re: correction to message

Walter Nissen (dk058@cleveland.freenet.edu)
Tue, 11 Aug 1998 17:13:42 -0400 (EDT)

Paul Maley writes: 
 
> We are hoping that Iridium will be able to post a comprehensive list that 
> will let all space trackers know the correct identities in the very near 
> future. It would hopefully tabulate the satellite number within the 
> designated plane, the USSpaceCommand catalog number, the international 
> designator and the common name (e.g. Iridium XX). 
 
If I've just seen, for example, Ir 68 pass me by going North to South low 
in the East, I know another Iridium is going to do the same thing a bit 
higher in the sky about 9 minutes and 7 seconds later.  It would be 
immensely convenient if that next Iridium were to be the one numbered 
next, i.e., Ir 69.  No such luck. 
 
Therefore, I propose here a naming convention for the Iridia which is 
extremely convenient for visual observers of the constellation.  It is 
much, much easier to use than it is to describe, as here. 
 
You think death and taxes are certain?  This is arguably more certain: 
The Earth will rotate you beneath the orbit plane of any high-inclination 
LEO twice per day, once with the object ascending (moving South to North), 
once descending (moving North to South). 
 
                               6 planes      11 objects per plane 
 
               P for plane + plane number  +   object number 
 
P00, P01, P02, ..., P09, P0A;  P10, ..., P19, P1A;  ...;  P50, ..., P59, P5A. 
 
For the Iridial array, we can say much more.  During any given day, any 
location on Earth (except a few Arctic and Antarctic points) will pass 
successively beneath planes 0 thru 5, in that order, with the objects 
ascending; and then successively beneath planes 0 thru 5, in that order, 
with the objects descending.  In any plane, the objects 0 thru A, i.e., 0 
thru 9 and then A, will pass by in that order, at 9 minute intervals, with 
object A followed 9 minutes later by object 0.  When object A passes by, 
still 20 some degrees up in the West, object 0 in the next higher-numbered 
plane, 0 being 1 higher than 5, is just about to pass by about that high 
in the East. 
 
E.g., if you see that Ir P41 has just culminated halfway up in the East 
moving South to North, then you know that 9 minutes from now, Ir P42 will 
culminate a bit higher in the East moving South to North, and that 100.4 
minutes from now, Ir P41 will culminate low in the West moving South to 
North, by which time the P5 plane will already be rising in the East, with 
its objects passing by in numerical order.  Just after P4A culminates low 
in the West, P50 will culminate low in the East.  After plane 5, P5, 
passes over with its objects ascending, planes 0 thru 5 will follow in 
that order with their objects descending. 
 
Please note that P18, P51, and P54 do not appear in the table below, nor 
in the sky, as they will have to be launched as replacements. 
 
Object numbers B thru H are reserved (or used) for objects standing by. 
Object numbers S thru Z are reserved (or used) to designate inoperative 
objects.  Replacement objects are suffixed by R.  E.g., the lamented Ir 71 
which recently failed, was once object P18, but having failed is given the 
(additional?) number P1T, Ir 46/24 already having taken P1S.  When its 
replacement goes up it will become P18, or, if thought necessary, P18R. 
Should, e.g., Ir P15 = Ir 69 happen to fail, its replacement would be 
P15R.  I have accepted Paul Maley's characterizations as definitive, 
(assigning S, T or U to each failed object).  Should they be updated, some 
object numbers would change.  E.g., if Ir P0B = Ir 75 is actually 
inoperative, and not on stand-by, then it should be P0S, being the first 
failure in plane 0.  Suffixes Q, P, etc., are available for subsequent 
replacements should they become necessary. 
 
Objects B thru H and S thru Z do not conform to the regular system of 
objects 0 thru A, but R objects do, according to their object numbers. 
 
The numeration chosen for objects is not the only possible one.  Any 
cyclic rotation of the digits 0 thru A would also be ok.  But do note that 
each of my objects 0 does follow not only object A from the same plane, 
but also object A from the previous plane.  The order of the planes is 
fixed, though if the counting were backwards, people would adapt, and 
space people might feel more at home, though anyone expecting one of Phil 
Chien's loud KSC rumbles when plane 0 goes over might be disappointed. 
8->  The planes could be 1 thru 6, if desired.  The initial letter could 
be something other than "P". 
 
But please don't complain that this nomenclature fails to give each object 
a unique name.  If you look closely, you might find that to be, oh, say, 
an existing deficiency of the current nomenclature.  8-> 
 
 
I would like to see these P numbers used as the primary numbers for visual 
observation. 
 
E.g., here is a fragment of Alan Pickup's elset file with the P numbers 
inserted in place of the relatively useless string "idium": 
 
Ir P1T  71 tum   3.0  0.0  0.0  6.0 d            778 x 777 km 
1 25320U 98026B   98222.54002975  .00000163  00000-0  50983-4 0   701 
2 25320  86.3980 252.5961 0000384  63.7826 296.3422 14.34225289 14402 
Ir P08  70       3.0  0.0  0.0  6.0 d            780 x 775 km 
1 25342U 98032A   98222.05464967  .00000028  00000-0  29270-5 0   820 
2 25342  86.3958 221.2037 0003416  77.5266 282.6313 14.34216584 12108 
Ir P06  72       3.0  0.0  0.0  6.0 d            779 x 776 km 
1 25343U 98032B   98222.04195909  .00000046  00000-0  93636-5 0   666 
2 25343  86.3970 221.2349 0002020  73.2653 286.8769 14.34216852 12101 
Ir P07  73       3.0  0.0  0.0  6.0 d            780 x 776 km 
1 25344U 98032C   98222.04830429  .00000111  00000-0  32544-4 0   887 
2 25344  86.3969 221.2297 0002955  52.0706 308.0757 14.34217192 12105 
Ir P05  74       3.0  0.0  0.0  6.0 d            780 x 776 km 
1 25345U 98032D   98222.52399888  .00000173  00000-0  54881-4 0   628 
2 25345  86.3968 221.0268 0002443  99.8701 260.2772 14.34217897 12172 
Ir P0B  75 ?     3.0  0.0  0.0  6.0 d            696 x 692 km 
1 25346U 98032E   98222.08722654  .00000183  00000-0  33594-4 0   596 
2 25346  86.5452 221.1265 0003244  44.3405 315.8065 14.59812304 12293 
 
I could easily live with "Ir P0B  75 ?" as shown here, or just plain 
IrP0B, the "?" being pretty much replaced by the "B" and the 75 of only 
minor historical interest (or interest only to technologists who know the 
objects as metal boxes, instead of lights in the sky).  Or Ir-P0B, or 
Ir P0B, or Ir p0b, or Ir P0B-75, or Ir P0B-75 ?, or Ir P0B-75-F31 ?, 
incorporating the frame number(?) from the assembly line, or IP0B, or 
anything like those.  Let's just pick one format and use it universally. 
The thing I would like to see is the unique P0B be right at the front so I 
don't have to (mis-)type so many characters and I can't choose the wrong 
object.  Adding the convenience I originally sought to those advantages 
ought to create a winning combination. 
 
 
Does this naming convention work?  I have to tell you that the first time 
I ran QuickSat for the whole night most all the way to the horizon on the 
whole file of Iridia, obtaining output in one-line form and egrepped it 
(searched) for "P0", the result was stunning, the beautiful geometry of 
the objects in the plane laid out before me with the P0B object wandering 
just a bit.  Simply stunning! 
 
Rather than display the regular geometry of that plane, here is the output 
for the messy plane 5 for one leg, i.e., 1/12 of the passes for a day: 
 
       H  M  S  TIM AL AZI C   U  MAG SHD  RNG  R A   DEC 
25077  7 27 28       3  72 C  44 28.9 715 2918  553  15.3  Ir P59  42 
25041  7 36 25       5  74 C  43 26.8 710 2738  551  15.3  Ir P5A  40 
24871  7 43 26       7  76 C  43 25.8 712 2596  549  15.4  Ir P5S  20 tu 
25042  7 45 25       7  76 C  43 25.7 705 2556  549  15.3  Ir P50  39 
25078  7 55 24      10  78 C  42 24.9 699 2355  546  15.6  Ir P5T  44 ? 
24870  8  3 28      12  79 C  42 24.3 697 2193  543  16.0  Ir P52  17 
24869  8 12 30      15  81 C  41 23.8 691 2007  539  16.6  Ir P53  15 
24873  8 14 17      35  89 C  41 21.3 344 1025  412  23.1  Ir P5U  21 ? 
25043  8 30 39      22  84 C  41 23.0 686 1652  526  18.7  Ir P55  38 
25040  8 39 44      27  85 C  41 22.5 685 1479  516  20.3  Ir P56  41 
25039  8 48 50      32  87 C  41 22.1 682 1310  5 2  22.6  Ir P57  43 
24872  8 57 56      39  89 C  41 21.6 681 1154  443  25.4  Ir P58  18 
25077  9  7  6      48  90 C  41 21.2 682 1017  417  29.0  Ir P59  42 
25041  9 16 13      59  92 C  41 20.7 681  901  339  33.3  Ir P5A  40 
24871  9 23 20      69  93 C  41 20.4 689  841  257  36.9  Ir P5S  20 tu 
25042  9 25 22      72  93 C  41 20.4 682  821  246  37.7  Ir P50  39 
25078  9 35 31      89  95 C  41 20.1 684  785  130  40.8  Ir P5T  44 ? 
24870  9 43 42      77 276 C  41 20.1 686  803  025  41.0  Ir P52  17 
24873  9 52 22      20 285 C  43 21.7 396 1485 20 5  24.0  Ir P5U  21 ? 
24869  9 52 54      63 278 C  41 20.2 687  869 2320  38.9  Ir P53  15 
25043 10 11 20      42 281 C  42 20.6 693 1102 2159  32.7  Ir P55  38 
25040 10 20 33      35 282 C  42 21.0 697 1251 2135  30.1  Ir P56  41 
25039 10 29 48      29 284 C  42 21.3 701 1415 2117  28.0  Ir P57  43 
24872 10 39  3      24 285 C  43 21.7 706 1584 21 5  26.4  Ir P58  18 
25077 10 48 21      20 287 C  43 22.0 711 1756 2056  25.2  Ir P59  42 
25041 10 57 37      16 289 C  44 22.4 716 1932 2049  24.4  Ir P5A  40 
24871 11  4 49      14 290 C  44 22.7 728 2077 2045  24.0  Ir P5S  20 tu 
25042 11  6 55      13 290 C  45 22.8 722 2109 2044  23.8  Ir P50  39 
25078 11 17 14      10 292 C  45 23.4 728 2307 2039  23.3  Ir P5T  44 ? 
24870 11 25 33       8 294 C  46 23.9 735 2466 2036  23.2  Ir P52  17 
24869 11 34 55       6 296 C  47 24.8 740 2645 2033  23.1  Ir P53  15 
25043 11 53 40       3 299 C  48 29.1 753 2990 2030  23.3  Ir P55  38 
 
Why is Ir P5U such an oddball, coming, as she does, earlier and earlier, 
and out of plane?  The U in P5U says it is a failed object.  P5T (and P1S) 
is close to in sync with the regular geometrical arrangement.  P5S is not 
so close.  Perhaps they will eventually become more asynchronous. 
 
But, if they exist, and P51 and P54 do not, the 0 thru A objects pass by 
in a completely predictable way.  E.g., spaced at 9 minute intervals, 
rising gently in the East, then more rapidly, then declining in the West. 
 
(I think you have to subtract about 14 or 15 from the magnitudes given to 
achieve reality; except during a glint, of course). 
 
In this tiny verbatim excerpt: 
 
       H  M  S  TIM AL AZI C   U  MAG SHD  RNG  R A   DEC 
25276  5 24  7       5 297 C  47 26.6 355 2775 1413  23.5  Ir P25  60 
25263  5 27 14      85 275 C  41 19.9-469  787 2049  41.3  Ir P36  61 
25172  5 32 43       6  75 C  43 25.8 112 2690  344  15.1  Ir P47  53 
 
we see successive passes from the 5, 6 and 7 objects, in planes 2, 3, and 
4, respectively.  One nearly invisible in the West, one high overhead and 
one still deep in the East. 
 
Don't worry about P47.  She gets her chances later at intervals of roughly 
100 minutes: 
 
       H  M  S  TIM AL AZI C   U  MAG SHD  RNG  R A   DEC 
25172  5 32 43       6  75 C  43 25.8 112 2690  344  15.1  Ir P47  53 
25172  7 12 33      62  92 C  41 20.4 -14  876  120  34.4  Ir P47  53 
25172  8 53 59      15 289 C  44 22.7 166 1978 1841  24.3  Ir P47  53 
 
I think it works. 
 
 
Can you make a better suggestion? 
 
 
Cheers. 
 
Walter Nissen                   dk058@cleveland.freenet.edu 
-81.8637, 41.3735, 256m elevation 
 
--- 
 
Carpe noctem! 
 
--- 
 
With credit to Alan Pickup, here is the whole table, sorted by catalog 
number: 
 
cat # COSPAR p-name          apogee & perigee  other number 
24792 97020A Ir P33  8       781 x 775 km 
24793 97020B Ir P32  7       781 x 775 km 
24794 97020C Ir P31  6       780 x 775 km 
24795 97020D Ir P30  5       781 x 775 km 
24796 97020E Ir P34  4       779 x 777 km 
24836 97030A Ir P45  14      780 x 776 km 
24837 97030B Ir P43  12      779 x 777 km 
24838 97030C Ir P40   9      778 x 778 km 
24839 97030D Ir P41  10      779 x 777 km 
24840 97030E Ir P44  13      778 x 777 km 
24841 97030F Ir P46  16      779 x 777 km 
24842 97030G Ir P4S  11 tum  773 x 752 km 
24869 97034A Ir P53  15      780 x 776 km 
24870 97034B Ir P52  17      779 x 777 km 
24871 97034C Ir P5S  20 tum  784 x 769 km      18 
24872 97034D Ir P58  18      780 x 776 km      20 
24873 97034E Ir P5U  21 ?    643 x 627 km 
24903 97043A Ir P14  26      780 x 775 km 
24904 97043B Ir P19  25      780 x 776 km 
24905 97043C Ir P10  24      779 x 776 km 
24906 97043D Ir P17  23      780 x 776 km 
24907 97043E Ir P16  22      779 x 776 km 
24944 97051A Ir P28  29      779 x 776 km 
24945 97051B Ir P20  32      779 x 776 km 
24946 97051C Ir P21  33      779 x 777 km 
24947 97051D Ir P2S  27 tum  558 x 547 km 
24948 97051E Ir P27  28      780 x 776 km 
24949 97051F Ir P29  30      779 x 776 km 
24950 97051G Ir P2A  31      779 x 776 km 
24965 97056A Ir P37  19      779 x 776 km 
24966 97056B Ir P39  37      780 x 776 km 
24967 97056C Ir P3A  36      780 x 776 km 
24968 97056D Ir P35  35      779 x 776 km 
24969 97056E Ir P38  34      779 x 776 km 
25039 97069A Ir P57  43      780 x 776 km 
25040 97069B Ir P56  41      779 x 776 km 
25041 97069C Ir P5A  40      780 x 776 km 
25042 97069D Ir P50  39      780 x 776 km 
25043 97069E Ir P55  38      779 x 776 km 
25077 97077A Ir P59  42      779 x 776 km 
25078 97077B Ir P5T  44 ?    781 x 775 km 
25104 97082A Ir P1A  45      779 x 777 km 
25105 97082B Ir P1S  46 tum  786 x 771 km      24 
25106 97082C Ir P11  47      779 x 777 km 
25107 97082D Ir P12  48      780 x 776 km 
25108 97082E Ir P13  49      779 x 776 km 
25169 98010A Ir P49  50      779 x 776 km 
25170 98010B Ir P48  56      779 x 777 km 
25171 98010C Ir P42  52      780 x 776 km 
25172 98010D Ir P47  53      780 x 775 km 
25173 98010E Ir P4A  54      780 x 776 km 
25262 98018A Ir P3B  51 man  757 x 751 km 
25263 98018B Ir P36  61      781 x 775 km 
25272 98019A Ir P26  55      780 x 776 km 
25273 98019B Ir P22  57      779 x 776 km 
25274 98019C Ir P23  58      778 x 777 km 
25275 98019D Ir P24  59      779 x 777 km 
25276 98019E Ir P25  60      779 x 776 km 
25285 98021A Ir P09  62      779 x 777 km 
25286 98021B Ir P0A  63      779 x 777 km 
25287 98021C Ir P00  64      779 x 776 km 
25288 98021D Ir P01  65      779 x 777 km 
25289 98021E Ir P02  66      784 x 772 km 
25290 98021F Ir P03  67      780 x 775 km 
25291 98021G Ir P04  68      779 x 777 km 
25319 98026A Ir P15  69      778 x 777 km 
25320 98026B Ir P1T  71 tum  778 x 777 km 
25342 98032A Ir P08  70      780 x 775 km 
25343 98032B Ir P06  72      779 x 776 km 
25344 98032C Ir P07  73      780 x 776 km
25345 98032D Ir P05  74      780 x 776 km
25346 98032E Ir P0B  75 ?    696 x 692 km