Perigee Attitude Maneuvers of Geostationary Satellites During Electric Orbit Raising

Abstract

When full-electric orbit-raising trajectories begin in a classic geostationary transfer orbit with low initial perigee altitude, the need for deployed solar arrays to power the propulsion system significantly increases the aerodynamic and gravity gradient torques. In fact, the torque magnitudes in the first few perigee passages may become a challenging requirement for the attitude control system. Apart from oversizing actuators, other solutions may include the need for a backup thruster system or raising the perigee altitude, implying mass penalties and cost. This paper presents the design of an optimal attitude maneuver at the perigee that can be undertaken using nominal reaction wheels. Attitude paths avoiding saturation of the wheels while dumping accumulated momentum are obtained performing a physically consistent modeling of aerodynamic torques and using pseudospectral methods to solve the trajectory optimization problem. The optimization of solar array positions is also explored to further constrain the problem or improve the maneuver performance. Resulting mass and cost savings can be significant, which could be used for additional payload or to significantly extend the operational life of the satellite.

System Modelling of Very Low Earth Orbit Satellites for Earth Observation

“…Proposals for orbit control include constellation deployment [25], formation keeping [26,27], rendezvous [28,29], inclination correction for sun-synchronous orbits [30], and atmospheric re-entry interface targeting [31,32]. Aerodynamics attitude control has also been proposed for pointing and momentum management manoeuvres that assist and reduce the requirements on traditional attitude actuators [33][34][35][36], with the potential for reducing system mass. Aerodynamic trim manoeuvres can also be considered to directly reject external disturbances, for example as a result of variations in the oncoming flow direction, solar radiation pressure, and residual magnetic dipole interactions.…”

The Benefits of Very Low Earth Orbit for Earth Observation Missions

“…Use of drag augmentation has been proposed for targeting of atmospheric re-entry location [67][68][69] and also collision avoidance [70], whilst adjustment of orbital inclination using out-of-plane forces [27] have also been studied. Passive aerodynamic stabilisation or aerostability (the pointing of a spacecraft in the direction of the oncoming flow) has been demonstrated in orbit by several missions [6,71,72], whilst further aerodynamic attitude control concepts including use of external surfaces to perform detumbling [73], internal momentum management [74], and pointing manoeuvres [75][76][77][78] have also been considered. Centre-of-mass shifting has also been proposed as a method to augment aerodynamic stabilisation [79,80].…”

A review of gas-surface interaction models for orbital aerodynamics applications

“…Increased knowledge of the interaction mechanisms occurring in the gas-solid phase system is crucial not only for scientific achievement, but also for the possibility of improving aerodynamic performance of spacecraft operating in VLEO [10,11]. This would reflect in increased confidence in assessing the advantages and the drawbacks of employing aerodynamic torques for orbit [12][13][14][15][16][17][18] and attitude control purposes [19][20][21][22][23][24][25][26][27][28]. Overestimating or underestimating the aerodynamic torques induced by the actuation of aerodynamic control surfaces has an impact on the altitude range for which aerodynamic manoeuvring is expected to be feasible.…”