Design Of Several Typical Non-Keplerian Orbits For Satellite With Continuous Low-thrust

Frozen orbit, sun-synchronous orbit and geostationary orbit are3typesof most widely used artificial earth satellite orbits as a result of their greatadvantage in remote sensing, communication, navigation, etc; however theirstringent requirements on orbit elements greatly limit the variety of orbitselections. After applying continuous low-thrust, the selection conditions oforbit elements can be appropriate relaxed, thus the artificial frozen orbit,displaced sun-synchronous orbit and displaced geostationary orbit are formed.Artificial frozen orbits are formed by applying radial or transversecontinuous low-thrust while maintaining the argument of perigee unchanged.Radial constant thrust， radial constant amplitude thrust with directionschanged every half orbit period, transverse constant amplitude thrust withdirections changed every half orbit period, radial and constant amplitudethrust with directions changed every half orbit period are4kinds of controlmethod that can be used to maintain an artificial orbit. In the design of thecontrol law, we should give special consideration to the eccentricity; fororbits with big eccentricity, only perturbation term J2needs to be considered,while perturbation terms J2~J4or even much higher degrees of non-sphericalperturbations should be considered for small eccentricity orbits.Displaced sun-synchronous orbits are formed by applying normal andtransverse (or radial) continuous low-thrust to raise or lower the orbit altitudewhile maintaining the orbit inclination and ground trace. The switching timeof the transverse thrust are concerned with argument of perigee. To simplifythe control algorithm, the argument of perigee is assumed invariant, thus the4control algorithms mentioned above can be used. In fact a displacedsun-synchronous frozen regressive orbit is obtained.Non-Spherical perturbation, lunar-solar perturbation will cause east-westdrift for the satellite, however the drifting bound of the geostationary satellite can be restricted by applying tangential low-thrust at proper times. Adisplaced geostationary orbit is formed by applying radial low-thrust andtangential impulses, positive displacement corresponds to negative continuouslow-thrust while negative displacement means positive thrust, moreover themagnitude of the thrust is proportional to the amount of displacement. Thedisplaced geostationary satellite traces a near-circular orbit with radiallow-thrust all the way; this phenomenon is identical to changing thegravitational constant μ to μnwhile getting rid of the low-thrust at the sametime. Since the displaced altitude Δr is much smaller than the orbit radius, theimpulse maneuver control method used in the east-west stationkeeping ofgeostationary orbit can also be transformed to that of the displacedgeostationary orbit with only a tiny change in the amplitude and working timeof the impulse.