DF-26 东风-26

choi

Liu Xuanzun, Missile Launch Shows China's DF-26 Able to Adjust Position Mid-Flight, Attack Moving Aircraft Carriers: Expert. Global Times, Jan 27, 2019.
http://www.globaltimes.cn/content/1137152.shtml

Note:
(a)
(i) 环球时报中文版 has not published a corresponding report.
(ii) 东风-26弹道导弹发射画面首次曝光 弹头细节清晰. 央视网, Jan 24, 2019 (video)
news.cctv.com/2019/01/24/VIDEg6GaFDUCtgz9CWjszwQH190124.shtml
("日前，央视曝光了火箭军某导弹旅从中原腹地，千里机动成建制展开野外驻训，进行导弹实射的画面。画面中的导弹就是东风-26中远程弹道导弹，发射全程震撼，导弹弹头细节清晰可见")

There is no need to watch it, because the video clip only shows the boost phase, without the critical parts how the missile may alter trajectory or seek a moving target.

(b) "China has inducted the world's first operational anti-ship ballistic missile, a 'carrier killer' capable of carrying a nuclear warhead, known as the DF-21D[:] In 2010, it was reported that China had entered the DF-21D into its early operational stage for deployment.  The DF-26 or 'Guam Killer,' first revealed in 2015, is also able to carry anti-ship warheads * * * to attack medium and large naval vessels out to ranges of 3500 km to 5000 km."  en.wikipedia.org for "anti-ship ballistic missile")

Please note the emphasis is on the 'ballistic" of "anti-ship ballistic missile."

(c) "Anti-ship missiles are guided missiles * * * Most anti-ship missiles are of the sea skimming variety, and many use a combination of inertial guidance and active radar homing. A good number of other anti-ship missiles use infrared homing to follow the heat that is emitted by a ship [passive homing]; it is also possible for anti-ship missiles to be guided by radio command all the way [semi-active homing]."  en.wikipedia.org for "anti-ship missile."
(i) "Most anti-ship missiles are of the sea skimming variety." That is, anti-ship missiles are definitely not ballistic missile. Most sea-skinning types are cruise missiles, but not necessarily so: such as an example given in this Wiki page: infantrymen firing shoulder-launched missiles. Cf HSV-2 Swift
https://en.wikipedia.org/wiki/HSV-2_Swift
(The HSV stands for "High Speed Vessel;" section 4.1 Attack off the coast of Yemen)
(ii) I talked about this before, and will not repeat it here. Search images.google.com with (active  semi-active  passive homing) -- no quotation marks. A summary: active (radar) homing of a missile indicates its head carries a radar to detect the target. Semi-active (radar) homing refers to a missile receiving and relying on radar reflection emitted by another source: the airplane that shoots the missile or ground radar. Passive homing means a missile that has a receiver to detect infrared or sound emitted by the target.
(A) All laser guidance for a missile is semi-active: the laser pointer comes from another source, not the missile itself.
(B) The disadvantage of active radar homing is described in semi-active radar homing
https://en.wikipedia.org/wiki/Semi-active_radar_homing
(section 1 Concept)
(iii) Modern TORPEDOES also uses three types of homing: active, semi-active and passive.
(A) Both active and semi-active homing in a torpedo uses, in lieu of a radar, sonar -- from, respectively, the torpedo itself and the submarine that launches the torpedo.  Passive homing in a torpedo means the torpedo carries a receiver to detect sounds (acoustic torpedo) or heat (infrared torpedo) emitted by the target.
(B) Sonar
https://en.wikipedia.org/wiki/Sonar
("Active sonar creates a pulse of sound, often called a 'ping,' and then listens for reflections (echo) of the pulse. This pulse of sound is generally created electronically using a sonar projector * * * A beamformer is usually employed to concentrate the acoustic power into a beam, which may be swept to cover the required search angles")
(C) "Homing 'fire and forget' torpedoes can use passive or active guidance, or a combination of both. Passive acoustic torpedoes home in on emissions from a target. Active acoustic torpedoes home in on the reflection of a signal, or "ping", from the torpedo or its parent vehicle; this has the disadvantage of giving away the presence of the torpedo. In semi-active mode, a torpedo can be fired to the last known position or calculated position of a target, which is then acoustically illuminated ("pinged") once the torpedo is within attack range."  en.wikipedia.org for torpedo.

choi

(d)
(i) "An inertial navigation system (INS) is a navigation device that uses a computer, motion sensors (accelerometers) and rotation sensors (gyroscopes) to continuously calculate by dead reckoning the position, the orientation, and the velocity (direction and speed of movement) of a moving object [missile here] without the need for external references. * * * relative to a known starting point, orientation and velocity."  en.wikipedia.org for "inertial navigation system."

That is the take-away message. There is no need to know how it is done, because I have tried for years but can not,
(ii) missile guidance
https://en.wikipedia.org/wiki/Missile_guidance
(section 4.3 Astro-inertial guidance: "The astro-inertial guidance is a sensor fusion/information fusion of the inertial guidance and celestial navigation. It is usually employed on submarine-launched ballistic missiles. Unlike silo-based intercontinental ballistic missiles, whose launch point does not move and thus can serve as a reference, SLBMs are launched from moving submarines, which complicates the necessary navigational calculations and increases Circular error probable. This stellar-inertial guidance is used to correct small position and velocity errors that result from launch condition uncertainties")
(iii) The following is an old paper, but the quotation probably remains true today. There is no need to read the rest of (d)(iii) or (iv).

William H Licata, INS/GPS for Strike Warfare Beyond the Year 2000. Paper presented at the RTO SCI Lecture Series on "Technologies for Future Precision Strike Missile Systems" held in June 2001 and published in RTO-EN-018, at page "4-1" (ADPO10954).
https://apps.dtic.mil/dtic/tr/fulltext/u2/p010954.pdf
("Moving or relocatable targets cannot be attacked with a weapon guided solely by INS/GPS. These targets require a seeker to correct for target location uncertainty. However, INS/GPS can help reduce the complexity of the relocatable target acquisition problem for the seeker of choice")
(iv) Chapter 15 Guidance and Control. In David R Frieden (ed), Fundamentals of Naval Weapons Systems. Weapons and Systems Engineering Department, United States Naval Academy, 1985
https://fas.org/man/dod-101/navy/docs/fun/part15.htm
("Homing is the most accurate of all guidance systems because it uses the target as its source when used against moving targets")

choi

(e)
(i) ballistic missile flight phases
https://en.wikipedia.org/wiki/Ballistic_missile_flight_phases
(boost phase _ post-boost phase + midcourse phase + terminal phase; "the post-boost phase when any last-minute changes to the trajectory are made by the upper stage or warhead bus and the warheads and any decoys are released")
(ii) ballistic missile
https://en.wikipedia.org/wiki/Ballistic_missile
("section 3 Advantages: "The course taken by ballistic missiles has two significant desirable properties. First, ballistic missiles that fly above the atmosphere have a much longer range than would be possible for cruise missiles of the same size. Powered rocket flight through thousands of kilometers of air would require vastly greater amounts of fuel, making the launch vehicles larger and easier to detect and intercept. Powered missiles that can cover similar ranges, such as cruise missiles, do not use rocket motors for the majority of their flight, but instead use more economical jet engines. However, cruise missiles have not made ballistic missiles obsolete, due to the second major advantage: ballistic missiles can travel extremely quickly along their flight path. An ICBM can strike a target within a 10,000 km range in about 30 to 35 minutes. With terminal speeds of over 5,000 m[eters]/s, ballistic missiles are much harder to intercept than cruise missiles, due to the much shorter time available. Therefore, ballistic missiles are some of the most feared weapons available, despite the fact that cruise missiles are cheaper, more mobile, and more versatile")

(f)
(i) "Ballistic missiles have a prescribed course that cannot be altered after the missile has burned its fuel, unless a warhead maneuvers independently of the missile or some form of terminal guidance is provided. A pure ballistic trajectory limits the effectiveness of a chemical or biological attack because, generally, the reentry speed is so high that it is difficult to distribute the agent in a diffuse cloud or with sufficient precision to ensure a release under the shear layer of the atmosphere. In addition, thermal heating upon reentry, or during release, may degrade the quality of the chemical or biological agent. U.S. experience has shown that often less than 5 percent of a chemical or biological agent remains potent after flight and release from a ballistic missile without appropriate heat shielding."
Ballistic Missile Basics. Federation of American Scientists, June 4, 2000
https://fas.org/nuke/intro/missile/basics.htm

The key is "after the missile has burned its fuel." So the last chance to alter trajectory of a ballistic missile is post-boost phase, mentioned in (e)(i).
(ii) But how?
(A) Examples of Control. NASA, undated (rocket)
https://www.grc.nasa.gov/www/k-12/rocket/rktcontrl.html

View only the graphic, which is self-explanatory, Control of a missile is the same, except that a ballistic missile in the space can not use aerodynamics (movable fin). You do not even have to understand the term used in the graphic. See next.
(B) thrust vectoring
https://en.wikipedia.org/wiki/Thrust_vectoring
("also thrust vector control or TVC * * * In rocketry and ballistic missiles that fly outside the atmosphere, aerodynamic control surfaces are ineffective, so thrust vectoring is the primary means of attitude control")

section 1 Thrust vectoring methods, section  1.1 Rockets and ballistic missiles: "Thrust vectoring can be achieved by four basic means:
Thrust vectoring can be achieved by four basic means:
Thrust vectoring can be achieved by four basic means:[2][3]
• Gimbaled engine(s) or nozzle(s)
• Reactive fluid injection  [obsolete]
• Auxiliary engines (fixed or movable)
• Exhaust vanes"


F-35B uses TVC to achieve vertical take-off and landing (VTOL). See Pratt & Whitney F-135
https://en.wikipedia.org/wiki/File:Jet_engine_F135(STOVL_variant)%27s_thrust_vectoring_nozzle_N.PNG
, the engine that Pratt & Whitney developed for F-35B.