The countdown for the final space shuttle launch began Tuesday at 1 p.m. EDT, starting at the T-43 hour mark. However, the launch-day weather forecast looks less than favorable for Friday's 11:26 a.m. liftoff.

At the 10 a.m. precountdown status briefing this morning, NASA Test Director Jeremy Graeber reported space shuttle Atlantis is ready for flight, and STS-135 payload manager Joe Delai said the payloads are ready to go as well.

The only issue standing in the way of liftoff on Friday is a 60 percent chance of showers and thunderstorms developing along the sea-breeze front reported Kathy Winters, shuttle weather officer.

After flying to NASA's Kennedy Space Center in Florida yesterday, the STS-135 astronauts are reviewing their flight data file and conducting checks of their launch and entry suits.

At Kennedy's Launch Pad 39A, technicians have completed space shuttle Atlantis' aft confidence checks and final preparations of the main propulsion system.

Despite storms in the area over the extended weekend, there were no reports of adverse weather or lightning strikes inside the launch pad.

Pratt and Whitney Rocketdyne SSMEs to Power Final Shuttle Flight to ISS
Canoga Park CA (SPX) Jul 06 - Three Space Shuttle Main Engines (SSMEs) will power the launch of Space Shuttle Atlantis on the program's final flight to the International Space Station (ISS) - just as NASA prepares to hot-fire test the new J-2X upper-stage rocket engine developed by Pratt and Whitney Rocketdyne.

The SSME is the only fully reusable high-performance rocket engine rated for human spaceflight, having delivered the majority of U.S. astronauts into space since its maiden Mission STS-1 on April 12, 1981. Pratt and Whitney Rocketdyne is the SSME prime integrator since program inception and is a United Technologies Corp. company.

"The Space Shuttle Main Engines have laid the foundation of safety, performance and innovation for continued space exploration," said Jim Paulsen, SSME program manager, Pratt and Whitney Rocketdyne. "It is only fitting that that the final flight of the program coincides with testing of the next-generation engine, which could power the upper stage of the nation's future heavy-lift launch vehicle."

Atlantis will launch from NASA's Kennedy Space Center on July 8 with a crew of four on Mission STS-135, which will carry the Raffaello multipurpose logistics module packed with supplies and spare parts for the station.

The orbiter will also deliver a system that will be used to investigate the potential for robotically refueling existing spacecraft, and return a failed ammonia pump module to help NASA better understand the failure mechanism and improve pump designs for future systems.

The Space Shuttle Main Engines have boosted every shuttle launch since the program began in 1981, allowing astronauts from 14 different countries to travel to the ISS to conduct scientific experiments that forever changed life on earth. Scientific experiments conducted in space now commonplace include everything from smoke detectors and firefighter gear, to cardiac pacemakers and breast-cancer screening technology, to de-icing systems for airplanes.

Also developed in space are nutrients now found in 90 percent of infant formulas sold worldwide.

The J-2X engine is scheduled to begin a series of hot-fire tests in June that will last several months at Stennis Space Center in Mississippi. Designed specifically to power heavy-lift launch vehicles into low-Earth orbit and beyond, the J-2X engine employs design concepts of its historic J-2 predecessor, with modern analyses, materials and processes for greater efficiency and increased power. Total thrust in a vacuum will be 294,000 pounds, and specific impulse will be 448 seconds.

Each J-2X is rated for a design life of eight starts and 2,600 seconds. and will be able to restart in space. The engine will use a gas-generator power cycle and burn liquid hydrogen with liquid oxygen.

Harris Corporation Audio Systems Headed to Space Station on Final Shuttle Flight
Melbourne FL (SPX) Jul 06 - Advanced audio systems developed by Harris Corporation will head to the International Space Station (ISS) when Atlantis blasts off for the last time on July 8, marking the final launch of the historic shuttle program. Technology from Harris has been onboard every space shuttle since the program began 30 years ago, either providing direct mission support via onboard computers and electronics, or as part of the spacecraft's payload.

The audio terminal units and controllers flying on Atlantis will become part of the ISS Audio/Video Distribution System (AVDS).

The AVDS provides audio communications among individual crewmembers in the station as well as with teammates on Earth, docked spacecraft, and crewmembers engaged in extravehicular activity, such as spacewalks. It also distributes video signals from various cameras to monitors within the Space Station or for transmission to Earth.

Harris also designed and built equipment for the Hubble Space Telescope, including electronics that point the telescope and move mirrors instrumental in sharpening the images taken by the spacecraft. In addition, six space shuttle missions have carried a dozen Harris-developed, unfurlable S- and Ku-band antennas into orbit as part of NASA's Tracking and Data Relay Satellite System (TDRSS).

Every space shuttle is equipped with Harris-designed and built payload monitoring electronics.

The PCM Master Unit, Payload Data Interleaver, and Master Timing Unit work together to provide sensor data from the shuttle and relay it to the ground, as well as monitor the health and performance of the shuttle's payload.

"Harris has supported major NASA programs since the 1960s, and the technology we developed for NASA has been advanced over the years and is now being applied to communications payload solutions for today's most advanced satellites," said Sheldon Fox, group president, Harris Government Communications Systems.

"The people of Harris are incredibly proud of their contributions to the shuttle program, and we are committed to continuing to support NASA and its dedicated people here on the Space Coast as our nation moves into a new era of space exploration."

In January 2012, a Harris-built software defined radio (SDR) is slated to be launched to ISS as part of NASA's CoNNeCT experiment. The Harris SDR enables NASA, industry, and other government agencies to develop and field communications, navigation, and networking technologies in a space environment. Harris radio technology is also being evaluated for the NASA-sponsored Commercial Crew Vehicle and the next generation space suits.

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