International audienceThe MAVEN spacecraft launched in November 2013, arrived at Mars in September 2014, and completed commissioning and began its one-Earth-year primary science mission in November 2014. The orbiter’s science objectives are to explore the interactions of the Sun and the solar wind with the Mars magnetosphere and upper atmosphere, to determine the structure of the upper atmosphere and ionosphere and the processes controlling it, to determine the escape rates from the upper atmosphere to space at the present epoch, and to measure properties that allow us to extrapolate these escape rates into the past to determine the total loss of atmospheric gas to space through time. These results will allow us to determine the importance of loss to space in changing the Mars climate and atmosphere through time, thereby providing important boundary conditions on the history of the habitability of Mars. The MAVEN spacecraft contains eight science instruments (with nine sensors) that measure the energy and particle input from the Sun into the Mars upper atmosphere, the response of the upper atmosphere to that input, and the resulting escape of gas to space. In addition, it contains an Electra relay that will allow it to relay commands and data between spacecraft on the surface and Earth

Launched June 18, 2009, with its primary mission scheduled to end September 2010, NASA's Lunar Reconnaissance Orbiter will be the first observatory ever to spend an entire year orbiting and observing the Moon at a low altitude of just 50 km. The spacecraft carries a wide variety of scientific instruments and will provide an extraordinary opportunity to study the lunar landscape at resolutions and over time scales never achieved before. This paper is intended as a companion to the series of papers released simultaneously in this journal detailing LRO's instruments and their planned measurements. The paper describes the design and key performance drivers of the LRO spacecraft and overall mission design. It presents a comprehensive description of the operation of the various systems that comprise the spacecraft and illustrates how these systems enable achievement of the mission requirements.

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The Disturbance Reduction System (DRS) is a space technology demonstration within NASA's New Millennium Program. DRS is designed to validate system-level technology required for future gravity missions, including the planned LISA gravitational-wave observatory, and for formation-flying interferometers. DRS is based on a freelyfloating test mass contained within a spacecraft that shields the test mass from external forces. The spacecraft position will be continuously adjusted to stay centered about the test mass, essentially flying in formation with the test mass. Colloidal microthrusters will be used to control the spacecraft position within a few nanometers, over time scales of tens to thousands of seconds. For testing the level of acceleration noise on the test mass, a second test mass will be used as a reference. The second test mass will also be used as a reference for spacecraft attitude. The spacecraft attitude will be controlled to an accuracy of a few milliarcseconds using the colloidal microthrusters. DRS will consist of an instrument package and a set of microthrusters, which will be attached to the European Space Agency's SMART-2 spacecraft with launch scheduled for August 2006.Keywords: formation flying, colloidal microthrusters, disturbance reduction DISTURBANCE REDUCTION SYSTEM OVERVIEWThe Disturbance Reduction System (DRS) is designed to validate system-level technology required for two types of future missions: measurements of planetary gravity and of cosmic gravitational waves, and precision formation-flying interferometers. The validated technology will feed directly into the LISA gravitational-wave observatory, the MAXIM X-ray interferometer mission, and several other missions within the NASA roadmap. The DRS is based on the concept of a freely floating test mass contained within a spacecraft that shields the test mass from external forces. The test mass will ideally follow a trajectory determined only by the local gravitational field. The spacecraft position must be continuously adjusted to stay centered about the test mass, essentially flying in formation with the test mass. The DRS performance is characterized by the extent to which unwanted accelerations appear on the test mass and the accuracy with which the spacecraft is centered on the test mass. The project goals are to demonstrate acceleration levels below 3×10 -14 m/s 2 /√Hz and position control to 10 nm/√Hz over a frequency range of 1 mHz to 10 mHz. In order to measure the level of accelerations appearing on the test mass, its trajectory must be compared with a reference trajectory. For DRS, the reference is provided by a second identical test mass located within the same instrument assembly. Being located in the same spacecraft, the second test mass must be controlled at frequencies below the measurement bandwidth to keeps its position relative to the primary test mass, while being free of control forces within the measurement bandwidth to provide a reference for acceleration measurements. The position of the second test ma...

This paper describes the IRIS-GUS upper stage system that will be used to launch NASA's Triana Observatory from the Space Shuttle. Triana is a pathfinder earth science mission being executed on a rapid schedule and small budget, therefore the mission's upper stage solution had to be a system that could be fielded quickly at relatively low cost and risk. The building of the IRIS-GUS system was necessary because NASA lost the capability to launch moderately sized upper stage missions from the Space Shuttle when the PAM-D system was retired. The IRIS-GUS system restores this capability.The resulting system is a hybrid which