RE: Are the orbits of the Tselinas and the Okeans distinguishable?

Ted Molczan (molczan@fox.nstn.ca)
Thu, 3 Oct 1996 00:54:26 -0400

Walter Nissen wrote:

>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"? 

I have never found any differences.
 
>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. 

The Tselina D constellation consists of 6 planes,
60 deg apart. Over time, the planes of the oldest
ones would have drifted apart, due to the effects 
of drag.
 
>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? 

It appears to me that the small eccentricity is
typical of other near-circular orbits. Probably
it represents an acceptable tolerance, instead 
of a special design.
 
>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. 

I sorted your Tselina data by ascending RAAN, then I consulted 
Soviet Year in Space from 1987-90 and Europe and Asia in Space
1991-94, which state the satellite being replaced by each new 
launch. I assigned arbitrary plane numbers to each thread of
replacements I identified. Many of the older satellites predate
my references, but it is clear which plane they belong to. I 
separated each plane by a blank line, and in fact there are
quite a few degrees separating them, so they could have been
detected even without the references. (The planes have a greater
separation than any two objects within a plane.) Also, if you
compare the leading edges or the trailing edges of successive
planes, they are about 60 deg apart.
 
NORAD  DESIG      Epoch     Inc     Plane    RAAN    MM    Cosmos 
10973	 78067A	69.80695	82.47			 10.46  15.024	1025
18421	 87088A	69.80653	82.50		1	 21.52  14.859	1892
15494	 85009A	69.83429	82.52			 27.62  14.875	1626
13552	 82092A	70.42531	82.56			 30.44  14.881	1408
17566	 87024A	70.42590	82.52		1	 34.12  14.865	1825
19210	 88050A	69.86269	82.52		1	 45.77  14.820	1953
16719	 86034A	69.89542	82.54		1	 50.52  14.861	1743

16791	 86046A	70.07017	82.47		2	 86.15  14.825	1758
15592	 85020A	70.02425	82.53			 93.53  14.875	1633
15889	 85058A	70.06864	82.52		   	 95.43  14.862	1666
18958	 88020A	70.04962	82.53		2	106.41  14.832	1933
14147	 83061A	70.05416	82.51			112.62  14.852	1470
17191	 86097A	70.08950	82.50		2	116.47  14.855	1805

16611	 86018A	70.08200	82.51		3	148.15  14.867	1733
18748	 88001A	69.73223	82.51		3	153.16  14.847	1908
16986	 86074A	69.77741	82.51		3	158.53  14.835	1782
14819	 84027A	69.78898	82.54			164.47  14.873	1544
21422	 91042A	69.98833	82.50		3	174.54  14.762	2151

14032	 83037A	69.86078	82.50			200.58  14.873	1455
12785	 81082A	69.89913	82.48			203.51  14.889	1300
16495	 86006A	69.87015	82.52		4	210.98  14.875	1726
15369	 84111A	69.89380	82.51			217.31  14.863	1606
17295	 87003A	69.93938	82.52		4	218.49  14.855	1812
20465	 90010A	69.91528	82.49		4	225.31  14.789	2058
22286	 92094A	70.01786	82.52		4	240.91  14.737	2228

17911	 87038A	70.51878	82.49		5	268.62  14.840	1842
22626	 93024A	70.07055	82.52		7	268.64  14.737	2242
14551	 83122A	70.10694	82.52			273.52  14.864	1515
16326	 85113A	70.08607	82.52		5	280.51  14.857	1707
12987	 81117A	70.11496	82.52			282.78  14.861	1328
22236	 92080A	70.12063	82.51		5	298.47  14.739	2221

16262	 85108A	70.13307	82.50		6	325.57  14.860	1703
15944	 85069A	70.03633	82.52			332.30  14.866	1674
18152	 87055A	70.07012	82.50		6	333.35  14.825	1862
19573	 88093A	70.07665	82.53		6	345.11  14.823	1975
14699	 84013A	69.73863	82.53			348.58  14.835	1536
13271	 82059A	69.75590	82.50			360.10  14.870	1378


>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). 

No it is not intentional. Originally, they were all assigned 
3.5 x 0.9 m, in accordance with the speculative values in the
RAE Table of Earth Satellites, 1957-89. As I recall, Mike McCants
found that the objects were brighter than would be expected
of those dimensions. So to yield more accurate standard magnitudes,
the dimensions were changes to 6 x 2 m, except for a the odd 
omission, which retained the older dimensions, or some provisional
value.

Your message, and my recent introduction of measured std mags, has
inspired me to look for accurate dimensions for the Okeans. 
According to Europe and Asia in Space, the main bus is 3 m long,
and its diameter varies from 0.8 to 1.4 m. taking the average, I
obtain 3 x 1.1, which will replace the 6 x 2 and the others. Of
course the Okeans have various appendages that yield a larger
overall size, but normally I include only the main bus.

I will stick with 6 x 2 m for the Tselina D's, because I do not have
a reference with their dimensions. At least this produces a 
std mag in reasonable agreement with observations. Europe and Asia 
in Space states that Okeans and Tselina D's have similar RCS (radar 
cross-section), and they are produced by the same organization, so 
perhaps they are similar. Their std mags are not vastly different.
  
Finally, I see that I omitted the measured std mag for Tselina D
86046A, so I will change that to 5.2 in the Predict database.

Ted Molczan