pure gravitational linkage of C/1999 J6 = C/2004 V9. I found a linkage of all three apparitions of the comet with a non-gravitational parameter of A2 = -0.1898 and Brian Marsden published his solution on MPEC 2010-J28 with A1 = +0.31 and A2 = -0.1892. More on Comet P/1999 J6 = 2004 V9 = 2010 H3 (SOHO) is here. The next perihelion will be on 2015 September 26 (NK2328).
The comet returned in 2015 only 0.10 days earlier than predicted by Nakano . Including the new observations of 2015 (178 measurements by Karl Battams in C2 and C3), I predict the next perihelion as 2021 Feb 16.57.
The return in 2021 was unfavourable for observations in C2 and the comet was not observed. The next perihelion will be around 2026 Jun 18.

2. 342P/SOHO: P/2000 O3 = 2005 W4 = 2011 E1 = 2016 N5 (SOHO)

As expected also two Kracht group comets could be linked. These were C/2000 O3 and C/2005 W4 in 2005 December. Brian Marsden wrote on MPEC 2005-X14:

     It seems likely that the Kracht-group comet C/2005 W4 is a return of
C/2000 O3 (cf. MPEC 2000-Q09), a suggestion made by S. Hoenig before the
observations above were available.  The following orbital linkage utilizes
just the C2 observations (those from July 30.89596 onward in the case of
C/2000 O3); although only the first three C/2005 W4 observations were obtained
with C2, the residuals of the C3 observations are not systematically displaced.

Epoch 2000 Aug. 4.0 TT = JDT 2451760.5
T 2000 July 30.95085 TT                                 MPC
q   0.0540305            (2000.0)            P               Q
n   0.18564064     Peri.   48.62874     -0.19907419     -0.95826026
a   3.0433648      Node    54.01707     +0.80630530     -0.27917308
e   0.9822465      Incl.   14.68978     +0.55699302     +0.06164143
P   5.31

Epoch 2005 Nov. 6.0 TT = JDT 2453680.5
T 2005 Nov. 23.49971 TT                                 MPC
q   0.0545674            (2000.0)            P               Q
n   0.18538265     Peri.   49.04300     -0.19881529     -0.95884640
a   3.0461877      Node    53.57283     +0.80638446     -0.27759260
e   0.9820867      Incl.   14.59109     +0.55697091     +0.05963155
P   5.32

The comet returned 2011 March 09 only eight hours earlier than expected from the pure gravitational linkage of C/2000 O3 and C/2005 W4.I sent my non-gravitational solution with A2 = -0.0075 to Gareth Wlliams and he published his solution on MPEC 2011-F14 with A2 = -0.0076. Sebastian H�nig's and my part in this linkage were published on IAUC 9201.The next perihelion of P/2000 O3 = 2005 W4 = 2011 E1 will be on 2016 July 01 (NK2530).
The comet returned in 2016 seven hours earlier than predicted by Nakano. The comet was designated as P/2016 N5 a new orbits with A2 = +0.0015 was published on MPEC 2016-P77. After that the comet was designated 342P/SOHO. The next perihelion will be on 2021 Oct 19.43.
But MPEC 2016-P77 shows no common solution for all four apparitions. Using only the observations made in LASCO C2, I can link P/2000 O3 = 2005 W4 = 2011 E1 with small residuals and A2 = -0.0070 and can link 2005 W4 = 2011 E1 = 2016 N5 with small residuals and A2 = -0.0141. The second solution gives the next perihelion as 2021 Oct 18.65.
NK3659 shows a common solution for all four apparitions with A2 = -0.0114 and T = 2021 Oct 18.84. The return in 2021 was unfavourable for observations in C2 and the comet was not observed. The next perihelion will be around 2027 Feb 04.

3. 322P/SOHO: P/1999 R1 = 2003 R5 = 2007 R5 = 2011 R4 (SOHO) = 2015/09/04

In the years 1999, 2002 and 2003 three low-inclination comets with similar orbits were found in SOHO LASCO images and a new group was announced on IAUC 8340: "C/2003 R5 belongs to a new group that certainly includes C/1999 R1 and probably includes C/2002 R5." The orbits of C/1999 R1 and C/2003 R5 were nearly identical and in 2005 September Sebastian H�nig showed that the observations of both comets could be represented by a common orbit. He predicted the next perihelion for 2007 September 11. This return was observed just as predicted. Brian Marsden wrote on MPEC 2007-S16:

The 2007 recovery is by B.
Zhou, following a prediction by S. Hoenig (2006, Astron. Astrophys.
445, 759).  Measurements by K. Battams, reductions by B. G. Marsden.
The 1999 and 2003 positions replace the C2 data on MPC 35772 and 52131.

Orbital elements:
    P/1999 R1 = 2003 R5 = 2007 R5 (SOHO)
Epoch 1999 Sept. 19.0 TT = JDT 2451440.5
T 1999 Sept. 5.51913 TT                                 MPC
q   0.0563788            (2000.0)            P               Q
n   0.24608380     Peri.   43.34320     +0.66144716     -0.74966325
a   2.5220133      Node     5.38591     +0.60723509     +0.51794024
e   0.9776453      Incl.   13.67849     +0.44017405     +0.41199869
P   4.01

Epoch 2003 Aug. 29.0 TT = JDT 2452880.5
T 2003 Sept. 8.81649 TT                                 MPC
q   0.0568899            (2000.0)            P               Q
n   0.24582013     Peri.   43.62425     +0.66148643     -0.74966633
a   2.5238164      Node     5.09358     +0.60721888     +0.51903693
e   0.9774588      Incl.   13.60425     +0.44013740     +0.41061060
P   4.01

Epoch 2007 Sept. 17.0 TT = JDT 2454360.5
T 2007 Sept. 11.31967 TT                                MPC
q   0.0537196            (2000.0)            P               Q
n   0.24695650     Peri.   48.56551     +0.66113917     -0.75026326
a   2.5160682      Node     0.04886     +0.60643757     +0.53425211
e   0.9786494      Incl.   12.64000     +0.44173348     +0.38946081
P   3.99

So the "new group" (also called "Kracht2 group") no longer existed. More about the history of this group is here. P/1999 R1 returned again in 2011 September and the observations from 1999 - 2011 could be linked without using non-gravitational parameters. The next perihelion of P/1999 R1 = 2003 R5 = 2007 R5 = 2011 R4 (SOHO) will be on 2015 September 04 (MPEC 2015-K01).

Already on 2015 May 22 it was recovered for the first time with an earth-based telescope (VLT UT1 FORS2/ESO) near opposition at a distance from earth of 1.2 AU. It was of magnitude 23 (MPEC 2015-K84).
NK 3010 has an orbital solution 1999 - 2015-06-18 with A2 = +0.000146. My solution for 1999 - 2015-07-24 has A2 = +0.000132.
The comet was observed by SOHO/LASCO in 2015 and 2019, but those observations are not yet published. The next perihelion will be on 2023 Aug 21.1.. This prediction uses the observations of 2015 (measured by Karl Battams), but not those of 2019 (not yet measured).

4. P/2002 R5 = 2008 L6/L7 = 2014 Ea/Eb (SOHO) = 2019/12/13

This is the third comet from the "new group" of IAUC 8340. After the identification of C/1999 R1 = 2003 R5 the "new group" had only two members, but when C/2002 R5 returned in 2008 it has split in two parts (C/2008 L6 and L7) - so there were three comets again in similar short-period orbits. Brian Marsden wrote on MPEC 2008-O23:

Comets C/2008 L6 and L7 appear to be members of the "Kracht 2" Group, and
R. Kracht suggests that they represent a return of comet C/2002 R5 (cf. MPEC
2002-S35).  The 15-deg shift in the line of nodes actually supports the
likely correctness of this linkage, as it is consistent with the comet's
passage within 1.1 AU of Jupiter in Jan. 2007.  The result of linking C/2002 R5
to C/2008 L6 (the brighter of the recent pair) is:

    C/2002 R5 = 2008 L6 (SOHO)
Epoch 2002 Sept. 3.0 TT = JDT 2452520.5
T 2002 Sept. 5.79262 TT                                 MPC
q   0.0471997            (2000.0)            P               Q
n   0.17076055     Peri.   45.76339     +0.51849414     -0.85321200
a   3.2176912      Node    13.34199     +0.69804357     +0.38417839
e   0.9853312      Incl.   14.17434     +0.49386132     +0.35275523
P   5.77

Epoch 2008 June 23.0 TT = JDT 2454640.5
T 2008 June 10.18275 TT                                 MPC
q   0.0459562            (2000.0)            P               Q
n   0.17099961     Peri.   58.89903     +0.51897653     -0.85478827
a   3.2146916      Node   359.83361     +0.69492611     +0.42233394
e   0.9857043      Incl.   12.15136     +0.49773594     +0.30161407
P   5.76

The fainter component (L7) was leading the brighter (L6) by 0.3 hours. Zdenek Sekanina wrote on IAUC 8983:

Z. Sekanina, Jet Propulsion Laboratory, reports that he made
an attempt to constrain the probable time of breakup of the SOHO
comet C/2002 R5 into its fragments, C/2008 L6 and C/2008 L7. The
approach was based on fitting the geocentric positional offsets of
C/2008 L7 from C/2008 L6, derived from the June 10 astrometric
observations made with the C2 coronagraph (MPEC 2008-O23). The
low-accuracy data and the short orbital arc available ruled out the
possibility of a more comprehensive modeling, and allowed him only
to conclude that the event occurred most probably between 2 and 10
weeks before the 2002 perihelion, when C/2002 R5 was 0.6 to 1.7 AU
from the sun. When imaged in 2002, the comet must have been
already double, but the separation distance did not exceed 2" and
the duplicity could not be resolved by either coronagraph. The rms
residual of these solutions was +/- 3".9, and for the seven used
offsets (of 11 measured) the residuals did not exceed 6". Another
positive sign of these solutions was a low separation velocity,
reaching submeter-per-second values for the early breakup times and
never getting greater than about 2 m/s. No outgassing-driven
differential nongravitational accelerations were found to have been
affecting the motions of the fragment comets between 2002 and 2008.

NK 2164 predicted the next perihelion of C/2008 L6 for 2014 March 14.98. But Zhijian Xu found the comet already 2014 March 07 in LASCO C2 images 04:17 - 05:00 UTC, seven days earlier than expected. The small, leading fragment from 2008 was now trailing by 2.6 hours. I could link my measurements of the new observations with those of 2002 and 2008 with A2 = -0.1012 (L6) and A2 = -0.0973 (L7). The next perihelion will be 2019 November 20.

Fragments of P/2002 R5 were observed with SOHO/LASCO on 2019 Nov 27 (SOHO-3870), Dec 06 (SOHO-3877), Dec 13 (SOHO-3882) and Dec 20 (SOHO-3885). Karl Battams measured the new fragments and also all previous fragments of P/2002 R5. The brightest fragment at each return is 2002 R5, 2008 L6, SOHO-2673 (2014) and SOHO-3882 (2019). The first three can be linked with A2 = -0.1005 and the next perihelion at 2019 November 20.9. So SOHO-3882 has returned about 22 days later than expected. 2008 L6, SOHO-2673 and SOHO-3882 can also be linked, but this linkage needs A2 = +0.2061. Such change in A2 is not totally unexpected as it has already been seen in Marsden comet P/2000 C4 = 2005 W1 = SOHO-2115 = 2017/01/31. The next perihelion of the brightest fragment will be around 2025 Sep 26, obviously uncertain by several weeks.

This solution is based on the identity of P/2002 R5 (mag 6.5), 2008 L6 (mag 6.5), SOHO-2673 (mag 7) and SOHO-3882 (mag 6.5). All other fragments were of mag 8 with the exception of SOHO-3885 from 2019-12-19 with mag 7 - which would need an even greater change to A2 = 0.2862 to link it with 2008 L6 and SOHO-2673 and such solution shows very strong trends in the residuals.

5. 321P/SOHO: P/2001 D1 = 1997 J6 = 2004 X7 = 2008 S2 = 2012 M2 (SOHO) = 2016/04/10 = 2020/01/17

The initial linkage was C/2001 D1 = C/2004 X7 = C/2008 S2. Later C/1997 J6 was found (more on this page). The comet returned in 2012 but those measurements were made not until 2015. The results were published on MPEC 2015-K1:

    P/2001 D1 = 1997 J6 = 2004 X7 = 2008 S2 = 2012 M2 (SOHO)
Epoch 1997 Apr. 22.0 TT = JDT 2450560.5
T 1997 May 1.66326 TT                                   MPCW
q   0.0493940            (2000.0)            P               Q
n   0.25936014     Peri.  172.03990     +0.92660946     +0.36734966
a   2.4351959      Node   165.59310     -0.36033004     +0.92850527
e   0.9797166      Incl.   18.83033     -0.10750425     +0.05414972
P   3.80
From 90 observations 1997 May 1-2012 June 30.  Nongravitational parameters
     A1 = +0.00, A2 = -0.0002.

    P/2001 D1 = 1997 J6 = 2004 X7 = 2008 S2 = 2012 M2 (SOHO)
Epoch 2001 Feb. 20.0 TT = JDT 2451960.5
T 2001 Feb. 18.76953 TT                                 MPCW
q   0.0498089            (2000.0)            P               Q
n   0.25917697     Peri.  172.03461     +0.92656986     +0.36749775
a   2.4363431      Node   165.59380     -0.36039389     +0.92839386
e   0.9795559      Incl.   18.77752     -0.10763152     +0.05504768
P   3.80
From 90 observations 1997 May 1-2012 June 30.  Nongravitational parameters
     A1 = +0.00, A2 = -0.0002.

    P/2001 D1 = 1997 J6 = 2004 X7 = 2008 S2 = 2012 M2 (SOHO)
Epoch 2004 Dec. 21.0 TT = JDT 2453360.5
T 2004 Dec. 7.82297 TT                                  MPCW
q   0.0469322            (2000.0)            P               Q
n   0.26072186     Peri.  172.39230     +0.92702386     +0.36503093
a   2.4267093      Node   165.28252     -0.35940409     +0.93021932
e   0.9806601      Incl.   19.76279     -0.10703018     +0.03800566
P   3.78
From 90 observations 1997 May 1-2012 June 30.  Nongravitational parameters
     A1 = +0.00, A2 = -0.0002.

    P/2001 D1 = 1997 J6 = 2004 X7 = 2008 S2 = 2012 M2 (SOHO)
Epoch 2008 Sept. 11.0 TT = JDT 2454720.5
T 2008 Sept. 17.95636 TT                                MPCW
q   0.0466880            (2000.0)            P               Q
n   0.26080580     Peri.  172.42124     +0.92713614     +0.36465643
a   2.4261886      Node   165.26922     -0.35914389     +0.93041537
e   0.9807567      Incl.   19.83515     -0.10693106     +0.03678222
P   3.78
From 90 observations 1997 May 1-2012 June 30.  Nongravitational parameters
     A1 = +0.00, A2 = -0.0002.

    P/2001 D1 = 1997 J6 = 2004 X7 = 2008 S2 = 2012 M2 (SOHO)
Epoch 2012 July 12.0 TT = JDT 2456120.5
T 2012 June 30.48402 TT                                 MPCW
q   0.0470010            (2000.0)            P               Q
n   0.26064312     Peri.  172.42539     +0.92707896     +0.36480975
a   2.4271980      Node   165.25710     -0.35925219     +0.93033930
e   0.9806357      Incl.   19.81045     -0.10706285     +0.03718386
P   3.78
From 90 observations 1997 May 1-2012 June 30.  Nongravitational parameters
     A1 = +0.00, A2 = -0.0002.

    P/2001 D1 = 1997 J6 = 2004 X7 = 2008 S2 = 2012 M2 (SOHO)
Epoch 2015 June 27.0 TT = JDT 2457200.5
T 2016 Apr. 10.32330 TT                                 MPCW
q   0.0457829            (2000.0)            P               Q
n   0.26099603     Peri.  172.53347     +0.92731582     +0.36375854
a   2.4250095      Node   165.17736     -0.35873519     +0.93096469
e   0.9811205      Incl.   20.14822     -0.10674477     +0.03137629
P   3.78
From 90 observations 1997 May 1-2012 June 30.  Nongravitational parameters
     A1 = +0.00, A2 = -0.0002.

    P/2001 D1 = 1997 J6 = 2004 X7 = 2008 S2 = 2012 M2 (SOHO)
Epoch 2016 Apr. 2.0 TT = JDT 2457480.5
T 2016 Apr. 10.37923 TT                                 MPCW
q   0.0455793            (2000.0)            P               Q
n   0.26143177     Peri.  172.55983     +0.92748896     +0.36326073
a   2.4223142      Node   165.17661     -0.35832629     +0.93118837
e   0.9811836      Incl.   20.20228     -0.10661376     +0.03049367
P   3.77
From 90 observations 1997 May 1-2012 June 30.  Nongravitational parameters
     A1 = +0.00, A2 = -0.0002.

The next perihelion will be on 2016 April 10. Closest approach to the earth will be on 2016 March 13 with 24.0 Gm (0.161 AU).
Update: SOHO LASCO has observed the returns in 2016 April and 2020 January. The next perihelion will be 2023 Oct 26.

6. 323P/SOHO: P/1999 X3 = 2004 E2 = 2008 K10 = 2012 Q2 (SOHO) = 2016/11/23 = 2021/01/17

After I had found C/2001 D1 = 2004 X7 = 2008 S2, I searched for other unrecognized identities among the non-group comets. I looked for comets with low inclinations, short observational arcs and similar time intervalls between their perihelion passages. I found C/199X3, 2004 E2 and 2008 K10 on 2008 September 24 (more on this page). The comet returned in 2012 but those measurements were made not until 2015. The results were published on MPEC 2015-K1:

    P/1999 X3 = 2004 E2 = 2008 K10 = 2012 Q2 (SOHO)
Epoch 1999 Dec. 8.0 TT = JDT 2451520.5
T 1999 Dec. 12.87923 TT                                 MPCW
q   0.0521168            (2000.0)            P               Q
n   0.23172330     Peri.  352.71358     +0.73295942     +0.67756510
a   2.6251629      Node   324.38769     -0.61876711     +0.62700415
e   0.9801472      Incl.    5.97661     -0.28266191     +0.38441037
P   4.25
From 47 observations 1999 Dec. 12-2012 Aug. 20.

    P/1999 X3 = 2004 E2 = 2008 K10 = 2012 Q2 (SOHO)
Epoch 2004 Mar. 16.0 TT = JDT 2453080.5
T 2004 Mar. 12.32668 TT                                 MPCW
q   0.0483164            (2000.0)            P               Q
n   0.23351330     Peri.  353.06258     +0.73457815     +0.67562583
a   2.6117301      Node   324.17472     -0.61727828     +0.62708466
e   0.9815002      Incl.    6.14423     -0.28171345     +0.38767843
P   4.22
From 47 observations 1999 Dec. 12-2012 Aug. 20.

    P/1999 X3 = 2004 E2 = 2008 K10 = 2012 Q2 (SOHO)
Epoch 2008 May 14.0 TT = JDT 2454600.5
T 2008 May 31.32615 TT                                  MPCW
q   0.0479308            (2000.0)            P               Q
n   0.23368002     Peri.  353.10953     +0.73481233     +0.67533804
a   2.6104878      Node   324.14740     -0.61705498     +0.62704024
e   0.9816392      Incl.    6.17515     -0.28159190     +0.38825129
P   4.22
From 47 observations 1999 Dec. 12-2012 Aug. 20.

    P/1999 X3 = 2004 E2 = 2008 K10 = 2012 Q2 (SOHO)
Epoch 2012 Aug. 21.0 TT = JDT 2456160.5
T 2012 Aug. 20.16460 TT                                 MPCW
q   0.0484802            (2000.0)            P               Q
n   0.23346412     Peri.  353.07839     +0.73470165     +0.67549910
a   2.6120969      Node   324.16950     -0.61717540     +0.62727109
e   0.9814401      Incl.    6.13542     -0.28161680     +0.38759767
P   4.22
From 47 observations 1999 Dec. 12-2012 Aug. 20.

    P/1999 X3 = 2004 E2 = 2008 K10 = 2012 Q2 (SOHO)
Epoch 2015 June 27.0 TT = JDT 2457200.5
T 2016 Nov. 23.14638 TT                                 MPCW
q   0.0376946            (2000.0)            P               Q
n   0.23706462     Peri.  353.10292     +0.73688905     +0.67360184
a   2.5855814      Node   324.33569     -0.61546239     +0.63357944
e   0.9854212      Incl.    5.61571     -0.27964364     +0.38057544
P   4.16
From 47 observations 1999 Dec. 12-2012 Aug. 20.

    P/1999 X3 = 2004 E2 = 2008 K10 = 2012 Q2 (SOHO)
Epoch 2016 Nov. 28.0 TT = JDT 2457720.5
T 2016 Nov. 23.86804 TT                                 MPCW
q   0.0396595            (2000.0)            P               Q
n   0.23728318     Peri.  352.89173     +0.73577660     +0.67501590
a   2.5839935      Node   324.45421     -0.61662256     +0.63438586
e   0.9846518      Incl.    5.39377     -0.28001680     +0.37670694
P   4.15
From 47 observations 1999 Dec. 12-2012 Aug. 20.

    P/1999 X3 = 2004 E2 = 2008 K10 = 2012 Q2 (SOHO)
Epoch 2016 Nov. 28.0 TT = JDT 2457720.5
T 2016 Nov. 24.04744 TT                                 MPCW
q   0.0397179            (2000.0)            P               Q
n   0.23728260     Peri.  352.87148     +0.73525400     +0.67518818
a   2.5839977      Node   324.42537     -0.61671735     +0.63010645
e   0.9846293      Incl.    5.85541     -0.28117834     +0.38351895
P   4.15
From 58 observations 1999 Dec. 12-2012 Aug. 20.

From these results the next perihelion will be on 2016 November 24.0. My best fit to the data uses A2 = -0.0003 and has T = 2016 November 23.9.
The comet was observed by SOHO LASCO in 2016. My best fit to the data uses A2 = -0.0006 and has T = 2016 November 23.64.
The next perihelion will be 2021 Jan 17.
The comet returned about two hours early in 2021 as first deduced by me from the SOHO observations. With the so improved orbital solution I could identify 
the comet in Subaru Hyper Suprime-Cam images of 2020 December taken by Man-To Hui. So the orbit was improved again, but probably not enough to find
the comet in the smaller fields of Gemini N or HST. Here Dave Tholen came to the rescue with many images from the CFHT. To our surprise 323P showed
a long tail of debris. Later images from Gemini N, LDT and HST were made of 323P. The first two runs with the HST showed two small fragments accompanying
the comet on March 02 and 03, but they were gone on HST images of March 22 and 26. A paper about the results of the observations is here.
In June 2022 Qicheng Zhang reported a fragment of 323P in SOHO LASCO C2 images of 2021 January 17 (close to perihelion). It was confirmed by Karl
Battams as SOHO-4462. It was leading 323P by about six pixels or about 70 arcseconds.
The next perihelion will be 2025 Mar 14.

7. P/2003 T12 = 2012 A3 (SOHO) = 2016/03/09

C/2003 T12 was found by Jim Danaher in LASCO C3 images of 2003 October 09. Brian Marsden derived an orbit from 71 observations spanning 2.01 days and wrote (MPEC 2004-K33):

Orbital elements:
Comet            T              q       e       Peri.    Node     Incl.     C
CK03T120   2003 Oct.  21.65   0.5192   1.0     234.69   181.11    14.47     X
...
     It is possible that C/2003 T12 has a short period and somewhat smaller
perihelion distance, but the latter is limited by the minimum solar
elongation of 5.3 deg.  The object seems to have been too faint to show on
SOHO-SWAN frames.

Eight years later Alan Watson found a comet in STEREO SECCHI HI1B images. William Thompson found that it had crossed the COR2B field before it entered HI1B. Michal Kusiak and Man-To Hui measured the COR2B positions and I could link them with the observations of C/2003 T12. Michal noted that the "comet might be visible in the evening (southern) sky on the end of January". Gareth Williams published these orbital elements (MPEC 2012-B96), due to the large perihelion distance the comet was not observed at his 1997 return.:

Observer details:
C50 STEREO-B.  SECCHI COR-2B/HI-1B coronagraphs.  Measurements by K. Battams,
    reduction by G. V. Williams.

Orbital elements:
    P/2003 T12 = 2012 A3 (SOHO)
Epoch 2012 Feb. 3.0 TT = JDT 2455960.5
T 2012 Jan. 26.53754 TT                                 MPC
q   0.5769327            (2000.0)            P               Q
n   0.23941646     Peri.  217.70408     +0.82640143     -0.56295170
a   2.5686211      Node   176.49004     +0.55262665     +0.80675389
e   0.7753921      Incl.   11.38550     +0.10800216     +0.17953706
P   4.12
From 112 observations 2003 Oct. 9-2012 Jan. 21, mean residual 8".15.

    P/2003 T12 = 2012 A3 (SOHO)
Epoch 2003 Oct. 8.0 TT = JDT 2452920.5
T 2003 Oct. 16.34717 TT                                 MPC
q   0.5910233            (2000.0)            P               Q
n   0.23820190     Peri.  214.71402     +0.82980624     -0.55804388
a   2.5773451      Node   179.18911     +0.54741013     +0.81294805
e   0.7706852      Incl.   11.98300     +0.10846081     +0.16644069
P   4.14
From 112 observations 2003 Oct. 9-2012 Jan. 21, mean residual 8".15.

The comet was found by T. Sato and Man-To Hui 2012 January 30 and 31 in the evening sky as an object of mag 15. It was last observed on March 04 by J95 (Great Shefford. Observer P. Birtwhistle. 0.40-m f/6.0 Schmidt-Cassegrain), the nuclear magnitude was then given as 20.1.The next perihelion will be on 2016 March 09 (NK 2489).

The comet was observed by COR2A on 2016 February 21-22 and by the 3.6m-telescope of Mauna Kea on 2016 May 05 when it was mag 22.3. The next perihelion was on 2020 May 6.9, but no observations were made.
The next perihelion is now on 2024 July 3.8.

8. P/2008 Y12

This comet was found in LASCO C2 images of 2008 December 22 and later also in STEREO HI-1A images of December 21/22.The orbit was definitely of short period and when an object with very similar elements were found in LASCO C2 images of 2014 May 17 (C/2014 K3), both objects could be linked (MPEC 2014-K37). Another object with very similar elements appeared in LASCO C2 images of 2019 August 26 (SOHO-3819). But the possible identity with C/2008 Y12 and C/2014 K3 got unnoticed because the comet appeared seven weeks earlier than computed from the pure gravitational solution for 2008 Y12 = 2014 K3. In 2023 February I have compared the path of SOHO-3819 in LASCO C2 with the paths of the other non-group comets and found that it was very similar th that of 2008 Y12. My measurements with Astrometrica confirmed that SOHO-3819 has very similar orbital elements as 2008 Y12 and 2014 K3. I could link all three apparitions but had to discard the STEREO HI-1A measurements of 2008, which gave much too large residuals. More about 2008 Y12 = 2014 K3 = SOHO 3819 is here.

The STEREO measurements of 2008 align well with LASCO C2 of 2008, so there was something wrong here. The error was found when I investigatated the orbital solutions for the short-arced non-group SOHO comets, which can have multiple solutions with similar residuals. The non-group comet of 2009 February 06 (SOHO-3794) showed one solution very similar to that of of the other three objects here discussed. From 2009/02/06 to 2014/05/17 we have 1926 days and from 2014/05/17 to 2019/08/26 we have 1927 days. SOHO-3819 appeared less than eight hours later than predicted from the pure gravitational solution SOHo-3794 = C/2014 K3. So only a small non-grav parameter (A2 = +0.0073) was needed to link SOHO-3794 = C/2014 K3 (SOHO-2730) = SOHO-3819.

P/2008 Y12 is similar to those objects, but not identical. There should be other apparitions of P/2008 Y12 in LASCO C2, but none were found until now.

9. P/2002 R4 = 2007 Y4 = SOHO-3139 = 2018/08/11 = 2023/12/09

This is a Marsden group comet. I have found that C/2002 R4 = 2007 Y4 = SOHO-3139 = 2018/08/11, but could not find a common solution.

C/2002 R4 = 2007 Y4 = SOHO-3139 can be linked with non-grav parameters
 A1:  0.00000000E+00
 A2: -3.92771768E-12  s= 1.47E-12
 A3:  0.00000000E+00
and 2007 Y4 = SOHO-3139 = 2018/08/11 can be linked with non-grav parameters
 A1:  0.00000000E+00
 A2:  8.31446633E-10  s= 2.64E-13
 A3:  0.00000000E+00

Using the second solution I get T = 2002 09 08.02 instead of 2002 09 03.31 for C/2000 C4 from the first solution.
Using the first solution I get T = 2018 08 06.81 instead of 2018 08 11.55 from the second solution.
The change in A2 causes differences in T of about five days.

The next return will be close to 2023 December 12.
The comet returned on 2023 December 09. SOHO-3139 = 2018/0811 = 2023/12/09 can be linked with non-grav parameters
A1: 0.00000000E+00
A2: 3.44321634E-10 s= 8.93E-12
A3: 0.00000000E+00

The next return will be close to 2029 April 14.

10. P/2000 C4 = 2005 W1 = SOHO-2115 = 2017/01/31 = 2022/07/19

This is a bright Marsden group comet. I have found that C/2000 C4 = 2005 W1 = SOHO-2115 = 2017/01/31, but could not find a common solution.

C/2000 C4 = C/2005 W1 = SOHO-2115 can be linked with non-grav parameters
 A1:  2.41025081E-08  s= 5.52E-11
 A2: -4.52728228E-09  s= 2.90E-13
 A3: -3.77543726E-08  s= 3.64E-09
and C/2005 W1 = SOHO-2115 = 2017/01/31 can be linked with non-grav parameters
 A1:  2.51828879E-08  s= 6.37E-11
 A2: -7.82394743E-09  s= 1.54E-12
 A3:  0.00000000E+00

This one of the larger fragments, which peaked at mag 5 to mag 6, and it seems that this fragment is quite active.

Using the second solution I get T = 2000 01 13.26 instead of 2000 02 05.17 for C/2000 C4 from the first solution.
The activity makes predictions inexact. Using the first solution I get T = 2017 02 23.75 for the last return, which is 23 days later than observed (2017 01 31.84 from the second solution).

This is a remarkable result. If I can link three consecutive returns with small residuals and with well determined nongrav accelerations, the next time of perihelion can be uncertain by three weeks! So the next return of C/2000 C4 can happen anytime from late May to early July in 2022.
The comet returned 2022 July 19, 31 days later than predicted by the second solution. The first solution gives T = 2022 Aug 29, this is 42 days after the observed return. So it returned close to to middle of the two solutions.

11. P/2004 B3 = 2009 Y10 = SOHO-3081 = SOHO-4464

This is a small Kracht group member with peak magnitudes of mag 7 - 8, which was only observed with LASCO C2. It was unobserved at the unfavourable perihelion around 1998 March 02. The pur gravitational linkage of C/2004 B3 = 2009 Y10 gave the next perihelion as 2015 November 26.6, but the comet returned 25 days late with T = 2015 December 21.4. The next perihelion will be around 2022 January 06. In May 2022 Hanjie Tan found the comet in archival C2 images of 2022 January 02. Karl Battams confirmed the find as SOHO-4464. The next perihelion will be around 2028 Feb 11.

This comet had a close encounter with Jupiter around 2008 July 21 with a smallest distance of 1.06 AU, which changed the longitude of the ascending node from 47.1 to 34.2 deg. Another encounter occured around 2020 July 03 with a smallest distance to Jupiter of 1.16 AU. This encounter changed the longitude of the ascending node from 33.7 to 18.3 deg.

12. P/1996 X5 = 2002 S11 = 2008 R7 = SOHO-2802 = 2020/10

This is the brightest Kracht group member with peak magnitudes of mag 5.5. It was first observed on 1996 December 05 and found again 2002 September 30. The pure gravitational linkage gave the next perihelion as 2008 July 22.9. A faint Kracht comet was observed on July 04 but the bright Kracht comet returned not before September 06, 46 days later than expected. But all three apparitions could be linked with these non-grav parameters:

A1: 0.00000000E+00
A2: 6.45952339E-09 s= 1.40E-12
A3: 0.00000000E+00

This linkage gave the next perihelion as T = 2014 September 27.9 and the comet was found again on September 12 with T = 2014 September 13.0, 15 days earlier than expected. The three apparitions of 2002, 2008 and 2014 could be linked with these non-grav parameters:

A1: 0.00000000E+00
A2: 4.46745180E-09 s= 1.56E-12
A3: 0.00000000E+00

The next perihelion was predicted as 2020 October 20.4. The bright fragment was found in images of October 22. The next perihelion will be around 2027 Jan 03.
The apparitions of 2008, 2014 and 2020 could be linked with these non-grav parameters:

A1: 0.00000000E+00
A2: 4.80478011E-09 s= 1.42E-12
A3: 0.00000000E+00

13. P/1996 V2 = 2002 V5 = SOHO-2825 = 2020/11/01

This Marsden precursor was observed in November 1996 (C3) and November 2002 (C2 and C3). It was not observed at its next return of November 2008 possibly due to data gaps during a keyhole period. The next perihelion was computed as 2014 November 04.1.It was found again on November 06/07 (C2 and C3) with T = 2014 November 06.9 (2.8 days late). The new linkage with A2 = +0.0140 gave the next perihelion as 2020 November 1.0. The comet was found again in C2 and C3 on 2020 October 31 and November 01, with T only several hours later than predicted. The next perihelion will be 2026 Oct 22.

14. SOHO-2295 = SOHO-3491

This is a Marsden precursor, which was first observed on 2012 May 24 and 25 with C2 and C3. The comet was found again on 2018 February 05 in C2.
A pure gravitational linkage shows the next perihelion on 2023 October 08 and a previous perihelion on 2006 09 17 - when it did not cross the C2 field of view and was not reported in C3. The perihelion around 2001 January 02 was more favourable, but the comet was there not reported.

15. SOHO-2378 = SOHO-3014 = SOHO-3604 = SOHO-4276

SOHO-2378 was found by H. Tan in LASCO C2 images of 2012-10-13/14. The comet was later found also in LASCO C3. Its peak magnitude was mag 7 in C2.
SOHO-4276 was found nine years later by W. Boonplod in C2 images of 2021-09-11. Its peak magnitude was mag 7.
I could link both apparitions with an orbital period of 4.5 years. More about this solution is here.

SOHO-3014 was found by B. Zhouin LASCO C2 images of 2015-10-03/04. The comet was later found also in LASCO C3. Its peak magnitude was mag 7.5 in C2.
SOHO-3604 was found three years later by W. Boonplod in C2 images of 2018-09-22/23. Its peak magnitude was mag 7.
I could link both apparitions with an orbital period of 3.0 years. With this solution the previous perihelion was on 2012-10-13 and the next perihelion on 2021-09-11,
the same as for SOHO-2378 and SOHO-4276. The orbital period of 2378 = 4276 was not 4.5 but 3.0 years.

I could link all four apparitions with a small A2 term of +0.0002. and small residuals. The next perihelion will be on 2024 August 30/31.

16. SOHO-2071 = SOHO-4848 = SOHO-4192

This comet was found bei M.Uchina in realtime C2 images of 2011 May 19. It was confirmed as a "possible Marsden" and was designated as SOHO-2071. Ten years later M.Biesiada found a nongroup comet in realtime C2 images of 2021 May 15, which was designated SOHO-4192. The orbital solutions of both comets turned out to be similar and that these comets belong to the Type 1 Precursors between 96 P and the Marsden group. I could link them with an orbital period of 5.0 years. So there was a missing return in 2016 May.

In 2019 April P.Berrett had found a nongroup comet in archival C2 images of 2016 May 17 (SOHO-3704), but the observations do not fit those of SOHO-2071 and -4192.
H. Tan found a nongroup comet in archival C2 images of 2016 May 31 (SOHO-4848) with similar orbital elements as those of SOHO-2071 and -4192. I could link the three apparitions using A2 = -0,6950. My solution used 117 of 133 observations with a mean RMS of 4.7 arcseconds.

The tracks of the comet were outside rhe C2 fov in 2001 and 2006 and will be outside in 2026.

17. SOHO-3651

This comet was found by W. Boonplod in LASCO C3 images of 2018-11-18. It entered the C2 field and later returned to C3. From November 18.9 to 21.8 Karl Battams measured 239 positions and described the comet as "short tail, quite diffuse, good obs" in C2 with a peak magnitude of 6. My orbital solution with Exorb (with uncertainties according to pixel size 12"/55") shows that this is a short-period comet:

 2018/11/18  JD=2458441.4044707   (ref. J2000.0)    File: SOHO3651.POS
 Equat. Pos. & Vel.                Ecliptic Oscul. Elements
     (Gm, km/s)                            (deg, AU)
Itr:  2   Converged              sw= 2.8213E-03°
 X0:  3.43594726E+01  s= 5.80E-01  Eccentricity:   0.88827371  s= 1.52E-02
 Y0:  4.59101507E+01  s= 8.16E-01  Inclination :   5.36285859  s= 1.05E-01
 Z0:  1.70052930E+01  s= 3.88E-01  Arg.of Perih: 309.70891987  s= 2.46E+00
Vx0: -4.51099515E+01  s= 7.80E-01  Long of Node:  83.20651931  s= 8.26E-01
Vy0:  4.04066195E+01  s= 1.06E+00  Semimaj.Axis:   3.45732215  s= 1.19E+00
Vz0:  2.26592968E+01  s= 5.16E-01  Mean Anomaly:   0.60850123  s= 5.52E-02
Rj0: -2.77462E-08     Used Observations:  232     Time Span:     1.917 d
 A1:  0.00000000E+00               M. Motion:    0.1533184078  s= 2.26E-02
 A2:  0.00000000E+00               Perih Dist :    0.38627377  s= 7.98E-03
 A3:  0.00000000E+00               Perih Long :   32.91543918  s= 2.32E+00
 AF:  1.11262000E-01               Period (JY):       6.42862  s= 9.49E-01
                                   Perih Time :      -3.96887  s= 3.73E-01

No other observations of SOHO-3651 have been found in LASCO images until now.
My orbital solution with FindOrb using the same 232 (but unweighted) observations has:

Orbital elements:  SO3651
   Perihelion 2018 Nov 14.339715 +/- 0.167 TT =  8:09:11 (JD 2458436.839715)
Epoch 2018 Nov 20.0 TT = JDT 2458442.5   Earth MOID: 0.0196   Ju: 0.2658
M   0.81036197 +/- 0.31             Ve: 0.0096   Me: 0.0196   Ma: 0.0346
n   0.14316628 +/- 0.0594           Peri.  302.78686 +/- 3.4
a   3.61889142 +/- 1                Node    83.79025 +/- 1.4
e   0.9015204 +/- 0.0212            Incl.    5.74923 +/- 0.27
P   6.88                   H 12.8   G  0.15   U 10.8  
q 0.35638664 +/- 0.024    Q 6.88139621 +/- 2.04               Kracht
232 of 239 observations 2018 Nov. 18-20 (45.4 hr); mean residual 14".61

Due to the small inclination of the orbit, there are small MOIDs for Mercury to Jupiter.
So strong pertiurbations may have occured.

18 C/2002 Q9 = 2006/07/15 = 2010/06/10 = SOHO-4838 = SOHO-3789 = SOHO-4392

This periodic comet has long been hidden among the SOHO non-group comets. First I found it in C2 images of 2002/08/19. It was designated SOHO-508 and C/2002 Q9. Not before 2019 it was found again. This time Peter Berrett found it in archival C2 images of 2018 April (SOHO-3789). Peter found it again in C2 realtime images of 2022 March (SOHO-4392). And in 2022 August was it found by Hanjie Tan in archival C2 images of 2014/05/07 (SOHO-4838).

In 2024 May I noticed that these four comets had low-inclination orbits with similar perihelion distances. The last three perihelia were 2022/3, 2018/4, 2014/5 and could be supplemented with (2010/6), (2006/7), 2002/8. This looked like a periodic comet with an orbital period of about four years. I could then link 2002 - 2014 - 2022 and finally found it in archival C2 images of 2006 and 2010.

19. SOHO-3794 = C/2014 K3 (SOHO-2730) = SOHO-3819

C/2014 K3 was found by Z.Xu in realtime C2 images of 2014 May 17. It was erroneously linked with P/2008 Y12 (#8 in this list). Five years later P. Berrett found SOHO-3794 in archival C2 images of 2009 February 6 and Z.Xu found SOHO-3819 in realtime C2 images of 2019 August 26. Another five years later I could show the identity of these three objects (and that P/2008 Y12 is a separate object).

This linkage gives a favourable apparition around 1998 July 01, but contact with SOHO was lost at that time. The next perihelion on 2003 October 21 was outside the C2 FOV. The next three perihelia were observed by LASCO C2 and give the next perihelion as 2024 December 05.

Uncertain linkages

A1: P/1996 X3 = 2002 S7 = 2008 N4

This was the faintest of the three Kracht group comets from 1996 December. A linkage with C/2002 S7 gave the next perihelion as 2008 July 04.16. The comet returned with T = 2008 July 04.38, only five hours later than computed. I could link the three apparitions with a small value of A2 (+0.0032) and Brian Marsden published the linkage on MPEC 2009-J14 as based on my work. The next return on 2014 April 15 was unfavourable with the path of the comet outside C2. Conditions were better for the return on 2020 January 25.2 but the comet was not observed. Several data gaps on January 24 and 25 may have prevented the recovery of the comet. The non-group comet from 2020 January 23 (SOHO-3893) does not belong to the Kracht group comets.
The next perihelion will be around 2025 November 05.

A2: P/1996 X3 = SOHO-4728 = 2008 N4 = SOHO-3943

In August 2022 Zhuoyang Chen found a Kracht group comet in archival C2 images of 2002 September 15.This comet became SOHO-4728. Its perihelion time was less than six days before that of 2002 S7. 1996 X3, SOHO-4728 and 2008 N4 can be linked with small residuals using A2 = +0.1584. This solution gives the next perihelion on 2014 May 02. Among the known Kracht group comets SOHO-3943 with a perihelion on 2014 June 06 appeared closest to this date. SOHO-4728, 2008 N4 and SOHO-3943 can be linked with small residuals using A2 = +0.6590. This solution gives the next perihelion as 2020 June 24.

B: SOHO-2071 = SOHO-4192 (linkage confirmed)

SOHO-2071 was found by M. Uchina on 2011 May 19 in C2 and described as a possible Marsden group comet. SOHO-4192 was found by M. Biesiada on 2021 May15 in C2 and described as a nongroup comet. The orbital computations showed very similar elements and that these comets belong to the Type 1 Precursors between 96 P and the Marsden group.

The comets can be linked with small residuals. Both apparitions were in the month of May and the orbital period is close to five years. But it was not observed in May 1996, 2001, 2006 and 2016.
The next perihelion will be around 2026 May 05.

The comet was found in archival C2 images of 2016 May 31 (see above #16).

C: C/2008 L7 = SOHO-2712 = SOHO-3885

This fragment of C/2002 R5 trails the main component (C/2008 L6 = SOHO-2673 = SOHO-3882) in 2014 and 2019. The linkage with C/2008 L6 gives large trends in the residuals and the linkage with C/2008 L7 looks much better. The solution with C/2008 L7 has these relative spacings of this fragment with the main component (C/2008 L6): 2008 -0.01d, 2014 +0.11d, 2019 +6.07d. A nongravitational acceleration of A2 = +0.2823 is needed for this solution (similar to the A2 = +0.2061 for the main component).

The perihelion in 2019 was between the Sun and the Earth. So the enhanced brightness in 2019 may be due to forward scattering.

D: C/2008 L6 = 2014/03/06 = SOHO-3870

This fragment of C/2002 R5 leads the main component (C/2008 L6 = SOHO-2673 = SOHO-3882) in 2014 and 2019. This linkage needs A2 = +0.0216 and gives the next perihelion as 2025/08/11. This fragment leads the main component by 1.28 days in 2014 and 16.03 days in 2019. A linkage C/2008 L7 = 2014/03/06 = SOHO-3870 is also possible with very similar results (A2 = +0.0219, next perihelion 2025/08/11).

E: C/2008 L6 = 201/03/07 = SOHO3877

This fragment of C/2002 R5 leads the main component (C/2008 L6 = SOHO-2673 = SOHO-3882) in 2014 and 2019. This linkage needs A2 = +0.0120 and gives the next perihelion as 2025/09/05. This fragment leads the main component by 0.23 days in 2014 and 6.76 days in 2019. A linkage C/2008 L7 = 2014/03/07 = SOHO-3877 is also possible with very similar results (A2 = +0.0121, next perihelion 2025/09/06).

F: C/2002 R1 = 2008 A3 = 2013/05/25

C/2002 R1 was found by me in realtime C2 images of 2002 Sep 02. Over a time span of 0.18 days 32 images were measured. These observations could be linked with those of C/2008 A3 (18 obs in C2 over 0.52 days) and the C2 comet of 2013/05/25 (16 obs, 0.15 days). The peak brightnesses were 7.8/7.5/8 mag. The next returns were calculated as 2018/09/29 and 2024/01/31, but both returns were not observed. A Marsden group comet of 2024/02/16 (SOHO-4986) could not be linked with 2013/05/25.

G: SOHO-2263 = SOHO-3524 = SOHO-4989

The Marsden group comet SOHO-2263 was found by S. Schmalz and K. Kida on 2012 April 13 in C2 and was later visible in C3. SOHO-3524 was found by me on 2018 May 03 in C2 and could be linked with SOHO-2263. The previous perihelion was around 2006 April 02 and the next perihelion should occur around 2024 May 06.

Residuals of 2263 = 3524 in arcseconds, black 2012 C2, red 2012 C3 and blue 2018 C2

The Marsden group comet SOHO-4989 was found by H. Tan on 2024 February 29 in C2. This comet could be linked with SOHO-3524 with A3 = -4.30670246E-07 ± 3.31E-08 and small residuals.

Residuals of 3524 = 4989 in arcseconds, black 2018 C2 and blue 2024 C2

The pxel size in C2 is about 12 arcseconds and in C3 about 55 arcseconds. Both solutions (2263 = 3524 and 3524 = 4989) look good and that means SOHO-22636 = SOHO-3524 = SOHO-4989.

H1/2: C/2000 V4, C/2001 T5 and SOHO-2291

These comets have similar orbital solution and are probably of short orbital period (more).

I: C/2007 S11 = SOHO-4813

C/2007 S11 (SOHO-1362) was found by me in C2 images of 2007 Sep 28. Karl Battams described it as "tiny, stellar, good obs" with a peak magnitude of mag 8. Nearly 16 years later
SOHO-4813 was found by J. Ruan in C2 images of 2023 Aug 29. Karl Battams described it as "faint, quite diffuse, ok obs" with a peak magnitude of mag 8.

The descriptions are different, but the orbital elements are quite similar:

These comets can be linked with small reiduals using P = 5.3 years (three revolutions around the sun). The next perihelion should be around 2028 Dec 20.

Pairs of SOHO non-group comets