"Pseudo-MPEC" for YS18A5C = YS16534 = A104ayW = A104lks = YT273BF = A104shw = YUA31FA = YU3F416 = (probably) MMS sat

Created 2017 Oct 2 14:43:02 UT using Find_Orb

A pseudo-MPEC based on more recent data is available.

Also available are separate orbits for YS16534 and YS18A5C. The linkage is not absolute and beyond doubt. The residuals in the linked orbit mean either it's a single object that's maneuvering, or maybe two or three bits associated with the same launch.

However, since only one has been seen at a time, and they all have similar orbits and H values... I think it's one object that's maneuvering.

Update: I ran this puzzler past Jonathan McDowell, artsat expert, maintainer of Jonathan's Space Report, and the guy I usually consult when I'm trying to identify artsats. Jonathan replied:

...No good suggestions, except that it seems a bit similar to the 4 MMS
satellites, maybe they changed their orbit and the TLEs for them are bogus? 

The MMS satellites have been tracked a bit. They orbit the earth in a tetrahedral configuration; the folks at SONEAR in Brazil posted a video of them.

Jonathan's comment led me to find a NASA press kit for MMS which says (page 6, the 'orbit' section) that the MMS satellites were slated to spend a year and a half in "day phase" orbits, then shift for six months of "night phase" orbits, exploring the earth's magnetic tail. And it's almost exactly 1.5 years since launch.

More recently (2017 October 2), ATLAS found two MMS satellites that are where the TLEs say they ought to be. These were on the NEOCP as A104mHe and A104mHa, imaged at the same time, but about 4' apart. So, at least as of that moment, two satellites hadn't moved to the night phase yet, and at least one (maybe two) had. If it's two, it might account for the problems in getting YS18A5C = YS16534 = A104ayW = A104lks to link. (If it's one, the raggedy residuals in linked orbits are just down to the object maneuvering a little. The "night phase" orbits are supposed to have a period of three days, so I assume they'll be raising the apogee a lot and lowering the perigee a little relative to the orbital elements shown below.)

I've e-mailed a few people affiliated with MMS to ask for comments, but haven't gotten a reply. I've also e-mailed JSpOC in hopes of persuading them to provide corrected TLEs. (They currently show "ghost" TLEs reflecting where the objects were last tracked... that tends to happen with JSpOC elements; tracking objects in multi-day orbits does not appear to be a priority for them.)

For the moment, you can get some rather approximate TLEs for this object computed from the observations below. The problem being that the object(s) maneuver, so these will get to be inaccurate.

Astrometry:
     YS16534  C2017 09 17.26883 22 52 40.91 -14 55 05.2         x17.4 VqNEOCP703
     YS16534  C2017 09 17.26898 22 52 41.52 -14 54 59.3         x17.7 VqNEOCP703
     YS16534  C2017 09 17.26913 22 52 42.13 -14 54 53.3         x17.8 VqNEOCP703
     YS16534  C2017 09 17.26927 22 52 42.73 -14 54 47.8         x17.6 VqNEOCP703
     YS16534  C2017 09 17.27324 22 52 58.62 -14 52 13.0         x17.6 VqNEOCP703
     YS16534  C2017 09 17.27392 22 53 01.37 -14 51 46.3         x17.7 VqNEOCP703
     YS16534  C2017 09 17.27511 22 53 06.09 -14 50 59.8         x17.4 VqNEOCP703
     YS16534  C2017 09 17.27587 22 53 09.16 -14 50 30.0         x17.4 VqNEOCP703
     YS16534  C2017 09 17.30610 22 55 08.71 -14 30 23.1         x17.0 VqNEOCP703
     YS16534  C2017 09 17.30729 22 55 13.36 -14 29 35.2         x17.9 VqNEOCP703
     YS16534  C2017 09 17.30988 22 55 23.55 -14 27 49.9         x17.8 VqNEOCP703
     YS18A5C  C2017 09 20.28675 00 42 59.37 -05 57 42.0         x17.6 VqNEOCP703
     YS18A5C  C2017 09 20.29210 00 43 24.79 -05 54 07.3         x17.4 VqNEOCP703
     YS18A5C  C2017 09 20.29746 00 43 50.42 -05 50 29.9         x18.4 VqNEOCP703
     YS18A5C  C2017 09 20.32598 00 46 07.40 -05 30 35.1         x17.1 VqNEOCPI52
     YS18A5C  C2017 09 20.32644 00 46 09.61 -05 30 15.0         x17.3 VqNEOCPI52
     YS18A5C  C2017 09 20.32689 00 46 11.80 -05 29 55.5         x17.1 VqNEOCPI52
     A104ayW  C2017 09 26.39904 00 21 38.21 -06 59 59.5          17.8 o      T05
     A104ayW  C2017 09 26(8AstrometryEb(eRbP1=*i-AO76DM^l9Fw)lL5j(ERd0^L;oiy^T05
     A104ayW  C2017 09 26.41032 00 22 08.151-06 53 40.69         17.8 w      F51
     A104ayW  C2017 09 26.41216 00 22 13.05 -06 52 38.2          17.8 o      T05
     A104ayW  C2017 09 26PA4g12oI%.ok;t=Qta3s9w*xIyGmx,Cste*,4Sevgh;_I5G\/:YmT05
     A104ayW  C2017 09 26.42212 00 22 39.160-06 46 56.48         17.9 w      F51
     A104ayW  C2017 09 26.43393 00 23 10.067-06 40 03.53         17.8 w      F51
     A104lks  C2017 09 308\l`OjFMd@lHVl23Dredacted;*O*S+i'EN89@RheRo)La+RA;xxT05
     A104lks  C2017 09 30NfBX;f31/o12C#KdUm)-c2Y$qe3dxaPtsE!_2fo'Q[KT`icSrJp^T05
     A104lks  C2017 09 30]O/IOBg']q!1pVp(C?0NT5):$FHPqhTGwWvtD#1oYBe5mHXf2aAGT05
     A104lks  C2017 09 30j5%j]/aVQ#(MTr14Aj0-#U8jAy1hCFG4see^VO:aEqisKFk]42'DT05
     A104lks  C2017 09 30saH(8IS#kQ#8?aHnU/:My3REXiYDqWX%2qJ@NoqR.6mV*#@x*s1\T05
     A104lks  C2017 09 30iLQhw.,/h`B_db4Z3@h#gx-jr,tkq1/;]:)ZIii7OeP:'tnNEOCPT05

Station data:
(703) Catalina Sky Survey  (N32.417003 W110.732640)  US/Arizona.  Observers
   E. J. Christensen, A. R. Gibbs, A. D. Grauer, R. E. Hill, J. A. Johnson,
   R. A. Kowalski, S. M. Larson, F. C. Shelly. 0.68 m Schmidt + CCD.
(F51) Pan-STARRS 1, Haleakala  (N20.707234 W156.255910)  US/Hawaii.
   Observers N. Primak, A. Schultz, S. Watters, J. Thiel, T. Goggia. Measurer
   PS1 Science Consortium. 1.8-m Ritchey-Chrétien + CCD.
(I52) Steward Observatory, Mt. Lemmon Station  (N32.442544 W110.788920)
   US/Arizona.
(T05) ATLAS-HKO, Haleakala  (N20.707571 W156.257010)  US/Hawaii.  Observers
   L. Denneau, A. Heinze, H. Weiland, B. Stalder, J. Tonry. Measurers L.
   Denneau, A. Heinze, J. Tonry. 0.5-m f/2.0 Schmidt + CCD.

Orbital elements:  YS18A5C = YS16534 = A104ayW = A104lks
   Perigee 2017 Sep 29.401743 +/- 0.00354 TT =  9:38:30 (JD 2458025.901743)
Epoch 2017 Sep 30.0 TT = JDT 2458026.5                        Gray
M 103.12381 +/- 0.6                 (J2000 equator)
n 172.37380777 +/- 0.00538          Peri.  159.75258 +/- 0.033
a 69016.9859 +/- 1.44               Node    20.43346 +/- 0.08
e   0.8336319 +/- 0.000188          Incl.   20.07627 +/- 0.007
P3007.36m/2.088d           H 32.6   G  0.15   U  9.2
q 11482.2233 +/- 12.8    Q 126551.748 +/- 15.1
13 of 30 observations 2017 Sept. 26-30; mean residual 1".976
Residuals in arcseconds: 
170917 703(248'+ 6038+)   170917 703(211'+ 4952+)   170926 T05 .120+ .903+
170917 703(248'+ 6034+)   170920 703(3696+  661+)   170926 T05 1.53- 2.68-
170917 703(248'+ 6030+)   170920 703(3788+  689+)   170926 F51 .242+ 1.35-
170917 703(248'+ 6026+)   170920 703(3885+  718+)   170926 F51 1.30+ 3.53-
170917 703(244'+ 5913+)   170920 I52(4410+  883+)   170930 T05 966µ+ 5.11-
170917 703(243'+ 5894+)   170920 I52(4419+  886+)   170930 T05 .380+ 2.11-
170917 703(242'+ 5861+)   170920 I52(4428+  888+)   170930 T05 .882+ .497+
170917 703(241'+ 5839+)   170926 T05 .040- 4.02+    170930 T05 .092- .515+
170917 703(214'+ 5045+)   170926 T05 6.2m+ 1.65+    170930 T05 .158+ 2.63+
170917 703(213'+ 5016+)   170926 F51 .442- 1.30+    170930 T05 1.15- 3.75+

Ephemerides (geocentric):
Date (UTC) HH   RA              Dec         delta   r     elong  mag " sig PA
---- -- -- --  ------------   ------------  ------ ------ -----  --- ---- ---
2017 09 30 00  23 12 10.567   -11 04 38.71   110600 1.0022 157.3 18.0  103  79
2017 09 30 01  23 18 02.062   -10 38 16.70   113542 1.0022 158.6 18.0 80.7  79
2017 09 30 02  23 23 35.781   -10 12 47.70   116158 1.0022 159.9 18.0 62.5  80
2017 09 30 03  23 28 54.793   -09 48 02.33   118461 1.0022 161.2 18.0 47.5  81
2017 09 30 04  23 34 01.645   -09 23 52.40   120460 1.0022 162.3 18.0 35.2  82
2017 09 30 05  23 38 58.492   -09 00 10.69   122166 1.0022 163.4 18.0 25.2  83
2017 09 30 06  23 43 47.193   -08 36 50.67   123585 1.0022 164.5 18.0 17.2  85
2017 09 30 07  23 48 29.381   -08 13 46.35   124723 1.0022 165.5 18.0 11.0  88
2017 09 30 08  23 53 06.522   -07 50 52.12   125585 1.0022 166.5 18.0  6.4  92
2017 09 30 09  23 57 39.956   -07 28 02.60   126175 1.0022 167.5 18.0  3.3  96
2017 09 30 10  00 02 10.938   -07 05 12.57   126494 1.0022 168.4 17.9  1.5  90
2017 09 30 11  00 06 40.665   -06 42 16.82   126543 1.0022 169.2 17.9  1.3  52
2017 09 30 12  00 11 10.312   -06 19 10.05   126324 1.0022 170.0 17.9  2.8  43
2017 09 30 13  00 15 41.054   -05 55 46.79   125835 1.0022 170.7 17.8  5.6  48
2017 09 30 14  00 20 14.093   -05 32 01.21   125074 1.0021 171.4 17.8  9.8  52
2017 09 30 15  00 24 50.694   -05 07 47.07   124038 1.0021 171.9 17.7 15.6  56
2017 09 30 16  00 29 32.213   -04 42 57.50   122723 1.0021 172.3 17.7 23.1  58
2017 09 30 17  00 34 20.134   -04 17 24.83   121124 1.0021 172.5 17.7 32.5  60
2017 09 30 18  00 39 16.124   -03 51 00.33   119234 1.0021 172.6 17.6 44.1  61
2017 09 30 19  00 44 22.087   -03 23 33.96   117044 1.0020 172.4 17.6 58.3  63
2017 09 30 20  00 49 40.241   -02 54 53.88   114545 1.0020 172.0 17.6 75.4  63
2017 09 30 21  00 55 13.230   -02 24 45.99   111724 1.0020 171.3 17.5 96.1  64
2017 09 30 22  01 01 04.258   -01 52 53.17   108567 1.0019 170.4 17.5  121  65
2017 09 30 23  01 07 17.300   -01 18 54.27   105056 1.0019 169.3 17.5  152  65
2017 10 01 00  01 13 57.388   -00 42 22.64   101170 1.0019 168.0 17.5  189  66
2017 10 01 01  01 21 11.060   -00 02 43.99    96884 1.0018 166.5 17.4  236  66
2017 10 01 02  01 29 07.033   +00 40 46.86    92166 1.0018 164.7 17.4  295  67
2017 10 01 03  01 37 57.308   +01 29 11.07    86977 1.0017 162.7 17.3  371  67
2017 10 01 04  01 47 59.038   +02 23 54.17    81270 1.0017 160.3 17.3  473  68
2017 10 01 05  01 59 37.882   +03 27 00.49    74981 1.0016 157.5 17.2  612  68
2017 10 01 06  02 13 34.515   +04 41 39.37    68028 1.0015 154.0 17.1  813  69
2017 10 01 07  02 30 58.494   +06 12 56.77    60300 1.0015 149.6 16.9 1121  69
2017 10 01 08  02 54 01.896   +08 09 44.82    51639 1.0014 143.8 16.8 1642  71
2017 10 01 09  03 27 37.265   +10 48 54.69    41821 1.0013 135.3 16.5 2659  72
2017 10 01 10  04 25 35.872   +14 44 10.95    30532 1.0012 120.9 16.3 5216  76
2017 10 01 11  06 49 16.891   +19 54 20.24    17757 1.0011  86.6 16.3 261'  87
2017 10 01 12  14 17 56.915   -05 05 33.75    12479 1.0010  26.9 21?? 591' 109
2017 10 01 13  18 37 43.712   -19 45 16.20    24488 1.0010  90.6 16.8 8944  94
2017 10 01 14  20 06 29.577   -19 44 07.74    36583 1.0011 111.2 16.9 3753  87
2017 10 01 15  20 52 24.736   -18 38 34.41    47069 1.0012 122.0 17.2 2118  83
2017 10 01 16  21 21 56.599   -17 33 28.72    56255 1.0012 128.9 17.4 1377  81
2017 10 01 17  21 43 18.091   -16 35 30.97    64411 1.0013 134.0 17.5  969  80
2017 10 01 18  21 59 54.341   -15 44 19.82    71722 1.0013 138.0 17.6  717  79
2017 10 01 19  22 13 27.473   -14 58 42.10    78321 1.0014 141.2 17.7  547  79
2017 10 01 20  22 24 54.782   -14 17 30.96    84302 1.0014 144.0 17.8  427  78
2017 10 01 21  22 34 51.273   -13 39 53.29    89735 1.0014 146.4 17.9  338  78
2017 10 01 22  22 43 39.745   -13 05 07.96    94677 1.0015 148.5 17.9  270  78
2017 10 01 23  22 51 35.813   -12 32 43.04    99169 1.0015 150.4 18.0  217  78
2017 10 02 00  22 58 50.606   -12 02 13.45   103247 1.0015 152.1 18.0  175  78
2017 10 02 01  23 05 32.333   -11 33 19.19   106939 1.0015 153.7 18.1  140  78