Night Side Maneuvers

We can minimize night light pollution, and advance perigee against light pressure orbit distortion, by turning the flat-sat as we approach eclipse. The overall goal is to perform 1 complete rotation of the flat-sat per orbit, with it perpendicular to the sun on the day-side of the earth, but turning it by varying amounts on the night side.

Another advantage of the turn is that if flat-sat maneuverability is destroyed by radiation or a collision on the night side, it will come out of night side with a slow tumble that won't be corrected. The passive radar signature of the tumble will help identify the destroyed flat-sat to other flat-sats in the array, allowing another sacrificial flat-sat to perform a "rendezvous and de-orbit". If the destroyed flat-sat is in shards, the shards will tumble. The tumbling shards ( or a continuously tumbling flat-sat ) will eventually fall out of the normal orbit, no longer get J_2 correction, and the flat-sat orbit will "eccentrify", decay, and reenter. This is the fail-safe way the arrays will reenter, if all active control ceases.

Maneuvering thrust and satellite power

Neglecting tides, the synodic angular velocity of the m288 orbit is \Large\omega = 4.3633e-4 rad/sec = 0.025°/s. The angular acceleration of a flat-sat is 13.056e-6 rad/sec2 = 7.481e-4°/s2 with a sun angle of 0°, and 3.740e-4°/s2 at a sun angle of 60°. Because of tidal forces, a flat-sat entering eclipse will start to turn towards sideways alignment with the center of the earth; it will come out of eclipse at a different velocity and angle than it went in with.

If the flat-sat is rotating at \omega and either tangential or perpendicular to the gravity vector, it will not turn while it passes into eclipse. Otherwise,


Full power night sky coverage, maximum night light pollution


Partial night sky coverage, no night light pollution


Complete night sky coverage, some night light pollution

This maneuver will put some scattered light into the night sky, but not much compared to perpendicular solar illumination all the way into shadow.

The orientation of the flat-sat over a 240 minute synodic m288 orbit at the equinox is as follows, relative to the sun:

time min

orbit degrees

rotation rate

sun angle

0 to 60

0° to 90°

0 ~ \Large\omega

60 to 100

90° to 150°

1 ~ \Large\omega

0° to 60°

100 to 140

150° to 210°

4 ~ \Large\omega

60° to 300°

140 to 180

210° to 270°

1 ~ \Large\omega

300° to 0°

180 to 240

270° to 0°

0 ~ \Large\omega

The angular velocity change at 0° takes 250/7.481 = 33.4 seconds, and during that time the server satellite turns 0.42° with negligible effect on thrust or power. The angular velocity change at 60° takes 750/3.74 = 200.5 seconds, and during that time the server satellite turns 12.5°, perhaps from 53.7° to 66.3°, reducing power and thrust from 59% to 40%, a significant change. The actual thrust change versus time will be more complicated (especially with tidal forces), but however it is done, the acceleration must be accomplished before the flat-sat enters eclipse.