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Beginning the National Reconnaissance Office’s campaign of four launches in 2016 using boosters big and small to deploy a varied collection of new intelligence satellites, a Delta 4 rocket stands ready for liftoff before sun-up Wednesday from California.

Liftoff of the United Launch Alliance vehicle is targeted to occur at 3:39 a.m. local (6:39 a.m. EST; 1139 GMT).

There is a 100 percent chance of allowable launch weather both Wednesday and the backup flight opportunity on Thursday.

The mission originates from the storied Space Launch Complex 6, the site once constructed for the Manned Orbiting Laboratory space station in the 1960s and the Air Force’s West Coast space shuttle program in the 1980s. Both were cancelled before a single launch.

But today it is home to the Delta 4 rocket, which will fly from Vandenberg for the sixth time and carry a classified payload into orbit for the National Reconnaissance Office.

The NRO is the secretive government agency responsible for the country’s fleet of spy satellites, operating electro-optical imaging, radar-imaging, eavesdropping and naval surveillance spacecraft and data-relay birds for persistant overhead intelligence-gathering.

“We are excited and ready to take on our first Delta launch of 2016,” said Col. J. Christopher Moss, 30th Space Wing commander at Vandenberg and the launch decision authority.

“We are proud to showcase this national capability and everyone involved has been working tirelessly to ensure this launch is a safe and successful one.”

This latest launch, known as the NROL-45 mission, almost certainly will deploy the fourth in a series of next-generation radar-imaging reconnaissance satellites, said Ted Molczan, a respected expert in satellite observing.

Known to the public as Topaz, this program operates the Boeing-built craft in backwards, retrograde orbits 685 miles high at 123 degrees inclination to the equator.

Hobbyist sky-watchers around the world easily observe the Topaz satellites and compare tracking data via the Internet.

The Delta 4 rocket’s upper stage will perform two firings to reach the intended orbit and deploy the payload less than 90 minutes after liftoff.

Based on previous experience, the spent stage then executes a deorbit burn to remove itself from space and plunge back into the southern Indian Ocean on its second orbit.

Radar satellites offer all-weather, day-and-night imaging for reconnoitering global hotspots to inform policy makers and warfighters.

These new, advanced spacecraft follow the legacy of five “Lacrosse” radar birds put up into standard, posigrade orbits by the space shuttle Atlantis and Titan 4 rockets between 1988 and 2005.

Lacrosse No. 5 remains in orbit and, presumably, continues in use, according to hobbyist sky-watchers.

The updated Topaz satellite design is smaller and lighter, enabling the craft to fly aboard mid-sized boosters.

Atlas 5 and Delta 4 rockets launched from Vandenberg have shared the lifting duties for Topaz since 2010. A fifth and final launch of the current series is planned for next year.

The NRO has a total of four missions scheduled this year at Vandenberg and Cape Canaveral Air Force Station in Florida.

NROL-45

Delta 4 Medium+(5,2)

Vandenberg

Wednesday

NROL-37

Delta 4-Heavy

Cape Canaveral

May 12

NROL-61

Atlas 5 (421)

Cape Canaveral

June 24

NROL-79

Atlas 5 (401)

Vandenberg

Dec. 1

The variety of booster sizes indicates the different types of payloads and their targeted orbits around the Earth.

The NRO has used the Atlas 5 rocket 12 times out of the vehicle’s 61 flights. Wednesday will mark the 9th Delta 4 rocket for the NRO in 31 launches.

Both boosters have been the workhorses for the NRO in recent years since retirement of the heritage Atlas 2 and 3 programs and the Titan 4 heavy-lifter.

For ULA, this will be the company’s second launch in less than a week. An Atlas 5 rocket propelled a Global Positioning System satellite into orbit last Friday from the Cape.

See earlier Delta 373 coverage.

Our Delta archive.