Second Sun

"What do we do now man?! Russian's got us outnumbered, shit's fallin' from the sky. We're screwed man, we are totally--" "Shut up! Get a grip Corporal. Our weapons still work, which means we can still kick some ass."

- Corporal Dunn and Sergeant Foley

Second Sun is the thirteenth level of Call of Duty: Modern Warfare 2.

Walkthrough
You start out just seconds before you left off in Of Their Own Accord where Pvt. Ramirez's team has just been shot down and is now defending its position. As Russian forces approach you, a search light whites-out the screen, then you play briefly as Sat1, an unnamed astronaut on an EVA mission outside the International Space Station (ISS). Mission Control in Houston asks you to look toward the dark side of the Earth for a bogey (the SLBM that Captain Price launched). You observe the missile's path until it eventually detonates in the atmosphere above Washington D.C. The shockwave soon reaches the ISS and destroys both the station and you. The explosion causes an EMP (electromagnetic pulse) that blacks out all the East Coast (except Florida), but it also saves the lives of many U.S. Army Rangers back in Washington. Aerial vehicles start to fall from the sky as your team makes its way to a building for shelter. After everything goes quiet, an Army runner tells the team to get to location Whiskey Hotel (aka White House). After plowing through some remaining Russian personnel in an office building, you get to the President's secret bunker under the East Wing.

Weapon Loadout
In this level, the player starts with an M4A1 Carbine with a Holographic Sight and M203 Grenade Launcher and an M9. However, there are three M4A1 Carbines with just M203 Grenade Launchers in the streets.

In the Streets
More Detailed Walkthrough

After all the fighting and the International Space Station scene, one of your men will remove the steel girders infront of the Heli preventing you from exiting it. After that, a large number of aircraft begin falling from the sky. Run with your allies to find cover, and stay away from the vehicles because they blow up as well. After a while, the debris of Planes and Helicopters are gone.

Follow your soldiers. Ahead, theres an Ammo Crate (which you'll need because you have no ammo). Also, you may note that your Red Dot isn't working (EMP effect), so its suggested you swap it with a Non-Red Dot weapon (unless you can aim without it). You'll see some guy running, telling you guys to go to Whiskey Hotel (aka White House) because your allies need assistance.

You'll reach an office filled with Russians. Shoot them down and move on. You'll reach outside where it appears to be raining. 3 Tangos are ontop of a vehicle arguing. Take them by surprise. Up ahead, you'll see some people running to a Bus, unknown if they're hostile or not. Foley throws one of the Flares on the ground, and it reveals the targets are hostile. Shoot them as well.

After you kill them all, move up. Enter the hole you see, and take point. You'll discover the President's "secret bunker", and the mission ends here.

Trivia

 * The timer in this level is 18:57 (6:57pm), 22 minutes after the timer in "Of Their Own Accord", 18:35 (6:35pm). Just for fun, if you are able to clear the previous two levels in under 22 minutes, the timelapse of these events should be accurate.

Last Stand

 * When you wake up in the chopper at the start of this level, your vision starts off clear, while in "Of Their Own Accord" it starts off mostly blurred.
 * Whether or not this goes throughout the entire game, when you are given the M4A1 at the beginning of the level, you can see for a brief moment that the third-person model has retained its iron-sights even though it is attached to a Holographic sight. However as soon as you pick it up from the soldier giving it to you, the first-person model is what a M4A1 with Holographic sights should look like, meaning the iron sights disappear.
 * If you look carefully, the Ranger who gives you a weapon after the crash may be different from the one who gave you the weapon in the mission Of Their Own Accord. This is because Pvt. Wade's appearance is randomly generated.
 * If you try to throw a grenade at the beginning of the level, it will say "No M2 Frag Grenades" just as in S.S.D.D.
 * When Foley throws you a magazine for your gun while you are trapped in the helicopter, the previous magazine given to you by Pvt. Wade disappears mysteriously. This most likely happens because Ramirez is supposed to use all of the magazine.
 * It is unusual that Sgt. Foley is carrying an M4A1 magazine considering he is using a SCAR-H and the two weapons use different types of ammunition, as well as having magazines in different shapes. One explanation is that it could be a 5.56 SCAR-L magazine, which can fit into a M4A1, or that he picked it up earlier/from one of the soldiers around him.

Low Orbit

 * The part where you control Sat1 was supposed to be in a separate level/interactive cutscene called "International Space Station", similar to The Coup and Aftermath. It was merged with this level in the final version of the game for unknown reasons.
 * The in-game appearance of ISS is modeled after the configuration the station from 2002-2005. The current configuration (as of November 2009) is different, in that the Station is slightly larger, with the second node and the European and Japanese labs installed and the P6 Solar Arrays have been relocated from the top of the Z1 truss as seen in-game to the port side of ISS, with another set of solar arrays on the starboard side. The 2009 configuration is actually close to how the station will look when completed in 2011.
 * The astronaut in the ISS scene appears to be grappled to some sort of a satellite. Such a spacewalk would be impossible to conduct from ISS, as all spacewalks conducted on ISS are tethered, where the astronaut is connected physically to the station, and it would be impractical to investigate a satellite from the ISS.
 * The crew of ISS as seen in game appear to be American. As ISS is an international venture, there are typically astronauts from all nations on board, and every ISS crew to date has included at least one Russian astronaut (or "cosmonaut"). It's possible with the political situation in Russia, space flights to ISS were suspended, although two Russian Soyuz spacecraft can be seen docked to the station. However, the spacecraft being docked is entirely plausible as the Soyuz are launched on a six-month basis (thus would have been launched just prior to the unrest) and remain up there until just before the next craft is launched for use as "escape pods" in case of an emergency.
 * If you (Sat1) don't look to the right as told, ISS Control will say "Sat1, rotate your view a little to the right, will ya?" And you only need a glance at the missile.
 * When "controlling" the astronaut, if you look anywhere but where the missile is coming from, ISS will say: "Sat1, rotate your view a little further to the right would ya?". Also, the missile seemingly will not appear until you look to the right, so no matter how long you keep looking left, the missile won't explode. If you look just a little, you can see the light from the missile at the horizon, but it won't fly any further.
 * While the concept of a low-orbit nuke detonating and causing a wide-spread EMP is feasible, no shockwave would ever reach the ISS because, at perigee (closest approach to earth) it is at 341 km altitude. The station would eventually be damaged by the electromagnetic pulse, and the heat from the nuke can damage the ISS, or even ignite the oxygen on board.
 * The EMP apparently did not knock out power in southern Georgia or Florida because you can see the lights when you are Sat1.

EMP

 * When helicopters are falling from the sky, you have unlimited sprint. Interestingly, you don't have unlimited sprint when replaying the level on the PC version.
 * The player cannot remain outside, despite avoiding the helicopters. If they look up, they will see a never-ending stream of helicopters falling from the sky (from altitudes no normal helicopter would fly at). One of these, a Little Bird, will actually "track" the player and will always crash close enough to kill them, regardless of where they are on the street.
 * As soon as you are released from the downed helicopter, turn left until you are on a grassy patch. If you quickly look up, a Little Bird will drop on you at an incredibly high speed. It seems to fall faster each time you spawn and run back to the same area.
 * After the EMP goes off your Holographic sight is immediately disabled (it contains an integrated circuit and is unshielded) while the helicopter and lights are still active. Also, the lights in the White House are still operational, yet the EMP shuts off power to nearly the entire East Coast (This alludes that the White House and everything within is shielded against EMP attacks).
 * An interesting thing to note is that the red dot is already down the moment you return to Ramirez.
 * Oddly enough, Cpl. Dunn yells "EMP!" when the debris is falling, but later on, he questions the "Red Dot" is working. This might be that Dunn does not completely know what an EMP does.
 * Dunn is the first to notice that optics are offline, saying "Hey, is your Red Dot workin'? Mine's out." However, if you look at his weapon, you'll see he is actually using a Thermal Scope, which appears to be working. Also, none of the other Rangers have Red Dot sights.
 * As with Game Over, there is a way to obtain three weapons. As the helicopters start falling, run to the area where the first helicopter crashes dangerously close to Dunn. If you maneuver around it carefully, you should be able to pick up an enemy weapon (Often an AK-47 or a FAL). Continue on as normal until you get to cover inside the building. When a deafening explosion goes off behind you, you gain max ammo in your M4 and you gain an M9, while also keeping your third weapon. Feel free to keep them for as long as you want and swap them out for other weapons.
 * The Boeing that crashes outside of the building where you take cover makes strange noises as you approach it, likely because of the metal warping under such intense heat.

Aftermath

 * When you run inside the cafe to take cover from the falling debris, your M4A1 automatically reloads and you pick up grenades and flashbangs, as there is a sizable ammo cache within.
 * There is a glitch when after Cpl. Dunn leaves the building after the little bird crashes blocking the way you came in, if you look to the left of the bus there is a police car that has not been destroyed by the EMP. This was most likely overlooked by Infinity Ward due to the fact that you most likely would not look towards that direction if you are trying to beat the level as fast as possible.
 * There is a scene during the helicopter rain where a US Ranger falls on top of a police car and it blows up on impact. If you are quick enough and put your crosshairs on him it will flash his name showing he is alive when he falls on the car. This could have been done to show the severity of the EMP (Ranger fell off the helicopter he was riding) or as an attempt at dark comedy by Infinity Ward.
 * Just before meeting the runner, you can see the traffic lights are still blinking red, even though the EMP was supposed to destroy all electronics.
 * Like in "Wolverines!", it is rumored that Ramirez can be heard speaking. After Cpl. Dunn says, "Is your red dot working? Mine's out." A ranger can be heard replying "Mine's out too, this is weird bro." This can be heard from anywhere, including the office in which you receive more ammunition for your M4A1. As with other trivial dialogue, no one's mouths move.
 * The aircraft on the street ahead that Cpl. Dunn comments on is a Boeing 777-200ER, which ironically is a fly-by-wire aircraft. This explains why it was downed so quickly after the EMP hits.
 * Swap the M4A1 holographic with a standard M4A1 with iron sights to make aiming easier and more accurate. One is found lying next to a dead Ranger on the street, and another is located by the ammo crate inside the offices.

Offices

 * Many of the buildings in this level and the next level have pictures of William Henry Harrison, the President who served the shortest term, after dying only a month into office.

Outside

 * At one part in the level you kill three men trying to open what looks like a fried BTR-80, After you kill the men Cpl. Dunn says, "What about the guys inside?" Sgt. Foley responds, "What about 'em?" If you listen closely you can hear trapped Russian soldiers banging on the inside walls and saying something in Russian. They only say this once when triggered and they do not speak again after. Dunn's remark about the Russians in the BTR could be a nod to earlier Call of Duty installments. In earlier titles, allied characters would always finish off a stricken vehicle by throwing a grenade down the hatch. However another possible alternative reason is that because the BTR's doors open electronically (bad design for emergency escapes). The Russians inside are trapped in a steel coffin, and will probably suffocate slowly.
 * Also, if the player fires at the BTR prematurely, the Russian soldiers both inside and outside the vehicle will not notice.
 * It is odd how the soldiers trying to get the soldiers out of the BTR don't even hear the gunfire happening in the office building less than 100 meters from their position. However, there was torrential rainfall in the area at the time.
 * If you happened to retrieve RPGs from the soldiers in the offices, they do no damage to the BTR.
 * It is strange that near the area where Foley sees several unidentified soldiers near the bus, there is a pickup truck with the twisted remains of a WWII-era M1919 Browning machinegun loaded in the back. It is possible that the pickup truck armed with a machinegun was used by local civilian resistance to defend themselves against the Russian forces. There is another one by the crashed plane by the cafe.
 * If you fire at the unidentified soldiers near the bus before the whole scene plays out, Foley will still throw the flare at them, even though they are shooting at him.
 * When you get to the President's bunker under the Eisenhower building Cpl. Dunn says he thought it was under the West Wing, but Sgt. Foley says that one's "for tourists" and this one must be the real thing. In a real map, the Eisenhower Building is actually west of the White House. When you start the next level, Whiskey Hotel, you somehow start east of the White House when in this level you ended west.
 * The President's bunker door is unrealistically thin, and looks like it could easily be destroyed by explosives. The roof is also too thin; no way would a bunker for such a high-profile person be penetrated so easily by what appears to be either a mortar or Howtizer round.

Miscellaneous

 * This is the only level, besides No Russian, that contains no intel.
 * This is the only level where you control two characters within the same level.
 * In the briefing part of the level, Shepherd is talking to the Secretary of Defense about the incoming ICBM possibly destroying Washington D.C., stating that "we've rebuilt it before, we can rebuild it again." This is a reference to the War of 1812 between the U.S. and Great Britain, in which the British burned down the White House.
 * As in Exodus and "Wolverines!" it is implied that during the five years in between Call of Duty 4, and Modern Warfare 2 there was a Second Cold War.
 * Ramirez sustained severe injuries to both hands, yet this doesn't affect his aim or use of weapons in the slightest. The gashes can be seen throughout this level when reloading or switching weapons. However, in the next level, Whiskey Hotel, it seems that they have been treated and/or he has been issued a new pair of gloves.
 * After leaving the building where you take shelter from the falling helicopters, if you look at the newspost, the headline for the newspapers reads "Call of Duty 2."