MSAS

MSAS
Name	MSAS
Type	Satellite-based augmentation system
Operator	Japanese Ministry of Land, Infrastructure, Transport and Tourism
Launched	2007 (service start 2007)
Status	Operational

MSAS

MSAS is a satellite-based augmentation system designed to improve the performance of the Global Positioning System constellation for aviation and other precision navigation users. It provides differential corrections, integrity, and enhanced positioning accuracy across the service area, interoperating with systems such as WAAS, EGNOS, and GAGAN. MSAS supports civil aviation procedures and contributes to navigation services used by agencies like the Japan Aerospace Exploration Agency and the Civil Aviation Bureau (Japan).

Overview

MSAS augments signals from the Global Positioning System by broadcasting correction messages and integrity information via geostationary satellites operated by entities including INMARSAT-constituents and Japanese communications satellites. The system architecture incorporates reference stations, master control stations, uplink facilities, and space segment links, coordinating with national authorities such as the Ministry of Land, Infrastructure, Transport and Tourism and technical partners like Japan Radio Co., Ltd. and NEC Corporation. MSAS provides improved horizontal and vertical accuracy for users operating under standards published by the International Civil Aviation Organization and works alongside regional augmentation systems such as SACCSA and SBAS initiatives.

History and Development

Development of MSAS traces to cooperative research among agencies including the Japan Aerospace Exploration Agency, the Ministry of Land, Infrastructure, Transport and Tourism, and manufacturers like Mitsubishi Electric and Fujitsu. Early trials leveraged technology demonstrated in projects associated with Navstar research and systems evaluated by the Federal Aviation Administration and European Space Agency. After system validation against ICAO performance criteria and flight validation involving carriers and operators regulated by the Civil Aviation Bureau (Japan), operational service commenced in 2007. Subsequent upgrades drew on international coordination through forums such as the United Nations Office for Outer Space Affairs and standardization bodies including the RTCA, Inc. and the International Organization for Standardization, while collaborations with satellite operators like Sky Perfect JSAT supported continuity and resilience.

Technical Specifications

MSAS transmits messages compatible with the RTCA DO-229 and ICAO SARPS satellite-based augmentation message formats, delivering correction and integrity data for GPS L1 C/A signals. Reference station networks sample pseudorange and carrier phase errors, feeding master control centers that compute ionospheric delay models, tropospheric corrections, and satellite orbit and clock offsets. The space segment uses geostationary transponders similar to those employed by INMARSAT I-4 and regional satellites such as MTSAT-class platforms. Performance parameters include protection levels, horizontal and vertical accuracy figures, and availability metrics benchmarked against ICAO Annex 10 criteria and national aviation requirements. MSAS also supports differential GPS augmentation for maritime users regulated under conventions like the International Maritime Organization standards.

Applications and Services

Primary services include precision approach support for airports administered by authorities such as the Narita International Airport Corporation and the Haneda Airport operators, situational navigation for airlines including carriers like Japan Airlines and All Nippon Airways, and enhancements used by civil agencies like the Japan Coast Guard for hydrographic surveying. MSAS messages are usable by certified avionics from manufacturers like Honeywell International Inc. and Rockwell Collins, and by equipment vendors supplying receivers to research institutions including University of Tokyo and Kyoto University. Non-aviation uses have included geodetic surveying projects coordinated with the Geospatial Information Authority of Japan and mobile services developed by telecommunications firms such as NTT DoCoMo for precision location-based applications.

Regulatory and Licensing Framework

Operation and use of MSAS are overseen by the Ministry of Land, Infrastructure, Transport and Tourism under frameworks that reference ICAO provisions and domestic aviation regulations enforced by the Civil Aviation Bureau (Japan). Spectrum and satellite coordination involves agencies such as the Ministry of Internal Affairs and Communications and international filings to the International Telecommunication Union. Certification of avionics and performance claims follows processes administered by the Japan Civil Aviation Bureau and harmonized with standards from organizations like RTCA, Inc. and the European Union Aviation Safety Agency, enabling interoperability with regional SBAS programs and compliance with bilateral agreements signed with partners including the United States Federal Aviation Administration.

Criticisms and Limitations

Critics have pointed to MSAS's regional scope compared with global augmentation concepts promoted by entities like the Galileo Programme and to constraints posed by geostationary-satellite visibility at high latitudes, impacting users in northern territories administered by municipal authorities such as Hokkaido Prefecture. Technical limitations include dependence on the GPS signal set and vulnerability to ionospheric disturbances documented in studies by institutions like the National Institute of Information and Communications Technology. Operational challenges have arisen from satellite replacement timelines involving commercial operators such as JSAT and from harmonizing certification with evolving standards from bodies including ICAO Annex 10 revisions. Nonetheless, MSAS remains an integral component of Japan's navigation infrastructure, complementing inland systems and international augmentation services administered by agencies such as the Federal Aviation Administration and the European Commission.

Category:Satellite-based augmentation systems