[IGSMAIL-1515] Urgent Request for L5 Input

[Capt.]

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IGS Electronic Mail      Fri Jan 10 13:04:10 PST 1997      Message Number 1515
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Author: Capt. Lewis A. Lapine
Subject: Urgent Request for L5 Input


Time Sensitive - Response due NLT 1600 January 15, 1997

Most Recent L5 Activities

The Departments of Defense (DOD) and Transportation (DOT)  have convened a
high level government panel assigned to a fast track decision making process
that will determine the future availability of dual frequency GPS operations
for the civil sector.   Joe Canny and  Mike Shaw from DOT and DOD,
respectively, are co-chairing the working group.  A subgroup composed of
myself; John Rush, National Aeronautics and Space Administration; and Dave
Olsen, Federal Aviation Administration, were selected to inform the user
communities of the working group activities.

DOD is exploring several options to maintain (perhaps improve) the
performance of civilian applications of GPS without compromising  military
utilities.  As a result, a new GPS frequency, L5, is being considered for
civil sector uses in order to reserve L2 for military purposes.  This new
frequency is targeted to provide both carrier phase and Course Acquisition
code range information.  Two frequencies are proposed for L5; the first
being 1207 MHz yielding a 368 MHz separation from L1, and the second being
1309 MHz having a separation of 266 MHz from L1. L2 currently has a 347 MHz
separation from L1.  

As users we must determine if there are any reasons why one of the
frequencies proposed  is desirable over the other.  The trade-offs represent
a smaller separation in frequency but a corresponding larger wide lane
capability.  Presently, DOD favors the 1309 MHz frequency while  DOT is
favoring the 1207 MHz frequency.  Both Departments have expressed valid
rationale based on interference rather than potential use.  The lower
frequency may interfere with a DOD navigation system, while the higher
frequency may have interference with ground based radar installations.  

The working group will provide a recommendation of the appropriate frequency
for L5 input prior to February 21, 1997, in order to meet a critical Block
IIF contract deadline.  For this reason, the working group must maintain a
fast track approach.  This announcement is to solicit your input for the
frequency selection process.  Please state clearly which frequency is more
suitable, why, and any substantiating cost benefits.  The next working group
meeting is scheduled for January 16, 1997.  As such, I will need your
response NLT 1600, January 15, 1997.


Capt. Lewis A. Lapine
Director, National Geodetic Survey (NOAA)

e-mail:  llapine at ngs.noaa.gov



[Mailed From: Jim Ray (NOAA 301-713-2850) <jimr at ray.grdl.noaa.gov>]