GPS III, the next-generation modernization project for the space and ground segments, is facing renewed uncertainty and possible schedule delays. At the same time, anticipated first launch of the follow-on block of satellites (Block IIF) with the new civil L5 signal has been postponed.

The GPS program appears to be struggling on several fronts recently.

GPS III, the next-generation modernization project for the space and ground segments, is facing renewed uncertainty and possible schedule delays. At the same time, anticipated first launch of the follow-on block of satellites (Block IIF) with the new civil L5 signal has been postponed.

The Air Force Acquisition Strategy Panel (ASP) will conduct a crucial meeting on June 7 to determine the new road map for GPS III. The Acquisition Strategy Panel is a panel of senior level acquisition personnel from offices of the Secretary of the Air Force for Acquisition (SAF/AQ), Air Force Materiel Command, and the user community, including Space & Missile Center (SMC) representation, that provides advice to program managers on their acquisition strategies.

Representatives of the NAVSTAR GPS Joint Program office, which is part of the SMC at Los Angeles AFB, told Inside GNSS that "pending results [from the ASP meeting] and approval of the acquisition strategy, a contract could be awarded as early as Dec 06/Jan 07." However, the JPO added, "the ASP may decide to have the program continue with payload risk reduction and system definition efforts."

This final observation reflects Air Force interest in keeping the GPS III satellites light and simple enough to keep costs down and possibly permit them to be launched two at a time, further reducing program costs. That was also the recommendation of a Defense Science Board Task Force on GPS report released earlier this year.

Should the ASP elect to recommend contract award, the RFP release would normally occur about five to six weeks after the panel’s decision, according to an SMC spokesperson. Contract award is then normally projected at seven months after the ASP decision.

If the contract is delayed for a substantial period of time, however, it will put pressure on the two competing GPS III consortia, led the Boeing Company and Lockheed Martin, to keep their engineering teams intact during the interim.

Meanwhile, the Air Force has increased its calculations for mean mission duration (or MMD, or projected lifespan) of the replenishment block satellites, including the modernized version with the new civil L2C and military M-code (Block IIR and IIR-M).

A longer MMD allows the Air Force to slow the rate at which it replaces satellites. For instance, the first Block IIR-M launch was in September 2005 and the next is not scheduled until next September.

Block IIF Difficulties. These developments are taking place at the same time that the U.S. Air Force is considering a plan to "truncate" the Block IIF buy at 12 satellites and introduce a phased GPS III technology development and acquisition plan.

That alternative calls for a GPS III contract in which the first set satellites would provide IIF-level capabilities that could be upgraded in later GPS III acquisition stages. It may also reflect unhappiness at what Air Force officials recently characterized as the "technical difficulties" encountered by IIF contractor Boeing that reportedly led to the launch delay from May 2007 to March 2008.

The continuing uncertainty in the GPS III program has not, however, dissuaded Lockheed Martin and EADS Astrium from announcing a teaming agreement to ensure interoperability of GPS III and the European GNSS, Galileo.

According to the agreement, the companies will perform systems engineering and technical assistance tasks for each other in the areas of interoperability, integrity and optimization of joint constellation performance. Additionally, the companies will offer reciprocal bids on operational hardware and software within the policy and export constraints of both programs.

A decision to award a single contract for modernized user equipment (MUE), the military handheld unit that will be able to process the M-code as well as legacy GPS signals, has also been delayed from its long-anticipated late-April decision deadline.

Failure to commit funds allocated for MUE by the end of March apparently led to the money being reprogrammed. However, according to Air Force and industry sources, the JPO is now looking at awarding three interim development contracts valued at about $7 million each in place of a single "down-select" award of about $11 million.

L3/Interstate Electronics, Rockwell Collins, and Raytheon are the three leading contenders for the contract and have been working under initial MUE contracts issued several years ago.

Copyright 2006 Gibbons Media and Research LLC

The post GPS III, Block IIF Programs Hit New Delays appeared first on Inside GNSS - Global Navigation Satellite Systems Engineering, Policy, and Design.

Within weeks of a bilateral working group’s recommendation for a common civil GNSS signal design, the European Galileo and U.S. GPS programs have filed draft interface specifications (IS) or interface control documents (ICDs) for the new signals planned for the L1 frequency (around 1575 MHZ).

The common design recommended by a technical working group set up under the 2004 US/EU agreement on GPS and Galileo is a multiplexed binary offset carrier (MBOC) signal, which is discussed in detail in the “Working Papers” column that begin on page 57 in this issue of Inside GNSS.

The working group recommendation and a joint statement, signed by the heads of the EU and U.S. delegations, can be found on the NAVSTAR GPS Joint Program Office (JPO) website as well as the Galileo Joint Undertaking (GJU) website.
 
On April 19 2006, they issued a draft IS-GPS-800 for the so-called L1C signal proposed as part of the GPS III program still under development. The document marks the culmination of a yearslong civil/military effort.

The L1C signal will use a BOC modulation and consists of two main components: a pilot signal without any data message, which is spread by a ranging code, and a carrier that is spread by a ranging code and modulated by a data message.

Galileo ICD Released. The long-awaited Galileo signal in space (SIS) ICD was posted May 23 on the Galileo Joint Undertaking (GJU) website. The ICD covers the Galileo signals and services that will be transmitted at E1, E5, and E6 frequencies. In particular, it contains the spreading codes and navigation message format for the signals, which have not previously been publicly available and are needed by GNSS receiver designers and manufacturers in order to build Galileo-capable receivers.

Under the 2004 agreement, a BOC (1,1) modulation (denoting a subcarrier frequency and spreading code chipping rates both at 1.023 MHz) represents the baseline design for a common signal. However, the MBOC would interweave (or multiplex) BOC (6,1) and BOC (1,1) modulations, which would provide superior performance, according to its advocates, particularly in dealing with multipath (reflected signals) and code tracking in noisy RF conditions.

MBOC Doubters. Despite the enthusiastic unanimous endorsement of the MBOC design by technical experts on the US/EU working group, others are not so sure — suggesting that MBOC will benefit applications requiring high- precision GNSS equipment to the disadvantage of consumers using low-cost GNSS receivers.

Receiver manufacturers of mass-market receivers use a narrower portion of the spread spectrum signal to reduce the costs of the equipment. They argue that, even though an MBOC signal could be received and processed on a BOC (1,1) receiver, the multiplexed signal will deliver between 0.5 and 1 decibel lower effective received power as well as lower effective signal bandwidth.

That arguably could raise difficulties for manufacturers and users who hope to employ high-sensitivity, but low-cost receivers, indoors or in other challenging environments. Qualcomm is among the skeptics of the multiplexed L1 design. The European Space Agency also reportedly would prefer to remain with the original BOC (1,1) design.

EU and U.S. officials are currently assessing the “relevant programmatic aspects of implementing the joint-optimization” as MBOC or BOC (1,1).

Copyright 2006 Gibbons Media and Research LLC

The post Civil L1 Signals: Galileo ICD, GPS L1C, New MBOC appeared first on Inside GNSS - Global Navigation Satellite Systems Engineering, Policy, and Design.