EUROPEANCOMMISSION

Satellite-Based Augmentation Systems (SBAS) Combined Performance

International Committee on GNSS (ICG-4)

Working Group ASaint Petersburg, Russia

15 September 2009

Frederic Bastide, European Commission

Ken Alexander, United States

Analysis by MITRE Center for Advanced Aviation System Development

EUROPEANCOMMISSION

Purpose

• Describe combined SBAS performance for single-frequency SBAS capable civil receivers

• Develop performance maps for existing SBAS services

• Establish methodology for illustrating performance for future evolutions of SBAS

2

EUROPEANCOMMISSION

Introduction

• The United States of America and the European Union are jointly working on the development of estimates of availability of worldwide aviation navigation service using SBASs* that will be operational in the 2010 timeframe. – WAAS

– MSAS

– EGNOS

• The work is conducted in cooperation between the US Federal Aviation Administration (FAA), The European Commission (EC) and the European Space Agency (ESA).

• GPS-only availability will also be estimated for comparison

• This briefing shows illustrative examples and describes planned analyses

• This work is intended to be shared in a multi-lateral environment

3

EUROPEANCOMMISSION

Scope of Simulation

• SBAS worldwide navigation services availability estimated using systems planed for 2010 operations*

– Wide Area Augmentation System (WAAS)

– Multi-functional Satellite Augmentation System (MSAS)

– European Geostationary Navigation Overlay Service (EGNOS)

• GPS unaugmented availability provided for comparison

• Current results are based on GPS L1 C/A for aviation Required Navigation Performance (RNP) services including Lateral Precision with Vertical Guidance (LPV)

* Opportunity to address GPS-aided Geo Augmented Navigation (GAGAN) and System of Differential Correction and Monitoring (SDCM) as follow-on activity

4

EUROPEANCOMMISSION

Assumptions

• Global map representation– Service Levels: RPN 0.3 and RNP 0.15 Nautical Miles

– Compares GPS, SBAS/GPS during periods when two primary slot GPS satellites are out of service

• GPS constellation– Specific days identified in 2008

• User equipment– User equipment compliant with the minimum performance

standards as described in RTCA DO-229D

• SBAS – Considers latest configurations (EGNOS, MSAS and WAAS) *

* Services are determined by number of factors, including: number and location of reference stations, actual system design details, and environmental conditions

5

EUROPEANCOMMISSION

Constellation Assumptions

• April 29, 2008, from 1014Z to 1214Z (GMT)

– 29 satellites operating, not including:

PRN 2 (D1 plane/slot)

PRN 30 (B2 plane/slot)

• June 7, 2008, from 1751Z to 2005Z (GMT)

– 28 satellites operating, not including:

PRN 9 (A1 plane/slot)

PRN 25 (A5 plane/slot) – not in primary orbital slot

• The following slides are examples of information these and future analyses can provide

• Improvement brought by SBAS in the case of close to nominal 24-sat GPS constellation would be even higher

6

EUROPEANCOMMISSION

Observed SBAS Availability

Courtesy: FAA Technical Center

* Localizer Performance with Vertical Guidance (LPV)

*

7

EUROPEANCOMMISSION

RNP 0.3 Availability - Using GPS RAIM (7 June 2008 from 1751Z to 2005Z)

8

Parameters:• Horizontal Alert Limit 0.3 nautical miles (NM)• Availability of GPS Receiver Autonomous Integrity Monitoring

(RAIM) Fault Detection (FD) function • Legacy user equipment with 5 mask angle

EUROPEANCOMMISSION

RNP 0.3 Availability – Using SBAS(7 June 2008 from 1751Z to 2005Z)

9

Parameters:• Horizontal Alert Limit 0.3 nautical miles (NM)• SBAS user equipment with 5 mask angle• EGNOS v2.2, MSAS Phase 2, WAAS Release 8/9.2

EUROPEANCOMMISSION

RNP 0.15 Availability - Using GPS RAIM (29 April 2008 from 1014Z to 1214Z)

10

Parameters:• Horizontal Alert Limit 0.15 nautical miles (NM)• Availability of GPS Receiver Autonomous Integrity Monitoring

(RAIM) Fault Detection (FD) function • Legacy user equipment with 5 mask angle

EUROPEANCOMMISSION

RNP 0.15 Availability - Using SBAS(29 April 2008 from 1014Z to 1214Z)

11

Parameters:• Horizontal Alert Limit 0.15 nautical miles (nm)• SBAS user equipment with 5 mask angle• EGNOS v2.2, MSAS Phase 2, WAAS Release 8/9.2

EUROPEANCOMMISSION

Future Cases for Consideration

• Availability for other phases of flight including:– RNP1 / RNP0.5

– Localizer Performance with Vertical Guidance (LPV)*

– LPV-200**

• Availability when GPS constellation is at minimum SPS Performance levels – Random or specific satellite outages

• SBAS availability when GAGAN and SDCM are operational

• Availability of modernized (dual-frequency) SBAS augmenting GPS broadcasting two civil signals

• Availability of combined SBAS-augmented GPS plus Galileo

12

* Similar to Approach with Vertical Guidance (APV) Type I (HAL= 40m - VAL = 50m)** LPV down to 200 ft Height Above Threshold (HAL= 40m - VAL = 35 m)HAL = Horizontal Alert Limit; VAL = Vertical Alert Limit

EUROPEANCOMMISSION

Conclusion

• Several SBAS systems are either already available or planned to be commissioned in the near to mid term

• Such systems provide high safety standards and very robust navigation services even under depleted core constellation scenarios

• The combined service area of SBAS systems is significant and should grow in the future as more systems are being deployed and as improvements are brought to existing systems

• Communicating on the combined performance of existing SBAS systems is seen as an important aspect to get full benefit of deployed infrastructure

• Work is on-going between the SBAS service providers to establish SBAS performance levels on a global basis.– Presently Includes Data from WAAS, MSAS and EGNOS

– Plan to Include GAGAN and other regional systems data when available

• The EU and the USA are committed to work in this direction and bring further information at subsequent UN-ICG meetings

13

EUROPEANCOMMISSION

Questions?

14

EUROPEANCOMMISSION

Backup

EUROPEANCOMMISSION

ICAO Global Mapping Assumptions

• Simulation Assumptions– User equipment (UE):

• GPS/RAIM UE assuming 100m accuracy (Most legacy GPS avionics are of this type)

• GPS/RAIM UE with barometric aiding and GPS SPS Performance Standard accuracy

• SBAS UE compliant with DO-229D

• 5-degree elevation masks for all UEs (Except for one map for HAL = 0.3, which will use a 2-degree elevation mask for comparison)

• Weighted RAIM solutions for all UEs

– SBAS

• WAAS and MSAS with GEO ranging

• EGNOS without GEO ranging

• MT 27 or 28 as applicable

EUROPEANCOMMISSION

ICAO Global Mapping Assumptions

• Simulation Assumptions– GPS Constellation

• 24 Satellite Nominal

• 28 Satellite constellation that existed on some day in the past year that approximates the average constellation observed over the time period (short satellite outages that may have occurred on that day can be ignored by the simulation)

– User locations

• Every 2 degrees of latitude (up to 70°N and down to 70°S) and longitude

– Sampling:

• 24 hours sampled every 5 minutes (288 epochs)