An Atlas 2AS rocket is scheduled to be launched from Vandenberg AFB on 2001 Sep
08, between 15:24 and 15:36 UTC. The following evidence points to a NOSS orbit:
- 14 min/d advance of launch window almost exactly as required by NOSS orbit
- 63.4 inclination (same as NOSS) reported by Spaceflight Now
- U.S. NMM (National Mission Model) lists LEO Atlas 2AS mission at NOSS
inclination
- orbital plane would fill largest gap in existing 2nd generation NOSS
constellation
Most of the above has been covered in detail in the following article by Justin
Ray of Spaceflight Now:
http://www.spaceflightnow.com/atlas/ac160/status.html
Justin obtained the launch window times that were key to determining that the
destination is a NOSS orbit.
The intended parking orbit of the Centaur stage and the payload is uncertain,
so I have produced search elements that I hope cover the range of
possibilities, beginning with a 100 nm (185 km) circular orbit, up to the 273
km x 672 km orbit of the Titan IVA NOSS launches from VAFB.
The following are based on launch on 2001 Sep 08 at 15:30 UTC:
Centaur 10.1 3.0 0.0 3.0 v 184 X 186 km
1 75001U 01251.64930557 .08000000 00000-0 10707-2 0 09
2 75001 63.4300 300.6500 0005000 167.0000 334.0000 16.35000000 09
273 X 274 km
1 75002U 01251.64930558 .01000000 00000-0 16682-2 0 02
2 75002 63.4300 300.5000 0001000 167.0000 334.0000 16.02500000 09
273 X 373 km
1 75003U 01251.64930559 .00100000 00000-0 34140-3 0 04
2 75003 63.4300 300.5000 0075000 167.0000 334.0000 15.84700000 02
273 X 473 km
1 75004U 01251.64930560 .00050000 00000-0 24852-3 0 00
2 75004 63.4300 300.5000 0148000 167.0000 334.0000 15.67100000 09
273 X 573 km
1 75005U 01251.64930561 .00070000 00000-0 43460-3 0 00
2 75005 63.4300 300.5000 0221000 167.0000 334.5000 15.49900000 05
273 X 673 km
1 75006U 01251.64930562 .00080000 00000-0 22023-3 0 05
2 75006 63.4300 300.4500 0291700 167.0000 335.0000 15.33000000 04
These elements should be predictive to within several minutes for the first few
days after launch, but it never hurts to make a generous allowance for
uncertainty.
The following discussion assumes a NOSS triad similar to the Titan IVA-launched
triads, but that can only be confirmed through visual observation. I am certain
that the destination orbit is NOSS, but not as certain that the payload will be
like previous NOSS. Perhaps they will be smaller than the 2nd generation NOSS.
Perhaps the triad has been retired in favour of a single spacecraft.
If this is the familiar NOSS, then its launch dispenser can be expected to
trail the Centaur by a short distance, until it manoeuvres to nearly the 1110
km operational orbit. On Titan IV NOSS missions, the launch dispenser
frequently was observed to flash, with a period of 3 to 5 s.
Observers north of about 55 N will have morning visibility of each of the
search orbits.
Observers north of about 50 N will barely have morning visibility of the two
highest orbits.
Observers near 35 S will have evening visibility for all but the lowest orbit.
South Africa will have a pass little more than 2 hours after launch.
The visibility windows will widen considerably after the payload manoeuvres to
1110 km, probably within a day or two of launch.
During high elevation passes, the errors in the orbit are likely to be great
enough for the object to miss the predicted path by several degrees, so the
wide field of view of the unaided eye is preferable to the narrow field of view
of binoculars. At low elevations, track errors should be less, and the objects
will be fainter, so binoculars are the better choice.
Happy Hunting!
Ted Molczan
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This archive was generated by hypermail 2b29 : Thu Sep 20 2001 - 17:55:52 EDT