Can the Tselinas and Okeans be distinguished by the size and shapes of their orbits? In other words, if you were shown an elset for one of them, could you examine it, and without reference to any database of current elsets, could you say "This is a Tselinan orbit" or "This is an Okean orbit"? (Ted Molczan, a question for you alone appears below, following a discussion of the question above.) I thought I might be able to answer this question in the affirmative, but I find that I have not been able to do so. The ndot/2's are very similar and occupy ranges which largely overlap. Ditto for the inclinations (i) and the eccentricities. The right ascensions of the ascending nodes, the arguments of perigee and the mean anomalies are all over the globe, reflecting the precise value for the epoch more than any constant characteristic of the orbit. I thought I might be able to ferret (pun possibly intended) out some detail which is not very obvious in the TLE elset, but I haven't; at least not yet. It seems to me that the small eccentricity of the orbits is quite deliberate. The objects must always be separated in 3D, even as their orbits age and shrink somewhat unpredictably. Their ma's cannot be phased and spaced because of the unpredictability of the atmosphreric drag. So the orbits are given a small eccentricity and chosen so as to prevent collisions. Is this so? Or does that small ecc have some other rationale? I thought I might detect some orbital characteristic which is: a) the same for all Tselinas b) the same for all Okeans c) but different for Tselinas and Okeans. Maybe a function of raan, argper, ma, etc. So far I haven't seen it. The objects are in various orbital planes. I haven't checked (I think the slight variation in epoch of the various elsets makes this a small (not clearly defined to me) task, instead of a simple, direct matter of comparing raans). Perhaps these planes can be distinguished (a separate and interesting question), but that requires a database reference. Ted Molczan, your sizes for the Okeans are not identical. Is this so? Is this intended? Or could it be typographical error? (My sympathies are entirely with anyone who has undertaken the difficult task of shepherding 1000+ elsets). Thanks for any insights. Cheers. Walter Nissen dk058@cleveland.freenet.edu --- To save space and facilitate analysis, I compressed the Tselina and Okean elsets into an 80-column format, throwing away the least significant digits and identical leading digits. cat cospar epoch ndot2 i raan ecc argper ma mm C* Molczan d's 10973 78067A 69.80695 3 82.47 10.46 127 140.35 219.86 15.024 1025 6.0 2.0 5.2v 12785 81082A 69.89913 1 82.48 203.51 145 191.70 168.37 14.889 1300 6.0 2.0 5.2v 12987 81117A 70.11496 1 82.52 282.78 157 190.25 169.83 14.861 1328 6.0 2.0 5.2v 13271 82059A 69.75590 2 82.50 0.10 195 95.19 265.15 14.870 1378 6.0 2.0 5.2v 13552 82092A 70.42531 2 82.56 30.44 207 31.17 329.07 14.881 1408 6.0 2.0 5.2v 14032 83037A 69.86078 2 82.50 200.58 182 51.30 308.97 14.873 1455 6.0 2.0 5.2v 14147 83061A 70.05416 1 82.51 112.62 197 284.90 74.99 14.852 1470 6.0 2.0 5.2v 14551 83122A 70.10694 0 82.52 273.52 188 98.69 261.64 14.864 1515 6.0 2.0 5.2v 14699 84013A 69.73863 1 82.53 348.58 185 311.78 48.17 14.835 1536 6.0 2.0 5.2v 14819 84027A 69.78898 2 82.54 164.47 189 20.29 339.90 14.873 1544 6.0 2.0 5.2v 15369 84111A 69.89380 2 82.51 217.31 215 18.01 342.18 14.863 1606 6.0 2.0 5.2v 15494 85009A 69.83429 2 82.52 27.62 179 296.16 63.77 14.875 1626 6.0 2.0 5.2v 15592 85020A 70.02425 2 82.53 93.53 125 29.72 330.46 14.875 1633 6.0 2.0 5.2v 15889 85058A 70.06864 1 82.52 95.43 203 163.63 196.55 14.862 1666 6.0 2.0 5.2v 15944 85069A 70.03633 2 82.52 332.30 166 254.37 105.56 14.866 1674 6.0 2.0 5.2v 16262 85108A 70.13307 0 82.50 325.57 164 267.87 92.05 14.860 1703 6.0 2.0 5.2v 16326 85113A 70.08607 1 82.52 280.51 179 314.10 45.86 14.857 1707 6.0 2.0 5.2v 16495 86006A 69.87015 2 82.52 210.98 199 36.56 323.69 14.875 1726 6.0 2.0 5.2v 16611 86018A 70.08200 1 82.51 148.15 180 122.61 237.68 14.867 1733 6.0 2.0 5.2v 16719 86034A 69.89542 2 82.54 50.52 214 69.13 291.21 14.861 1743 6.0 2.0 5.2v 16791 86046A 70.07017 1 82.47 86.15 235 243.57 116.30 14.825 1758 6.0 2.0 5.9d 16986 86074A 69.77741 1 82.51 158.53 164 214.61 145.40 14.835 1782 6.0 2.0 5.2v 17191 86097A 70.08950 2 82.50 116.47 177 54.86 305.42 14.855 1805 6.0 2.0 5.2v 17295 87003A 69.93938 1 82.52 218.49 175 167.37 192.78 14.855 1812 6.0 2.0 5.2v 17566 87024A 70.42590 2 82.52 34.12 172 311.21 48.75 14.865 1825 6.0 2.0 5.2v 17911 87038A 70.51878 1 82.49 268.62 201 162.76 197.42 14.840 1842 6.0 2.0 5.2v 18152 87055A 70.07012 1 82.50 333.35 234 47.53 312.79 14.825 1862 6.0 2.0 5.2v 18421 87088A 69.80653 2 82.50 21.52 185 11.22 348.94 14.859 1892 6.0 2.0 5.2v 18748 88001A 69.73223 1 82.51 153.16 174 260.25 99.67 14.847 1908 6.0 2.0 5.2v 18958 88020A 70.04962 1 82.53 106.41 184 124.00 236.29 14.832 1933 6.0 2.0 5.2v 19210 88050A 69.86269 2 82.52 45.77 239 90.63 269.76 14.820 1953 6.0 2.0 5.2v 19573 88093A 70.07665 1 82.53 345.11 243 100.22 260.17 14.823 1975 6.0 2.0 5.2v 20465 90010A 69.91528 2 82.49 225.31 202 258.69 101.20 14.789 2058 6.0 2.0 5.2v 21422 91042A 69.98833 2 82.50 174.54 203 115.95 244.37 14.762 2151 6.0 2.0 5.2v 22236 92080A 70.12063 0 82.51 298.47 239 46.10 314.21 14.739 2221 6.0 2.0 5.2v 22286 92094A 70.01786 1 82.52 240.91 263 161.55 198.66 14.737 2228 6.0 2.0 5.2v 22626 93024A 70.07055 1 82.52 268.64 245 164.64 195.55 14.737 2242 6.0 2.0 5.2v Tselinas appear above; Okeans below. 11266 79011A 69.77947 9 82.52 5.92 123 338.60 21.46 15.157 1076 6.0 2.0 5.5v 11671 80005A 70.12432 2 82.51 296.13 140 305.60 54.38 14.962 1151 6.0 2.0 5.5v 14372 83099A 70.50009 2 82.53 67.79 187 185.20 174.89 14.861 1500 3.5 0.9 5.5v 15331 84105A 69.80255 2 82.53 18.75 201 341.26 18.77 14.847 1602 6.0 2.0 5.5v 16881 86055A 70.01114 1 82.51 76.25 200 8.89 351.26 14.837 1766 6.0 2.0 5.5v 18214 87062A 70.07044 1 82.51 136.84 218 80.53 279.82 14.831 1869 6.0 2.0 5.5v 19274 88056A 70.09323 1 82.51 177.14 199 146.92 213.32 14.825 Ok 1 4.0 0.0 5.5v 20510 90018A 70.07628 1 82.52 132.08 195 352.31 7.77 14.786 Ok 2 6.0 2.0 5.5v 21397 91039A 69.88654 2 82.52 46.82 244 66.13 294.24 14.765 Ok 3 6.0 2.0 5.5v 23317 94066A 70.11245 0 82.54 326.18 277 110.06 250.35 14.740 Ok 4 6.0 2.0 5.5v 23657 95046A 70.04240 1 82.53 107.73 295 81.34 279.10 14.734 Si 1 3.0 0.0 6.0d Cosmos 1025 6.0 2.0 0.0 5.2 v 1 10973U 78067 A 96269.80695366 .00000308 00000-0 23265-4 0 3169 2 10973 82.4743 10.4654 0012781 140.3534 219.8611 15.02433109990823 The elset above is the same as the elset below. The arrowed portions appear in line 1 of the table above; largely in the same order. Cosmos 1025 6.0 2.0 0.0 5.2 v ^^^^ ^^^ ^^^ ^^^ ^ 1 10973U 78067 A 96269.80695366 .00000308 00000-0 23265-4 0 3169 ^^^^^ ^^^^^ ^ ^^^^^^^^ ^ 2 10973 82.4743 10.4654 0012781 140.3534 219.8611 15.02433109990823 ^^^^^ ^^^^^^ ^^^ ^^^^^^ ^^^^^^ ^^^^^^