통신위성 영국의 가장 오래된 통신위성이 예상을 벗어난 위치에서 발견

[위종민]

1969년 발사된 영국군의 군용 통신위성 Skynet-1A는 아프리카 동부 해안 상공에서 영국군의 통신을 중계하다가 몇 년 뒤 작동을 멈췄고, 예상대로라면 동쪽으로 이동해 인도양 상공에 있어야 하는데 실제로는 남아메리카 대륙 서쪽에 있다고 합니다. 

작동을 멈춘 뒤 1970년대 중반에 추진기를 이용해 서쪽으로 이동하도록 명령을 내린 것 같은데, 누가 왜 그런 명령을 내렸는지 알 수가 없다고 하네요. Skynet-1A는 미국의 Philco Ford사에서 제조돼 델타 로켓에 실려 발사됐고, 미국에서 궤도에 있는 위성ㅇ을 통제하다 영국으로 통제권을 넘겼기 때문에 위성 수명이 다한 뒤 미국이 통제권을 되가져갔을 수도 있지만 확실하진 않다고 합니다. 

지금은 수명이 다한 위성을 'orbital graveyard'에 모아 관리하는 것이 표준이지만 1970년대에는 그런 개념이 없었기 때문에, 우주 쓰레기 상태가 된 Skynet-1A가 궤도상을 비행하는 다른 위성에 위협이 되고 있다고 하네요. 

Skynet-1은 A, B 2대가 발사됐는데 A는 18개월만에 기기고장으로 작동을 중지했고, 1970년 발사된 B도 킥모터 고장으로 폐기됐었네요. 

정지궤도를 벗어나려면 Delta-V가 1,500m/s가 필요한데 이 위성을 graveyard orbit으로 옮기는 데에는 11m/s로 충분하다고 합니다. 

Skynet-1A: Why did the UK's oldest space satellite end up thousands of miles from where it should have been?

Skynet-1A: Why did the UK's oldest space satellite end up thousands of miles from where it should have been?

Somebody moved UK's oldest satellite, and no-one knows who or why

6 days ago

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Jonathan Amos

Science correspondent•@JCDAmos

BBC/Gerry Fletcher

Artwork: The half-tonne Skynet-1A satellite was launched in November 1969

Someone moved the UK's oldest satellite and there appears to be no record of exactly who, when or why.

Launched in 1969, just a few months after humans first set foot on the Moon, Skynet-1A was put high above Africa's east coast to relay communications for British forces.

When the spacecraft ceased working a few years later, gravity might have been expected to pull it even further to the east, out over the Indian Ocean.

But today, curiously, Skynet-1A is actually half a planet away, in a position 22,369 miles (36,000km) above the Americas.

Orbital mechanics mean it's unlikely the half-tonne military spacecraft simply drifted to its current location.

Almost certainly, it was commanded to fire its thrusters in the mid-1970s to take it westwards. The question is who that was and with what authority and purpose?

It's intriguing that key information about a once vital national security asset can just evaporate. But, fascination aside, you might also reasonably ask why it still matters. After all, we're talking about some discarded space junk from 50 years ago.

"It's still relevant because whoever did move Skynet-1A did us few favours," says space consultant Dr Stuart Eves.

"It's now in what we call a 'gravity well' at 105 degrees West longitude, wandering backwards and forwards like a marble at the bottom of a bowl. And unfortunately this brings it close to other satellite traffic on a regular basis.

"Because it's dead, the risk is it might bump into something, and because it's 'our' satellite we're still responsible for it," he explains.

BBC/Gerry Fletcher

If a satellite died at 40E it would drift to the nearest gravity well, which is 75E.

Dr Eves has looked through old satellite catalogues, the National Archives and spoken to satellite experts worldwide, but he can find no clues to the end-of-life behaviour of Britain's oldest spacecraft.

It might be tempting to reach for a conspiracy theory or two, not least because it's hard to hear the name "Skynet" without thinking of the malevolent, self-aware artificial intelligence (AI) system in The Terminator movie franchise.

But there's no connection other than the name and, in any case, real life is always more prosaic.

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What we do know is that Skynet-1A was manufactured in the US by the now defunct Philco Ford aerospace company and put in space by a US Air Force Delta rocket.

"The first Skynet satellite revolutionised UK telecommunications capacity, permitting London to securely communicate with British forces as far away as Singapore. However, from a technological standpoint, Skynet-1A was more American than British since the United States both built and launched it," remarked Dr Aaron Bateman in a recent paper on the history of the Skynet programme, which is now on its fifth generation.

This view is confirmed by Graham Davison who flew Skynet-1A in the early 70s from its UK operations centre at RAF Oakhanger in Hampshire.

"The Americans originally controlled the satellite in orbit. They tested all of our software against theirs, before then eventually handing over control to the RAF," the long-retired engineer told me.

"In essence, there was dual control, but when or why Skynet-1A might have been handed back to the Americans, which seems likely - I'm afraid I can't remember," says Mr Davison, who is now in his 80s.

Sunnyvale Heritage Park Museum

Could the command to move Skynet-1A have come from the US Air Force's 'Blue Cube'?

Rachel Hill, a PhD student from University College London, has also been scouring the National Archives.

Her readings have led her to one very reasonable possibility.

"A Skynet team from Oakhanger would go to the USAF satellite facility in Sunnyvale (colloquially known as the Blue Cube) and operate Skynet during 'Oakout'. This was when control was temporarily transferred to the US while Oakhanger was down for essential maintenance. Perhaps the move could have happened then?” Ms Hill speculated.

The official, though incomplete, logs of Skynet-1A’s status suggest final commanding was left in the hands of the Americans when Oakhanger lost sight of the satellite in June 1977.

But however Skynet-1A then got shifted to its present position, it was ultimately allowed to die in an awkward place when really it should have been put in an "orbital graveyard".

This refers to a region even higher in the sky where old space junk runs zero risk of running into active telecommunications satellites.

Graveyarding is now standard practice, but back in the 1970s no-one gave much thought to space sustainability.

Astroscale

British engineers are developing technologies to snare defunct satellites in low orbits

Attitudes have since changed because the space domain is getting congested.

At 105 degrees West longitude, an active satellite might see a piece of junk come within 50km of its position up to four times a day.

That might sound like they’re nowhere near each other, but at the velocities these defunct objects move it’s starting to get a little too close for comfort.

The Ministry of Defence said Skynet-1A was constantly monitored by the UK's National Space Operations Centre. Other satellite operators are informed if there's likely to be a particularly close conjunction, in case they need to take evasive action.

Northrop Grumman

The Americans have already shown it's possible to grab a high-orbiting satellite

Ultimately, though, the British government may have to think about removing the old satellite to a safer location.

Technologies are being developed to grab junk left in space.

Already, the UK Space Agency is funding efforts to do this at lower altitudes, and the Americans and the Chinese have shown it's possible to snare ageing hardware even in the kind of high orbit occupied by Skynet-1A.

"Pieces of space junk are like ticking time bombs," observed Moriba Jah, a professor of aerospace engineering at the University of Texas at Austin.

"We need to avoid what I call super-spreader events. When these things explode or something collides with them, it generates thousands of pieces of debris that then become a hazard to something else that we care about."

Skynet (satellite) - Wikipedia

Skynet (satellite) - Wikipedia

Skynet 1[edit]

There were two Skynet 1 satellites (1A and 1B); Skynet 1A was launched on a Delta M on 22 November 1969,[14] and stationed over the east coast of Africa.[22] However, the satellite ceased operating after about 18 months when all of its Traveling Wave Tube Amplifiers (TWTAs) failed, probably when soldered high voltage joints failed after cycling between extreme temperatures.[14] Some time in the mid-1970s, the now-defunct satellite was moved far from its original position; its current location in a stable "gravity well" (see Geostationary orbit#Stability) at longitude 105° W off the Pacific coast of Latin America is 36,000 km away from its original position, and it could not have simply drifted and ended up in this stable orbit.[22] The new location is near satellite traffic and it has to be monitored for collision risks. In 2024, the BBC reported that there is no record of who moved it or why.[22] Skynet 1B was launched on a Delta M on 19 August 1970. Skynet 1B was placed in a geostationary transfer orbit (GTO) and was abandoned in transfer orbit (270 x 36058 km) due to a failure of the Thiokol Star 17A apogee kick motor.[23]

Skynet 1 series satellites had an orbit mass of 122 kg (269 lb), were spin-stabilised with a single despun antenna with 3 watts of output on two channels (2 MHz and 20 MHz).[12] The North Atlantic Treaty Organization, NATO 2A and NATO 2B satellites, launched 1970 and 1971, were identical except for an antenna shaped to only cover NATO countries.[24]

Skynet (satellite) - Wikipedia

Graveyard orbit - Wikipedia

Graveyard orbit - Wikipedia

[백선호]

우주 쓰레기가 하도 많아서 일본의 가와사키중공업은 우주 쓰레기를 청소해서 돈을 벌 궁리를 하고 있습니다.

https://cafe.daum.net/NTDS/51Tm/162

[위종민]

이젠 한 번 발사해서 위성 수 십개를 궤도에 올리고 있고, 스타링크 위성 포함한 군집위성들 때문에 지상천문대 관측이 방해된다고 하는 세상이니 우주쓰레기 수거 방안을 진지하게 고민해야 될 것 같습니다. 쏘아올린 나라 보고 처리하라고 하는 게 합리적일 텐데, 많이 쏘아올린 나라들이 강대국이니 맘처럼 될 진 ㅋㅋ