A pair of covertly developed inspector satellites to monitor collision threats and nefarious activities in geosynchronous orbit for U.S. Strategic Command blasted off Monday aboard a Delta 4 rocket.

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The next Delta 4 launch is the much-anticipated Heavy launch with NASA's Orion capsule on Exploration Flight Test No. 1, set to lift off from Cape Canaveral on Dec. 4.

MISSION SUCCESS. United Launch Alliance has announced tonight's flight of the Delta 4 rocket has successfully launched the AFSPC 4 mission. "The ULA team is proud to have delivered the twin Geosynchronous Space Situational Awareness Program (GSSAP) spacecraft to orbit today," said Jim Sponnick, ULA vice president, Atlas and Delta Programs. "We are privileged to work with a top notch U.S. government and contractor mission team that is committed to mission success."

The United Launch Alliance Delta 4 rocket has flown into a pre-arranged news blackout following jettison of the rocket's payload shroud. The veil of secrecy surrounding the launch of this clandestine satellite cargo means no further information about the progress of the ascent, upper stage engine firings or release of the payload will be announced in real-time.

T+plus 4 minutes, 49 seconds. The protective payload fairing enclosing the payload atop the rocket has separated.

T+plus 4 minutes, 34 seconds. The cryogenic RL10B-2 upper stage engine has ignited!

T+plus 4 minutes, 23 seconds. The Common Booster Core first stage and the attached interstage have been separated in one piece from the Delta 4's upper stage. The upper stage engine's extendible nozzle is dropping into position.

T+plus 4 minutes, 9 seconds. MECO! Main engine cutoff confirmed as the RS-68 powerplant shuts down.

T+plus 4 minutes, 5 seconds. The main engine is throttling down to its minimum power setting in preparation for shutdown.

T+plus 3 minutes, 5 seconds. Passing Mach 10.

T+plus 3 minutes. The main engine continues to perform well, consuming its liquid hydrogen and liquid oxygen propellants.

T+plus 2 minutes, 35 seconds. Passing Mach 5.

T+plus 2 minutes, 30 seconds. The RS-68 is consuming nearly a ton of propellants per second as the powerplant pushes the Delta 4 rocket closer to the edge of space.

T+plus 2 minutes. The vehicle weighs half of what it did at liftoff.

T+plus 1 minute, 44 seconds. Solid motor separation! The spent boosters have been shed from the first stage. Delta 4 continues powering its way toward space on the thrust generated by the RS-68 main engine.

T+plus 1 minute, 35 seconds. The twin solid rocket boosters have burned out of their propellant. Standing by for jettison.

T+plus 60 seconds. Now passing through the region of maximum aerodynamic pressure as the vehicle accelerates through the lower atmosphere.

T+plus 50 seconds. The launcher has broken through the sound barrier.

T+plus 30 seconds. The Delta 4 rocket is climbing away from Cape Canaveral with its main engine firing at full throttle and the two strap-on boosters giving a powerful extra kick.

T-minus 10 seconds, sequencer now controlling, 8, 7, 6, 5, ignition sequence start, 2, 1, and LIFTOFF! Liftoff of the Delta 4 rocket and the Air Force Space Command mission No. 4, providing space situational awareness in geosynchronous orbit. And the vehicle has cleared the tower!

T-minus 12 seconds. Residual hydrogen burnoff ignitors have been fired beneath the main engine.

T-minus 22 seconds. The steering system for the solid rocket motor nozzles has been activated.

T-minus 30 seconds. Green board. All systems remain "go" for launch.

T-minus 40 seconds. Upper stage liquid hydrogen tank is confirmed at flight level.

T-minus 55 seconds. The Air Force-controlled Eastern Range has given its "go" for launch.

T-minus 1 minute and counting. The ignition conditions for the RS-68 main engine are "go." Engine start comes at T-minus 5 seconds.

T-minus 75 seconds. The liquid hydrogen fuel tank on the upper stage is being secured for launch.

T-minus 80 seconds. Upper stage liquid oxygen tank has been secured at flight level.

T-minus 1 minute, 50 seconds. The first stage liquid hydrogen tank has reached flight level and pressure.

T-minus 2 minutes. The rocket's upper stage liquid oxygen tank is being secured.

T-minus 2 minutes, 30 seconds. The liquid oxygen tank in the first stage is confirmed at the proper level and pressure for flight.

T-minus 3 minutes and counting. Ordnance devices aboard the vehicle are being armed.

T-minus 3 minutes, 25 seconds. The systems of the first and second stages of the Delta 4 rocket have switched from ground-fed power to internal batteries for launch.

T-minus 3 minutes, 30 seconds. Replenishment of liquid hydrogen and liquid oxygen to the Common Booster Core first stage is being secured in preparation to pressurize the tanks for launch.

T-minus 4 minutes and counting! Now into the final phase of the countdown for liftoff at 7:28 p.m. by the Delta 4 rocket from pad 37B at Cape Canaveral Air Force Station.

Permission to launch has been granted by the ULA launch director and Air Force mission director.

Weather is observed GO and forecast GO for launch.

The final readiness polls of the launch team and mission managers have been completed. No technical problems are being worked and all rocket, spacecraft and ground systems are "go" for liftoff at 7:28 p.m. Just awaiting the final OK from the weather officer.

Standing by for the launch team readiness check for continuing the countdown.

The anvil cloud rule has gone GREEN. Just lightning is left to clear.

Now 12 minutes to launch! The launch team will be polled in the next few minutes to confirm all systems are "go" to press onward for 7:28 p.m. liftoff.

Launch minus 20 minutes!

The ULA launch team and management are guiding the countdown from the Delta Operations Center, located about 9,200 feet from the pad. The engineers overseeing the rocket and ground systems are located on the third floor and the Mission Directors Center room is on the fourth floor. Both rooms have a view of pad 37B and the Delta 4 rocket out their windows. Other rooms are also set up for engineering support.

The DOC was formerly built to support the Titan-Centaur program but was refurbished to support Delta 4.

Just waiting on anvils and lightning rules to clear. A final go from the weather may not come until just moments before picking up the countdown.

NEW TIME! Liftoff has been reset for 7:28 p.m. EDT.

The cumulus cloud rule has lifted.

Now expecting all the rules to be clear by 7:22 p.m.

The electrical potential rule just went GREEN.

The following rules are RED currently: electrical potential, lightning, anvils and cumulus clouds.

The team has caught up on activities, so they are holding for the weather.

The flight thru precip. rule just went GREEN.

Flight slews are complete.

The following rules are RED currently: electrical potential, flight thru precip., lightning, anvils and cumulus clouds.

The weather officer expects the RED rules to clear around 7:15 p.m. EDT.

HOLD EXTENDED. This hold has been extended at least a few minutes to wait for the weather to clear.

The launch conductor has given a briefing to the launch team for procedures inside the final four minutes of the count.

The flight slews and commanding tests for the vehicle steering systems are underway. The first stage Common Booster Core, the strap-on solid rocket motors and upper stage engine steering checks were run through a pre-launch test pattern.

The Phase 2 lightning warning for the launch pad area has been lifted.

T-minus 4 minutes and holding. The countdown has entered the planned 15-minute hold leading toward the 6:43 p.m. EDT liftoff of the Delta 4 rocket.

This pause is designed to give the launch team the opportunity to catch up on any work running behind schedule and verify all is in readiness for the final moments of the count. A series of management polls will be conducted during the hold to give approval to proceed with the launch.

The weather officer expects the RED rules to clear around 6:50 p.m. EDT and the Phase 2 lightning warning to lift around 6:25 p.m.

The countdown is entering the final 30 minutes until the Delta 4 rocket launch from Cape Canaveral at 6:43 p.m. EDT. Here's a look at some stats about today's mission. This will be:

• The 368th Delta rocket launch since 1960
• The 27th Delta 4 rocket mission since 2002
• The 12th Medium+ 4,2 configuration to fly
• The 41st main engine from RS-68 family used
• The 41st-42nd GEM-60 solid rocket motors flown
• The 449th production RL10 engine to be launched
• The 30th RL10B-2 engine launched
• The 22nd Delta 4 rocket launch from Cape Canaveral
• The 22rd use of Delta 4 by the Air Force
• The 73rd Evolved Expendable Launch Vehicle flight
• The 85th United Launch Alliance mission since 2006
• The 33rd ULA launch for the Air Force
• The 20th Delta 4 under the ULA banner
• The 8th ULA launch this year
• The 4th launch of the Delta family in 2014
• The 1st and 2nd GSSSAP satellites
• The 1st secondary payload ring on Delta 4

There is an isolated storm moving across the Cape. The following rules are RED currently: electrical potential, flight thru precip., lightning, anvils and cumulus clouds.

Now 45 minutes till launch. The Delta 4 rocket launching GSSAP and ANGELS is known as the Medium+ (4,2) model. It has a common first stage with two solid rocket boosters, a cryogenic second stage and a 4-meter-diameter payload shroud.

The first stage is fueled by supercold liquid hydrogen and liquid oxygen. The RS-68 main engine, made by Aerojet Rocketdyne, generates about 663,000 pounds of thrust. Known as the Common Booster Core, or CBC, the stage measures about 150 feet in length, 16 feet in diameter and weighs 54,000 pounds unfueled.

The strap-on solids are known as Graphite Epoxy Motors, or GEM 60s, built by ATK. They are five feet in diameter, 53 feet long and generate 280,000 pounds of thrust each.

The second stage features a restartable Aerojet Rocketdyne RL10B-2 engine burning liquid hydrogen and liquid oxygen. The total thrust is 24,750 pounds.

Protecting the payload during atmospheric ascent is the payload fairing measuring 39 feet in length and 13 feet in diameter. It is a composite nose cone built in two halves.

The Delta 4 stands 205 feet tall, weighs 721,000 pounds at launch and generates about 1.2 million pounds of thrust at liftoff.

A Phase 2 lightning warning has been issued for the pad area. The following rules are RED currently: electrical potential, flight thru precip. and cumulus clouds.

Vehicle propellant conditioning for flight is complete.

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The flight hazard area has been established.

Now entering into the final 75 minutes of the countdown to launch of Delta 368 and the Geosynchronous Space Situational Awareness Progress satellites.

The rocket stands fueled and ready for launch at 6:43 p.m. EDT today.

A check of the weather shows only two rules RED right now: lightning and cumulus clouds.

If you are need tips on picking a good viewing spot, check out this authoritative guide on where to go.

Engineers are conducting the standard evaluation of the Delta 4 rocket's thermal insulation following the loading of supercold propellants into the vehicle.

The vehicle is fully fueled! Loading of the upper stage liquid oxygen tank has been accomplished.

Now two hours until launch.

The first stage liquid oxygen loading just finished. The tank has been loaded with its supercold oxidizer that is chilled to Minus-298 degrees F. Topping will be completed as the count rolls on.

A check of the weather shows a current NO GO condition for various rules. The launch time forecast still calls for scattered decks of clouds, thunderstorms in the vicinity, westerly winds of 15 to 22 knots and a temperature of 85 degrees F.

Loading of the upper stage liquid hydrogen tank has been accomplished as fueling proceeds this afternoon at Complex 37. The launch team has filled the tank with propellant for the RL10 engine.

Fast-filling of the first stage liquid hydrogen tank is complete. After post-filling checks and valve tests, the tank will be placed in topping mode. The launch team will confirm the propellant is conditioned for flight.

The Delta 4 rocket's Common Booster Core first stage and upper stage are being loaded with supercold liquid oxygen and liquid hydrogen.

Complex 37 has two giant sphere-shaped fuel tanks to store the cryogenic liquid oxygen and liquid hydrogen. The LOX tank holds 250,000 gallons and LH2 sphere about 850,000 gallons.

The cryogenics are fed from the storage tanks through pipelines to the pad. For the Common Booster Core, the propellants are routed up to the launch table upon which the rocket sits. Tail service masts, the large box-like structures at the base of the vehicle, feed the oxygen and hydrogen to the booster via separate umbilicals.

The upper stage receives its cryos from the middle swing arm that extends from the Fixed Umbilical Tower to the front-side of the rocket.

Chilldown of the upper stage liquid oxygen system is complete for loading the rocket's tank. This is the last of the rocket's four cryogenic supplies to be filled in today's countdown to launch.

The Phase 2 lightning warning for the launch pad area has ended.

Chilldown is complete on the upper stage liquid hydrogen system.

The "go" has been given for the upper stage liquid oxygen chilldown in advance of filling that tank.

The first stage liquid oxygen chilldown is complete. "Slow-fill" mode is beginning to load a small percentage of the tank. The process then speeds up to the "fast-fill" mode until the tank is nearly full.

The launch team is preparing to start fueling the Delta 4 rocket's upper stage. The "go" has been given to start the chilldown conditioning of the upper stage liquid hydrogen system.

A Phase 2 lightning warning for the launch pad area is going into effect through 4 p.m.

First stage liquid hydrogen tanking operation is switching from "slow-fill" to "fast-fill" mode.

And now the chilldown of Delta's first stage liquid oxygen system is starting. This preps the tank and pumping to guard against shock when the supercold oxidizer begins flowing into the rocket a short time from now.

The cold gas chilldown conditioning of the liquid hydrogen system has been accomplished. Liquid hydrogen propellant will begin to flow into the first stage in "slow-fill" mode. That is sped up to "fast-fill" after a small portion of the tank is loaded.

Chilled to Minus-423 degrees Fahrenheit, the liquid hydrogen will be consumed by the RS-68 main engine along with liquid oxygen during the first four minutes of the launch.

And fueling operations have begun. The hydrogen system's cold gas chilldown conditioning is underway.

A "go" has been given to start the cold gas chilldown conditioning of the first stage liquid hydrogen system. This is the precursor to filling the vehicle with propellant.

The following rules are RED: lightning, electrical potential, cumulus clouds and flight thru precip.

A check of the weather shows some isolated storms moving into the area. The weather board is RED for lightning at the current time.

T-minus 4 hours, 15 minutes and counting! The team has been polled and is ready for cryogenic fueling as the countdown is underway for today's opportunity to launch the Delta 4 rocket with the GSSAP satellites.

The launch team is manning stations for the start of fueling operations.

T-minus 4 hours, 15 minutes and holding. The countdown has entered a 15-minute built-in hold, a pre-planned pause designed to give the team time to catch up on any work that could be running behind schedule.

A check of the current weather shows the storms are more scattered and isolated today. The forecast for launch time predicts a 60 percent chance of acceptable weather.

The rocket's avionics have been turned on, preparations to load liquid hydrogen and liquid oxygen are underway and the launch pad has been cleared of all workers as the countdown begins.

The 330-foot tall mobile service tower has been retracted from the Delta 4 rocket at Cape Canaveral's pad 37B for this evening's launch that will place the GSSAP geosynchronous orbit surveillance satellites into space.

The wheeled structure just moved along rail tracks to its launch position about the length of a football field away from the rocket. The 9-million pound tower shielded the Delta from the elements during the its stay on the pad, provided workers 360-degree access to the various areas on the vehicle and was used to attach the strap-on solid motors and the payload during the launch campaign. The tower is 90-feet wide and 40-feet deep.

Crews will spend the next couple of hours securing the complex for launch before leaving the danger area around the pad. All workers must be clear of the area for the start of hazardous operations in the countdown, which include fueling the Delta 4's Common Booster Core first stage and the second stage with supercold liquid oxygen and liquid hydrogen propellants.

Testing of communications links between the rocket and Air Force Eastern Range will occur after fueling is accomplished. Steering checks of the first stage RS-68 engine and second stage RL10 powerplant are on tap in the last hour of the count.

A build-in hold is slated for T-minus 4 minutes, during which time teams will go through final polling to grant clearance to launch. The Delta 4 will transition to internal power as the count resumes, ordnance will be armed and the propellant tanks pressurized as clocks target the main engine ignition time at T-minus 5 seconds.

Liftoff remains scheduled for 6:43 p.m. EDT (2343 GMT).

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Read our earlier status center coverage.