Re: STS-72/Hubble Solar Array

jvarney@quiknet.com
Sun, 14 Jan 1996 13:34:46 -0500

>I thought it was interesting to see that Endeavor (312km X 303km) and
>the Hubble Array (559km X 555km) cat#22920 are on the nearly same orbital
>track although the solar array is much higher.  I can understand why they
>have the same inclination but is it because both Shuttles launched from
>the same location that their tracks are nearly identical or just coincidence?
>Jeff Hunt <jhunt@eagle1.eaglenet.com>

Coincidence.  The rate of change in the right ascension of the ascending
node (RAAN) varies with inclination, eccentricity, and height.  Delta RAAN is 
caused by the earth's irregular shape, and decreases with increasing height.

The orbital tracks of satellites with like inclinations appear coincident 
whenever the longitude of the ascending node are equal.  The coincidence is 
momentary.  The different delta RAAN for the two objects will steadily move the longitudes of ascending nodes apart.  The diffence will increase until the 
longitudes are 180 degrees apart, only to close again until they appear coincident
again at some later date.

Good Passes,

Jim



----------------------------------------------------------------------------
Jim Varney          |  121^ 23' 54" W,  38^ 27' 28" N   |     Sacramento, CA
Civil Engineer      |            Elev. 20 ft.           |jvarney@quiknet.com
----------------------------------------------------------------------------