Satellite Can Take The Shakes
BY RICHARD MULLEN
An advanced communications satellite that Lockheed Martin Corp. is producing for the Pentagon has passed a significant test of physical durability, the company said.
The Advanced Extremely High Frequency (AEHF) satellite showed that it could withstand the heavy dose of vibrations to which it might be subjected and still perform its vital mission, according to Lockheed Martin.
Having passed the vibrations test, the spacecraft is on track for a first launching about two years from now, according to Steve Tatum, a Lockheed Martin spokesman.
The tested spacecraft is one of three AEHF satellites that Lockheed Martin is building for the Department of Defense (DOD), for the purpose of providing "global, highly secure, protected, survivable communications" for all of the armed services, the company said.
The direct customer for the satellites is the MILSATCOM Joint Program Office, located at the Space and Missile Systems Center, Los Angeles Air Force Base, Calif., the company said.
As prime contractor producing the satellites, Lockheed Martin serves as developer of the ground segment, satellite bus provider, space vehicle integrator, and overall systems integrator, Tatum said.
Lockheed also will build replacement command and control and planning systems, he said in an email interview.
Northrop Grumman Corp. will provide "the payload and associated components," Tatum said.
To do its job, each AEHF satellite will have to be able to tolerate the physical stress of the launch and subsequent mechanical operations, Lockheed Martin said. These forces will subject the satellite to vibrations from "reaction wheels, solar arrays and various deployable and steerable mechanisms," among other sources, the company said.
The object of the recent test, formally called a "modal survey," was to ensure that all of that shaking would not affect "the critical mission of the communications payload," the company said. The satellite passed a test "designed to validate the rigid characteristics of the spacecraft," the company said.
The company tested the aircraft by subjecting it to the force of "mechanisms used to test the dynamic structural characteristics of a spacecraft," Tatum said. These mechanisms, the company said, included "292 accelerometers, 508 accelerometer channels and six shakers," which company engineers attached to the body of the spacecraft and the surrounding ground surface.
Lockheed Martin carried out the test, the date of which it did not specify, at company facilities in Sunnyvale, Calif.
"Our highly successful modal testing and analysis has verified that we have a robust spacecraft design for achieving success on this critical mission," said Julie Sattler, vice president of Lockheed Martin Space Systems. The AEHF satellites will serve "our military personnel and allies worldwide," she said.
With the modal testing successfully completed, the company said, the spacecraft will be shipped to another California site "for refurbishment and final painting," the company said. From there, the satellite will go to Lockheed Martin’s Mississippi Space & Technology Center, which will perform the integration of its propulsion subsystem, the company said.
Launches for the three AEHF satellites are scheduled for April 2008, April 2009 and April 2010, according to Tatum.
The AEHF satellites, based on Lockheed Martin’s A2100 spacecraft series, "will provide greater total capacity and offer channel data rates higher than that of Milstar communications satellites," the company said.
Tatum characterized Milstar as "the Defense Department’s current advanced telecommunications satellite system that provides critical, secure links to U.S. national leaders, air, land and sea forces around the globe. The Advanced EHF system ultimately will replace the Milstar," he said.
The AEHF satellites will feature higher data transmission rates than Milstar, thereby enabling the "transmission of tactical military communications such as real-time video, battlefield maps and targeting data," according to Lockheed Martin.