Ballute aerocapture trajectories at Titan
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Engineering topics
Publications and source records attributed to Lyons, D. T..
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This paper describes the analysis and design evolution of the Mars Reconnaissance Orbiter trajectory from launch to end-of-mission.
This paper addresses the constraints, analysis and design evolution of the Mars Reconnaissance Orbiter Primary Science Orbit.
Talks abuot the primary purpose of the MRO mission to be launched in August of 2005 is to obtain very high resolution images of the surface of Mars.
This paper describes the aerobraking baseline trajectory that formed the basis of the reference mission presented at the Mars Reconnaissance Orbiter Preliminary Design Review.
We investigate the automation of a Mars aerobraking vehicle that uses reaction wheels for attitude and angular momentum control during atmospheric flythrough.
This paper describes the analysis and design evolution of the Mars Reconnaissance Orbiter trajectory from launch to end-of-mission. The mission uses a combination of propulsive maneuvers and aerobraking techniques to deliver the orbiter to a low-altitude frozen orbit at Mars. The launch/arrival space for the 2005 Earth-Mars opportunity will be described as well as the particular launch strategy chosen for this mission. Details of the aerobraking profile will be provided. Finally, the Primary Science Orbit will be examined, and the trade-offs between science objectives and orbiter capability will be presented.
The orbit of the Magellan spacecraft will be circularized by aerobraking by the end of August, 1993. The nearly circular orbit is necessary to obtain meaningful gravity science at high latitudes.
The Magellan spacecraft has been systematically mapping the surface of Venus since September 15, 1990, using side-looking synthetic aperture radar imaging and nadir-pointed altimetry. Venus rotates slowly under the nearly polar mapping orbit, completing a full revolution in 243 days, one 'mapping cycle'. The altimeter collects a 10 km swath of altitude measurements each orbit. The groundtrack advances 21 km each orbit due to the rotation of Venus, leaving an 11 km gap of unmeasured terrain. To obtain global surface coverage by the altimeter, these gaps are eliminated by interleaving the swaths collected during the second mapping cycle with those from the first mapping cycle. Interleaving was put into effect by a propulsive maneuver, executed at the end of the first mapping cycle, on May 17, 1991. The orbit node was changed by +0.106 degrees, so that the cycle 2 groundtracks would bisect adjacent cycle 1 groundtracks. This paper describes the maneuver design and execution results, including the problem and solution of the groundtrack prediction to the end of the first mapping cycle.
Polynomial functions of time are used to specify the components of the quaternion which represents the nominal attitude of the Venus Radar mapper spacecraft during mapping. The following constraints must be satisfied in order to obtain acceptable synthetic array radar data: the nominal attitude function must have a large dynamic range, the sensor orientation must be known very accurately, the attitude reference function must use as little memory as possible, and the spacecraft must operate autonomously. Fitting polynomials to the components of the desired quaternion function is a straightforward method for providing a very dynamic nominal attitude using a minimum amount of on-board computer resources. Although the attitude from the polynomials may not be exactly the one requested by the radar designers, the polynomial coefficients are known, so they do not contribute to the attitude uncertainty. Frequent coefficient updates are not required, so the spacecraft can operate autonomously.