File:NASA Adds Leap Second to Master Clock (31834258342).jpg
原始文件 (2,001 × 1,619像素,文件大小:2.72 MB,MIME类型:image/jpeg)
摘要
描述NASA Adds Leap Second to Master Clock (31834258342).jpg |
On Dec. 31, 2016, official clocks around the world will add a leap second just before midnight Coordinated Universal Time — which corresponds to 6:59:59 p.m. EST. NASA missions will also have to make the switch, including the Solar Dynamics Observatory, or SDO, which watches the sun 24/7. Clocks do this to keep in sync with Earth's rotation, which gradually slows down over time. When the dinosaurs roamed Earth, for example, our globe took only 23 hours to make a complete rotation. In space, millisecond accuracy is crucial to understanding how satellites orbit. "SDO moves about 1.9 miles every second," said Dean Pesnell, the project scientist for SDO at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "So does every other object in orbit near SDO. We all have to use the same time to make sure our collision avoidance programs are accurate. So we all add a leap second to the end of 2016, delaying 2017 by one second." The leap second is also key to making sure that SDO is in sync with the Coordinated Universal Time, or UTC, used to label each of its images. SDO has a clock that counts the number of seconds since the beginning of the mission. To convert that count to UTC requires knowing just how many leap seconds have been added to Earth-bound clocks since the mission started. When the spacecraft wants to provide a time in UTC, it calls a software module that takes into consideration both the mission's second count and the number of leap seconds — and then returns a time in UTC. |
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来源 | NASA Adds Leap Second to Master Clock |
作者 | NASA Goddard Space Flight Center from Greenbelt, MD, USA |
许可协议
这幅图片原始出处为Flickr的https://flickr.com/photos/24662369@N07/31834258342 ,作者为NASA Goddard Photo and Video 。经机器人FlickreviewR 2在2018年5月12日审查后确定为采用cc-by-2.0的协议授权使用。 |
2018年5月12日
Public domainPublic domainfalsefalse |
本文件完全由NASA创作,在美国属于公有领域。根据NASA的版权方针,NASA的材料除非另有声明否则不受版权保护。(参见Template:PD-USGov/zh、NASA版权方针页面或JPL图片使用方针。) | ||
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30 12 2016
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当前 | 2018年5月12日 (六) 00:11 | 2,001 × 1,619(2.72 MB) | OceanAtoll | Transferred from Flickr via #flickr2commons |
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宽度 | 4,096 px |
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高度 | 4,096 px |
每部件位数 |
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像素构成 | RGB |
方位 | 标准 |
像素数 | 3 |
水平分辨率 | 72 dpi |
垂直分辨率 | 72 dpi |
使用软件 | Adobe Photoshop CC 2015.5 (Windows) |
文件修改日期时间 | 2016年12月30日 (五) 09:46 |
Exif版本 | 2.21 |
色彩空间 | 无标定 |
原始文件唯一ID | 53EC560DCC7103582DDBDB155481F19E |
数字化日期时间 | 2016年12月30日 (五) 03:32 |
原始数据最后修改日期 | 2016年12月30日 (五) 04:46 |