celestri.tcl

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#
# Celestri LEO constellation from Motorola.
#
# information used from the Motorola FCC application, June 1997.
# Was available online in Adobe Acrobat pdf format from Motorola; see:
# http://www.ee.surrey.ac.uk/Personal/L.Wood/constellations/celestri/
# Full details are in the pdf/section titled part two, 1.9Mb, pp36-38,
# including 3D position plot and unprojected coverage map showing
# subsatellite points. Unfortunately, that copy got damaged.
#
# this script for SaVi 1.2, by Lloyd Wood ([e-mail])
# http://www.ee.surrey.ac.uk/Personal/L.Wood/constellations/
#
# $Id: celestri.tcl,v 1.5 2004/12/26 14:47:19 lloydwood Exp $

set SATS_PER_PLANE 9
set NUM_PLANES 7


# setup orbital elements
set a [expr 1400.0+$RADIUS_OF_EARTH]
set e 0.0013
set inc 48
set omega 0.0
set T_per [expr 2 * $PI * pow($a,1.5) / sqrt($MU)]

# mask elevation angle is 16 degrees, according to page 42.
set coverage_angle 16.0

# Plane offset is really a function of harmonic factor in Ballard constellations.
# (Rosette Constellations of Earth Satellites, A. H. Ballard, TRW,
#  IEEE Transactions on Aerospace and Electronic Systems, Vol 16 No 5, Sep. 1980)
# 360 / 9 / 7 = 360/63 = 5.714 degrees.
# quoted 28.57 degrees is 5x that, or fifth harmonic factor.

set interplane_phasing [expr 360.0 / $NUM_PLANES / $SATS_PER_PLANE * 5]

satellites GV_BEGIN

for {set j 0} {$j < $NUM_PLANES} {incr j} {

   # FCC application gives 51.43 degrees between planes, but since it's a rosette
   # we can assume that they're just rounding off. More accurate:

   set Omega [ expr $j * 360 / $NUM_PLANES ]

   set plane_offset [expr ($T_per / 360) * ($j * $interplane_phasing)  ]

   for {set i 0} {$i < $SATS_PER_PLANE} {incr i} {

       set T [expr ($T_per * $i / $SATS_PER_PLANE) + $plane_offset ]
       satellites LOAD $a $e $inc $Omega $omega $T
   }
}

satellites GV_END