Subject: [IGSMAIL-1491] GPS Second Civil Frequency (L5)
From: G Preiss / J Canny
Date: Thu, 5 Dec 1996 7:00:23 PST

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IGS Electronic Mail      Thu Dec  5  7:00:23 PST 1996      Message Number 1491
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Author: G Preiss / J Canny
Subject: GPS Second Civil Frequency (L5)

Frankfurt, 4 December 1996

International Information Sub-Committee (IISC)
Civil GPS Service Interface Committee (CGSIC)

Ladies and Gentlemen,

At the 5th European IISC Meeting held in Frankfurt on 
3 and 4 December 1996, the U.S. Department of Transportation
asked whether there is a need for a second civil frequency (L5)
on the new Block IIF GPS Satellites. The following paper gives
the L5 proposal and urgently requests opinions from the 
international GPS community.

All are asked to answer the questions given and to reply to 
the U.S. Coast Guard Navigation Information Service (NIS) at:

Fax: +1 703 313 5805
E-Mail: [email-masked]

Replies are required no later than 31 December 1996.

George Preiss
Chairman IISC

E-Mail: [email-masked]

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Frankfurt, 2 December 1996

Subject: The L5 Frequency Question

The U.S. Department of Transportation (DoT) is continuing to
investigate the need for a second civil frequency to be added to
the Block IIF GPS Satellites. There are several options that need
to be explored to determine the actual needs of the civilian
community. These include adding a new frequency with either a
simple carrier and coarse acquisition (C/A) code, or
C/A code and navigation message. A critical part of these options
is finding a frequency that could be ,cleared" worldwide of
existing systems to allow the insertion of the new GPS signal.
The frequency chosen must be in a band that is acceptable to all
users from a regulatory standpoint, able to be cleared of
interfering signals from existing systems, and yet capable of
providing ionospheric correction information.

An additional option is to be much more innovative with the
signal and open it up for new ideas in how a second civilian
signal could be used. DoT is open to all ideas at this time.
Feasibility, development time, frequency spectrum limitations,
and cost will be some of the determining factors for examining
suggestions for this option.

With the above reasoning defined, the DoT would like to ask the
following questions of the civilian user community:

1. Is there a clear need for a separate second SPS signal
that is a full or partial mirror image of the L1 SPS signal? If
so, what should the signal look like and where in the frequency
spectrum should it be located?

2. Are there any other new and innovative things that can be
done with a second SPS signal to improve the overall SPS
accuracy, reliability, integrity, and availability? If so, what
should the signal look like and where in the frequency spectrum
should it be located?

3. Can the benefits of these alternatives for a second civil
frequency be quantified? If so, what are they? Can the costs of
clearing a frequency be quantified either worldwide, regionally,
or nation by nation?

Information in response to these questions is urgently needed, so
that if a decision is made to have the second frequency, it can
be put on all or substantially all of the Block IIF
constellation.

Joseph Canny
Deputy Assistant Secretary 
U.S. Department of Transportation

[Mailed From: [email-masked]]