Atlas V launches classified PAN satellite for US Government

A United Launch Alliance Atlas V rocket has launched with PAN, a classified satellite which will be operated by the US Government. The launch was on time, at the start of a two hour, nine minute launch window which opened at 21:35 GMT (17:35 local time). Unusually for an American government satellite, the agency responsible for operating the spacecraft has not been disclosed.

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PAN, which officially stands for “Palladium At Night”, is also known as P360. It is a communications satellite, which was built by the Special Programs division of Lockheed Martin Space Systems.

The satellite was constructed under a fixed-price, in-orbit delivery contract; meaning that Lockheed Martin is responsible for arranging launch services, and operating the satellite until it reaches its operational orbit. Because Lockheed Martin is the customer for the rocket rather than the US Government, the launch is officially considered to be commercial.

PAN was built around the A2100 satellite bus, and is reported to use commercial off-the-shelf components. The A2100 satellite bus was developed in the early to mid 1990s. The first A2100 to be launched was GE-1, which flew in June 1996. Most such satellites have a design life of fifteen years.

The contract to construct PAN was awarded in October 2006, with launch initially expected 30 months later, however it has since slipped a few months – mostly due to knock-on delays from earlier Atlas launches.

The orbit into which PAN will be launched has not been officially confirmed, however maps of the launch hazard area for the flight show that it will follow an azimuth usually associated with launches to equatorial orbits. As it is a communications satellite, it is therefore almost certain to be deployed into a geosynchronous transfer orbit, from which it will subsequently raise itself into a geostationary orbit. Typical A2100 satellites use LEROS-1C apogee motors to perform this manoeuvre.

PAN will lift off from Cape Canaveral’s Space Launch Complex 41; a launch complex which was originally built for the Titan IIIC rocket in the 1960s. It was first used in December 1965. During the mid 1970s, Titan IIIE rockets, which featured Centaur upper stages, were launched from SLC-41 with spacecraft including the Helios, Viking and Voyager probes. It was then converted for the Titan IV, which made its maiden flight from the complex in 1989.

The final Titan launch from the complex occurred in April 1999, and ended in failure when the upper stage malfunctioned. Later the same year, the pad’s towers were levelled in controlled explosions. Following conversion work, the Atlas V made its maiden flight from the complex in 2002.

Atlas V rockets are assembled in the Vertical Integration Facility, about 550 metres south of the launch pad, and are subsequently rolled out atop a mobile platform. AV-018, which will be used to launch PAN, departed the VIF at 14:06 GMT on 7 August, taking around half an hour to reach the pad. The countdown is scheduled to begin at 14:25 GMT Tuesday; five hours and ten minutes before the opening of the launch window.

An Atlas V 401 rocket will be used to conduct the launch; a configuration which consists of a single Common Core Booster first stage with no strap-on solid rocket motors, a Centaur upper stage powered by a single engine, and a payload fairing with a diameter of four metres. For this flight, a Large Payload Faring (LPF) will be used. This was originally developed for the Atlas III, and has a length of twelve metres.

Despite its name, it is the shortest payload faring available for the Atlas V. The Centaur has been painted white in order to provide better thermal protection during the coast phase of the flight than is provided by the usual orange-coloured variant.

The first stage will be powered by a Russian RD-180 engine, developed by NPO Energomash. It will ignite 2.7 seconds before launch, burning RP-1 propellant in liquid oxygen. At T-0 seconds, the rocket will be released from the launch pad and begin its ascent towards orbit. Seventeen seconds into the flight, it will begin manoeuvring to the correct attitude to achieve its target orbit. Seventy-nine seconds after launch, the rocket will be travelling at Mach 1, and twelve seconds later it will pass through the area of maximum dynamic pressure, max-Q.

Four minutes and three seconds after lifting off, the first stage will cut off, having depleted its fuel. Six seconds later it will be jettisoned with the aid of eight retro-rockets, and following a further ten seconds of coasting the Centaur’s RL10A engine will ignite for the first of two burns.

The RL10A was developed by Pratt and Whitney Rocketdyne, and burns cryogenic propellants – liquid hydrogen and oxygen. Eight seconds after the Centaur ignites the payload faring will separate, and at this point official updates on the status of the launch will be discontinued.

Seventeen minutes and twenty seven seconds after launch, the RL10A engine will shut down, completing the thirteen-minute and eight-second first burn. Shortly thereafter, it will be reoriented to a more suitable attitude for the coast phase of the mission, which will last for almost 100 minutes. At the end of the coast phase, the Centaur will again be reoriented, this time for main engine start.

The Centaur will restart for its second and final burn one hour, fifty five minutes and ten seconds after launch. The burn will last one minute and twenty six seconds, and will be followed by the upper stage reorienting for spacecraft separation. One hour, fifty nine minutes and twenty five seconds after lifting off, PAN will separate from the carrier rocket.

This will be the seventeenth launch of an Atlas V rocket, and the eighth to use the 401 configuration. It is also the third Atlas launch of 2009. The next Atlas launch is scheduled to occur from Vandenberg AFB towards the end of the month, carrying a DMSP weather satellite into low Earth orbit. The exact date for that launch is currently unclear, but is likely to be either 23 or 25 September.

Before that, ULA will use a Delta II rocket flying from Cape Canaveral to orbit the two STSS Demo satellites. The Delta launch is currently scheduled for midnight GMT on 18 September, and is being flown under a contract with NASA.

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