Aerospace and Defense

One-Centimeter Accuracy with PPP

The navigation message has always been considered an inherent and essential feature of a global satellite navigation system. Its primary objective is to provide receivers with information on the errors of satellite clocks and parameters to compute the positions of satellites, as well as other parameters that help generate more accurate measurements.  

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By Inside GNSS
February 29, 2012

GPS Program Budget: A Lot, But Is It Enough?

The details of President Obama’s 2013 budget have been gradually filtering out and, in general, the GPS system and those programs closely linked to satellite navigation, have escaped deep cuts.

On the hardware side the White House has requested $58.2 for GPS IIF satellite procurement. According to Air Force budget documents, the plan is to then wrap up the total IIF procurement of 12 satellites with a request for $77.6 million in FY14 and $7.3 million in FY15.

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By Inside GNSS

Code Tracking and Pseudoranges

FIGURE 2: Pseudorange computation based on transmission. On the left side, the satellites are transmitting mes¬sages synchronously. On the right side, the four subframes are received asynchronously, due to the different propagation time. The TLM word is taken as a referene. The time differences ?i are computed on the basis of the relative arrival times of the front of the first bit of the TLM word.

Q: How can pseudorange measurements be generated from code tracking?

A: Every GNSS receiver processes the received signals to obtain an estimate of the propagation time of the signal from the satellites to the receiver. These propagation times are then expressed in meters to solve for the user position using trilateration.

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By Inside GNSS

New Austerity Squeezes GPS as DoD Tightens Its Belt

Embracing the need for debt-driven discipline, the White House has revised its strategy for the nation’s defense, taking a more fiscally constrained approach that reduces the number of troops and future spending on defense systems.

The new plan, formally announced January 5, was already being put into effect last summer. “The strategic guid­ance was the compass by which we steered the budget review leading to the president’s budget for fiscal year ‘13 and the years thereafter,” Deputy Secretary of Defense Ashton B. Carter told reporters.

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By Dee Ann Divis
January 12, 2012

USAF Awards Lockheed Additional GPS IIIA Satellite Buy

The U.S. Air Force has awarded Lockheed Martin a $238 million contract for production of the third and fourth satellites in the next-generation GPS constellation, known as GPS III.  The acquisition of the next two GPS IIIA satellites at one time will allow the Lockheed Martin-led team to maximize efficiencies in satellite manufacturing.

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By Inside GNSS