ID your UnIDs the easy way / need help w/UnID

Walter Nissen (dk058@cleveland.Freenet.Edu)
Sat, 17 Aug 1996 12:58:30 -0400

Sometimes indentifying an object you have observed as an UnID can be 
quite a challenge.  Sometimes it's really quite easy.  This note explains 
in detail how to use QuickSat to identify members of one class of objects 
that are very easy to identify. 
 
A large percentage of all the bright LEO satellites are in orbits of 
similar inclination.  There are many objects in sun-synchronous orbits of 
82 or 98 degrees inclination.  Even a casual stroll thru Ted Molczan's 
file of elsets will demonstrate this. 
 
Thus, it is very common, while observing one of these objects, to detect 
another object moving on a directly opposing course, i.e., in the opposite 
direction. 
 
Typically these objects are at heights of 600 to 1000 km, so that these 
objects move at roughly similar speeds. 
 
This means that you may be able to identify the UnID very readily, just by 
looking at the times of culmination of other bright objects.  If you see 
the UnID appulse the known object 1 minute after the known object 
culminates, then it is a very good guess that the UnID will itself 
culminate 1 further minute later.  (Conversely, if you see the UnID 
appulse the known object 1 minute before the known object culminates, then 
it is a very good guess that the UnID itself culminated 1 minute prior to 
the appulse). 
 
Let's see how this works in practice.  At 960810 023350.61 I was observing 
MOS 1 just as it was appulsed by an UnID (which was also flashing) moving 
on an opposite course.  I wasn't able to get much info on the UnID, just 
that it was a little ways to the right of MOS 1. 
 
But according to a QuickSat run I had made earlier, MOS 1 culminated at 
023312, or 38.61 s prior to the appulse with the UnID.  Thus, as a first 
approximation, I would predict that the UnID didn't culminate until 
38.61 s after that, or 023429.22.  (I think Mike McCants could tell us 
that there is a slight offset of 1 or 2 seconds in QS between objects 
headed North and objects headed South, so he might be able to compute an 
even closer estimate of the culmination time of the UnID). 
 
But I had already calculated the culmination times of all(?) the bright 
objects around that time, in the same list from which I plucked the info 
for MOS 1.  If I hadn't done that already, I would have had to cobble 
together a QUICKSAT.CTL file that would look something like this: 
 
 1996  8 Year, month number 
 09 09 Start date, end date 
   .8 -6.3 Start time, end time 
   41.3735   81.8637      840.    Nissen, OH 
  0 UT  correction and time zone name for UT to CDT 
 F True means generate Radio predictions 
 1950 Epoch of predicted RA, Dec 
 11.0 Magnitude limit 
  5 Altitude cut-off value 
 0.1 The search/step parameter value 
 T True means accept only the most recent elements for each object 
 F True means ignore shadow test 
 F  0 True means generate multiple prediction points, how many each way 
 F True means output distance values in miles 
 F True means generate a blank line before each object's prediction. 
QUICKSAT.MAG Intrinsic magnitudes input file 
UNID.TK      Output file 
MOLCZAN.TLE  Elements input file 
EOF 
 
The only tricky part of this is the time specification.  If you get truly 
desperate trying to subtract in sexagesimal, "-1.0  1.0" should cover all 
possibilities. 
 
However I obtained it, I ended up looking at this list of objects: 
 
  41.374  81.864  840.    Nissen, OH            1950 11.0  5 F F F F F 
***  1996 Aug  10  *** Times are UT ***   127  936 
       H  M  S  TIM AL AZI C   U  MAG SHD  RNG  R A   DEC 
12389  2 26 27      66  97 C  41  3.3 432  979 2011  34.3  C* 1263 r 
22196  2 27 24      16 239   114  3.9  21  908 1426 -11.2  Lageos-II r 
13992  2 27 50      56 108 C  41  3.6 253  926 2036  24.8  C* 1452 r 
21734  2 28  4      82  79 C 138  4.81027 1443 1855  42.2  C* 2157 r 
17974  2 29 41      49 249 C 138  3.5 554 1062 1534  19.2  C* 1844 r 
11080  2 29 53      69 284 C 137 20.8 669 1012 1624  43.1  Nimbus 7 
20433  2 30 16      48 107 C  41  3.7 163  991 21 7  20.2  C* 2056 r 
20465  2 31  0      83 100 C  41  3.0 215  629 1854  39.6  C* 2058 
 6323  2 31  2      49 296 C  45 21.1 579 1004 1427  46.0  C* 540 
22219  2 32 44      85 296 C  44  3.3 488  865 1756  43.1  C* 2219 
22220  2 33  3      25 308 C  51  5.2 783 1627 12 3  45.0  C* 2219 r 
17527  2 33 12      86  77 C  41  3.3 499  913 1841  41.9  MOS 1 
21153  2 34 26      87  80 C 138  3.9 550  967 1834  41.5  Nadezhda 3 r 
21656  2 34 39      40  91 C  40 21.5 417 1679 22 8  24.1  Meteor 3-5 R 
12457  2 36 26      70 284 C  42 20.5 500  881 1637  43.0  M* 2-7 r 
11286  2 38 18      54 295 C  45  4.2 442  865 15 5  46.5  IntCos 19 r 
22286  2 38 19      20  67    45  5.4  32 1499  020  29.9  C* 2228 
11155  2 38 23      58  76 C 137  2.9  35  615 2117  40.7  C* 1063 
21305  2 39 36      80 262 C 138 21.51079 1486 1736  39.1  C* 2143 R 
23751  2 42 23      36  71 C  44 21.1 212 1271 23 9  36.0  IRS-1C 
 
Now I have to find an object that culminates at 023429.22, or thereabouts. 
Hmmm, not too hard.  Nadezhda 3 r culminated at 023426.  Pretty close.  I 
guess that's it.  Actually, we may be done. 
 
We'll go on and confirm the identification.  The UnID should culminate at 
about the same altitude and azimuth as the known object.  Nadezhda 3 r 
fits beautifully.  It should be going the opposite direction (U should be 
totally different, or more precisely should be the supplement of the U for 
the known object, 180 - U).  Nadezhda 3 r fits beautifully.  Computing the 
locations of the two objects at the observed time of the appulse (this can 
be done with a tiny step in QS using just 1 or 2 input elsets, or in most 
any tracking program) confirms that Nadezhda 3 r was just to the right of 
MOS 1.  Checking Flash, we confirm that Nadezhda 3 r is a known flasher. 
Pretty solid.  The truly obsessive-compulsive (like the typical 
SeeSat-Ler) will obtain updated elsets from OIG and bracket both positions 
by using one elset from immediately before the pass and one from 
immediately after. 
 
That is a successful identification.  The other major possibility is 
failure.  At 960816 021458.09 I was observing C* 1077 when a much fainter 
object, maybe mag 7, appulsed it very closely (10' or 15'?) going the 
opposite direction.  The QS output looks like this: 
 
  41.374  81.864  840.    Nissen, OH            1950 11.0 30 F F F F F 
***  1996 Aug  16  *** Times are UT ***   118  943 
       H  M  S  TIM AL AZI C   U  MAG SHD  RNG  R A   DEC 
20443  2  6 37      72  77 C  42  3.5 429  827 1952  42.6  Spot 2 r 
18585  2  7  4      59 295 C  44 20.8 608  916 1528  46.9  C* 1898 
  192  2  7 27      86  97 C 138  8.33189 3554 1836  40.6  Midas 4 
18121  2  7 29      59 105 C  40  5.71056 1882 2034  27.2  C* 1851 r 
15427  2  9 26      38  71 C  44  7.0 349 1266 2251  37.0  NOAA 9 
13553  2  9 56      70 262 C 138  5.4 369  690 1641  35.7  C* 1408 r 
11309  2 11 16      35 288 C  43  8.5 906 1524 1337  35.3  C* 1089 r 
21305  2 11 20      70 263 C 138 21.71217 1534 1643  36.3  C* 2143 R 
 8688  2 12 53      33 310 C  50  8.1 393  916 1240  50.0  C* 803 
 5105  2 14 27      53 311 C  51 21.5 856 1235 1453  55.3  C* 402 
11268  2 14 31      80  78 C 138  3.5 113  496 1916  42.5  C* 1077 
19038  2 15  7 12.7 44 298 C  46 21.5 633 1087 14 4  45.1  C* 1937 
 7727  2 15 22      41 116 C  42 20.8 168 1270 2118  10.5  C* 724 
 9482  2 16 21      38 289 C  43 22.0 721 1278 1350  36.9  M* 1-26 r 
11458  2 17 51      66 283 C  42  3.5 193  550 1618  42.4  C* 1116 r 
17535  2 19 28      83 293 C  43 21.51158 1503 1754  43.6  C* 1823 
 3129  2 21 20      79 293 C  43 21.1 873 1223 1733  44.7  C* 203 
 5729  2 21 54      80 251 C 137 22.01541 1918 1745  37.3  Aureole 1 
 8343  2 22 22      41  62 C 133 20.8 272 1120 23 7  44.1  C* 773 
20528  2 23 26      43  92 C  40  4.5 280 1390 2210  24.7  C* 2061 r 
23324  2 23 47      43  72 C  43 20.8 257 1149 2242  37.8  IRS-P2 r 
10142  2 24 20      67 282 C  42  6.0 705 1082 1631  42.1  C* 928 r 
 9443  2 25 13      82 292 C  43 20.2 419  812 1752  43.9  C* 858 
22207  2 25 14   .4 52  94 C  40 20.7 323 1198 2134  28.5  C* 2218 
 
C* 1077 culminated at 021431.  So the UnID culminated about 021525.18. 
But C* 724 didn't go high enough, nor did C* 1937.  It couldn't have been 
as late as C* 1116 r. 
 
It appears that my file of 1000 bright objects doesn't contain an elset 
for the UnID.  Perhaps someone with a larger file will step in and satisfy 
my curiosity about the identity of this UnID. 
 
Cheers. 
 
Walter Nissen                   dk058@cleveland.freenet.edu