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The spacecraft Deep Space 1 was launched October 24, 1998 on top of a Delta II rocket. As part of NASA's New Millennium program, the primary goal was the testing of twelve advanced technologies that have the potential to lower the cost and risk of future missions. Among the technologies tested were: Deep Space 1 succeeded in its tasks and also achieved its secondary goals: flybys of the asteroid Braille and of Comet Borrelly, returning valuable science data and stunning pictures. Deep Space 1 was retired on December 18, 2001.
Technologies The NSTAR ion thruster achieves a specific impulse of over one to three thousand seconds. This is an order of magnitude higher than traditional space propulsion methods, resulting in a mass savings of approximately half. This leads to much cheaper launch vehicles. Although the engine produces just 92 millinewtons of thrust at maximum power (about a third of an ounce-force), the craft achieved high speeds because ion engines thrust continuously for long periods. The engine fired for 678 total days, a record for such engines. The next spacecraft to use NSTAR engines is the Dawn Mission, with three redundant units. Powering the engine are the SCARLET (Solar Concentrator Array of Refractive Linear Element Technologies) solar arrays. These use linear Fresnel lenses made of silicone to concentrate sunlight onto solar cells. Combined with more efficient, dual-junction cells, the SCARLET arrays generate 2.5 kilowatts with less size and weight than conventional arrays. The Autonav system takes images of known bright asteroids. The asteroids in the inner Solar System move in relation to other bodies at a noticeable, predictable speed. Thus a spacecraft can determine its relative position by tracking such asteroids across the star background, which appears fixed over such timescales. Two or more asteroids let the spacecraft triangulate its position; two or more positions in time let the spacecraft determine its trajectory. Existing spacecraft are tracked by their interactions with the transmitters of the Deep Space Network (DSN), in effect an inverse GPS. However, DSN tracking requires many skilled operators, and the DSN is overburdened by its use as a communications network. The use of Autonav reduces mission cost and DSN demands. The Autonav system can also be used in reverse, tracking the position of bodies relative to the spacecraft. This is used to acquire targets for the scientific instruments. The spacecraft is programmed with the target's coarse location. After initial acquisition, Autonav keeps the subject in frame, even commandeering the spacecraft's attitude control. The next spacecraft to use Autonav was Deep Impact. Remote Agent was the first artificial intelligence control system to control a spacecraft without human supervision. Remote Agent successfully demonstrated the ability to plan onboard activities and correctly diagnose and respond to simulated faults in spacecraft components. Autonomous control will enable future spacecraft to operate at greater distances from Earth, and to carry out more sophisticated science-gathering activities in deep space. Components of the Remote Agent software have been used to support other NASA Missions. Major components of Remote Agent were a robust planner (EUROPA), and a model-based diagnostic system (Livingstone). EUROPA was used as a ground-based planner for the Mars Exploration Rovers, and EUROPA II is being used to support the upcoming Phoenix and Mars Science Laboratory. Livingstone2 was flown onboard Earth Observing 1, and an F-18 at NASA Dryden. Another method for reducing DSN burdens is the Beacon Monitor experiment. During the long cruise periods of the mission, spacecraft operations are essentially suspended. Instead of data, the craft emits a carrier signal on a predetermined frequency. Without data decoding, the carrier can be detected by much simpler ground antennas and receivers. If the spacecraft detects an anomaly, it changes the carrier between four tones, based on urgency. Ground receivers then signal operators to divert DSN resources. This prevents skilled operators and expensive hardware from babysitting an unburdened mission operating nominally. The SDST (Small Deep-Space Transponder), as the name implies, is a compact radio communications system. Aside from using miniaturized components, the SDST is capable of communicating over the Ka band. Because this band is higher in frequency than bands currently in use by deep-space missions, the same amount of data can be sent by smaller equipment in space and on the ground. Conversely, existing DSN antennas can split time among more missions. At the time of launch, the DSN had a small number of Ka receivers installed on an experimental basis; Ka operations and missions are increasing. Once at a target, DS1 senses the particle environment with the PEPE (Plasma Experiment for Planetary Exploration) instrument. It maps the objects with the MICAS (Miniature Integrated Camera And Spectrometer) imaging channel, and discerns chemical composition with infrared and ultraviolet channels. All channels share a 10 cm telescope, which uses a silicon carbide mirror. Other, secondary technologies are built in, at the component level, and in the spacecraft built by Spectrum Astro. Achievements
Current status NASA decided not to pursue a further extended mission after the Borrelly encounter, and on December 18, 2001, Deep Space 1 was switched off and left to orbit the Sun. Statistics | ||||||||||
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