| 词条 | Deep Space Atomic Clock |
| 释义 |
| Name = Deep Space Atomic Clock (DSAC) | Image = Deep Space Atomic Clock-DSAC.jpg | Caption = The miniaturized Deep Space Atomic Clock was designed for precise and real-time radio navigation in deep space | Operator = Jet Propulsion Laboratory (JPL) | Manufacturer = JPL | Type = Atomic clock | Function = Navigation aid in deep space, gravity and occultation science | Mission_Duration = Planned: 1 year[1] | Began = | Ceased = | Webpage = {{URL|https://www.nasa.gov/mission_pages/tdm/clock/index.html}} | Mass = {{cvt|17.5|kg|abbr=on}} | Dimensions = 29 × 26 × 23 cm[2] (11 × 10 × 9 in) | Number = 1 | Power_consumption = 44 W | Spacecraft = Orbital Test Bed (OTB) | SC_Operator = | Launch = Planned: March 2019[3] | Rocket = Falcon Heavy | Launch_Site = LC-39A, Kennedy Space Center | COSPAR = | Orbit = Low Earth orbit | Decay = }} 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.[2] It is expected that a DSAC would incur no more than 1 microsecond of error in 10 years of operations.[3] 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 and it will be deployed as part of the U.S. Air Force's Space Test Program 2 (STP-2) mission aboard a SpaceX Falcon Heavy rocket in March 2019.[4] OverviewCurrent 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.[3] The Deep Space Atomic Clock (DSAC) is a miniaturized and stable mercury ion atomic clock that is as stable as a ground clock. [3] 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.[2] 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.[2][5] Its applications in deep space include:[3]
Principle and developmentOver 20 years, engineers at NASA's Jet Propulsion Laboratory have been steadily improving and miniaturizing the mercury-ion trap atomic clock.[6] The DSAC technology uses the property of mercury ions' hyperfine transition frequency at 40.50 GHz to effectively "steer" the frequency output of a quartz oscillator to a near-constant value. DSAC does this by confining the mercury ions with electric fields in a trap and protecting them by applying magnetic fields and shielding.[3][7] Its development will include a test flight in low-Earth orbit,[8][9] while using GPS signals to demonstrate precision orbit determination and confirm its performance in radio navigation. DeploymentThe flight unit will be hosted —along with other four payloads— on a spacecraft called Orbital Test Bed (OTB) satellite, provided by General Atomics Electromagnetic Systems, using the Swift satellite bus.[10][11][12] It will be deployed as a secondary spacecraft during the U.S. Air Force's Space Test Program 2 (STP-2) mission aboard a SpaceX Falcon Heavy rocket,[13] probably in March 2019.[14] References1. ^[https://www.nasa.gov/mission_pages/tdm/clock/index.html Deep Space Atomic Clock (DSAC)]. NASA's Space Technology Mission Directorate. Accessed on 10 December 2018. 2. ^1 2 {{cite web |url=http://www.nasa.gov/mission_pages/tdm/clock/clock_overview.html |title=Deep Space Atomic Clock (DSAC) |last=Boen |first=Brooke |work=NASA |date=January 16, 2015 |accessdate=2015-10-27 }} 3. ^1 2 3 4 {{cite web |url=http://www.nasa.gov/sites/default/files/files/DSAC_Fact_Sheet.pdf |format=PDF |title=Deep Space Atomic Clock |work=NASA |date=2014 |accessdate=2015-10-27 }} 4. ^1 {{cite web|url=http://www.sworld.com.au/steven/space/usmil-man.txt|title=United States Military Manifest|last=Pietrobon|first=Steven|date=8 June 2018|website=|archive-url=|archive-date=|dead-url=|access-date=2 November 2018}} 5. ^{{cite news |url=http://www.gizmag.com/deep-space-atomic-clock/37231/ |title=NASA to test atomic clock to keep space missions on time |work=NASA |publisher=Gizmag |date=30 April 2015 |accessdate=2015-10-28 }} 6. ^{{cite web |url=http://www.nasa.gov/mission_pages/tdm/clock/clock_overview.html#.VGK5sPnF81J |title=Technology Demonstration Missions: Deep Space Atomic Clock (DSAC) |work=Jet Propulsion Laboratory |publisher=NASA |date=16 January 2015 |accessdate=2015-10-28 }} 7. ^1 {{cite news |url=https://directory.eoportal.org/web/eoportal/satellite-missions/content/-/article/dsac-deep-space-atomic-clock- |title= DSAC (Deep Space Atomic Clock) |work=NASA |publisher=Earth Observation Resources |date=2014 |accessdate=2015-10-28 }} 8. ^{{cite tweet |user=StephenClark1 |author=Stephen Clark |number=704690601074229249 |date=2016-03-01 |title=Payload officials with satellites aboard STP-2 mission (second Falcon Heavy) say launch has slipped from Oct. 2016 to March 2017. }} 9. ^{{cite news |last=David |first=Leonard |url=http://www.space.com/32567-nasa-green-propellant-mission-gpim.html |title=Spacecraft Powered by 'Green' Propellant to Launch in 2017 |work=Space |date=April 13, 2016 |accessdate=2016-04-15 }} 10. ^[https://www.nasa.gov/mission_pages/tdm/clock/overview.html Deep Space Atomic Clock (DSAC) Overview]. NASA. Accessed on 10 December 2018. 11. ^General Atomics Completes Ready-For-Launch Testing of Orbital Test Bed Satellite. General Atomics Electromagnetic Systems, press release on 3 April 2018. 12. ^OTB: The Mission. Surrey Satellite Technology. Accessed on 10 December 2018. 13. ^{{cite news |url=http://www.jpl.nasa.gov/news/news.php?feature=4567 |title=Deep Space Atomic Clock |work=NASA's Jet Propulsion Laboratory |publisher=NASA |date=27 April 2015 |accessdate=2015-10-28 }} 14. ^{{Cite web| url=http://www.sworld.com.au/steven/space/usmil-man.txt|title=United States Military Manifest| last=Pietrobon| first=Steven| date=October 19, 2017|website=|archive-url=|archive-date=|dead-url=|access-date=October 23, 2018}} External links
6 : Atomic clocks|Electronic test equipment|Astronautics|Gravimetry|2019 in spaceflight|Future SpaceX commercial payloads |
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