[Server-sky] Orbital alignment for cubesat experiment

[Keith Lofstrom]

Thinsats are mostly pushed antisunwards by light pressure; 
tilting a thinsat adds less than 8% lateral acceleration. 

Thinsat experiments in a drag-matched cubesat container
will be brief ( a few minutes ) when the sun angle is 
co-linear with the orbit, so that the drag on the cubesat
pushes it in the same direction as the thinsat.

Given the high inclination ISS orbit (51.6°), this only
happens during the sunward or antisunward parts of the orbit,
at times of year when the longitude of the ascending node
of the ISS orbit is sunwards or antisunwards.  The ascending
node precesses because of the earth's equatorial bulge - I
haven't done the calculations yet. 

At other times and in other parts of the orbit, the vectors
don't line up, and experiment times will be limited to the
traverse time of the experimental chamber.  At 8 cm/minute²
from light pressure, that won't be long!

I may find time in a week or two to put some detailed calculations
on the wiki, but it would be great if someone else beat me to it.
It would be really useful to find some historical data on the
precession of the ascending node for ISS, or do the calculation.

The limits on launch time may be too restrictive for most cubesat
opportunities.

Keith

-- 
Keith Lofstrom          keithl at keithl.com         Voice (503)-520-1993