QZSS

QZSS
Title	QZSS
Edited by	GMV
Level	Basic
Year of Publication	2011

The Quasi-Zenith Satellite System (QZSS) is a regional navigation satellite system commissioned by the Japanese Government as a National Space Development Program.

QZSS Introduction

Jaxa logo

QZSS was authorized by the Japanese government in 2002. At the beginning the system was developed by the Advanced Space Business Corporation (ASBC) team, including Mitsubishi Electric Corp., Hitachi Ltd., and GNSS Technologies Inc. When in 2007 ASBC collapsed, the work was taken over by JAXA together with Satellite Positioning Research and Application Center (SPAC), established in February 2007 and approved by the Ministers associated with QZSS research and development. In 2011, the Office of National Space Policy designated it to the top priority of Japan's space policy . In 2020, it still remained as one of the main keys to ensure Japanese space security .

QZSS System description

QZSS satellites groundtrack

The QZSS service area covers East Asia and Oceania region and its platform is multi-constellation GNSS. The QZSS system is not required to work in a stand-alone mode, but together with data from other GNSS satellites.

The space segment consists of three satellites placed in periodic Highly Elliptical Orbit (HEO) and a fourth in a geo-stationary orbit. For the satellites in HEO, the perigee altitude is about 32000 km and apogee altitude about 40000 km, and all of them will pass over the same groundtrack so they are visible at all times from locations in the Asia-Oceania region. QZSS is designed so that at least one satellite out of three satellites exists near zenith over Japan. Given its orbit, each satellite appears almost overhead most of the time (i.e., more than 12 hours a day with an elevation above 70°). This gives rise to the term "quasi-zenith" for which the system is named. The design life of the quasi-zenith satellites is of 10 years. The first satellite Michibiki (QZS-1) was launched on 11 September 2010 and injected into the Quasi-Zenith Orbit on 27 September. In 2017 all three remaining satellites were launched: QZS-2 on 1 July 2017, QZS-4 on 9 October 2017 and the geostationary QZS-3 on 19 August 2017.

The ground segment is composed of a master control station (MCS), tracking control stations (TT&C), laser ranging stations and monitoring stations. The network of monitoring stations covers East Asia and Oceania region, with stations in Japan (Okinawa, Sarobetsu, Koganei, Ogasawara) and abroad: Bangalore (India), Guam, Canberra (Australia), Bangkok (Thailand) and Hawaii (USA). The MSC is the responsible of the navigation message generation that are uplinked to the quasi-zenith satellite via a TT&C station place in Okinawa.

The signals planned and in operation for the QZSS system are:

Signal name	QSZ-1	QSZ-2, QSZ-3 and QSZ-4		Transmission service	Center frequency
	Block IQ	Block IIQ	Block IIG
	Quasi zenith satellite orbit (QZO)	Quasi zenith satellite orbit (QZO)	Geostationary orbit (GEO)
	One satellite	Two satellites	One satellite
L1C/A	◎	◎	◎	Satellite Positioning, Navigation and Timing Service (PNT)	1575.42MHz
L1C	◎	◎	◎	Satellite Positioning, Navigation and Timing Service (PNT)
L1S	◎	◎	◎	Sub-meter Level Augmentation Service (SLAS)
				Satellite Report for Disaster and Crisis Management (DC Report)
L1Sb	-	-	◎ Will be transmitted from around 2020	SBAS Transmission Service
L2C	◎	◎	◎	Satellite Positioning, Navigation and Timing Service (PNT)	1227.60MHz
L5	◎	◎	◎	Satellite Positioning, Navigation and Timing Service (PNT)	1176.45MHz
L5S	-	◎	◎	Positioning Technology Verification Service
L6 (LEX)	◎	◎	◎	Centimeter Level Augmentation Service (CLAS)	1278.75MHz
S-band	-	-	◎	QZSS Safety Confirmation Service	2GHz band

The multi-constellation GNSS interoperable signals, L1 C/A, L2C, L5 and L1C, are to be provided on the basis of no direct user fee. Compatibility is a mandatory requirement for QZSS system, working in the same frequency bands among the multi GNSS systems without harmful interference. For the GPS performance enhancement signals, L1S and L6, a charging policy has been under examination. SPAC leads the investigation for L1S (sub meter class) and L6 (centimeter class) user terminals.

QZSS applications are: mobile mapping, IT aided precise farming, IT aided construction, fleet management, marine and transportation applications, among others.

QZSS Services

All QZSS services are freely available to any user. However, the receivers and/or applications developed based on them may not receive signals or may receive incorrect signals due to no warranty of those

Satellite Positioning, Navigation and Timing Service (PNT)

This service can be used in an integrated way with GPS which translates in a higher number of visible satellites that allows for an improvement in the DOP. Moreover, the high elevation angles of the QZSS satellites allow for less multipath error. The system uses the same methods (double frequency, Klobuchar, etc.) to produce ionospheric correction parameters. QZSS produces two types of those parameters: ones for the Southeast Asia and Oceania, and others for Japan.

Sub-meter Level Augmentation Service (SLAS)

Sub-meter level augmentation data is transmitted in the L1S signals that are the same type as the L1C/A used in GPS. This service is intended for applications outside the mobile service range that are not heavily affected by time lags (pedestrians, bicycles, ships, etc.) as the augmentation information needs to be crafted before being sent and visibility of QZSS satellites can affect the service performance.

Centimeter Level Augmentation Service (CLAS)

Two-phase system installations for the overseas deployment of CLAS

Using data from the GNSS –based control stations of the Geospatial Information Authority of Japan, highly precise satellite positioning can be achieved. This information is transmitted by L6 signals that require dedicated receivers. This service is expected to be used in limited areas or in an auxiliary way as the augmentation information creation and transmission times may render immediate operation impossible. The CLAS service started broadcasting a trial signal compliant with IS-QZSS-L6-003 using the L6D signal of QZS-3 the 1st of July 2020 and began its official broadcast of augmentation information in November 30 of 2020 . This service has been evaluated and tested by 6 countries in the Asia-Pacific region since 2018. An ongoing overseas implementation of the service will provide wide area ionospheric correction data to regions with partnership agreements .

Positioning Technology Verification Service

QZSS satellites can be used by institutions to test their newly developed positioning technologies using L5S signals. Satellite Report for Disaster and Crisis Management (DC Report) This service uses the same L1S signals used by SLAS service and allows for transmission of crisis management information released by organizations for disaster prevention in intervals of four seconds. Powered street furniture and moving devices can be equipped with receivers to broadcast and display disaster-related information even in remote regions. This service is currently being distributed in Japan but it is planned to be available for the Asia – Oceania region in 2024-2025 .

QZSS Safety Confirmation Service (Q-ANPI)

It has been proposed for this service to be used as an evacuation shelter data relay so that information about the location and opening of evacuation shelters, number of evacuees, and circumstances at evacuation shelters can be sent even with a damaged ground infrastructure. The system uses QZS and GEO satellites and is available on S-band devices that support Q-ANPI.

Public Regulated Service

This service allows for positioning augmentation and time information acquisition via QZSS alone, even when GPS signal is jammed of spoofed. It is restricted to authorized users.

SBAS Transmission Service

Using the QZSS satellites placed on a GEO orbit, this service transmits the SBAS data crafted by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) that used to be transmitted from MTSAT.

Performance

The specification performances are:

• The Signal in Space (SIS) User Range Error: less than 2.6 m (95%).
• SLAS positioning accuracy: from under 2 m to under 1 m in the horizontal plane and from less than 2 m to less than 3 m in the vertical plane.
• CLAS positioning accuracy: less than 6 cm for horizontal and 12 cm for vertical (static).

The evaluated performances for 2020 were :

• The Signal in Space (SIS) User Range Error: between 0.52 and 1.10 m (95%).
• SLAS positioning accuracy: from 0.38 m to 0.84 m in the horizontal plane and from 0.55 m to 1.11 m in the vertical plane (95%).
• CLAS positioning accuracy: from 1.3 cm to 2.7 cm in the horizontal plane and from 3.7 cm to 6.3 cm in the vertical plane (95%).

QZSS Development

The Initial Phase Operation that started in September 2010 with the launch of the first JAXA-operated quasi-zenith satellite, Michibiki, was completed in 2011, with all functions of the satellite and the ground segment confirmed.

During the initial phase, technical verifications and applications demonstrations were made using Michibiki. The demonstrations showed that in a case of a car driving route inside Tokyo, time percentage when a GPS+QZSS user could get his position improved more than 10% of the GPS-only user, with a best improvement over 40% in the worst GPS DOP situation.

In 2011 the Government of Japan decided to accelerate the QZSS deployment in order to reach a 4-satellite constellation by the late 2010s, while aiming at a final 7-satellite constellation in the future.

Later on March 2013, the Japanese Cabinet Office formally announced a ¥50 billion (US$540 million) contract award with Mitsubishi to build one geostationary satellite and two additional quasi-zenith satellites (QZSs). That would complete the 4-satellite constellation by the end of 2017 that has been operated since November 2018 . In addition, another contract was also signed with a special purpose company (led by NEC and supported by Mitsubishi UFJ Lease & Finance and Mitsubishi Electric Corporation) to fund the design and construction of the ground control system as well as its verification and maintenance for a period of 15 years .

Development and operation are conducted via a private finance initiative (PFI) project and Quasi-Zenith Satellite System Services Inc. (QSS) operates the four satellites, including QZS-1 . The replacement of QZS-1, QZS-1R, was initially scheduled for mid-2020 but has been delayed to 2021 ". The three new satellites to complete the 7-satellite constellation were scheduled to launch between 2022 and 2023 and have now all three been delayed further into 2023 .

Constellation plans as of June 2021

This 7-satellite constellation will feature QZSS standalone PNT function with 1.0 meter (horizontal RMS error) for dual frequency code phase positioning, open service with Navigation Message Authentication (NMA), two-way ranging (ground-satellite) and inter satellite ranging to improve accuracy, availability and integrity, as well as PPP augmentation service and Disaster and Crisis management Report (DCR) for all the Asia-Pacific region.