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Time-warp: Why June 30 will be a bit longer

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Washington: Strictly speaking, a day lasts 86,400 seconds. On June 30, the day will officially be a bit longer than usual because an extra second or “leap” second will be added and NASA has an explanation for this.

“The Earth’s rotation is gradually slowing down a bit, so leap seconds are a way to account for that,” said Daniel MacMillan, NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

This is the case according to the time standard that people use in their daily lives – Coordinated Universal Time or UTC.

UTC is “atomic time” — the duration of one second is based on extremely predictable electromagnetic transitions in atoms of cesium.

These transitions are so reliable that the cesium clock is accurate to one second in 1,400,000 years.

However, the mean solar day — the average length of a day, based on how long it takes the Earth to rotate — is about 86,400.002 seconds long.

“That is because the Earth’s rotation is gradually slowing down a bit owing to a kind of braking force caused by the gravitational tug of war between the Earth, the Moon and the Sun,” the US space agency said in a statement.

Scientists estimate that the mean solar day has not been 86,400 seconds long since the year 1820 or so.

This difference of two milliseconds, or two thousandths of a second — far less than the blink of an eye — hardly seems noticeable at first.

But if this small discrepancy were repeated every day for an entire year, it would add up to almost a second.

Typically, a leap second is inserted either on June 30 or December 31.

Normally, the clock would move from 23:59:59 to 00:00:00 the next day. But with the leap second on June 30, UTC will move from 23:59:59 to 23:59:60, and then to 00:00:00 on July 1.

In practice, many systems are instead turned off for one second.

Previous leap seconds have created challenges for some computer systems and generated some calls to abandon them altogether.

“In the short term, leap seconds are not as predictable as everyone would like,” said Chopo Ma, geophysicist at Goddard.

“The modelling of the Earth predicts that more and more leap seconds will be called for in the long-term but we cannot say that one will be needed every year,” Ma said.

From 1972, when leap seconds were first implemented, through 1999, leap seconds were added at a rate averaging close to one per year.

Since then, leap seconds have become less frequent.

This June’s leap second will be only the fourth to be added since 2000.

(IANS)

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Rocket Lab is Set To Launch 10 NASA CubeSats

They will be placed in RailPODs aboard the Electron rocket that will ferry them to space

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Rocket Lab to launch 10 NASA CubeSats on Sunday. Pixabay

In its first mission for NASA, the American aerospace manufacturer Rocket Lab is set to launch 10 small research satellites, or CubeSats, from New Zealand, the US space agency said.

Owing to bad weather, Rocket Lab was forced to postpone the earlier decided launch on December 12.

Rocket Lab is now targeting the ELaNa-19 launch on December 15 with a launch window opening at 11 p.m. EST from the company’s launch complex on the Mahia Peninsula in New Zealand, NASA said in a statement on Friday.

The CubeSats were built by three NASA centres, seven universities, and a middle school under the NASA’s Educational Launch of Nanosatellites, or (ELaNa-19) mission.

ElaNa-19 is NASA’s first to be completely dedicated to launching CubeSats under the agency’s Venture Class Launch Services program for small-satellite launches.

More than 250 students have been involved in the design, development and construction of the CubeSats scheduled to be flown as payloads on Rocket Lab’s Electron rocket.

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Owing to bad weather, Rocket Lab was forced to postpone the earlier decided launch on December 12. Flickr

“The major difference between today’s launch and previous #ELaNa missions is that for the first time, NASA will have a launch completely dedicated to CubeSats rather than having the small satellites ride along with a much larger spacecraft that is the primary mission,” NASA Launch Services Program officials wrote on Twitter on December 12.

The 10 CubeSats are named as CubeSail, CeREs, NMTSat, CHOMPTT, ALBus, STF-1, ISX, RSat, Shields-1 and DaVinci, NASA said.

These are built to standard dimensions of one unit (1U), and can be 1U, 2U, 3U or 6U in size. They generally weigh less than 1.33 kg per U — 6U may be up to 12 kg.

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They will be placed in RailPODs aboard the Electron rocket that will ferry them to space.

After the main payload deploys, the CubeSats will separate from their RailPODs. After 45 minutes in orbit, the CubeSat transmitters will turn on and university ground stations will listen for their beacons, determine their small satellites’ functionality and announce operational status.

CubeSat mission durations and orbital life vary but are anticipated to last at least three years. Upon mission completion, the CubeSats fall to Earth, burning up in the atmosphere, NASA noted. (IANS)