What is Chinese going to test?

Recently, there have been rumor that China will test its anti-satellite (ASAT) weapon in the coming months. This post tries to analyze what kind of ASAT weapon China try to test, and which target China is aiming at.

There are two types of ASAT deployed in the world. One is Kinetic energy ASAT, a weapon head to head hit to kill a satellite, the other is Co-Orbit ASAT, a weapon fly close to a satellite and explode itself to destroy the satellite.

Of course, there are other ASAT weapons, for example, Laser weapon. However, even if China tests a Laser ASAT, it is unlikely for other countries to figure that out. . Therefore it is unlikely for China to announce that. So, I am not going to discuss it in this blog.

I divide the ASAT weapon into four types, based on the target orbits and killing mechanisms, and then estimate probabilities that each weapon is to be tested by China. See below table:

Orbit KE-ASAT Co-Orbit ASAT
Low Earth Orit (LEO) "Zero"

Low

Medium Earth orbit (MEO) / Geostationary Earth Orbit (GEO) High Low

LEO KE-ASAT

China could test LEO KE-ASAT again. But, the probability of another 2007 ASAT test is almost "Zero". The reason is, even if China does want to test the weapon again, it will not aim at an on-orbit satellite, but a missile. China will call it "missile defense test" instead of ASAT test, just like what it did in 2009. Debris created in such test will decay right after the test.

LEO Co-Orbit ASAT

The probability of testing a co-Orbit ASAT in LEO also seem to be very low. The reason is comparing to KE-ASAT, Co-orbit ASAT has many disadvantages:

It takes much longer time for the weapon to approach target, so that the target might have the chance to escape. That also gives adversary opportunity to destroy the weapon.

It is also much more expensive to deploy a co-orbit ASAT. The weapon has to accelerate to the orbital velocity, i.e. 7.7km/s, while the KE-ASAT does not have to. Moreover, the mass of co-orbit ASAT warhead is also higher than KE-ASAT. For example the Kinetic Energy Kill Vehicle of US missile defense system only weighs tens kilogram, while mass of Russia co-orbital ASAT warhead is 1,400 kilogram.

image

1986 DIA illustration of the Russia Co-orbit ASAT system attacking a target.

The advantage of co-orbital ASAT is it is relatively easy, because Slowly approaching a satellite is much easier than hitting the satellite with relative speed of 10 km/s. Chinese already had the KE-ASAT technology, it seems not necessary for them to develop outdated co-orbit ASAT.

But, if China really wants to test a Co-Orbit ASAT weapon, it is very likely to be a ground based system. Since testing a space based co-orbit system can be described as testing rendezvous technology. Which is a dual use technology, widely used in manned space flight. Test such technology probably will not raise any international concern.

Co-Orbital ASAT would also create a lot of space debris. Russian did many ground based co-orbit ASAT tests during 1960s to 1980s. There are still thousand pieces of space debris left in orbit from these tests.

MEO/GEO KE-ASAT

If China really want to do something "new" this time, I think, it is more likely to be a KE-ASAT against satellite at MEO or GEO.

The ASAT weapon is likely to be ground based. The Outer Space Treaty bans to put weapons of mass destruction (WMD) into outer space. ASAT may not be considered as WMD, but there is no country really put a destructive weapon in space, even during the cold war. If China tests a space based ASAT weapon, it will open Pandora’s box. Arms race in space will be inevitable, which might not be in China’s interests. If Chinese really want to do that, I personally think, it should also be U.S. interests to persuade Chinese not to do that.

If China want to blow up a satellite this time , these two satellites can be used as a target:

NORAD ID

COSPAR ID

Name

Source

Period

Inclination (Deg)

Apogee (Km)

Perigee (Km)

29516

2006-048A

SINOSAT 2

PRC

1,550.7

3.10

38,182

37,820

21833

1991-088A

STTW-5

PRC

632.6

31.5

33,928

2,135

 

SINOSAT is a dead TV satellite, it failed right after the launch. The orbit of SINOSAT 2 is 2,500 km above the GEO orbit, therefore debris created in the kinetic energy collision will not pose hazard to other GEO satellites.

In MEO, China has several Beidou satellites, but all these satellites are active. Moreover, if one of Beidou satellite is destroyed, debris created in the collision will threatens other Beidou satellites. STTW-5/DFH-2 is the only dead Chinese MEO satellite. If China want to test the ability to attack a MEO satellite, it could be used as target. Debris created in this attack would not pose significant hazard to existence satellites.

China already tested kinetic kill technology from previous tests, it may not need to blow up satellite this time. Instead, what China could test is how to deliver the kinetic energy weapon into appropriate orbit. Since it takes couple hours for the weapon to reach the target, target could maneuver away from original orbit, China may also test how to adjust the orbit of the weapon.

MEO/GEO Co-orbit ASAT

The probability for China to test MEO/GEO co-orbit ASAT is very small.

As I said, it is unlikely for China to test a space based weapon, unless it wants to be the first country to put a destructive weapon in space.

If China want to test a ground based co-orbit ASAT, it must have a missile that can deliver the warhead into MEO/GEO. To kill the target, the mass of the warhead should be hundreds kilogram. However, current Chinese ICBMs, i.e.
DF-4/31/41 are unable to deliver a 100 kg payload into GEO orbit.

Of course, China could use its Long March Rocket to launch the weapon, but such weapon system is very vulnerable and expensive. Since China already have the KE-ASAT technology, it would be stupid for China to develop ground based co-orbital ASAT.

All in all, The probability of testing co-orbital ASAT should be very small. China is more likely to have another missile defense test or test a kinetic energy ASAT against MEO/GEO satellites.

North Korea launched its first Satellite

After fourth failure attempts, North Korea finally launched its first satellite.

So far, there is not a lot of information about the satellite. It is reported the mass of the satellite is about 100 km. North Korean space officials also said the satellite would be used to study crops and weather patterns, that means the satellite has a camera.

The satellite might use gravity stabilization, since gravity stabilization is the simplest and robust attitude control method, and is widely used in the camera micro satellites. If that is true, the satellite should not have maneuver capability. It may take more than 10 days until the satellite is stabilized and takes photos.

Up to Now, NORAD has found four objects. See figure below, and Google earth kmz file. The orbits of these objects are around 500km * 580 km * 97.5 deg, at the sun-synchronize orbit.

image

update Dec 14 2012:

It is reported that the satellite launched this time is same as the satellite launched on April, called Kwangmyongsong-3. There is a very good article on Kwangmyongsong-3

fig1 

Kwangmyongsong-3 shown to the media on 8 April 2012. (Photo: KCNA)

The satellite  is reported to use three-axis  attitude control system.  so it can not be gravity stabilization. My previous guess is wrong. Three-axis stable is an active control system, which is far more difficult than the gravity stabilization. Considering that it is their first satellite, North Koreans are quite aggressive. 

There is a report saying that the satellite is “tumbling ,out of control”. If it is true, that means the attitude control system failed to work. 

Oct 16 Breeze M Breakup

On Oct 16th 2012, a Russian Breeze M stage, which was launched on Aug 6th, exploded. This explosion is the biggest debris creation event this year. Right now, there are 500 fragments tracked by US Space surveillance network, and 81 of them have been catalogued.

The below figure show the orbits of these fragments.


The google earth kml file can be download at here.

The perigee of these fragments are only 250km. The good news is these fragments will not stay at orbit for decades, so there will not be long term effects. The bad news is that they will eventually pass the International space station(ISS) orbit. It is very likely that the ISS will perform several more collision avoidance maneuvers to dodge these fragments.

It is actually third time that the Breeze M stages exploded since 2007. In each previous cases, nearly a hundred fragments was catalogued. These fragments stay at much higher altitude, and many of them would have lifetime for more than a thousand years.

The IADC space debris mitigation guidelines suggest that “Residual propellants and other fluids of (rocket bodies, satellites), such as pressurant, should be depleted” to avoid explosion. Apparently, Russian does not seem to do a good job.

IRAN’s second-ever domestically built satellite

image

Iran launched its second-ever domestically built satellite into orbit on June 15.   the U.S. Space surveillance network already published its orbit:

Semimajor Axis 6645.762 km

Eccentricity 0.0037

Inclination 55.6 deg

Click here to see its orbit in Google Earth.

Iran launched its first homemade satellite 2 years ago. That satellite was already decayed. Iran also bought a satellite from Russia, called SINAH 1. It is a communication satellite launched in 2005 at Plesetsk Cosmodrome. The satellite is still believe to be active.

SJ-12 and SJ-6H

Igor Lissov firstly found that the Chinese SJ-12 satellites will be likely to “meet” the SJ-6H, which is also a Chinese satellite launched last month(Oct-6th,2010), in the next few days.

The SJ-12 rendezvoused with SJ-06F on August 15, 2010.

See these two satellites at Google Earth.

SJ-12,SJ-6H

Orbits of Fragments from the iridium 33 Cosmos 2251 Collision

The collision between the Iridium 33 and Cosmos 2251 created roughly 2,000 fragments greater than 10 cm. 

The fragments from each satellite first spreads out along the orbit of the original satellite. But in time the debris spreads to form a shell around the earth, and is concentrated near the altitude at which the original satellites orbited. Since the relative speed of Cosmos 2251 fragments is higher, the orbit of the fragments spread out more quickly, and will be distributed around the Earth within 3 years. However, even orbits are not spread out, the fragments still threat all satellites that pass through that altitude.

image           image

See the orbits of these fragments at Google Earth.

7 days after the collision.

1 month after the collision.

3 months after the collision.

1 year after the collision.

3 years after the collision.

Evolution of Space Debris

This link gives a file, which shows evolution of all the 15,000 space objects in Google Earth.

You can use it to check whether you need update your computer Smile