Bang! Bang! I shot you down

Zaphod

See the Doomed Spy Satellite!
By now you've probably heard news reports about a super-secret spy satellite, designated USA 193, that will tumble uncontrolled from orbit within the next few weeks. The National Reconnaissance Office, which owns the doomed bird, has been mum on its mission and description.

But in a remarkable press conference on February 14th, a deputy national security adviser announced that President Bush has agreed to let the U.S. Navy try to destroy the satellite prior to its reentry by slamming a ship-fired SM-3 into it.

Apparently, DoD computer models have shown that, if left alone, more than half of USA 193's roughly 5,000-pound mass would survive the atmospheric plunge and reach the ground. In particular, there's a 20-inch diameter tank containing about a half ton of the highly toxic propellant hydrazine. So the decision was made to break up the satellite if possible.

You'll notice that I didn't say "shoot it down," as I've seen in many news reports. USA 193 isn't some aircraft that will simply drop from the sky if hit. Nor will some of the resulting fragments end up in long-lasting orbits that will threaten other spacecraft, as others have speculated.

None of the debris will survive more than a few weeks. That's because while, conceivably, the fragments' orbital apogees (high points) might end up somewhat higher, their perigees (low points) will not — and those perigees are already so low that fairly rapid decay is assured. All else being equal, breaking up the satellite will actually hasten reentry because virtually all the pieces will have higher area/mass ratios that the intact satellite did.

Whether this concern for public safety is genuine, or the NRO spooks don't want souvenir hunters combing through whatever wreckage might land on solid ground, or the Navy wants a good excuse for target practice isn't why I'm telling you all this.


The reconnaissance satellite USA 193 has a highly inclined orbit that carries over all the world's populated areas — increasing risk of injury during its forthcoming reentry, but also providing excellent opportunities to spot it as it sails overhead in twilight.
Chris Peat / Heavens-Above
Instead, I want you to go spot this satellite while you still can. The first interceptor missile won't be fired until sometime after February 20th. Until then, USA 193 will be left alone — and, as spy satellites go, it's easy to spot if you know where and when to look.

Right now the satellite's altitude is averaging just 163 miles (262 km), and it'll lose another 10% of altitude by the time the shooting starts. Because its orbit is inclined 58½° to the equator, USA 193 passes over virtually every city and town on Earth. If it were to pass directly over you after sunset or before sunrise, it might be as bright as a 1st-magnitude star. That should make it easy to spot with your eyes alone even from a light-polluted urban setting.

Even better, right now the satellite is making a series of favorable early-evening passes over North America and Europe. To determine where and when to look for it, get free predictions from our Satellite Tracker. After selecting your location and time zone, you'll be able to create predictions customized for your location. Be forewarned, though, that the predictions for USA 193 might be off by a minute or two.

Good luck! If you succeed in spotting it, add a comment below to let me know how accurate the prediction was for your location.

http://www.skyandtelescope.com/observing/highlights/15715337.html

The Yanks were bitching and moaning when the Chinese shot down (more like crashed into) a sat recently, littering space with dangerous junk. Do as I say but not as I do?

IS CHINA'S SATELLITE KILLER A THREAT?
James Oberg
Guest Blogger
The Chinese anti-satellite shot on 12 January produced fireworks that are now branching into the non-celestial spheres of politics, national security, and space technology. I covered the issue for the general reader a few years ago (see "Taikonauts Prepare for Liftoff") for IEEE Spectrum,—where I foresaw some of these developments—and yesterday for MSNBC online (see "Bold move escalates space war debate"). This blog gives me a chance to elaborate on the more technical parts of the story.

Fifty years ago this May, Russia test-fired its first intercontinental ballistic missile, the R-7, and some time later used it to launch the Sputnik satellite into orbit. The R-7 was lousy as a weapon, and the Soviets soon scrapped it. It was potent as a symbol, though, because it began what became known as the Space Race.

The question now is whether China's ASAT missile is a serious weapon or merely a symbol, meant to put pressure on other countries, particularly the United States. To answer it, we must examine the gap separating the satellite-killing demonstration and the needs of a real weapon—one that would be a genuine threat to other countries' satellites.

The missile's kill mechanism is that of a bullet: It crashes head-on into a target moving at 28 000 km/hr, adding its own speed to the total impact velocity. Such an impact creates a hypersonic shock wave that propagates from the inside of the target outward and, at the outer edge, shreds the target into metallic confetti that moves away at up to hundreds of meters per second. That's why the mechanism is called "kinetic kill."

Now it's important to keep in mind that the Chinese carefully timed the launch of their kinetic kill vehicle so that it would intercept the known position and orbit of the satellite it was aiming for—intercepting a target in an arbitrary orbit is a much more difficult proposition.

The Chinese targeted a low-orbiting, obsolete, weather satellite, where the kinetic kill energy was very great. However, the really strategic satellites fly much higher—the navigation network is 20 000 km up, and the communications constellations are in a geosynchronous arc at 40 000 km. At geosynchronous altitudes, the orbital velocities are so much lower that the impact energy would be only about a tenth as high as in last week's test.

Distance introduces a second burden: terminal navigation. When a target satellite is close to the Earth, ground radars can track it and relay final course corrections, both to the rocket during its ascent and to the kill vehicle, once it has been deployed on its hoped-for collision course. Radar operates at an inverse fourth power law, which means that for the Chinese system to aim many times farther than low Earth orbit—as it would have to do to track objects geosynchronously—the demands on a ground-based radar would be simply impossible. The engineering challenges don't need much description for this audience.

The Chinese weapons system has so far demonstrated only that it can pose a threat to low-orbiting objects, of which the most important are reconnaissance satellites. But these satellites have backup. If anyone interferes with them, countries can dispatch aircraft to conduct the reconnaissance. Although this might entail trespassing on other nations' airspace, an act forbidden by international law, such restrictions no longer apply once war has broken out.

Nor are space targets helpless victims to such kinetic kill attacks, especially at higher altitudes. In such cases, the best defense is usually a good pretense—the intended victim has options to degrade the accuracy of the attacker's critical terminal guidance.

During the final moments of a high-speed intercept, the attacking missile is able to make increasingly accurate sightings of the target, and therefore the uncertainty as to the target's relative position shrinks. The missile's navigation must be robust enough so that the uncertainty doesn't shrink so fast that the onboard control jets can't alter the expected impact point (or the attacker will get locked into a trajectory that will zoom by the target), and in the end the uncertainty has to be smaller than the physical size of the target. When it isn't, the attacker misses, and in this game, "close" doesn't count. To an even greater extent than with the anti-ballistic missile solution problem, a target satellite can take steps to interfere with the attacker obtaining a workable targeting solution, and the farther from Earth the attack occurs, the more the odds favor the target.

Objects can hide in space, to a greater or lesser degree, by lowering their radar reflectivity or optical brightness along the attacker's expected line of approach. This makes terminal navigation and guidance more difficult. That effect can be augmented with decoys, which can either be deployed when an attack is detected or can be sent, as a matter of routine, to fly in formation with the high-value target. A decoy doesn't have to be a throwaway subsatellite, it could be an inflatable spar a few tens of meters long with a pseudo-target at the end to attract the on-rushing kinetic kill vehicle away from the real spacecraft. Such a decoy could be deployed in a matter of minutes, and even re-stowed afterwards for future re-use.

Even the simple suspicion that a target may have such a capability would discourage a potential attacker. And the realization that a target might also be able to detect and characterize even a failed attack would be an additional deterrent. There would be no way for the attacking country to get away with attempted mayhem.

These engineering angles to China's ground-launched kinetic kill system suggest to me that the hardware's intended target isn't up in space at all. It is more probably a calculated move on the board—in this case, not for chess but for Go. If we focus too closely on the specific man and its neighborhood, we may miss the strategy for the game as a whole and wind up losing.

Ultimately, the central issue of this ASAT demonstration isn't about engineering. But good engineering assessment may enable us to determine what the issue is not, and that's a clue toward figuring out what it really could be. Then, and only then, can we develop a fruitful strategy.

http://spectrum.ieee.org/jan07/comments/1691

Thanks to Nancy for the musical quote.

Zaphod

US missile hits 'toxic satellite'

The Pentagon used a missile to shoot down the satellite

The US has successfully struck a disabled spy satellite with a missile fired from a warship in waters west of Hawaii, military officials say.

Operatives had only a 10-second window to hit the satellite - USA 193 - which went out of control shortly after it was launched in December 2006.

Officials were worried its hydrazine fuel could do harm, but it is not yet known if the fuel tank was destroyed.

The controversial operation has been criticised by China and Russia.

On Thursday, China called on the US to provide more information about the mission.

Russia suspects the operation was a cover to test anti-satellite technology under the US missile defence programme.

The US denies the operation was a response to an anti-satellite test carried out by China last year, which prompted fears of a space arms race.


The operation went ahead hours after the space shuttle Atlantis landed, removing it as a safety issue for the military.

The satellite - believed by some commentators to be a radar imaging reconnaissance satellite - was passing about 130 nautical miles (250km) over the Pacific.

Earlier the military said it would use an SM-3 missile fired from the cruiser USS Lake Erie, which is posted on the western side of Hawaii along with the destroyers USS Decatur and USS Russell.

But it is not yet known how successful the operation was - the missile needed to pierce the bus-sized satellite's fuel tank, containing more than 450kg (1,000lbs) of toxic hydrazine, which would otherwise be expected to survive re-entry.

The Pentagon said confirmation that the fuel tank has been hit should be available within 24 hours.

US officials said without an attempt to destroy the fuel tank, and with the satellite's thermal control system gone, the fuel would now be frozen solid, allowing the tank to resist the heat of re-entry.

If the tank were to land intact, it could leak toxic gas over a wide area - harming or killing humans if inhaled, officials had warned.

Debris

Officials expect that over 50% of the debris will fall to Earth within the first 15 hours after the strike - or within its first two revolutions of Earth.

Left to its own devices, about half of the spacecraft would have been expected to survive the blazing descent through the atmosphere, scattering debris in a defined "corridor" which runs across the Earth's surface.

Professor Richard Crowther, a space debris expert with the Science and Technology Facilities Council (STFC), said that if struck with the missile, about 25% of USA 193 is likely to survive the fall to Earth.

"The smaller the debris is the more likely you are to get burn-through. So if you fragment something before re-entry, less mass will survive to hit the Earth," he told BBC News.

Russian suspicion

But Russia's defence ministry has effectively branded the US operation a cover for testing an anti-satellite weapon.

The Russian defence ministry argued that various countries' spacecraft had crashed to Earth in the past, with many using toxic fuel on board, but that this had never before merited "extraordinary measures".

A spokesman for the Chinese foreign ministry in Beijing, Liu Jianchao, said China was concerned about the "possible damage to security in outer space and to other countries".

"We demand that the US... swiftly brief the international community with necessary data and information in time, so that relevant countries can take preventative measures," he said.

Last year, China carried out a test using a ground-based ballistic missile to destroy a satellite in space, prompting international alarm and fears of a space arms race.

On Tuesday, a US State Department spokesman stressed that the action was meant to protect people from the hazardous fuel and was not a weapons test.

The US government has also denied claims that the main aim of the operation was to destroy secret components on USA 193.

Officials say classified parts would be burned up in the atmosphere and, in any case, that would not be a reason for shooting down the satellite.

http://news.bbc.co.uk/2/hi/science/nature/7254540.stm

watty

The US shot down a satellite 50km further away than this one in 1989.


I don't beleive any of the consipracy theories, but don't beleive the official reports either.

mick.fr

The conspiracy theory is only serving the fools interests who have nothing else to do than doing...theories and generating traffic on their websites.

mick.fr

mick.fr wrote: »

The conspiracy theory is only serving the fools interests who have nothing else to do than doing...theories and generating traffic on their websites.

Other then the sheep who are believing what they are told .