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