[time-nuts] Satellite Glitch Rekindles GPS Concerns

Brooke Clarke brooke at pacific.net
Thu Jun 18 12:55:46 EDT 2009


Hi Mike:

The current issue of Inside GNSS has two articles about this and their web page 
has a new article dated 17 June 2009.
http://www.insidegnss.com/

Also on line is a story that directly relates to GPS:
"eLoran: The Never-Ending Story?"
http://www.insidegnss.com/node/1571
-------------------------
Glen Gibbons
June 15, 2009

To say that enhanced Loran (eLoran) has been an on-again off-again program 
would give short shrift to multiple generations of official ambivalence about 
the proposed backup for GPS.

The latest chapter began on June 4 when Senator Maria Cantwell (D-Washington) 
introduced S. 1194, the Coast Guard Authorization Act for Fiscal Years 2010 and 
2011 (FY2010/11).

Among other details, the measure directs the Secretary of Transportation to 
continue the Loran system until a plan has been drawn up and implemented to 
transition the program to eLoran.

In effect, this would reverse the course set by President Obama, whose FY10 
budget proposal calls for termination of Loran in the coming year. At a May 7 
press conference the president described Loran as a system that’s been eclipsed 
by the rise of GPS.

“Year after year, this obsolete technology has continued to be funded even 
though it serves no government function and very few people are left who still 
actually use it,” Obama said.

The president’s proposal had overruled plans set in motion last year for the 
Department of Homeland Security (DHS) to complete the upgrade to eLoran as a 
backup to GPS.

Now, S. 1194 would authorize the appropriation of $37 million for each of 
fiscal years 2010 and 2011 and direct the U.S. Coast Guard (USCG) to modernize 
and upgrade the Loran infrastructure to provide eLoran services. Under the 
legislation, the Department of Transportation (DoT) could transfer funds from 
the Federal Aviation Administration (FAA) or other DoT agencies to reimburse 
the USCG for costs of the modernization.

The activity comes at the same time that a Government Accountability Office 
(GAO) report warns about the possibility that the GPS constellation may decline 
substantially in the coming years.

Prospects for passage of S. 1194 appear promising. Cantwell is chairwoman of 
the Oceans, Atmosphere, Fisheries, and Coast Guard subcommittee of the Senate 
Committee on Commerce, Science, and Transportation to which S. 1194 has been 
referred.

Three senators join her as cosponsors of the measure: Sen. Olympia Snowe 
(R-Maine), the ranking Republican member of the subcommittee; John D. 
Rockefeller IV (D-West Virginia), chairman of the Commerce, Science, and 
Transportation Committee itself, and Kay Hutchison (R-Texas), the committee’s 
ranking Republican.

The legislation implicitly confirms the findings of an Independent Assessment 
Team (IAT) on eLoran, funded by the office of the under secretary of 
transportation policy and chaired by Brad Parkinson, the first program manager 
for GPS.

DoT contracted with the Institute for Defense Analysis (IDA), which organized 
the IAT with IDA staff member Jim Doherty serving as the IAT’s executive director.

If offset by an estimated $146 million decommissioning cost of existing Loran 
infrastructure, the IAT concluded that eLoran could be established effectively 
for free.

Going forward, eLoran would require only the current $37 million per year in 
USCG operations and management base funds for Loran plus $20 million a year in 
new funds for five to eight years to complete all upgrades, new transmitters, 
and “jump start” deferred maintenance.

After that time, savings from substantially reduced staffing at the modernized 
facilities would offset eLoran operational and sustainment costs.

In December 2006 the IAT unanimously recommended that for, at least the next 20 
years, eLoran “be completed and retained as the national backup system for 
critical safety of life, national and economic security, and quality of life 
applications currently reliant on position, time, and/or frequency from GPS.”

Among the IAT’s key findings: “eLoran is the only cost-effective backup for 
national needs; it is completely interoperable with and independent of GPS, 
with different propagation and failure mechanisms, plus significantly superior 
robustness to radio frequency interference and jamming.”

Despite the report’s acceptance by the Bush administration, which relied on it 
for the DHS decision to move forward with eLoran, a summary of the IAT findings 
and supporting charts was only released in May. Parkinson told Inside GNSS that 
he estimates the probability of Congress approving eLoran at 75 to 80 percent.

Currently, the Radio Technical Commission for Maritime Services (RTCM) is 
developing performance standards for eLoran in the maritime environment. eLoran 
also has strong support from the General Lighthouse Authorities (GLA) of the UK 
and Ireland (equivalent to USCG for maritime safety, which have committed to 
e-Navigation for maritime safety, using GPS/DGPS as primary input, eLoran as 
secondary or backup, and electronic charting.
----------------------------

Have Fun,

Brooke Clarke
http://www.prc68.com

Mike Monett wrote:
>   An article in NetWork World discusses performance degredation in the
>   new Lockheed-built  GPS  IIR-2  satellite.  Apparently.  the  new L5
>   transmissions are interfering with other signals from the satellite.
> 
>   This reduces  the accuracy an order of magnitude, from 2 feet  to 20
>   feet. It  should have a corresponding effect on the accuracy  of the
>   decoded time signals.
> 
>   The Air  Force said it has identified several parameters in  the GPS
>   IIR-20 (M)'s  navigation  message  that   can  be  corrected  and is
>   studying the impact these may have on military and civil GPS users.
> 
>   Presumably, the  problem  will  be corrected in  the  12  Boeing GPS
>   satellites currently being built that also feature the L5 signal.
> 
>   The article  discusses  issues   such   as  delays  due  to techical
>   problems, cost overruns, and aging of the fleet. These  could affect
>   system performance in the future.
> 
>   However, Col. Dave Buckman stated
> 
>   "The issue  is  under control. We are working hard  to  get  out the
>   word. The issue is not whether GPS will stop working. There's only a
>   small risk we will not continue to exceed our performance standard,"
>   he said.
> 
>   http://www.networkworld.com/community/node/42767
> 
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