In this issue:

GNSS TestBed Concept presented in Asia....................1

FAA holds workshop for Navigation Community.........2

ICAO GNSS Panel meet in Philadelphia......................3

LAAS Availability Explained...........................................3

SISAT Version (2.3) Released.........................................4

GNSS Takes Of akes Of akes Off in Asia f in Asia

By Jennifer Campbell, GPS TAC (AND-730)

Representatives from the Asia Pacific Economic Cooperation (APEC), the FAA Office of International Research and

Acquisition (ASD-500), the FAA Wide Area Augmentation

System Product Team (AND-730), and the FAA Navigation

Systems Implementation Product Team (AND-720) presented the Global Navigation Satellite System (GNSS) TestBed

Concept and Implementation in four cities across Asia from

August 27 to September 8, 2001. Approximately 150 attendees from the APEC Satellite Navigation and Communication (SN&C) Systems Advisory Committee and their technical and political experts attended one of the four meetings

hosted by Japan, Hong Kong, the Philippines, and Thailand.

The meetings focused on the implementation of a GNSS

Southeast Asia TestBed capability to promote research and

to launch the implementation of GNSS technology in the region. The meeting topics included the detailed steps necessary to successfully transition from current ground-based

navigation systems to a satellite-based navigation system.

These meetings were a part of the FAA’s continuing interna-
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tional cooperative effort and commitment to provide information and technical assistance with the implementation of

satellite-based navigation technologies to countries and regions worldwide.

Navigation Workshop orkshop

By Carol Wheeler, ANN TAC (AND-700)

The following article was written in anticipation of the FAA Navigation Workshop. Please look for an update in the next edition of the SatNav News.

The FAA Navigation Integrated

Product Team (IPT), AND-700, is

conducting a National Navigation

Workshop in San Antonio, TX

from September 11-13 of this year.

The National Workshop provides

the opportunity for the FAA navigation community to meet, learn,

and discuss current issues affecting the management of navigation

aids (NAVAIDS), and the recently

released FAA Operational Evolution Plan (OEP).

The June 6th release of the OEP

will have an impact on the decisions and plans for managing NAVAIDS. The OEP, in brief,

is a ten-year plan designed to reduce airline delays by increasing commercial airline traffic by 30%. This goal will

be met by expanding the airspace around airports, and by

adding new equipment in aircraft.

Navigation issues to be discussed in the framework of the

OEP include sustainment of the current infrastructure and

the transition from ground-based to satellite-based

NAVAIDS.

In preparation for the workshop, the Navigation IPT management team visited each of the nine FAA regional offices

and two centers during a whirlwind six-week schedule. The

visits included a two-hour briefing on the current state of

NAVAIDS in the morning, then a question and answer session in the afternoon. The issues discussed were recorded

and sent to the regions and centers for their review and

approval. These final minutes are being used to shape the

specific agenda items for discussion and instruction at the

National Workshop.

Workshop participants will find a busy agenda upon their

arrival. During the first day, all participants will attend a

general session. They will hear from experts in their field

on the “State of Navigation”, “OEP-Future of Navigation”,

“Challenges today and in the year 2010”, and more. During the second day, the workshop will offer four breakout

groups to discuss specific issues gathered from the visits to

the regions and centers. During the third and final day, the

breakout groups will meet for a half-day session to prepare

a report on the conclusions reached or actions to be followed up by the teams. The entire group will reconvene in

the afternoon to hear what conclusions and actions each

group reports and to discuss and agree on them as a community.

Registration for the workshop is underway and currently

includes participants from each of the AND-700 Navigation Product Teams--Systems Engineering, Local Area Augmentation System, Navigation Systems Implementation,

Wide Area Augmentation System, and Navigation and Landing Systems Acquisition. Regional representatives have

registered from the ANI Engineering Center, Airway Facilities Operations Branch, Air Traffic and Flight Standards

Divisions. The Mike Monroney Aeronautical Center representatives include the Logistics Center, Flight Inspection,

and the Operations Branch. Key Headquarters Organizations include Requirements, NAS Operations, Airway Facilities Service, Resource Management, and more. The Engineering and Test Division located at the William J. Hughes

Technical Center has also registered for participation.

The Navigation IPT is confident that the workshop will benefit each participant for the time invested by providing a

broad perspective on the tasks to be accomplished through

the diversity of the representatives. The workshop aims to

provide an opportunity for the navigation community to improve communication and understanding through interaction. The enthusiastic response to this workshop shows

evidence that the community is eager to work together to

enhance its effectiveness.
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ICAO GNSS Panel Update ICAO GNSS Panel Update

By Tom Meyer, GPS TAC/NAS Implementation Team (AND-720)

ICAO’s Global Navigation Satellite System Panel (GNSSP)

Working Group A held a week long meeting in Philadelphia, PA from April 22–27, 2001. Twenty-seven operational

and technical experts from 14 countries participated in the

meeting. Recommendations from this meeting were to be

drafted into version 5 of the manual at the author’s group

meeting in Montreal on August 27, 2001.

The highlight of this meeting was the drafting of recommended inputs to update ICAO’s Global Air Navigation Plan

for CNS/ATM Systems, in preparation for the upcoming meeting of intersted states in Rio de Janeiro this fall. Version 4

of the draft GNSS Manual, set to replace ICAO Circular

267, was reviewed to capture recently recommended updates to ICAO Standards and Recommend Practices

(SARPS) that will become effective in November 2001.

Other areas of discussion included issues relating to the

use of the Ground Based Augmentation System Differential

Position Service (GBAS/P or GDPS) and Satellite Based Augmentation System (SBAS) NOTAM and Status Monitoring

issues related to PANS RAC Phraseologies, PANS-ABC, and

Annex 15 requirements.

Technical and operational experts from the US, Germany,

and Canada were chosen to participate in international sub

working group activities that will provide updates to the

navigation and air traffic management sections of the Global Plan continuing to convey ICAO’s vision for GNSS.

LAAS Availability vailability

by Navin G. Mathur, GPS TAC (AND-710)

Random House Dictionary defines availability as “suitable or ready to use”. Availability for a system such as

LAAS is defined in terms of how long the system can provide suitable service without interruptions. In other words,

it is the amount of time the system provides required accuracy, integrity, and continuity in the coverage volume.
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The Local Area Augmentation System (LAAS) has a LAAS

ground facility (LGF) that is installed at the airport where

LAAS service is desired. LAAS service supports precision

approach and Area Navigation. The LAAS Service Availability is defined as the probability that LAAS service will

be available. Evaluation of service availability requires the

evaluation of GPS constellation availability and LGF inherent availability.

Inherent availability (Ai) for a particular equipment is defined by the Mean-Time-Between-Failure (MTBF) and MeanTime-To-Repair (MTTR). In equation form, Ai = MTBF/

(MTBF+MTTR). Thus for a system that has an MTBF of 5000

hours and MTTR of 30 minutes, the inherent availability is

0.9999. Whether this simple formula can be used for complex systems with MTBF of the order of 50,000 hours is still

under debate. The LAAS ground facility specification (draft

specification, dated August 22, 2001) defines two configurations to accommodate the range of availability requirement from the LAAS requirements document. A standard

configuration with 0.9999 of inherent availability is defined

and then an upgraded configuration is defined which would

be able to achieve 0.99999 of inherent availability with an

MTTR of 30 minutes.

An August 2001 study from MITRE indicates that the average GPS constellation availability without including any

WAAS GEOs is of the order of 0.9998 at the 176 airports

chosen for providing LAAS service. Furthermore, the study

states that with four WAAS GEO satellites, in addition to

the GPS satellites in the constellation, the average constellation availability increases to 0.9999. This study takes into

account the final draft GPS SPS performance specification

and other conservative assumptions on the error terms that

are characteristic to local LGF locations. This study also

includes results for 78 different airports where LAAS CAT

II/III service is envisioned. With current CAT II/III requirements described in the RTCA MASPS (DO-245), the average GPS (alone) constellation availability is of the order of

0.9994, while the average availability with four WAAS GEOS

turns out to be 0.99997.

As mentioned above, the LAAS service availability at any

given airport is a probabilistic combination of the inherent

LGF availability and the GPS satellite constellation availability. It turns out that the service availability achieved with

existing satellite constellation definition is 0.999 (average

over 176 airports) using a standard LGF configuration and

0.9999 (average over 176 airports) with an enhanced version of the LGF.

There are other various availabilities that are associated

with LAAS such as true availability, predictive availability,

and short-term operational availability. The LAAS program

office is in the process of putting together an Availability

Working Group that will be tasked to make the definitions

of all availabilities consistent. Furthermore, the charter of

the Availability Working Group will include defining availability requirements for CAT II/III and quantifying availability enhancement due to WAAS and to pseudolites.

SISAT Update T Update

By Todd Lardy, Flight Test Engineer, Naval Air Systems

Command, NAS Implementation Team (AND-720)

An article appeared in the March edition of SatNav News

describing a tool that analyzes satellite-based augmentation

system (SBAS) signals known as the SBAS Signal-In-Space

Analysis Tool (SISAT). Since March, several modifications

have been made to improve the functionality and utility of

this tool. The latest SISAT version (2.3) was released on

August 17, 2001 and is being mailed on CD ROM to the

30+ government and industry organizations that are currently

using earlier SISAT versions.

Included in version 2.3 are:

· Processing improvements to allow longer data files to be

read and processed including conversion from ASCII to

binary files and from DOS-based executables to MEXbased libraries

· The addition of a carrier smoothing filter with a user

selectable parameter to control the filter time constant

· An interface to allow WAAS data from the National Satellite Test Bed to be downloaded from the FAA Technical

Center web-site and analyzed using SISAT

· An interface to decode Novatel receiver data to allow

data from the European SBAS analysis tool (Pegasus) to

be processed

· Various improvements to the user interface and input

 and output data formats
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For additional information or to obtain a copy of the SignalIn-Space Analysis Tool, contact Bob Beal at (703) 841-2246

or robert.ctr.beal@faa.gov.

We want your feedback. We encourage your questions,

suggestions, and recommendations for improvement.

Please e-mail our editor at Shelby.ctr.Wheeler@faa.gov.

Federal Aviation Administration

800 Independence Avenue, SW

Washington, DC 20591 http://gps.faa.gov