The CNET Lounge

General discussion

U.S. satellite gonna come down on Earth in...somewhere...

by shawnlin / January 27, 2008 12:48 AM PST

U.S. satellite gonna come down on Earth in...somewhere...
http://www.iht.com/articles/2008/01/27/america/satellite.php
http://www.space.com/news/ap-080126-spy-satelite.html

So you may be wondering how often this happens...and that depends on what you mean by "often". Tim the Rocket Scientist and any other satellite experts - please correct me if I'm wrong on this thread as satellites are not my forte...

Most satellites go through a deorbit, burn-up, and dunk in the ocean. I don't really have a number, but I think it's in the 10-25 per year range.

Most are controlled trajectories, some are not controlled, but they the trajectory has been safely set. However, this seem to be a case where the de-orbit trajectory has not been and it won't be a controlled either - this can be dangerous. Calculations on the landing area accurate to up to +/-1000miles - that's why aiming to "land" the satellite in a huge uninhabited part of Earth, like an ocean, is attractive.

There are some clever ideas for deorbit "bolt-on" modules: http://www.tethers.com/papers/SmallSat_nanoTerminator.pdf
Also, the Hubble Space Telescope is expected to be deorbited by a "bolt-on" de-orbit module that is expected to automatically mate to the telescope and safely deorbit.

As far as why they forced to deorbit - a few major reasons: if they have become or are at risk of becoming less than flight-worthy, if they are simply too expensive to maintain/operate, and/or if they are not useful enough to use (even as a back-up).

So...how paranoid should you be considering the satellite has some nasty, toxic hydrazine? Well, not really any because many, many people and organizations will be calculating where the impact area is and considering ~2/3rds of Earth is covered by water - probably not gonna hit land. But I'm sure information about both hydrazine and impact location will be forthcoming in the next couple weeks.

Best,
Shalin

Post a reply
Discussion is locked
You are posting a reply to: U.S. satellite gonna come down on Earth in...somewhere...
The posting of advertisements, profanity, or personal attacks is prohibited. Please refer to our CNET Forums policies for details. All submitted content is subject to our Terms of Use.
Track this discussion and email me when there are updates

If you're asking for technical help, please be sure to include all your system info, including operating system, model number, and any other specifics related to the problem. Also please exercise your best judgment when posting in the forums--revealing personal information such as your e-mail address, telephone number, and address is not recommended.

You are reporting the following post: U.S. satellite gonna come down on Earth in...somewhere...
This post has been flagged and will be reviewed by our staff. Thank you for helping us maintain CNET's great community.
Sorry, there was a problem flagging this post. Please try again now or at a later time.
If you believe this post is offensive or violates the CNET Forums' Usage policies, you can report it below (this will not automatically remove the post). Once reported, our moderators will be notified and the post will be reviewed.
Collapse -
(NT) hehe i was definitely wondering how 'often'
by udayan71 / January 27, 2008 2:00 AM PST
Collapse -
U.S. DoD to shoot down wayward satellite...
by shawnlin / February 14, 2008 3:31 AM PST
http://www.space.com/news/ap-080214-spy-satellite-shootdown.html
excerpt:
*****
The U.S. Defense Department is planning to shoot down a broken spy satellite expected to hit the Earth in early March, the Associated Press has learned.
U.S. officials said Thursday that the option preferred by the Bush administration will be to fire a missile from a U.S. Navy cruiser, and shoot down the satellite before it enters Earth's atmosphere.
[...]
Shooting down a satellite is particularly sensitive because of the controversy surrounding China's anti-satellite test last year, when Beijing shot down one of its defunct weather satellites, drawing immediate criticism from the U.S. and other countries.
*****

http://www.msnbc.msn.com/id/23166344/
excerpt:
*****
The disabled satellite is expected to hit the Earth the first week of March. Officials said the Navy would likely shoot it down before then, using a special missile modified for the task.

The Navy will fire two or three SM-3 missiles from a cruiser and destroyer off the Northwest coast of Hawaii. The SM-3's which are more of a medium-range interceptor have to be modified ? more fuel and new software ? to reach the disabled spy satellite in orbit. If the intercept and kill are successful and the satellite is destroyed, it appears most of the debris will become orbitting "space junk" and not reenter Earth's atmopshere.
*****


darn it! I don't think it's a good idea to blow up stuff in space - the debris field can be a hassle to deal with for current and future uses of Low Earth Orbit.

Best,
Shalin
Collapse -
Video: How and why the satellite is to be shot down...
by shawnlin / February 14, 2008 10:55 PM PST
Collapse -
additional details about the frozen hydrazine issue...
by shawnlin / February 14, 2008 11:09 PM PST
http://www.msnbc.msn.com/id/23172469

excerpt:
*****
Hydrazine is a nasty chemical that could poison the area where it is released. Until recently, U.S. officials were saying that the tank would be crushed as the satellite fell through the atmosphere, sometime in early March. If that were the case, the toxic hydrazine would almost certainly be burned off and safely dispersed during the fiery fall.

NASA Administrator Michael Griffin sketched out a different scenario, however, during Thursday's news conference with Gen. James Cartwright, the vice chairman of the Joint Chiefs of Staff. Griffin said NASA experts calculated that the hydrazine was frozen solid due to the satellite?s yearlong drift through the cold of space. The tank, with its half-ton ice core of hydrazine, would thus become one of the most perfect re-entry vehicles ever to fall back to Earth.

Griffin explained that the contents of the tank could turn to slush during the fall, but would very likely survive and leak toxic gas over the crash site. Another expert told msnbc.com privately that the solid ice would provide structural support against the 20 to 25 G?s of deceleration experienced by the satellite during re-entry.
*****

okay, last thread addition until something more significant is worth informing folks about Happy

Best,
Shalin
Collapse -
transcript of 2/20 DoD background briefing on shoot-down...
by shawnlin / February 20, 2008 12:29 PM PST
Collapse -
controversy surrounds purpose behind satellite shoot-down...
by shawnlin / February 19, 2008 5:40 AM PST

controversy surrounds purpose behind satellite shoot-down...

http://dsc.discovery.com/news/2008/02/15/spy-satellite-challenge.html

http://www.washingtontimes.com/apps/pbcs.dll/article?AID=/20080215/NATION/190574197/1001

http://blog.wired.com/defense/2008/02/fishy-rationale.html

http://www.reuters.com/article/scienceNews/idUSL1587228120080215?feedType=RSS&feedName=scienceNews&rpc=22&sp=true

...who knows! ya know? I mean...

All I gotta say is that I'm pretty disappointed that there's gonna be more debris up there.

--S

Collapse -
Two Good Reasons
by Renegade Knight / February 20, 2008 3:46 AM PST

First, We need the target practice. Our military has a job to do and this lets them practice it. Should the need ever arise.
Second, if you shoot it at the right time you can control the fall, or at least break it up into smaller pieces that don't cause as much harm or burn up.
Third (I lied about two) if they blow up the tank of nasty stuff it also burns up or dissapates on the way in. Ok this is really related to #2.

Collapse -
yeah, I hear ya...; deorbit objective?; deorbit module
by shawnlin / February 20, 2008 5:10 AM PST
In reply to: Two Good Reasons

Yeah, I can understand the issue of practicing it - and who knows whether this is a genuine coincidence or a convenient cover...

I just haven't heard/read that a safe deorbit and burn-up is the end-goal - I've just heard/read that the end goal is to eliminate or drastically reduce the implications of hydrazine coming down on people and we'll just have to deal with more space debris. If you know of something that says a re-entry burn-up is a top tier objective after addressing the hydrazine, lemme know 'cause I guess I missed it.

Too bad and automated deorbit module isn't available, that'd help out a lot in both verifying new launch and guidance systems as well as reducing space debris. There was a program that tested a portion of such a system a few years ago, but I dunno what, if anything is going on with it now:
http://www.msfc.nasa.gov/news/dart/
http://www.nasa.gov/mission_pages/dart/main/
http://en.wikipedia.org/wiki/DART_(spacecraft)
http://www.space.com/missionlaunches/050422_dart_update.html

Best,
Shalin

Collapse -
hmmm...deorbit...
by shawnlin / February 20, 2008 12:37 PM PST

based on Frank's e-mail to BOL and some other things I've read recently, I guess the idea was to still deorbit the whole thing, including any debris. Good idea...but a still better idea would be a deorbit module.

-- S

Collapse -
If I'm killed by a falling satellite...
by kwahhn / February 14, 2008 11:09 PM PST

it's my time to go.

Collapse -
Anti-Satellite weapons are not new...
by shawnlin / February 19, 2008 6:03 AM PST

*Disclaimer: Shalin is not a missle expert, Shalin is not a satellite expert, Shalin is not an anti-satellite missile expert either...but Shalin does know some aerospace stuff that maybe helpful to understand regarding the shoot-down of the wayward satellite...

Although they haven't had as much use or testing as conventional weapons, Anti-Satellite (ASAT) weapons are not new - they've been around for decades. The last known test the US performed were in the 80's. ASAT weapons were basically conceived as strategic solutions to threats (use of space as a battleground) during the Cold War.

As far as why 3 are being fired - 1 as a first shot and 2 "second chances" seems the likely logic to me. Guidance systems are more sophisticated these days, so I would actually expect the first shot to be successful.
I don't think they'll be fired all at once. If they don't hit the target, they'll likely be directed back through the atmosphere to burn up, self destruct, or both.

More info:
http://en.wikipedia.org/wiki/Anti-satellite_weapon
http://en.wikipedia.org/wiki/ASM-135_ASAT
http://www.fas.org/spp/military/program/asat/overview.htm
http://en.wikipedia.org/wiki/Aegis_Ballistic_Missile_Defense_System
http://www.fas.org/man/dod-101/sys/ship/weaps/aegis.htm

I've said it before and I'll say it again - it's disappointing to me that this shoot-down is going forward 'cause it'll just create more debris up there that isn't really helpful.

--S

Collapse -
...and China destroyed a satellite in January...
by papachungo13 / February 19, 2008 9:00 PM PST

an old Chinese weather satellite was destroyed 537 miles above Earth. The missile carried a "kill vehicle" and destroyed the satellite by ramming it.

The test took place on January 11.

One difference between both scenarios is that the debris from the China satellite remains in orbit.

Collapse -
right the Chinese did do an ASAT test last year, however...
by shawnlin / February 19, 2008 10:33 PM PST

I think the debris from the US sat is also expected to stay in orbit...or did I read something incorrectly?
--S

Collapse -
Most debris should burn up
by QueMike / February 20, 2008 1:14 PM PST

Most of the debris should de-orbit and burn up within the 3 days. I believe they said that they would know more in the next 24 hrs. One thing they are really looking for is whether or not they successfully hit the fuel tank to rupture and disperse the hydrazine in orbit.

-Mike

Collapse -
Break out the popcorn...
by Dawgfanclark / February 19, 2008 11:01 PM PST

and chill pill for Molly as this is gonna ROCK!!!

Collapse -
Just face it...
by doompod / February 20, 2008 5:54 AM PST

Let's the face the fact that we're all going to die, except for little Buzz of course because he's immortal.

Collapse -
Is there a reason for the location?
by Jill808 / February 20, 2008 7:42 AM PST
In reply to: Just face it...

Why are they trying to shoot it down in the Pacific...um close to Hawaii. In other words, why so close to me?

Collapse -
The last US Satellite landed in my country...
by DaveBinM / February 20, 2008 8:11 AM PST
Collapse -
Why? Because the Pacific Ocean is an easy target to "hit"..
by shawnlin / February 20, 2008 9:28 AM PST

Jill,

Why? Because the Pacific Ocean is an easy target to "hit"

There is a moral issues here: Most people in the world lives on land and therefore value land more than water. So "we" don't mind "hitting" water - as long as it's not close to anything valuable man-made (cruise ships, coastal towns, etc.) or hard to get to resource (fossil fuels, etc.)

But this is simply the best (or least bad, depending on your view) that there is for ensuring public safety. Part "what do we value and how do we avoid it" and part statistical probability of carrying out the deorbit/re-entry.

Best,
Shalin

BTW - You live in Hawaii! That's awesome! ...I'm sure you get that a lot, but seriously - must be nice, yes? Maybe the BOL cruise will come out there and we'll all go out for walks on the beach, surfing, and all the good food, scenery, culture, and wildlife we can stand...yes, I look forward to that Wink

Collapse -
hmm...it might hit "land in the ocean"...8th continent...
by shawnlin / February 20, 2008 9:30 AM PST
Collapse -
Yay
by Jill808 / February 20, 2008 1:02 PM PST

Good news for now. I hope the good news continues in the days to come.

Living in Hawaii is awesome. At least it is now. A few hours ago, it wasn't that great. Happy

Collapse -
expert commentary on why it's a bad idea...just for balance.
by shawnlin / February 20, 2008 11:57 PM PST
http://www.globalsecurity.org/space/library/news/2008/space-080220-satellite-shootdown.htm

excerpt:
*****
This action is not only unnecessary (over the decades many space objects including the large Skylab manned space station have re-entered the atmosphere and no one on Earth has ever been hit by the resulting de-orbiting debris), but it is illogical. [...]

We have more objects in space than any other nation and it is counterproductive to intercept the errant U.S. spy satellite. The explosive encounter will create a cloud of debris that rivals or perhaps even surpasses that caused by the recent Chinese government's test of their anti-satellite intercept technology. In effect, the U.S. intercept mission will serve as yet another ASAT test (continuing a series of such experiments performed by both America and Russia in the Eighties).

[...]

Once again, this whole affair points to one of the major flaws in humankind's utilization of outer space. [...] These so-called "space tugs" have been written about for decades. But, it is wasteful, and illogical for NASA and other space agencies not to have invested significant funding into the development of such orbital maintenance platforms. Imagine how many space assets (the Mir space station, Skylab, Apollo command modules, not to mention ultrasecret intelligence satellites and countless other strategically (and historically) significant objects) could have been salvaged over the last few decades IF mankind had developed this technology.
*****

Okay, no more posts on this topic from me unless something truly newsworthy happens.

Best,
Shalin
Collapse -
satellite
by einfopedia / April 3, 2012 8:36 PM PDT

i think that the according to the news which is the satellite will hit until two hours before it enters the Earth's atmosphere, moving at 5 miles per second.

What are your chances of being hit by debris from it? About one in 21 trillion, NASA said. When you add up the 7 billion people now alive, the chances that someone, somewhere on the planet could get hit are 1 in 3,200.

Popular Forums
icon
Computer Help 47,885 discussions
icon
Computer Newbies 10,322 discussions
icon
iPhones, iPods, & iPads 3,188 discussions
icon
Security 30,333 discussions
icon
TVs & Home Theaters 20,177 discussions
icon
HDTV Picture Setting 1,932 discussions
icon
Phones 15,713 discussions
icon
Windows 7 6,210 discussions
icon
Networking & Wireless 14,510 discussions

Tech Tip

Know how to save a wet phone?

It's not with a dryer and it's not with rice. CNET shows you the secret to saving your phone.