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The Deep Space Atomic Clock (DSAC) is a miniaturized, ultra-precise mercury-ion atomic clock for precise radio navigation in deep-space. It is orders of magnitude more stable than existing navigation clocks, and has been refined to limit drift of no more than 1 nanosecond in 10 days.〔 〕 It is expected that a DSAC would incur no more than 1 microsecond of error in 10 years of operations. It is expected to improve the precision of deep-space navigation, and enable more efficient use of tracking networks. The project is managed by NASA's Jet Propulsion Laboratory. ==Overview== Current ground-based atomic clocks are fundamental to deep space navigation; however, they are too large to be flown in space. This results in tracking data being collected and processed here on Earth (a two-way link) for most deep-space navigation applications.〔 The Deep Space Atomic Clock (DSAC) is a miniaturized and stable mercury ion atomic clock that is as stable as a ground clock. 〔 The technology could enable autonomous radio navigation for spacecraft's time-critical events such as orbit insertion or landing, promising new savings on mission operations costs.〔 It is expected to improve the precision of deep-space navigation, enable more efficient use of tracking networks, and yield a significant reduction in ground support operations.〔 Its applications in deep space include:〔 *Simultaneously track two spacecraft on a downlink with the Deep Space Network (DSN) *Improve tracking data precision by an order of magnitude using the DSN's Ka-band downlink tracking capability. *Mitigate Ka-band's weather sensitivity (as compared to two-way X-band) by being able to switch from a weather-impacted receiving antenna to one in a different location with no tracking outages. *Track longer by using a ground antenna's entire spacecraft viewing period. At Jupiter, this yields a 10 to 15 percent increase in tracking; at Saturn, it grows to 15 to 25%, with the percentage increasing the farther a spacecraft travels. *Make new discoveries as a Ka-band—capable radio science instrument with a 10 times improvement in data precision for both gravity and occultation science and deliver more data because of one-way tracking's operational flexibility. *Explore deep space as a key element of a real-time autonomous navigation system that tracks one-way radio signals on the uplink and, coupled with optical navigation, provides for robust absolute and relative navigation. *Fundamental to human explorers requiring real-time navigation data. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Deep Space Atomic Clock」の詳細全文を読む スポンサード リンク
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