FAA’s Plan for the Future Use of GPS

Briefed By: Kanwaljit S. Sandhoo

(MITRE/CAASD)

8th European CGSIC/IISC Meeting, Prague

December 2-3, 1999

Overview

Background

FAA Objectives

Operational Use of L5

Dual Frequency SBAS/GBAS

FAA’s Plan

Summary

Background

In January 1999 the United States announced, that as a part of the GPS Modernization effort, two additional GPS signals will be made available for civil use— L2 at 1227.60 MHz will be available on GPS satellites to

be launched beginning in 2003 for non-safety critical applications

— L5 at 1176.45 MHz will be available on GPS/WAAS Satellites to be launched in 2005 for safety-of-life services like civil aviation ARNS/RNSS allocation will ensure its protection for safety-

of-life services The Interagency GPS Executive Board (IGEB) performed

the analysis to support the selection of L5 and minimizing its impact on the existing system in the band

Background(Cont’d)

RNSS

(GLONASS)

ARNS

1215

ARNS/RNSS

(GLONASS)

1176.45 MHz+12 MHz

1227.6 MHz+12 MHz

1575.42 MHz+12 MHz

15591260 1610960

(GPS)(GPS)

L5 L2 L1

GNSS Frequency Allocations

Need RNSS Allocation for L5 to Support Civil Aviation Safety-of-Life Operations

FAA Objective

Improve the safety within NAS— Provide precision approach service at every qualified

runway Improve the safety throughout the World

— Provide precision approach service throughout the World

Increase the capacity of NAS— Direct & flexible routing not based on the location of

ground-based navigation aids

Operational Use of L1 & L5

Current SBAS/WAAS and GBAS/LAAS broadcast corrections on a single GPS frequency (L1)

Independent Study by John Hopkins University Applied Physics Laboratory— Confirmed the technical feasibility of WAAS & LAAS— Recommended FAA make every effort to mitigate

effects of intentional & unintentional interference In response to John Hopkins Study, the FAA is planning to

use a more robust L5 signal as a Backup to L1— L5 will have the same data as L1— L5 will be a 20 MHz signal with 6dB more power than L1

Operational Use of L1 & L5 (Cont’d)

Availability of L5 will facilitate the development and use of dual frequency avionics to eliminate ionospheric errors— Facilitates precision approach throughout the World at

minimum or no cost to many countries

Dual Frequency SBAS/WAAS

L5 - 1176.45 MHz

L5 - 1176.45 MHz

L5 - 1176.45 MHz

Dual Frequency GBAS/LAAS

Pseudolite ReferenceAntennas

VHFTransmitter

Processing

Receiver

DataBroadcast

L1 - 1575.42 MHzL5 - 1176.45 MHz

SBAS GEOs Coverage

SGC=SBAS GEO Coverage SGCOIG=SGC Outside Ionospheric-Correction Grid

SGCIIG=SGC Inside Ionospheric-Correction Grid

SGCOIG

SGC

SGCOIG

SGCIIG

SGCOIG

SGCOIG

SGCOIG

SBAS Operations Inside Ionospheric-correction Grid

WAAS will broadcast ionospheric corrections and integrity data (satellite clock and ephemeris corrections) on both L1 and L5

When Both L1 & L5 are available the users will use both the frequencies to provide the most accurate service possible— Onboard generated dual frequency corrections with

integrity data from WAAS corrections broadcast at L1/L5

In the event of interference on any one of the frequencies (L1 or L5), the users will be able to use WAAS broadcast ionospheric corrections and integrity data

SBAS Coverage Outside Ionospheric-correction Grid

The availability of L5 offers the potential of providing immediate access to the precision approach capability throughout the Footprint of SBAS GEO satellites at minimal or no cost to many nations

Users will be able to use dual frequency avionics with integrity data from SBAS corrections broadcast at L1 or L5

In the event of Interference on L1 or L5 these regions can revert to non-precision approach — GPS with integrity data from SBAS correction

broadcast at L1/L5 or use RAIM

Summary

FAA plans to use both L1 & L5 to achieve seamless global navigation

Safety-critical civil aviation and land-based application will benefit from the availability of L5

L5 is being designed to be more robust and resistant to interference

L5 will be redundant to L1 L5 will provide immediate access to precision approach

capability throughout the World, within the footprint of SBAS GEO satellites at minimal or no cost to many nations