iridia status

richard.keen@kingsmarket.com
Wed, 25 Mar 98 03:32:37

                                  
 Hi all -
 Here's an extract from a recent issue of Jonathan's Space Report,
which some of you are probably already familiar with.  Since this one
concerns the Iridium satellites, I thought I'd repost it:
 
 Jonathan's Space Report No. 352 1998 Mar 11 Cambridge, MA
 Recent Launches
 The five Iridium satellites launched on Feb 18 began raising their
orbits to operational altitude in early March. Most of the Iridium
constellation is in a 100.4 min, 774 x 780 km x 86.4 deg operational
orbit to which the satellites maneuver after launch into a much lower
parking orbit. However, some satellites have been placed in a reserve
orbit 10-15 km lower than the operational one. One satellite was
temporarily placed in a higher 785 x 790 km orbit. Of the 51 Iridium
satellites launched to date, two failed and remained in parking orbit;
six are currently in the reserve orbit; four were still raising their
orbits from parking to operational as of March 9; and the remaining 39
satellites are in the operational orbit. Details of orbital changes for
individual satellites are as follows:
 1997 Jul:    SV021 failed, stayed in parking orbit
 1997 Sep 6:  SV011 to reserve orbit since this date
 1997 Sep 11: SV004 to reserve orbit for 19 days, now operational
 1997 Sep:    SV027 failed, stayed in parking orbit
 1997 Oct:    SV036 delayed 2 weeks in move from parking orbit
 1997 Nov 22: SV040 deployed to reserve orbit until Jan 27
 1997 Nov 23: SV038 deployed to reserve orbit, remains there
 1997 Dec 11: SV020 to high reserve for 9 days, now operational
 1997 Dec 20: SV018 to reserve orbit since this date
 1997 Dec 23: SV042 to reserve orbit since this date
 1997 Dec 27: SV026 to reserve orbit for 1 month, now operational
 1998 Jan 11: SV005 to reserve orbit since this date
 1998 Feb 3:  SV048 to reserve orbit since this date
 1998 Feb 21: SV024 drifting higher, probably will move to reserve
 Jonathan McDowell
 Harvard-Smithsonian Center for Astrophysics
 60 Garden St, MS6
 Cambridge MA 02138, USA
 phone: (617) 495-7176
 jcm@urania.harvard.edu
 jmcdowell@cfa.harvard.edu
 JSR: http://hea-www.harvard.edu/~jcm/space/jsr/jsr.html
 Back issues: ftp://sao-ftp.harvard.edu/pub/jcm/space/news/news.*
 
 To check on the status of the constellation, I sorted the orbital
elements (from Mike McCants' CS980319 set) by RA of node and by mean
motion, then grouped the results.
 
 Ir  Norad  Int Des  Epoch  Node  MM
 Low MM:
 24  24905  97-43C  98074  314  14.3332
 37  24966  97-56B  98078   16  14.3365
 
 Operational MM = 14.342:
 Node = 16
  4  24796  97-20E  98078   16  14.3420
  6  24794  97-20C  98075   16  14.3421
  7  24793  97-20B  98076   16  14.3421
  8  24792  97-20A  98076   16  14.3421
 19  24965  97-56A  98077   16  14.3422
 34  24969  97-56E  98078   16  14.3421
 35  24968  97-56D  98077   16  14.3421
 36  24967  97-56C  98075   16  14.3421
 
 Node = 48
  9  24839  97-30D  98074   49  14.3421
 10  24838  97-30C  98076   48  14.3421
 12  24837  97-30B  98076   48  14.3421
 13  24840  97-30E  98074   49  14.3421
 14  24836  97-30A  98074   49  14.3421
 16  24841  97-30F  98074   48  14.3421
 
 Node = 80
 15  24869  97-34A  98075   80  14.3421
 17  24870  97-34B  98076   80  14.3421
 20  24872  97-34D  98076   79  14.3421
 39  25042  97-69D  98074   80  14.3421
 40  25041  97-69C  98074   80  14.3421
 41  25040  97-69B  98077   79  14.3421
 43  25039  97-69A  98072   81  14.3421
 44  25078  97-77B  98076   80  14.3421
 
 Node = 314
 22  24907  97-43E  98077  313  14.3421
 23  24906  97-43D  98076  313  14.3421
 25  24904  97-43B  98076  313  14.3421
 26  24903  97-43A  98072  315  14.3421
 45  25104  97-82A  98075  314  14.3421
 46  25105  97-82B  98077  313  14.3421
 47  25106  97-82C  98076  313  14.3421
 49  25108  97-82E  98074  314  14.3421
 
 Node = 346
 28  24948  97-51E  98075  345  14.3421
 29  24944  97-51A  98077  344  14.3421
 30  24949  97-51F  98076  345  14.3421
 31  24950  97-51G  98072  347  14.3421
 32  24945  97-51B  98077  344  14.3421
 33  24946  97-51C  98078  344  14.3421
 
 High MM:
 Node = 48 (latest launch)
 50  25169  98-10A  98078   47  14.3452
 52  25171  98-10C  98078   47  14.6003
 53  25172  98-10D  98076   48  14.3429
 54  25173  98-10E  98075   48  14.3425
 56  25170  98-10B  98078   47  14.3423
 
 Various nodes (spares being maneuvered?):
  5  24795  97-20D  98077   16  14.3696
 18  24871  97-34C  98076   80  14.3704
 38  25043  97-69E  98074   80  14.3728
 42  25077  97-77A  98076   80  14.3758
 48  25107  97-82D  98074  314  14.3718
 
 "Anomalous" objects with very high MM; Iridiums 21 and 27 have failed:
 11  24842  97-30G  98077   47  14.3907
 21  24873  97-34E  98077   72  14.7805
 27  24947  97-51D  98077  341  15.0401
 
 From this, you can see how the 6 orbital planes are filling up.  Five
of the 6 planes now have between 6 and 8 satellites in operational
orbits, and it looks like the Node = 58 plane is about to get filled as
the five 98-10 objects move in.
 It's interesting that Iridiums 24 and 37 are in HIGHER parking orbits
(lower MM), while the other "spares" are in lower orbits (with higher
MM).
 Then there's the failed Iridiums 21 and 27, of which 27 is clearly out
of control with a flash period of about 3 seconds.  This object will be
making evening passes in the northern hemisphere in April, and should
be fun to watch for its flashes.
 Finally, Rob Matson notes in his Iridflar program that Iridium 11
doesn't produce "normal" flashes.  Has anyone ever seen a flash from
this object?  I've looked several times, but have never seen any.
 
 Cheers, Rich Keen
 Coal Creek Canyon, Colorado, USA (39.877 N, 105.391 W, elevation
2728m)