Engineering topics
Doody, Dave
Publications and source records attributed to Doody, Dave.
Magellan mapping update - A matter of gravity
In order to obtain gravity data for Venus, the Magellan spacecraft will furnish an unmodulated downlink carrier signal which is coherent with a highly stable uplink from the NASA-JPL Deep Space Network. After the removal of gross Doppler shifts induced by planetary motions and Magellan's primary orbital motion, residual Doppler shifts will indicate miniscule gravity variations in the mass distributions at, and below, the Venusian surface. These gravity measurements are valuable for understanding the nature and origin of features identifiable with imaging data.
Magellan in transition
Aerobraking Magellan would provide the possibility of obtaining gravity field data for Venus all the way to the poles. Attempts to accomplish aerobraking, which began on May 25, 1993 in the Magellan Transition Experiment, are discussed.
Mapping Magellan's prospects
An overview is presented of the mapping cycles of Venus performed to date by NASA's Magellan spacecraft. Attention is given to the operating aspects of controlling the different orbits about the planet to obtain the desired mapping data.
Magellan flight operations update
The flight operations of the Magellan spacecraft are discussed with specific attention given to spacecraft conditions, the execution of a limbtracking maneuver, and results of mapping Venus. A list of spacecraft component failures is given, and the mapping effort is shown to yield information on the subsurface Venusian magma, the south pole, and the impact craters. The Magellan is capable of further mapping cycles, radio-science investigations of the solar corona, and aiding in the development of a high-resolution 'gravity model' to characterize the mass distribution of Venus.
NASA's Magellan mission to Venus
At the end of its planned 243-day mission, by which time Venus will have completed a full rotation beneath Magellan's orbit, over 70 percent of the Venus surface shall have been mapped to high resolution; the volume of data thus obtained will exceed that from all previous U.S. planetary missions combined. An innovative SAR instrument will map Venus to an order-of-magnitude higher resolution than that possible with previous probes. Parameters controlling the spacing of SAR S-band pulses' transmission and reception, their number and frequency of repetition, etc., are changed as many as 300 times per mapping pass in order to accommodate the spacecraft's constantly varying orbital geometry.
Magellan space flight operations
This paper describes the Magellan spacecraft designed to collect information from the surface of Venus while orbiting this planet. Special attention is given to the attitude and articulation control of the spacecraft; the command, data, and data storage; the thermal control; and instrumentation. The operations at Venus, which will include Venus orbit insertion and in-orbit checkout and to both routine and nonroutine (at a period when Venus will be in superior conjunction, and the solar plasma will drive Magellan's telecommunications signal-to-noise ratio to a very high value) mapping of the surface, are discussed. Also discussed are operations on earth, carried out by the new Space Flight Operations Control Center.