A method of estimating the Martian neutral atmospheric density at 130 km, and comparison of its results with Mars Global Surveyor and Mars Odyssey aerobraking observations based on the Mars Climate Database outputs

Profiles of the Martian dayside ionosphere can be used to derive the neutral atmospheric densities at 130 km,which can also be obtained from the Mars Climate Database(MCD)and spacecraft aerobraking observations.In this research,we explain the method used to calculate neutral densities at 130 km via ionosphere observations and three long-period 130-km neutral density data sets at northern high latitudes(latitudes>60°)acquired through ionospheric data measured by the Mars Global Surveyor(MGS)Radio Occultation Experiment.The calculated 130-km neutral density data,along with 130-km density data from the aerobraking observations of the MGS and Mars Odyssey(ODY)in the northern high latitudes,were compared with MCD outputs at the same latitude,longitude,altitude,solar latitude,and local time.The 130-km density data derived from both the ionospheric profiles and aerobraking observations were found to show seasonal variations similar to those in the MCD data.With a negative shift of about 2×10^10 cm^−3,the corrected 130-km neutral densities derived from MCD v4.3 were consistent with those obtained from the two different observations.This result means that(1)the method used to derive the 130-km neutral densities with ionospheric profiles was effective,(2)the MCD v4.3 data sets generally overestimated the 130-km neutral densities at high latitudes,and(3)the neutral density observations from the MGS Radio Science Experiment could be used to calibrate a new atmospheric model of Mars.

Spacecraft aerodynamics and trajectory simulation during aerobraking

This paper uses a direct simulation Monte Carlo （DSMC） approach to simulate rarefied aerodynamic characteristics during the aerobraking process of the NASA Mars Global Surveyor （MGS） spacecraft. The research focuses on the flowfield and aerodynamic characteristics distribution under various free stream densities. The vari- ation regularity of aerodynamic coefficients is analyzed. The paper also develops an aerodynamics-aeroheating-trajectory integrative simulation model to preliminarily calculate the aerobraking orbit transfer by combining the DSMC technique and the classical kinematics theory. The results show that the effect of the planetary atmospheric density, the spacecraft yaw, and the pitch attitudes on the spacecraft aerodynamics is significant. The numerical results are in good agreement with the existing results reported in the literature. The aerodynamics-aeroheating-trajectory integrative simulation model can simulate the orbit transfer in the complete aerobraking mission. The current results of the spacecraft trajectory show that the aerobraking maneuvers have good performance of attitude control.

Mars orbit insertion via ballistic capture and aerobraking

A novel Mars orbit insertion strategy that combines ballistic capture and aerobraking is presented.Mars ballistic capture orbits that neglect the aerodynamics are first generated,and are distilled from properly computed stable and unstable sets by using a pre-established method.A small periapsis maneuver is implemented at the first close encounter to better submit a post-capture orbit to the aerobraking process.An adhoc patching point marks the transition from ballistic capture to aerobraking,from which an exponential model simulating the Martian atmosphere and a box-wing satellite configuration are considered.A series of apoapsis trim maneuvers are then computed by targeting a prescribed pericenter dynamic pressure.The aerobraking duration is then estimated using a simplified two-body model.Yaw angle tuning cancels the inclination deflections owing to out-of-plane perturbation from the Sun.A philosophy combining in-plane and out-of-plane dynamics is proposed to simultaneously achieve the required semi-major axis and inclination.Numerical simulations indicate that the developed method is more efficient in terms of the fuel consumption,insertion safety,and flexibility when compared with other state-of-the-art insertion strategies.

Transfer Trajectory Design for Mars Exploration

With regard to the human exploration of Mars, low energy transfer trajectory is designed for Mars exploration based on the combination of invariant manifolds, differential correction and aerobraking methods. The whole transfer trajectory is composed of four stages: 1) from the Earth parking orbit to the Lyapunov orbit around Lagrange point L2 in the Sun-Earth system;2) from the Lyapunov orbit around L2 to the Lyapunov orbit around L1 in the Sun-Mars system;3) from the Lyapunov orbit around L1 in the Sun-Mars system to the large elliptical orbit around Mars;and 4) from the large elliptical orbit around Mars to the near-Mars parking orbit. In the first three stages, the circular restricted three-body problem is considered, and the trajectory is designed by using invariant manifolds and the differential correction method. The simulation results show that the transfer trajectory designed by means of the invariant manifolds of the Lyapunov orbit costs lower energy and shorter time of flight than that designed by means of the invariant manifold of the Halo orbit. In the fourth stage, the two-body problem is considered, and the aerobraking method is applied. A comparative performance analysis of static and rotating atmospheric models is carried out by using the details of duration, aerodynamic loading of the Mars vehicle, and other orbital parameters. It is shown that, on the low periareon where the influence of the atmospheric density increases, the changes of orbit parameters between rotating and static atmospheric environments are in large difference, such as orbital semimajor axis, orbital eccentricity, and so on. The influence of Martian rotating atmospheric environment should be considered.