Myth Busted: Civilian GPS Receivers Actually do have Access to the L2 Frequency

摘要

Rarely does our space cadre professional journal inform the community on technical topics that provide us intellectual insight into our trade. The intent of this article is to add some technical know-how to our space rucksacks. It is the authors' intent to discuss one such topic in this paper and to also encourage more technical discussions of our tradecraft in the future. Space operations officers are charged to be subject matter experts on Position, Navigation and Timing and on the Global Positioning System (GPS) constellation. In the course of educating FA40s in the Space Operations Officer Qualification Course, in less than three months, students receive as many as six briefs dealing with GPS. These briefs range from introductory to in-depth lessons from Space 200, NAVWAR, Space Operations Officer Qualification Course GPS, the Space Symposium, and a briefing from GPS experts at Los Angeles Air Force Base. In each of the briefs, usually within the first 4-7 slides, these technical experts tell us that the L1 band has the course acquisition (C/A) code with free access to the public, while access to the L2 band is restricted to only those military receivers with encryption to access the P-code. While this was the intended design of the system, it is simply no longer a true statement. For several years, specific civilian GPS receivers have the capability to utilize the L2 GPS band. Therefore, it is important to clarify this misconception and make a recommendation on how, as a community of professionals, the correct knowledge should be disseminated.