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At least 19 records

Adaptive Orbit Determination for Interplanetary Spacecraft

The interplanetary orbit problem has been traditionally solved using least-squares techniques. Due to operational limitations of this method, a Kalman filter approach has been proposed for future missions which includes all spacecraft and measurement modeling states in the filter.

adaptive

The long life of Pioneer interplanetary spacecraft

The Pioneer 6 to 9 interplanetary spacecraft were launched in 1965, 66, 67, and 68. All continue to operate in various orbits about the sun, gathering data on the solar system environment. Pioneer 10 was launched in 1972, and is now more than halfway to Jupiter, with all systems performing their required functions. The paper reviews these programs and the few anomalies which have been observed. The long-term mission success is discussed in terms of possible causative factors: simplicity in design and operation, redundancy in function and in equipment, comprehensive development and acceptance tests, the mildness of the space environment, and luck.

Dixon, W. J.

Computer Aided Design of Ka-Band Waveguide Power Combining Architectures for Interplanetary Spacecraft

Communication systems for future NASA interplanetary spacecraft require transmitter power ranging from several hundred watts to kilowatts. Several hybrid junctions are considered as elements within a corporate combining architecture for high power Ka-band space traveling-wave tube amplifiers (TWTAs). This report presents the simulated transmission characteristics of several hybrid junctions designed for a low loss, high power waveguide based power combiner.

Vaden, Karl R.

Contingency Operations during Failure of Inertial Attitude Acquisition Due to Star Tracker Blinding for Three-Axes-Stabilized Interplanetary Spacecraft

The three interplanetary ESA missions Mars-Express, Rosetta and Venus-Express (launched 2003, 2004 and 2005 resp.) are three-axes stabilized spacecraft (s/c) that estimate their inertial attitude (i.e. the attitude of the s/c w.r.t. the inertial frame) using measurements from a redundant set of star trackers (STR). Each s/c is equipped with four reaction wheels, a reaction control system based on thrusters and a redundant set of ring laser gyroscopes (gyros). The STR h/w layout of the three s/c is identical whereas there is a difference in the star pattern recognition algorithm of Rosetta which uses five neighbouring stars around a central star instead of star triads. The Rosetta algorithm has been implemented to cope with the presence of false stars which are expected to be seen during operations around the comet. The attitude acquisition capability from lost in space is different also in terms of AOCMS: The survival mode of Rosetta which is entered upon STR failure is presented. The AOCMS of Mars- and Venus-Express manages temporary STR outages during sky occultation by the planet not even by using redundancy. Though, a blinding of both STR during cruise lasting for the order of days confronts the ground operators with the limits of the AOCMS design. The operations and analyses that have been planned and partially been performed to compensate for the outage of the STR are demonstrated for Mars-Express. The caution measures taken before Venus orbit insertion of Venus-Express are detailed.

Keil, Joachim