MGEX
QZSS

This page provides an overview of the Satellites in the Quasi-Zenith Satellite System Constellation. Technical parameters of the indivdual satellites and related conventions applied within the MGEX project are summarized in the Spacecraft Characteristics section. Furthermore, a list of Events of interest for the QZSS data processing is given.

Satellites

The Quasi-Zenith Satellite System (QZSS) currently comprises a single satellite in an inclined geo-synchronous orbit.

Common Name SVN Int. Sat. ID NORAD ID PRN Notes
QZS-1 (Michibiki) J001 2010-045A 37158 J01 launched 2010/09/11
QZS-2 (Michibiki-2) J002 2017-028A 42738 J02 launched 2017/06/01
Spacecraft Characteristics

A comprehensive collection of technical information with associated references for the QZSS spacecraft can be obtained at ESA's eoPortal . Physical key parameters of the spacecraft are summarized below:

Parameter QZS-1 QZS-2 QZS-3 QZS-4
Orbit IGSO IGSO GEO IGSO
Launch mass 4100 kg 4000 kg 4700 kg 4000 kg
Dry mass 1800 kg 1550 kg 1700 kg 1550 kg
Body size 2.9 m x 3.1 m x 6.2 m 2.8 m x 2.9 m x 6.2 m n/a 2.8 m x 2.9 m x 6.2 m
Solar array size n/a n/a n/a n/a
Span width 25.3 m 19 m n/a 19 m
Cross section n/a n/a n/a n/a
SRP acceleration 156 nm/s2 n/a n/a n/a

The QZS-1 spacecraft is equipped with a primary L-band antenna (L-ANT) for transmission of the L1 C/A, L1C, L2C, L5, and L6 LEX signals, whereas a separate (LS-ANT) antenna is used for the L1 SAIF signal. In addition, a laser retroreflector array (LRA) is provided to enable precise distance measurements using satellite laser ranging.


Fig. 1 QZSS spacecraft reference system and sensor locations. Reproduced from DOI 10.1016/j.asr.2015.06.019 with permission of Elsevier; satellite image courtesy JAXA.

Phase center coordinates of the GNSS antennas and the LRA as recommended for QZS-1 processing within the MGEX project are provided in the following table. All values refer to the spacecraft coordinate system illustrated in Fig. 1. The spacecraft coordinate system is aligned with the main body axes and originates near the center of the launch adapter plane. In accord with IGS conventions, the individual axes are aligned in the following way:
  • the +zIGS-axis is oriented along the boresight direction of the L-ANT antenna;
  • the +yIGS-axis is parallel to the rotation axis of the solar panels and oriented such that the LRA is located in the first quadrant of the xIGS/yIGS-plane relative to the L-ANT;
  • the +xIGS-axis completes a right handed system;
While the center of mass (CoM) may shift by roughly 3 cm over the mission life-time, the value for mid 2012 is adopted as a conventional value for a harmonized processing. Begin-of-life (BoL) and End-of-life (EoL) values are given for information, only. CoM coordinates previously reported in [2] for satellite laser ranging support are superseded by more recent values provided in [1].

A machine-readable version of the phase center offset information for QZS-1 is provided as part of the IGS08 ANTEX product.

QZS-1
  Coordinates (w.r.t. origin) Coordinates (w.r.t. CoM) Reference
xIGS yIGS zIGS xIGS yIGS zIGS
L-ANT L1 0.0 mm 0.0 mm +5017.8 mm -0.9 mm +2.9 mm +3197.9 mm [1]
L-ANT L2 0.0 mm 0.0 mm +4812.8 mm -0.9 mm +2.9 mm +2992.9 mm [1]
L-ANT L5 0.0 mm 0.0 mm +4897.8 mm -0.9 mm +2.9 mm +3077.9 mm [1]
L-ANT L6 0.0 mm 0.0 mm +4967.8 mm -0.9 mm +2.9 mm +3147.9 mm [1]
LS-ANT L1 -1150.0 mm -700.0 mm +4835.0 mm -1150.9 mm -697.1 mm +3015.1 mm [1]
LRA   +1150.0 mm +550.0 mm +4505.3 mm +1149.1 mm +552.9 mm +2685.4 mm [2]
CoM (BoL)   +0.9 mm -2.9 mm +1819.2 mm       [1]
CoM (Jul 2012)   +0.9 mm -2.9 mm +1819.9 mm       [1]
CoM (EoL)   +0.9 mm -3.1 mm +1851.2 mm       [1]


The attitude law that describes the orientation of the QZS-1 satellite in space, depends on the elevation of the Sun relative to the orbital plane (also known as β angle):
  • For |β|>20° the satellite is operated in "yaw-steering mode". Here, the +zIGS-axis is pointed to the Earth, while the yIGS-axis is oriented perpendicular to the plane made up by the Sun, Earth, and satellite. Furthermore, xIGS-axis is oriented such that the Sun is always located in the +xIGS hemisphere, while the -xIGS-axis points to "deep space" at all times to minimize heating of the onboard clocks. The QZS-1 yaw-steering mode matches the standard attitude law of the GPS, GLONASS, and Galileo satellites.
  • For |β|<20° the satellite is operated in "orbit normal mode". While the +zIGS-axis is again pointed towards the center of the Earth, the +yIGS-axis is held perpendicular to the orbital plane and parallel to the orbital angular momentum vector. The +xIGS-axis is roughly oriented in anti-flight direction.
While the location of the L-ANT phase center relative to the center of mass is essentially independent of the yaw-angle (i.e. the rotation about the +zIGS-axis), knowledge of the actual attitude is required for phase wind-up modeling and for the computation of the absolute LS-ANT and LRA positions.

Further details and the mathematical formulations of the QZS-1 attitude modes are provided in [3] and [4].

QZS-2 satellite information is provided in [5].

References

[1] S. Kogure, priv. comm. (20 July 2012)
[2] QZS-1 ILRS SLR Mission Support Request Form - Retroreflector Information
[3] Y. Ishijima, N. Inaba, A. Matsumoto, K. Terada, H. Yonechi, H. Ebisutani, S. Ukawa, T. Okamoto, "Design and Development of the First Quasi-Zenith Satellite Attitude and Orbit Control System", Proceedings of the IEEE Aerospace Conference, March 7-14 2009, Big Sky, MT, USA, (2009). DOI 10.1109/AERO.2009.4839537
[4] Montenbruck O., Schmid R., Mercier F., Steigenberger P., Noll C., Fatkulin R., Kogure S., Ganeshan A. S. (2015) GNSS satellite geometry and attitude models. Advances in Space Research 56(6):1015-1029. DOI 10.1016/j.asr.2015.06.019
[5] Cabinet Office (2017) QZSS Satellite Information


Events

Date UTC Satellite PRN Description Notes
~2010/12/15   QZS-1 J01 Transmission of standard codes Kishimoto et al. (2012)
2011/02/16 07:00 QZS-1 J01 Transition to orbit normal mode Hauschild (2011); CONGO monitoring
2011/02/16   QZS-1 J01 Orbit maneuver Hauschild (2011); TUM/CONGO
2011/02/16 17:30 QZS-1 J01 Return to yaw steering mode Hauschild (2011); CONGO
2011/03/07 10:00 QZS-1 J01 Transition to orbit normal mode
2011/04/20 08:13 QZS-1 J01 Return to yaw-steering mode
2011/05/22   QZS-1 J01 L1-C/A and L2C signals set healthy Kishimoto et al. (2012)
2011/07/14   QZS-1 J01 L1C and L5 signals set healthy Kishimoto et al. (2012)
2011/07/16 01:30 QZS-1 J01 Start of RESSOX NAQU 2011002
2011/07/23 08:10 QZS-1 J01 End of RESSOX NAQU 2011004
2011/09/07 09:20 QZS-1 J01 Transition to orbit normal mode
2011/10/22 08:05 QZS-1 J01 Return to yaw-steering mode
2012/01/04 09:21 QZS-1 J01 Unusable (until 21:19 UTC) NAQU 2012001-002
2012/01/21 01:28 QZS-1 J01 Start of RESSOX NAQU 2012003-005
2012/01/28 06:55 QZS-1 J01 End of RESSOX NAQU 2012003-005
2012/02/24 11:04 QZS-1 J01 Unusable (until 12:40 UTC) NAQU 2012006-007
2012/03/03 09:55 QZS-1 J01 Transition to orbit normal mode
2012/03/07 05:35 QZS-1 J01 Unusable (until 16:18 UTC) NAQU 2012008-009
2012/04/16 08:12 QZS-1 J01 Return to yaw-steering mode
2012/05/02 01:32 QZS-1 J01 Unusable (until 2012/05/03 01:13 UTC) NAQU 2012010-011
2012/06/03 16:42 QZS-1 J01 Unusable (until 2012/06/04 01:15 UTC) NAQU 2012013-014
2012/07/04 21:30 QZS-1 J01 Unusable (until 2012/07/05 12:11 UTC); switched from Rb clock 2 to Rb clock 1 NAQU 2120015-016
2012/09/03 09:21 QZS-1 J01 Transition to orbit normal mode
2012/09/29 14:07 QZS-1 J01 Unusable (until 2012/09/29 18:25 UTC) NAQU 2012017-018
2012/10/18 08:07 QZS-1 J01 Return to yaw-steering mode
2012/11/07 12:56 QZS-1 J01 Unusable (until 2012/11/08 21:24 UTC) NAQU 2012019-020
2012/11/07 QZS-1 J01 Orbit Maneuver
2012/12/05 21:21 QZS-1 J01 Unusable(until 2012/12/06 02:05 UTC) NAQU 2012021-022
2013/01/30 06:25 QZS-1 J01 Unusable(until 2013/01/30 08:35 UTC) NAQU 2013001-002
2013/02/27 09:55 QZS-1 J01 Transition to orbit normal mode
2013/04/13 08:18 QZS-1 J01 Return to yaw-steering mode
2013/05/01 01:14 QZS-1 J01 Unusable (until 2013/05/02 00:16 UTC) NAQU 2013003-004
2013/05/01 QZS-1 J01 Orbit Maneuver
2013/08/30 09:27 QZS-1 J01 Transition to orbit normal mode
2013/10/30 12:15 QZS-1 J01 Unusable (until 2013/10/31 13:24 UTC) NAQU 2013005-006
2013/11/11 19:56 QZS-1 J01 Unusable (until 2013/11/11 23:30 UTC) NAQU 2013007-008
2014/04/10 00:34 QZS-1 J01 Unusable (until 2014/04/10 13:18 UTC) NAQU 2014001-002
2014/04/30 01:03 QZS-1 J01 Unusable (until 2014/05/01 02:34 UTC) NAQU 2014003-004
2014/05/02 23:35 QZS-1 J01 L5 unavailable (until 2014/05/03 02:31 UTC) NAQU 2014005
2014/10/29 12:39 QZS-1 J01 Start of 2-day transmission outage CONGO/MGEX monitoring, NAQU 2014008
2014/10/31 QZS-1 J01 End of transmission outage CONGO/MGEX monitoring, NAQU 2014008
2015/02/20 10:00 QZS-1 J01 Mode change YS to ON DLR analysis
2015/04/05 07:23 QZS-1 J01 Unusable (until 2014/04/05 15:06 UTC) NAQU 2014001-002
2015/04/06 18:33 QZS-1 J01 Unusable (until 2014/04/06 19:31 UTC) NAQU 2014003
2015/04/22 01:07 QZS-1 J01 Unusable (until 2014/04/23 03:21 UTC) NAQU 2014004-005
2015/04/22 01:24 - 11:24 QZS-1 J01 ON mode due to orbit maneuver DLR analysis
2015/10/07 07:50 QZS-1 J01 Mode change ON to YS DLR analysis
2015/10/21 12:20 QZS-1 J01 Unusable (until 2015/10/23 12:20 UTC) NAQU 2015007
2015/10/21 13:17 - 23:21 QZS-1 J01 ON mode due to orbit maneuver DLR analysis
2015/11/20 08:32 QZS-1 J01 Start of SAIF transmission outage CONGO/MGEX monitoring
2015/11/23 23:21 QZS-1 J01 End of SAIF transmission outage CONGO/MGEX monitoring
2015/11/27 08:04 QZS-1 J01 Start of SAIF transmission outage CONGO/MGEX monitoring
2015/12/04 11:50 QZS-1 J01 End of SAIF transmission outage CONGO/MGEX monitoring
2015/12/06 23:30 QZS-1 J01 Start of SAIF transmission outage CONGO/MGEX monitoring
2015/12/09 08:40 QZS-1 J01 End of SAIF transmission outage CONGO/MGEX monitoring
2015/12/20 23:30 QZS-1 J01 Start of SAIF transmission outage CONGO/MGEX monitoring
2015/12/22 08:36 QZS-1 J01 End of SAIF transmission outage CONGO/MGEX monitoring
2016/01/08 09:04 QZS-1 J01 Start of SAIF transmission outage CONGO/MGEX monitoring
2016/01/15 10:47 QZS-1 J01 End of SAIF transmission outage CONGO/MGEX monitoring
2016/02/16 10:00 QZS-1 J01 Mode change YS to ON DLR analysis
2016/04/01 07:48 QZS-1 J01 Mode change ON to YS DLR analysis
2016/04/20 00:10 QZS-1 J01 Unusable (until 2016/04/22 00:10 UTC) NAQU 2016001
2016/08/18 09:42 QZS-1 J01 Mode change YS to ON DLR analysis
2016/10/03 07:53 - 08:25 QZS-1 J01 Mode change ON to YS DLR analysis
2016/10/05 13:48 - 24:00 QZS-1 J01 ON mode due to orbit maneuver DLR analysis


Notes:
  • Complementary information on the current status of QZSS is provided at the QZ-Vision web site. This site also provides the QZSS Interface Specification and Notice Advisory to QZSS Users (NAQU) messages.
  • Supplementary information related to Michibiki operations can also be found at the QZSS project web site.
  • QZSS employs distinct PRNs for the L1 SAIF SBAS signal (PRN(SAIF) = 183, 184, ...) and the other ranging signals (PRN(std) = 193, 194,...). In order to ensure a unique RINEX satellite number for each QZSS satellite, it is recommended to consistently use the satellite number "Jnn" with n = PRN(std)-193=PRN(SAIF)-183. Use of an SBAS RINEX satellite number "Snn" with nn = PRN(SAIF)-100 is deprecated.
  • The experimental remote synchronization system for an onboard crystal oscillator (RESSOX) of QZSS aims at the use of a ground-controlled low cost oscillator onboard a GNSS satellite as an alternative to a high-performance atomic frequency standard.


Last Updated: 2017/07/31 10:15:54
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