Ron Lee's Iridium Elsets
Jim Varney (jamesv@softcom.net)
Sat, 16 May 1998 12:53:30 -0700
ronlee@pcisys.net (Ron Lee) wrote:
> Iridium, Delta, 5/17/98, 21:15:56 UT
> 1 98765U 980XXA 98138.40157280 -.00378067 00000-0 -55178-1 0 12
> 2 98765 86.5706 256.3573 0009801 264.3271 95.7271 14.78175419 89
>
> There still remains the unresolved issue about differences between my
> elset and data provided by another individual. I am standing by my
> elset until proven wrong!
Please continue with your efforts, Ron. I looked at a previous launch and
it seems to support your estimated RAAN. Take a look at Iridium 15, also
launched from Vandenberg last year. These are historical elsets from the
initial deployment through the orbit-raising:
Iridium 3.0 0.0 0.0 6.0 d
1 24869U 97034A 97191.60090288 -.00075400 00000-0 00000+0 0 78
2 24869 86.3961 185.1083 0012750 230.5657 129.5039 14.78583180 153
Iridium 15 3.0 0.0 0.0 6.0 d
1 24869U 97034A 97198.23609660 -.00047509 00000-0 -66900-2 0 258
2 24869 86.3967 182.1374 0010716 211.6608 148.3966 14.77668236 1137
Iridium 15 3.0 0.0 0.0 6.0 d
1 24869U 97034A 97212.52541236 -.00023892 00000-0 -52883-2 0 435
2 24869 86.3965 175.7281 0005185 126.5468 233.6260 14.57497542 3227
Iridium 15 3.0 0.0 0.0 6.0 d
1 24869U 97034A 97226.23536500 .00000299 00000-0 99666-4 0 690
2 24869 86.4010 169.8932 0004434 60.9512 299.2128 14.34280923 5202
Precession of the nodes of these orbits is about -0.4 deg per day.
Applying this factor to the 97191 elset predicts a precessed RAAN of 171.5
for the 97226 elset. This tells me that little or no plane changing is
done when the Iridiums raise their orbits, at least not more than a degree
or two.
Today the only plane of the six planes that isn't filled with 11 satellites
is Plane 1:
Ir RAAN MM Plane
62 257.44 14.3421 1
63 257.02 14.3421 1
64 257.64 14.3421 1
65 257.26 14.3422 1
66 257.28 14.3421 1
67 257.64 14.3420 1
68 257.04 14.3422 1
It's obvious that the final RAAN will also be 257 degrees for the upcoming
launch for four of the satellites. I presume the others will be spares.
The data that Keith Stein forwarded to us had
RA OF ASCENDING NODE (DEG): 265.257 SV-1
So, based on the Iridium 15 history above, I'd have to agree that the 265
degree RAAN is suspect or this launch is being deployed in a different way.
If there's a flaw in my crude little analysis please point it out.
______________________________________________
Jim Varney
Member, Sacramento Valley Astronomical Society
www.softcom.net/users/jamesv/index.htm